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Dietary supplements containing usnic acid have been increasingly marketed for weight loss over the past decades, even though incidences of severe hepatotoxicity and acute liver failure due to their overuse have been reported. To date, the toxic mechanism of usnic acid‐induced liver injury at the molecular level still remains to be fully elucidated. Here, we conducted a transcriptomic study on usnic acid using a novel in vitro hepatotoxicity model employing human induced pluripotent stem cell (iPSC)‐derived hepatocytes. Treatment with 20 μM usnic acid for 24 h caused 4272 differentially expressed genes (DEGs) in the cells. Ingenuity Pathway Analysis (IPA) based on the DEGs and gene set enrichment analysis (GSEA) using the whole transcriptome expression data concordantly revealed several signaling pathways and biological processes that, when taken together, suggest that usnic acid caused oxidative stress and DNA damage in the cells, which further led to cell cycle arrest and eventually resulted in cell death through apoptosis. These transcriptomic findings were subsequently corroborated by a variety of cellular assays, including reactive oxygen species (ROS) generation and glutathione (GSH) depletion, DNA damage (pH2AX detection and 8‐hydroxy‐2′‐deoxyguanosine [8‐OH‐dg] assay), cell cycle analysis, and caspase 3/7 activity. Collectively, the results of the current study accord with previous in vivo and in vitro findings, provide further evidence that oxidative stress‐caused DNA damage contributes to usnic acid‐induced hepatotoxicity, shed new light on molecular mechanisms of usnic acid‐induced hepatotoxicity, and demonstrate the usefulness of iPSC‐derived hepatocytes as an in vitro model for hepatotoxicity testing and prediction. Treatment with 20 μM usnic acid for 24 h caused 4272 differentially expressed genes (DEGs) in human iPSC‐derived hepatocytes. Functional analysis of the transcriptomic data revealed signaling pathways and biological processes suggesting that usnic acid caused cellular oxidative stress and DNA damage, which further led to cell cycle arrest and eventually resulted in apoptosis. Results of a variety of cellular assays corroborated these transcriptomic findings, including ROS generation, GSH depletion, DNA damage, cell cycle arrest, and increased caspase 3/7 activity. Treatment with 20 μM usnic acid for 24 h caused 4272 differentially expressed genes (DEGs) in human iPSC‐derived hepatocytes. Functional analysis of the transcriptomic data revealed signaling pathways and biological processes suggesting that usnic acid caused cellular oxidative stress and DNA damage, which further led to cell cycle arrest and eventually resulted in apoptosis. Results of a variety of cellular assays corroborated these transcriptomic findings, including ROS generation, GSH depletion, DNA damage, cell cycle arrest, and increased caspase 3/7 activity. [ABSTRACT FROM AUTHOR]

Objective: To investigate impacts of usnic acid （UA） on malignant behavior of gastric cancer cells by regulating the chemokine （C-C motif） ligand 2 （CCL2）-CCL2 receptor （CCR2） signal axis. Methods: SGC-7901 cells, a well growing human gastric cancer cell line, were treated with different concentrations of UA, which were grouped into low concentration （UA-L） group （62.5 μmol/L UA）, medium concentration （UA-M） group （125 μmol/L UA） and high concentration （UA-H） group （250 μmol/L UA）; meantime, the cells were transfected with CCL2 overexpression vector （pc DNA3.1 CCL2）, empty vector （pc DNA3.1）, silenced CCL2 （si CCL2） and negative control （si control）, and SGC-7901 cells were treated with 250 μmol/L UA, labeled as UA-H+pc DNA3.1 CCL2 group, UA-H+pc DNA3.1 group, UA-H+si control group and UA-H+si CCL2 group, another untreated SGC-7901 cells were taken as the control group. Flow cytometry, MTT and qRT-PCR were applied to detect cell apoptosis, proliferation, and expression levels of CCL2 and CCR2 mRNA; Western blot was applied to detect expression levels of PD-L1, apoptotic protein（ Bax）, proliferative protein （CyclinD1, CCL2, CCR2） and immune escape related protein （B7H1）; after co-culturing with CD8+T cells isolated and cultured in vitro, ELISA was applied to detect levels of IL-4, IFN-γ and IL-10 in the supernatant. Gastric cancer cells in each group were co-cultured with activated peripheral blood mononuclear cell （PBMC） 1∶1 for 72 hours, and the sensitivity of gastric cancer cells in each group to T-cell-mediated killing was compared. Results: Compared with control group, cell proliferation rate, IL-10 level, CyclinD1, PD-L1, CCL2, CCR2 and B7H1 protein and mRNA expressions, cell counts after co-culturing with activated PBMC 1∶1 for 72 hours in UA-L group, UA-M group and UA-H group were obviously reduced, while apoptosis rate, IL-4 and IFN-γ levels, Bax protein expression were obviously increased （P<0.05）; compared with UA-H+pc DNA3.1 group, cell proliferation rate, IL-10 level, CyclinD1, PD-L1, CCL2, CCR2 protein and mRNA expressions, cell counts after co-culturing with activated PBMC 1∶1 for 72 hours in UA-H+pc DNA3.1 CCL2 group were obviously increased, while apoptosis rate, IL-4 and IFN-γ levels, and Bax protein expression were obviously reduced （P<0.05）; compared with UA-H+si control group, cell proliferation rate, IL-10 level, CyclinD1, PD-L1, CCL2, CCR2 and B7H1 protein and mRNA expressions, cell counts after co-culturing with activated PBMC 1∶1 for 72 hours in UA-H+si CCL2 group were obviously reduced, while apoptosis rate, IL-4 and IFN-γ levels and Bax protein expression were obviously increased（ P<0.05）. Conclusion: UA can inhibit gastric cancer cells proliferation, immune escape, and induce apoptosis, which may be related to the inhibition of the CCL2-CCR2 signaling axis. [ABSTRACT FROM AUTHOR]

6‐phosphogluconate dehydrogenase (6PGD) and Glucose‐6‐phosphate dehydrogenase (G6PD) are crucial enzymes involved in generating cellular reducing power. Modifying the balance of reduced NADPH is considered essential for cancer advancement and combined therapeutic strategies. Usnic acid (UA) is a physiologically active dibenzofuran derivative. Carnosic acid (CA) is a phenolic diterpene that has been isolated from several plants. This work evaluated the inhibitory effects of UA and CA on G6PD and 6PGD by in vitro tests. Molecular docking studies were employed to predict the mechanisms of inhibition. IC50 values for UA and CA were determined to be 49.50 μM and 77.00 μM for G6PD, and 69.30 μM and 57.75 μM for 6PGD, respectively. The Ki values for UA and CA were determined to be 35.01±7.69 μM and 43.46±10.48 μM for G6PD, and 104.87±11.86 μM and 31.17±2.55 μM for 6PGD, respectively. UA was identified as the most effective inhibitor against G6PD, whereas CA exhibited the best inhibitory activity against 6PGD, with estimated binding energies of −8.0 and −7.8 kcal/mol, respectively, in molecular docking studies. Ultimately, it was shown that the results obtained from in vitro and in silico methods in the study were strongly associated. These chemicals′ structure might assist in creating medications that focus on the pentose phosphate pathway. [ABSTRACT FROM AUTHOR]

Diabetic foot ulcer caused by vancomycin-resistant Enterococcus strains is a troublesome concern that threatens public health. Due to the few treatment options, it is essential to develop a new alternative antibacterial agent with high efficacy. In the current study, we evaluated the antibacterial and antibiofilm properties of usnic acid (UA), a secondary metabolite of lichens. Microdilution broth and crystal violet methods were applied to determine the antibacterial and antibiofilm activities, respectively. To further elucidate the biofilm inhibition, scanning electron microscopy imaging was performed. In addition, the antioxidant activity of UA was investigated by 2, 2-diphenyl-1-picrylhydrazyl assay. The bacteriostatic and bactericidal activity of UA was observed as an amount of 23.02 and 312.5 μg/mL, respectively. UA suppressed biofilm formation and motivated the reduction of free oxygen radicals. The present study may open up a new perspective to combat biofilm-forming enterococci. [ABSTRACT FROM AUTHOR]

With the increasing use of invasive, interventional, indwelling, and implanted medical devices, healthcare-associated infections caused by pathogenic biofilms have become a major cause of morbidity and mortality. Herein, we present the fabrication, characterization, and in vitro evaluation of biocompatibility and anti-biofilm properties of new coatings based on Fe3O4 nanoparticles (NPs) loaded with usnic acid (UA) and ceftriaxone (CEF). Sodium lauryl sulfate (SLS) was employed as a stabilizer and modulator of the polarity, dispersibility, shape, and anti-biofilm properties of the magnetite nanoparticles. The resulting Fe3O4 functionalized NPs, namely Fe3O4@SLS, Fe3O4@SLS/UA, and Fe3O4@SLS/CEF, respectively, were prepared by co-precipitation method and fully characterized by XRD, TEM, SAED, SEM, FTIR, and TGA. They were further used to produce nanostructured coatings by matrix-assisted pulsed laser evaporation (MAPLE) technique. The biocompatibility of the coatings was assessed by measuring the cell viability, lactate dehydrogenase release, and nitric oxide level in the culture medium and by evaluating the actin cytoskeleton morphology of murine pre-osteoblasts. All prepared nanostructured coatings exhibited good biocompatibility. Biofilm growth inhibition ability was tested at 24 h and 48 h against Staphylococcus aureus and Pseudomonas aeruginosa as representative models for Gram-positive and Gram-negative bacteria. The coatings demonstrated good biocompatibility, promoting osteoblast adhesion, migration, and growth without significant impact on cell viability or morphology, highlighting their potential for developing safe and effective antibacterial surfaces. [ABSTRACT FROM AUTHOR]

Usnic acid, a secondary metabolite of lichen Usnea sp., has several pharmacological activities, but it is poorly soluble in water. This study aimed to improve the solubility and dissolution rate of usnic acid loaded in mesoporous silica SBA-15 at a mass ratio of 1:1. and evaluate its physical stability. Physicochemical characterization was carried out via the nitrogen adsorption desorption isotherm, differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and powder X-ray diffraction (PXRD). Usnic acid-loaded SBA-15 was stored at 40 °C with various relative humidities (RH) and then analyzed by PXRD for the physical stability. Usnic acid adsorbed well in the pores of SBA-15, as shown by a decrease in the volume pore and surface area of SBA-15 according to the nitrogen adsorption. Moreover, usnic acid-SBA-15 showed a decrease in the degree of crystallinity according to PXRD analysis and no melting point based on DSC analysis. The FTIR spectrum of usnic acid–SBA-15 corresponds to the spectra of each raw material. The solubility of usnic acid increased 5.15 times after adsorbed on SBA-15. The dissolution rate also showed a significant increase (p < 0.05) from 19.51% to 84.27%. Usnic acid–SBA-15 was relatively stable at RH 75%. Thus, the adsorption of usnic acid on SBA-15 can increase its solubility, dissolution rate, and physical stability.

The rapid spread of SARS-CoV-2 and its infection severity require an urgent development of antiviral agents. In this respect, Usnic acid (UA), a natural dibenzofuran derivative, exerts antiviral activity against several viruses, though presenting very low solubility and high cytotoxicity. Here, UA was complexed with β-cyclodextrins (β-CDs), a pharmaceutical excipient used to improve drug solubility. The cytotoxic activity, tested on Vero E6 cells, revealed no effect for β-CDs alone whereas significant cytotoxicity for the UA/β-CDs complex was recorded at concentrations ≥ 0.05%. The neutralizing activity towards the fusion of SARS-CoV-2 Spike Pseudovirus showed no effects for β-CDs alone whereas the UA/β-CDs complex, when pre-incubated with the viral particles, efficiently inhibited the Pseudoviral fusion of about 90 and 82% at non-cytotoxic concentrations of 0.03 and 0.01%, respectively. In conclusion, although further evidences are needed to clarify the exact inhibition mechanism, UA/β-CDs complex could be useful in SARS-CoV-2 infection. [ABSTRACT FROM AUTHOR]

Objectives: Lichens are complex symbiotic organisms that generate various bioactive compounds with significant therapeutic value. We investigated the chemical composition and bioactivity of the acetone extract of the Algerian lichen Physconia venusta (Ach.) poet. Materials and Methods: Phytochemical screening was performed using gas chromatography-mass spectrometry (GC-MS). The antibacterial activity was assessed against Escherichia coli, Pseudomonas aeruginosa, Salmonella enteritidis, Salmonella typhi, Staphylococcus aureus, Listeria monocytogenes, and Bacillus subtilis using an agar diffusion test with the determination of the minimal inhibition concentration (MIC), while the antioxidant activity was determined using different chemical methods (DPPH, ABTS, CUPRAC, reducing power, superoxide anion scavenging, ß-carotene bleaching, and metal chelate). In addition, cytotoxic activity was tested using Artemia salina (Brine shrimp) bioassay. Results: The studied extract exhibited intense antibacterial activity against E. coli and S. aureus with inhibition diameters of 28 ± 0.01 and 22 ± 0.01 mm, respectively, with a MIC value of 6.25 mg/mL and a selectivity index of 2.8. The obtained extract showed different antioxidant trends depending on the selected assay. GC-MS analysis revealed many secondary metabolites. Conclusion: P. venusta, a type of lichen, is a potential source of bioactive substances that could be used in pharmaceuticals. [ABSTRACT FROM AUTHOR]

Although the COVID-19 pandemic caused by SARS-CoV-2 viruses is officially over, the search for new effective agents with activity against a wide range of coronaviruses is still an important task for medical chemists and virologists. We synthesized a series of thiazolo-thiophenes based on (+)- and (−)-usnic acid and studied their ability to inhibit the main protease of SARS-CoV-2. Substances containing unsubstituted thiophene groups or methyl- or bromo-substituted thiophene moieties showed moderate activity. Derivatives containing nitro substituents in the thiophene heterocycle—just as pure (+)- and (−)-usnic acids—showed no anti-3CLpro activity. Kinetic parameters of the most active compound, (+)-3e, were investigated, and molecular modeling of the possible interaction of the new thiazolo-thiophenes with the active site of the main protease was carried out. We evaluated the binding energies of the ligand and protein in a ligand–protein complex. Active compound (+)-3e was found to bind with minimum free energy; the binding of inactive compound (+)-3g is characterized by higher values of minimum free energy; the positioning of pure (+)-usnic acid proved to be unstable and is accompanied by the formation of intermolecular contacts with many amino acids of the catalytic binding site. Thus, the molecular dynamics results were consistent with the experimental data. In an in vitro antiviral assay against six strains (Wuhan, Delta, and four Omicron sublineages) of SARS-CoV-2, (+)-3e demonstrated pronounced antiviral activity against all the strains. [ABSTRACT FROM AUTHOR]

The present study investigates the utilization of nanoparticles based on poly-l-lactide (PLLA) and polyglycerol adipate (PGA), alone and blended, for the encapsulation of usnic acid (UA), a potent natural compound with various therapeutic properties including antimicrobial and anticancer activities. The development of these carriers offers an innovative approach to overcome the challenges associated with usnic acid's limited aqueous solubility, bioavailability, and hepatotoxicity. The nanosystems were characterized according to their physicochemical properties (among others, size, zeta potential, thermal properties), apparent aqueous solubility, and in vitro cytotoxicity. Interestingly, the nanocarrier obtained with the PLLA-PGA 50/50 weight ratio blend showed both the lowest size and the highest UA apparent solubility as well as the ability to decrease UA cytotoxicity towards human hepatocytes (HepG2 cells). This research opens new avenues for the effective utilization of these highly degradable and biocompatible PLLA-PGA blends as nanocarriers for reducing the cytotoxicity of usnic acid. [ABSTRACT FROM AUTHOR]

The mat-forming fruticose lichens Cladonia stellaris and Cetraria islandica frequently co-occur on soils in sun-exposed boreal, subarctic, and alpine ecosystems. While the dominant reindeer lichen Cladonia lacks a cortex but produces the light-reflecting pale pigment usnic acid on its surface, the common but patchier Cetraria has a firm cortex sealed by the light-absorbing pigment melanin. By measuring reflectance spectra, high-light tolerance, photosynthetic responses, and chlorophyll fluorescence in sympatric populations of these lichens differing in fungal pigments, we aimed to study how they cope with high light while hydrated. Specimens of the two species tolerated high light equally well but with different protective mechanisms. The mycobiont of the melanic species efficiently absorbed excess light, consistent with a lower need for its photobiont to protect itself by non-photochemical quenching (NPQ). By contrast, usnic acid screened light at 450–700 nm by reflectance and absorbed shorter wavelengths. The ecorticate usnic species with less efficient fungal light screening exhibited a consistently lower light compensation point and higher CO2 uptake rates than the melanic lichen. In both species, steady state NPQ rapidly increased at increasing light with no signs of light saturation. To compensate for less internal shading causing light fluctuations with a larger amplitude, the usnic lichen photobiont adjusted to changing light by faster induction and faster relaxation of NPQ rapidly transforming excess excitation energy to less damaging heat. The high and flexible NPQ tracking fluctuations in solar radiation probably contributes to the strong dominance of the usnic mat-forming Cladonia in open lichen-dominated heaths. [ABSTRACT FROM AUTHOR]

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Usnic acid is a potential active pharmaceutical ingredient derived from Usnea sp. It has a low bioavailability because of poor aqueous solubility. Particle size reduction by nanosizing has been applied to improve the solubility of active pharmaceutical ingredients which is achieved by preparation of nanocrystals. This study aimed to prepare usnic acid nanocrystals by employing a wet grinding method with a planetary ball mill and using Poloxamer 188 as a stabilizer. The solid state properties of the resulting usnic acid nanocrystals were characterized with a particle size analyzer, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and dissolution rate profile. Usnic acid nanocrystals had a particle size of 358.77 ± 21.18 nm, evenly distributed with a polydispersity index of 0.591±0.02 and a zeta potential of -24.4 ± 0.1. The DSC thermogram showed a sharp endothermic peak at 193.413°C. The XRD pattern contained a high-intensity crystalline peak at 2O=10.213°. The dissolution rate of the usnic acid nanocrystals was 2.7 fold faster than that of the intact usnic acid. This study concluded that nanocrystals of usnic acid have improved physicochemical properties and a significantly increased dissolution rate. [ABSTRACT FROM AUTHOR]

In this study, we investigated the chemopreventive efficacy of usnic acid (UA), an effective secondary metabolite component of lichens, against 7,12‐dimethylbenz[a]anthracene (DMBA)‐induced oral squamous cell carcinoma (OSCC) in the hamster model. Initially, the buccal pouch carcinogenesis was induced by administering 0.5% DMBA to the HBP (hamster buccal pouch) region about three times a week until the 10th week. Then, UA was orally treated with different concentrations (25, 50, 100 mg/kg b.wt) on alternative days of DMBA exposure, and the experimental process ended in the 16th week. After animal experimentation, we observed 100% tumor incidence with well‐differentiated OSCC, dysplasia, and hyperplasia lesions in the DMBA‐induced HBP region. Furthermore, the UA treatment of DMBA‐induced hamster effectively inhibited tumor growth. In addition, UA upregulated antioxidant levels, interfered with the elevated lipid peroxidation by‐product of thiobarbituric acid reactive substances, and changed the activities of the liver detoxification enzyme (Phase I and II) in DMBA‐induced hamsters. Furthermore, immunohistochemical staining of inflammatory markers (iNOS and COX‐2) and proliferative cell markers (cyclin‐D1 and PCNA) were upregulated in the buccal pouch part of hamster animals induced with DMBA. Notably, the oral administration of UA significantly suppressed these markers during DMBA‐induced hamsters. Collectively, our findings revealed that UA exhibits antioxidant, anti‐inflammatory, antitumor, and apoptosis‐inducing characteristics, demonstrating UA's protective properties against DMBA‐induced HBP carcinogenesis. [ABSTRACT FROM AUTHOR]

Usnic acid (UA) is a common lichenic secondary metabolite with therapeutic potential. Anticancer, antimicrobial, and antioxidant effects have been demonstrated and UA-enriched extracts are often used to treat various diseases in traditional medicine. First, we performed a viability assay of UA in human uterine leiomyosarcoma (SK-UT-1) since no in vitro cytotoxicity data have been reported so far. For this purpose, the cytotoxicity of UA on SK-UT-1 and embryonic kidney (HEK293) cells was studied at 24 and 48 hours. The toxicity of UA was investigated by the MTT test. In addition, we assessed UA colony formation and migration properties against SK-UT-1 cells in 6-well plates. Our results showed a significant cytotoxic effect of UA at the 5.34 µM; UA was also effective against colony formation ability and wound healing assay. In conclusion, our study suggests that UA exerts anti-proliferative effects on SK-UT-1 cells by inducing cell death. Moreover, our results suggest that the potential anticancer activities of UA should be further studied by additional molecular biological approaches.

With the increasing use of invasive, interventional, indwelling, and implanted medical devices, healthcare-associated infections caused by pathogenic biofilms have become a major cause of morbidity and mortality. Herein, we present the fabrication, characterization, and in vitro evaluation of biocompatibility and anti-biofilm properties of new coatings based on Fe3O4 nanoparticles (NPs) loaded with usnic acid (UA) and ceftriaxone (CEF). Sodium lauryl sulfate (SLS) was employed as a stabilizer and modulator of the polarity, dispersibility, shape, and anti-biofilm properties of the magnetite nanoparticles. The resulting Fe3O4 functionalized NPs, namely Fe3O4@SLS, Fe3O4@SLS/UA, and Fe3O4@SLS/CEF, respectively, were prepared by co-precipitation method and fully characterized by XRD, TEM, SAED, SEM, FTIR, and TGA. They were further used to produce nanostructured coatings by matrix-assisted pulsed laser evaporation (MAPLE) technique. The biocompatibility of the coatings was assessed by measuring the cell viability, lactate dehydrogenase release, and nitric oxide level in the culture medium and by evaluating the actin cytoskeleton morphology of murine pre-osteoblasts. All prepared nanostructured coatings exhibited good biocompatibility. Biofilm growth inhibition ability was tested at 24 h and 48 h against Staphylococcus aureus and Pseudomonas aeruginosa as representative models for Gram-positive and Gram-negative bacteria. The coatings demonstrated good biocompatibility, promoting osteoblast adhesion, migration, and growth without significant impact on cell viability or morphology, highlighting their potential for developing safe and effective antibacterial surfaces.

Objective: Nuclear factor kappa B (NF-κB) is one pathway that controls the expression of genes involved in many cancer events such as proliferation, apoptosis, metastasis, and invasion. Usnic acid is a molecule with many biological effects such as being anticholinergic, gastroprotective, anti-inflammatory, anti-cancerous, and especially antioxidant. This study aims to mechanistically examine the apoptotic behaviors of usnic acid in DU145 prostate cancer cells and the molecules it acts on in the NF-κB pathway. Materials and Methods: This study investigates the apoptotic changes in DU145 cells after usnic acid administration through JC-1 staining and caspase-3 activity measurements. In addition, it tests the effects of usnic acid on subunit p50 and p65 protein and gene expressions in the NF-κB pathway through the respective Western blot and qPCR measurements. Results: The IC50 values of usnic acid at 24 and 48 h in DU145 cells were calculated as 167.06±12.35 μM and 42.15±3.76 μM, respectively. In addition, JC-1 staining showed usnic acid-treated DU145 cells to trigger apoptosis by increasing the membrane permeability of their mitochondria. NF-κB p50 protein expression was also found to be suppressed after usnic acid administration. Conclusion: The results of this study show usnic acid administration to suppress proliferation and to induce mitochondrial apoptosis by suppressing the NF-κB pathway in DU145 cells. This effect of usnic acid indicates it to be combinable with chemotherapeutic agents and evaluable as an alternative in cancer treatment. [ABSTRACT FROM AUTHOR]

The finest sources of therapeutic agents are natural products, and usnic acid is a secondary metabolite derived from lichen that has a wide range of biological actions, including anti-viral, anti-cancer, anti-bacterial, and anti-diabetic (hyperglycemia). Based on the hyperglycemia activity of UA, this work seeks to identify new anti-hyperglycemia medicines by virtual screening of pyrazole derivatives of UA. Seven hit compounds (Compounds 1, 5, 6, 7, 17, 18 and 33), which finally go through docking-based screening to produce the lead molecule, were identified by the physicochemical attributes, drug-likeliness, and ADMET prediction. The docking score for the chosen compounds containing PPARγ agonists ranged from -7.6 to -9.2 kcal/mol, whereas the docking goal for compounds 5, 6, and 7 was -9.2 kcal/mol. Based on the binding energy and bound amino acid residues as well as compared to the reference compound, compound-6 considered as lead compound. Furthermore, the MD simulation of 3CS8-Compound-6 and 3CS8-Rosiglitazone complexes were performed to verify the stability of these complexes and the binding posture acquired in docking experiments. The compound-6 had strong pharmacological characteristics, bound to the PPARγ agonist active site, and was expected to reduce the activity of the receptor, according to the virtual screening results. It must be justified to conduct both in-vitro and in-vivo experiments to examine the efficacy of this compound. [ABSTRACT FROM AUTHOR]

Background: Lichens are complex symbiotic associations between a fungus and an alga or cyanobacterium. Due to their great adaptability to the environment, they have managed to colonize many terrestrial habitats, presenting a worldwide distribution from the poles to the tropical regions and from the plains to the highest mountains. In the flora of the Antarctic region, lichens stand out due to their variety and development and are a potential source of new bioactive compounds. Methods: A phytochemical study of the Antarctic lichen Usnea aurantiaco-atra (Jacq) Bory was conducted with the intention of determining the most important metabolites. In addition, the cytotoxic and antioxidant activities of its extracts were determined. Results: Cytotoxicity studies revealed that the hexane extract contains usnic acid as a majority metabolite, in addition to linoleic acid, ergosterols and terpenes, and demonstrates cytotoxic activity against an A375 melanoma cell line. On the other hand, the presence of total phenols in the extracts did not influence their antioxidant activity. Conclusions: U. aurantiaco-atra contains mainly usnic acid, although there are terpenes and ergosta compounds that could be responsible for its cytotoxic activity. The presence of phenols did not confer antioxidant properties. [ABSTRACT FROM AUTHOR]

Objective To discuss the effect of usnic acid on the proliferation, apoptosis, migration, and invasion of the hypertrophic scar fibroblasts(HSFBs), and to clarify its regulatory effect on the c-Jun N-terminal kinase(JNK)/mitogen-activated protein kinase(MAPK) signaling pathway. Methods The HSFBs at logarithmic growth phase were divided into control group, 10 μmol·L－1 usnic acid group, 20 μmol·L－1 usnic acid group, and 50 μmol·L－1 usnic acid group. Except for control group, the cells in the other groups were treated with the corresponding concentrations of usnic acid. The survival rates of the cells in various groups were detected by methylthiazolyidiphenyl-tetrazolium bromide（MTT) method； the apoptotic rates of the cells in various groups were detected by flow cytometry；the invasion and migration abilities of the cells in various groups were detected by Transwell chamber experiment；the expression levels of phosphorylated JNK(p-JNK), JNK, B-cell lymphoma-2（Bcl-2), and Bcl-2-associated X protein(Bax) proteins in the cells in various groups were detected by Western blotting method. Results The MTT and flow cytometry results showed that compared with control group, the survival rates of the cells in 10, 20, and 50 μmol·L－1 usnic acid groups were decreased(P<0.05), and the apoptotic rates were increased(P<0.05). Compared with 50 μmol·L－1 usnic acid group, the survival rates of the cells in 10 and 20 μmol·L－1 usnic acid groups were decreased(P<0.05), and the apoptotic rates were increased(P<0.05).The Transwell chamber experiment results showed that compared with control group, the numbers of invasion and migration cells in 10, 20 and 50 μmol·L－1 usnic acid groups were decreased（P<0.05)； compared with 10 μmol·L－1 usnic acid group, the numbers of invasion and migration cells in 20 and 50 μmol·L－1 usnic acid groups were decreased（P<0.05)；compared with 20 μmol·L－1 usnic acid group, the numbers of invasion and migration cells in 50 μmol·L－1 usnic acid groups were decreased（P<0.05).The Western blotting results showed that compared with control group, the expression levels of Bcl-2 protein in the cells in 10, 20, and 50 μmol·L－1 usnic acid groups were decreased（P<0.05), and the expression levels of Bax and p-JNK proteins were increased（P<0.05)；compared with 10 μmol·L－1 usnic acid group, the expression levels of Bcl-2 protein in the cells in 20 and 50 μmol·L－1 usnic acid groups were decreased, and the expression levels of Bax and p-JNK proteins in the cells were increased（P<0.05)； compared with 20 μmol·L－1 usnic acid group, the expression level of Bcl-2 protein in the cells in 50 μmol·L－1 usnic acid group was decreased（P<0.05), and the expression levels of Bax and p-JNK proteins were increased（P<0.05). Conclusion Usnic acid can inhibit the proliferation, invasion, and migration of the HSFBs, induce the apoptosis of the HSFBs, and activate the JNK/MAPK signaling pathway. [ABSTRACT FROM AUTHOR]

Tyrosyl-DNA phosphodiesterase 1 and 2 (Tdp1 and Tdp2) are DNA repair enzymes that repair DNA damage caused by various agents, including anticancer drugs. Thus, these enzymes resist anticancer therapy and could be the reason for resistance to such widely used drugs such as topotecan and etoposide. In the present work, we found compounds capable of inhibiting both enzymes among derivatives of (−)-usnic acid. Both (+)- and (−)-enantiomers of compounds act equally effectively against Tdp1 with IC50 values in the range of 0.02–0.2 μM; only (−)-enantiomers inhibited Tdp2 with IC50 values in the range of 6–9 μM. Surprisingly, the compounds protect HEK293FT wild type cells from the cytotoxic effect of etoposide (CC50 3.0–3.9 μM in the presence of compounds and 2.4 μM the presence of DMSO) but potentiate it against Tdp2 knockout cells (CC50 1.2–1.6 μM in the presence of compounds against 2.3 μM in the presence of DMSO). We assume that the sensitizing effect of the compounds in the absence of Tdp2 is associated with the effective inhibition of Tdp1, which could take over the functions of Tdp2. [ABSTRACT FROM AUTHOR]

Abstract Background Pancreatic cancer is one of the leading causes of cancer death in Western societies. Its late diagnosis and resistance to chemotherapies result in a high mortality rate; thus, the development of more effective therapies for the treatment of pancreatic cancer is strongly warranted. Usnic acid (UA) is a secondary metabolite of lichens that shows modest antiproliferative activity toward cancer cells. Recently, we reported the synthesis of a UA pyrazole derivative, named 5, which was more active than the parent compound toward cervical cancer cells. Here, its anticancer potential has been evaluated in detail in other cancer cells, particularly pancreatic cancer cells. Methods The impact of UA and derivative 5 on cell viability, morphology, cell cycle, and death was assessed using the MTT test, electron microscopy, flow cytometry, and immunoblotting, respectively. The calcium ions level was detected fluorometrically. In vivo, the anticancer activity of 5 was evaluated in a murine xenograft model. Results Derivative 5 inhibited the viability of different cancer cells. Noncancerous cells were less sensitive. It induced the release of calcium ions from the endoplasmic reticulum (ER) and ER stress, which was manifested by cell vacuolization. It was accompanied by G0/G1 cell cycle arrest and cell death of pancreatic cancer cells. When applied to nude mice with xenografted pancreatic cancer cells, 5 inhibited tumor growth, with no signs of kidney or liver toxicity. Conclusions UA derivative 5 is superior to UA inhibiting the growth and proliferation of pancreatic cancer cells. ER stress exaggeration is a mechanism underlying the activity of derivative 5.

Background: Pancreatic cancer is one of the leading causes of cancer death in Western societies. Its late diagnosis and resistance to chemotherapies result in a high mortality rate; thus, the development of more effective therapies for the treatment of pancreatic cancer is strongly warranted. Usnic acid (UA) is a secondary metabolite of lichens that shows modest antiproliferative activity toward cancer cells. Recently, we reported the synthesis of a UA pyrazole derivative, named 5, which was more active than the parent compound toward cervical cancer cells. Here, its anticancer potential has been evaluated in detail in other cancer cells, particularly pancreatic cancer cells. Methods: The impact of UA and derivative 5 on cell viability, morphology, cell cycle, and death was assessed using the MTT test, electron microscopy, flow cytometry, and immunoblotting, respectively. The calcium ions level was detected fluorometrically. In vivo, the anticancer activity of 5 was evaluated in a murine xenograft model. Results: Derivative 5 inhibited the viability of different cancer cells. Noncancerous cells were less sensitive. It induced the release of calcium ions from the endoplasmic reticulum (ER) and ER stress, which was manifested by cell vacuolization. It was accompanied by G0/G1 cell cycle arrest and cell death of pancreatic cancer cells. When applied to nude mice with xenografted pancreatic cancer cells, 5 inhibited tumor growth, with no signs of kidney or liver toxicity. Conclusions: UA derivative 5 is superior to UA inhibiting the growth and proliferation of pancreatic cancer cells. ER stress exaggeration is a mechanism underlying the activity of derivative 5. [ABSTRACT FROM AUTHOR]

Usnic acid (UA) is a common lichenic secondary metabolite with therapeutic potential. Anticancer, antimicrobial, and antioxidant effects have been demonstrated and UAenriched extracts are often used to treat various diseases in traditional medicine. First, we performed a viability assay of UA in human uterine leiomyosarcoma (SK-UT-1) since no in vitro cytotoxicity data have been reported so far. For this purpose, the cytotoxicity of UA on SK-UT-1 and embryonic kidney (HEK293) cells was studied at 24 and 48 hours. The toxicity of UA was investigated by the MTT test. In addition, we assessed UA colony formation and migration properties against SK-UT-1 cells in 6-well plates. Our results showed a significant cytotoxic effect of UA at the 5.34 μM; UA was also effective against colony formation ability and wound healing assay. In conclusion, our study suggests that UA exerts anti-proliferative effects on SK-UT-1 cells by inducing cell death. Moreover, our results suggest that the potential anticancer activities of UA should be further studied by additional molecular biological approaches. [ABSTRACT FROM AUTHOR]

The highest amount of the world's polyethylene terephthalate (PET) is designated for fiber production (more than 60%) and food packaging (30%) and it is one of the major polluting polymers. Although there is a great interest in recycling PET-based materials, a large amount of unrecycled material is derived mostly from the food and textile industries. The aim of this study was to obtain and characterize nanostructured membranes with fibrillar consistency based on recycled PET and nanoparticles (Fe3O4@UA) using the electrospinning technique. The obtained fibers limit microbial colonization and the development of biofilms. Such fibers could significantly impact modern food packaging and the design of improved textile fibers with antimicrobial effects and good biocompatibility. In conclusion, this study suggests an alternative for PET recycling and further applies it in the development of antimicrobial biomaterials. [ABSTRACT FROM AUTHOR]

Mountain ecosystems offer a unique opportunity to investigate organism responses to different climatic patterns. In this study, we aimed to test the hypothesis that the usnic acid (UA) content per mass unit and the total extract yield of Usnea amblyoclada (Müll. Arg.) Zahlbr. would increase in exposed microsites (i.e., northern and flat microsites) and at higher elevations (i.e., 1800 m.a.s.l. and 2100 m.a.s.l.). A total of 27 U. amblyoclada extract samples were analyzed to assess UA concentration and total extraction yield. Generalized linear models revealed a significant difference in UA concentration among elevations (p > 0.01). Tukey’s post hoc test indicated that UA concentration was significantly lower at higher elevations (i.e., between 900 and 2100 m.a.s.l.), with no significant differences observed between the 1800 and 900 m.a.s.l. elevations, nor between the 1800 and 2100 m.a.s.l. elevations. In conclusion, our study provides insights into the relationship between UA content, elevation, and temperature in U. amblyoclada. These findings highlight the importance of considering temperature as the primary driver of UA concentration variations in this species, shedding light on the responses of organisms to distinct climatic patterns in mountain ecosystems. [ABSTRACT FROM AUTHOR]

Since cancer is a continuously increasing concern for the general population, more efficient treatment alternatives ought to be developed. In this regard, a promising direction is represented by the use of magnetite nanoparticles (MNPs) to act both as a nanocarrier for the targeted release of antitumoral drugs and as hyperthermia agents. Thus, the present study focused on improving the control upon the outcome properties of MNPs by using two synthesis methods, namely the co-precipitation and microwave-assisted hydrothermal method, for the incorporation of usnic acid (UA), a natural lichen-derived metabolite with proven anticancer activity. The obtained UA-loaded MNPs were thoroughly characterized regarding their morpho-structural and physicochemical properties through X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS) and zeta potential, scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). Results demonstrated the formation of magnetite as the unique mineralogical phase through both types of synthesis, with increased uniformity regarding the drug loading efficiency, size, stability, and magnetic properties obtained through the microwave-assisted hydrothermal method. Furthermore, the cytotoxicity of the nanostructures against the HEK 293T cell line was investigated through the XTT assay, which further proved their potential for anticancer treatment applications. [ABSTRACT FROM AUTHOR]

Injuries and diseases of the skin require accurate treatment using nontoxic and noninvasive biomaterials, which aim to mimic the natural structures of the body. There is a strong need to develop biodevices capable of accommodating nutrients and bioactive molecules and generating the process of vascularization. Electrospinning is a robust technique, as it can form fibrous structures for tissue engineering and wound dressings. The best way of forming such meshes for wound healing is to choose two polymers that complement each other regarding their properties. On the one hand, PVA is a water-soluble synthetic polymer widely used for the preparation of hydrogels in the field of biomedicine owing to its biocompatibility, water solubility, nontoxicity, and considerable mechanical properties. PVA is easy to subject to electrospinning and can offer strong mechanical stability of the mesh, but it is necessary to improve its biological properties. On the other hand, CS has good biological properties, including biodegradability, nontoxicity, biocompatibility, and antimicrobial properties. Still, it is harder to electrospin and does not possess as good mechanical properties as PVA. As these structures also allow the incorporation of bioactive agents due to their high surface-area-to-volume ratio, the interesting point was to incorporate usnic acid into the structure as it is a natural and suitable alternative agent for burn wounds treatment which avoids an improper or overuse of antibiotics and other invasive biomolecules. Thus, we report the fabrication of an electrospun nanofibrous mesh based on PVA, chitosan, and usnic acid with applications in wound healing. The obtained nanofibers mesh was physicochemically characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). In vitro biological assays were performed to evaluate the antimicrobial properties of the samples using the MIC (minimum inhibitory concentration) assay and evaluating the influence of fabricated meshes on the Staphylococcus aureus biofilm development, as well as their biocompatibility (demonstrated by fluorescence microscopy results, an XTT assay, and a glutathione (GSH) assay). [ABSTRACT FROM AUTHOR]

The present study investigates the utilization of nanoparticles based on poly-l-lactide (PLLA) and polyglycerol adipate (PGA), alone and blended, for the encapsulation of usnic acid (UA), a potent natural compound with various therapeutic properties including antimicrobial and anticancer activities. The development of these carriers offers an innovative approach to overcome the challenges associated with usnic acid’s limited aqueous solubility, bioavailability, and hepatotoxicity. The nanosystems were characterized according to their physicochemical properties (among others, size, zeta potential, thermal properties), apparent aqueous solubility, and in vitro cytotoxicity. Interestingly, the nanocarrier obtained with the PLLA-PGA 50/50 weight ratio blend showed both the lowest size and the highest UA apparent solubility as well as the ability to decrease UA cytotoxicity towards human hepatocytes (HepG2 cells). This research opens new avenues for the effective utilization of these highly degradable and biocompatible PLLA-PGA blends as nanocarriers for reducing the cytotoxicity of usnic acid.

Although the COVID-19 pandemic caused by SARS-CoV-2 viruses is officially over, the search for new effective agents with activity against a wide range of coronaviruses is still an important task for medical chemists and virologists. We synthesized a series of thiazolo-thiophenes based on (+)- and (−)-usnic acid and studied their ability to inhibit the main protease of SARS-CoV-2. Substances containing unsubstituted thiophene groups or methyl- or bromo-substituted thiophene moieties showed moderate activity. Derivatives containing nitro substituents in the thiophene heterocycle—just as pure (+)- and (−)-usnic acids—showed no anti-3CLpro activity. Kinetic parameters of the most active compound, (+)-3e, were investigated, and molecular modeling of the possible interaction of the new thiazolo-thiophenes with the active site of the main protease was carried out. We evaluated the binding energies of the ligand and protein in a ligand–protein complex. Active compound (+)-3e was found to bind with minimum free energy; the binding of inactive compound (+)-3g is characterized by higher values of minimum free energy; the positioning of pure (+)-usnic acid proved to be unstable and is accompanied by the formation of intermolecular contacts with many amino acids of the catalytic binding site. Thus, the molecular dynamics results were consistent with the experimental data. In an in vitro antiviral assay against six strains (Wuhan, Delta, and four Omicron sublineages) of SARS-CoV-2, (+)-3e demonstrated pronounced antiviral activity against all the strains.

Introduction: Usnic acid (UA) and barbatic acid (BA), two typical dibenzofurans and depsides in lichen, have a wide range of pharmacological activities and hepatotoxicity concerns. This study aimed to clarify the metabolic pathway of UA and BA and illuminate the relationship between metabolism and toxicity. Methods: An UPLC-Q-TOF-MS method was developed for metabolite identification of UA and BA in human liver microsomes (HLMs), rat liver microsomes (RLMs), and S9 fraction (RS9). The key metabolic enzymes responsible for UA and BA were identified by enzyme inhibitors combined with recombinant human cytochrome P450 (CYP450) enzymes. The cytotoxicity and metabolic toxicity mechanism of UA and BA were determined by the combination model of human primary hepatocytes and mouse 3T3 fibroblasts. Results: The hydroxylation, methylation, and glucuronidation reactions were involved in the metabolic profiles of UA and BA in RLMs, HLMs, and RS9. CYP2C9, CYP3A4, CYP2C8, and UGT1A1 are key metabolic enzymes responsible for metabolites of UA and CYP2C8, CYP2C9, CYP2C19, CYP1A1, UGT1A1, UGT1A3, UGT1A7, UGT1A8, UGT1A9, and UGT1A10 for metabolites of BA. UA and BA did not display evident cytotoxicity in human primary hepatocytes at concentrations of 0.01-25 and 0.01-100 μM, respectively, but showed potential cytotoxicity to mouse 3T3 fibroblasts with 50% inhibitory concentration values of 7.40 and 60.2 μM. Discussion: In conclusion, the attenuated cytotoxicity of BA is associated with metabolism, and UGTs may be the key metabolic detoxification enzymes. The cytotoxicity of UA may be associated with chronic toxicity. The present results provide important insights into the understanding of the biotransformation behavior and metabolic detoxification of UA and BA. [ABSTRACT FROM AUTHOR]

Usnic acid is a well-known secondary lichen metabolite exhibiting a broad spectrum of biological activity. Previously it was shown that the reaction of usnic acid with various amines resulted in enamine-bond formation instead of the C(11)=O carbonyl group. Enamines obtained have a pronounced biological activity. In this work, we have shown that the reaction of usnic acid with ammonia can be regioselective if the solvent is replaced by water. The regioselectivity of that reaction depends on temperature and ammonia quantity. The C-1 enamine as only product formation has been obtained by the usnic acid reaction with an excess of ammonia (20 eq.) in water with cooling (+9 °C). [ABSTRACT FROM AUTHOR]

Acetylcholinesterase inhibitors remain the mainstay of symptomatic treatment for Alzheimer's disease. The natural world is rich in acetylcholinesterase inhibitory molecules, and research efforts to identify novel leads is ongoing. Cladonia portentosa, commonly known as reindeer lichen, is an abundant lichen species found in Irish Boglands. The methanol extract of Irish C. portentosa was identified as an acetylcholinesterase inhibitory lead using qualitative TLC-bioautography in a screening program. To identify the active components, the extract was deconvoluted using a successive extraction process with hexane, ethyl acetate and methanol to isolate the active fraction. The hexane extract demonstrated the highest inhibitory activity and was selected for further phytochemical investigations. Olivetolic acid, 4-O-methylolivetolcarboxylic acid, perlatolic acid and usnic acid were isolated and characterized using ESI-MS and two-dimensional NMR techniques. LC-MS analysis also determined the presence of the additional usnic acid derivatives, placodiolic and pseudoplacodiolic acids. Assays of the isolated components confirmed that the observed anticholinesterase activity of C. portentosa can be attributed to usnic acid (25% inhibition at 125 µM) and perlatolic acid (20% inhibition at 250 µM), which were both reported inhibitors. This is the first report of isolation of olivetolic and 4-O-methylolivetolcarboxylic acids and the identification of placodiolic and pseudoplacodiolic acids from C. portentosa. [ABSTRACT FROM AUTHOR]

For decades, influenza virus infection has been a serious health concern due to seasonal epidemics and pandemics, and it is continuing on the rise today, yet there is no gold-standard medication available for treating influenza viral infection. As a result, better influenza medicine is necessary to prevent illness. The purpose of this work was to investigate how effective usnic acid derivatives were as antiviral medications against the influenza virus in a computational approach. To discover the prospective medication as an anti-influenza agent, we employed pharmacophore-based molecular docking, ADMET, and drug-likeness studies, CYP isoform analysis and MD simulation approaches. Using pharmacophore filtering processes, twenty-three (23) usnic acid derivatives were acquired from an in-house database of 340 usnic acid derivatives. A docking simulation on the Influenza A H1N1 polymerase resulted in four molecules with a high affinity for the protein. The pharmacokinetics and drug-likeness predictions yielded two hit compounds, which were then subjected to cytochrome P450 enzyme screening to provide the lead molecule, denoted as compound-4. In addition, MD simulation of lead compound (Compound-4) was performed to verify the stability of the docked complex and the binding posture acquired in docking experiments. The findings revealed that compound-4 is a promising option for antiviral treatment of influenza illness in the future. [ABSTRACT FROM AUTHOR]

Inflammation is a response of the organism to an external factor that disrupts its natural homeostasis, and it helps to eliminate the cause of tissue injury. However, sometimes the body's response is highly inadequate and the inflammation may become chronic. Thus, the search for novel anti-inflammatory agents is still needed. One of the groups of natural compounds that attract interest in this context is lichen metabolites, with usnic acid (UA) as the most promising candidate. The compound reveals a broad spectrum of pharmacological properties, among which anti-inflammatory properties have been studied both in vitro and in vivo. The aim of this review was to gather and critically evaluate the results of the so-far published data on the anti-inflammatory properties of UA. Despite some limitations and shortcomings of the studies included in this review, it can be concluded that UA has interesting anti-inflammatory potential. Further research should be directed at the (i) elucidation of the molecular mechanism of UA; (ii) verification of its safety; (iii) comparison of the efficacy and toxicity of UA enantiomers; (iv) design of UA derivatives with improved physicochemical properties and pharmacological activity; and (v) use of certain forms or delivery carriers of UA, especially in its topical application. [ABSTRACT FROM AUTHOR]

Termites are usually associated with the decomposition of dead wood, although the diets of many species encompass other resources such as cactus, humus, feces, carcasses and lichens. Some components of their diets, however, may be associated with non-nutritional functions. The termite Constrictotermes cyphergaster has a varied diet, with dead wood being the main item consumed, but with lichens as secondary resources. The question concerning why lichens are consumed appears complicated, and needs careful study in a step-wise analysis. The present study was designed to examine and understand the effects of usnic acid, a secondary lichen metabolite, on the growth of bacteria associated with the gut microbiota of C. cyphergaster. Our results showed significant control of termite gut bacteria by usnic acid as compared with a treatment without it. Thus usnic acid appears to help the termite, possibly by controlling gut microbiota and avoiding diseases associated with entomopathogenic bacteria. [ABSTRACT FROM AUTHOR]

Lichen secondary metabolites are well explored medicinal agents with diverse pharmacological properties. One of the important antibiotic lichen secondary metabolites is usnic acid. Its diverse medicinal profiles prompted us to explore it as a potential antitubercular molecule. Towards this direction, continuing our efforts on the discovery and development of new analogs with potent antitubercular properties we designed, synthesized, and evaluated a set of 37 usnic acid enaminone-coupled aryl-n-hexanamides (3–39). The study yielded a 3,4-dimethoxyphenyl compound (13, 5.3 µM) as the most active anti-TB molecule. The docking studies were performed on 7 different enzymes to better understand the binding modes, where it was observed that compound 13 bound strongly with glucose dehydrogenase (Gscore: − 9.03). Further antibacterial investigations revealed compound 2 with potent inhibition on Salmonella typhi and Bacillus subtilis (MIC 3 µM) and MIC values of 7 and 14 µM on Streptococcus mutans and Escherichia coli respectively. Compound 19 (3-F-5-CF3-phenyl) displayed encouraging antibacterial profiles against E. coli, S. typhi and S. mutans with MIC values of 10 µM respectively. Interestingly, compound 20 (2,6-difluorophenyl) also displayed good antibacterial activity against E. coli with an MIC value of 6 µM. These encouraging pharmacological results will help for better designing and developing usnic acid-based semi-synthetic derivatives as potential antimicrobial agents. A set of 37 new usnic acid enaminone-coupled aryl-n-hexanamides were synthesized and evaluated as potential antimicrobial agents. Compound 13 was identified as the most active antitubercular molecule. 13 was further docked against 7 different enzymes of tuberculosis. The molecule displayed maximum binding energy with the enzyme Glucose dehydrogenase (Gscore: − 9.03), indicating that these hexanamides possibly act by inhibiting the glucose metabolic pathway of the bacterium. Surprisingly, the intermediate hexanoic acid 2 was identified as potent antibacterial agent, acting on both gram-positive and gram-negative bacterial strains (3–14 μM). The active compounds may be subjected to structural iterations to develop further leads. [ABSTRACT FROM AUTHOR]

Introduction: Cerebral ischemia-reperfusion causes complex pathological mechanisms that lead to tissue damage, such as neuronal apoptosis. Usnic acid is a secondary metabolite of lichen and has various biological properties including antioxidant and anti-inflammatory activities. This study aimed to investigate the neuroprotective effects of usnic acid on apoptotic cell death and apoptotic-related proteins (Bax and Bcl-2) in the CA1 area of the hippocampus following cerebral ischemia-reperfusion. Material & Methods: A total of 42 male Wistar rats were randomly divided into three groups (sham, ischemia-reperfusion, and ischemia-reperfusion+usnic acid). Ischemia was induced by occlusion of both common carotid arteries for 20 min. Usnic acid (25 mg/kg, intraperitoneally) was injected at the beginning of reperfusion time. The expression levels of Bax and Bcl-2 proteins were measured using the immunofluorescence method, and the rate of apoptotic cell death was determined using the TUNEL staining method. (Ethic code: IR.SHMU.REC.1397.186) Findings: In this study, cerebral ischemia increased apoptotic cell death in the CA1 area of the hippocampus. It was demonstrated that usnic acid significantly decreased apoptotic cell death by decreasing the expression of Bax pro-apoptotic protein and increasing the expression of Bcl-2 (anti-apoptotic protein). Discussion & Conclusion: It can be concluded that usnic acid has a neuroprotective effect against cerebral ischemia-reperfusion damages by reducing cell death.

This paper carries out a bibliometric analysis of the literatures of usnic acid published in the past 30 years to discuss its current research status, hotspots and development trend. The relevant research literatures of usnic acid published on Web of Science from 1990 to 2021 are retrieved. Then, scientometrics tools like VOSviewer1.6.17 and CiteSpace5.8.R3 are used to create network knowledge maps of usnic acid, and co-occurrence and cluster analysis of countries, authors and keywords are done. Finally, a total of 998 foreign articles are included in the quantitative analysis. The annual publication volume of usnic acid-related research fields is increasing year by year, showing a trend of dynamic development, with a high research interest especially in the past 15 years. Research authors from 76 countries around the world have formed a number of close contact teams. China ranks the fifth in the number of foreign literatures published from 1990 to 2021, and has cooperated with 15 countries in usnic acid researches. In the past 30 years, scholars from all over the world have carried out comprehensive researches on usnic acid in terms of natural sources, extraction and separation, pharmacological activity and toxicity. In the past 5 years, compared with the early and mid-term research stages, the research hotspots of usnic acid have gradually shifted from sources, extraction and isolation, anti-inflammation and anti-bacteria, and antioxidant activities to anti-tumor activity evaluation and mechanism researches, and the research of new delivery systems transforms. A visualization method is used to analyze usnic acid related literatures, and the research status of usnic acid is displayed in the form of knowledge graphs, which can better predict the research frontier, hotspots and development trend of usnic acid, and provide reference and suggestions for the follow-up research. [ABSTRACT FROM AUTHOR]

Nasal sprays are medical devices useful for preventing infection and the subsequent spread of airborne pathogens. The effectiveness of these devices depends on the activity of chosen compounds which can create a physical barrier against viral uptake as well as incorporate different substances with antiviral activity. Among antiviral compounds, UA, a dibenzofuran derived from lichens, has the mechanical ability to modify its structure by creating a branch capable of forming a protective barrier. The mechanical ability of UA to protect cells from virus infection was investigated by analyzing the branching capacity of UA, and then the protection mechanism in an in vitro model was also studied. As expected, UA at 37 °C was able to create a barrier confirming its ramification property. At the same time, UA was able to block the infection of Vero E6 and HNEpC cells by interfering with a biological interaction between cells and viruses as revealed also by the UA quantification. Therefore, UA can block virus activity through a mechanical barrier effect without altering the physiological nasal homeostasis. The findings of this research could be of great relevance in view of the growing alarm regarding the spread of airborne viral diseases. [ABSTRACT FROM AUTHOR]

Lichen secondary metabolites have tremendous pharmaceutical and industrial potential. Although more than 1000 metabolites have been reported from lichens, less than 10 have been linked to the genes coding them. The current biosynthetic research focuses strongly on linking molecules to genes as this is fundamental to adapting the molecule for industrial application. Metagenomic-based gene discovery, which bypasses the challenges associated with culturing an organism, is a promising way forward to link secondary metabolites to genes in non-model, difficult-to-culture organisms. This approach is based on the amalgamation of the knowledge of the evolutionary relationships of the biosynthetic genes, the structure of the target molecule, and the biosynthetic machinery required for its synthesis. So far, metagenomic-based gene discovery is the predominant approach by which lichen metabolites have been linked to their genes. Although the structures of most of the lichen secondary metabolites are well-documented, a comprehensive review of the metabolites linked to their genes, strategies implemented to establish this link, and crucial takeaways from these studies is not available. In this review, I address the following knowledge gaps and, additionally, provide critical insights into the results of these studies, elaborating on the direct and serendipitous lessons that we have learned from them. [ABSTRACT FROM AUTHOR]

Hexedra+® is a nasal spray containing hydroxypropyl methylcellulose, beta-cyclodextrin, and usnic acid. It has been developed with the aim of reducing the risk of transmission of airborne viral infections, with particular reference to influenza and COVID-19. As part of the preclinical development of the product, we carried out a study on thirty male Wistar rats divided into three study groups and treated with Hexedra+, an alternative formulation containing a double concentration of usnic acid (0.015% instead of 0.0075%) or saline solution. Products were administered at the dose of 30 μL into each nostril, three times a day for seven consecutive days by means of a micropipette. By the end of the treatment period, no significant changes were observed in body weight. Histological examination of nasal mucosa and soft organs did not show any significant difference in the three study groups. Serum transaminase level remained in the normal limit in all the animals treated. The serum level of usnic acid was measured in order to assess the absorption of the molecule through the nasal mucosa. By the end of the study period, the usnic acid serum level was negligible in all the animals treated. In conclusion, the safety profile of Hexedra+ appears favorable in the animal model studied. [ABSTRACT FROM AUTHOR]

Lichen Usnea sp. is one of the sources of natural bioactive compounds which are currently being developed as medicinal ingredients. The purpose of this study was the isolation and identification of secondary metabolites from methanol extract, toxicity test and antioxidant activity of Usnea sp. Lichen was isolated by maceration using methanol solvent, then separated by liquid-liquid partition and separation using vacuum chromatography. Based on the results of the study, NMR-1D spectral data and FTIR spectrum is the presence of functional groups showed the presence of F15 compound is usnic acid consisting of 18 carbons with 3 carbons from the C=O carbonyl group. The results of the toxicity test showed that all of them were active against Artemia salina L. shrimp larvae with LC50 values of 0.820 μg/mL (Usnea sp.), 1.030 μg/mL (n-hexane), 1.056 μg/mL (ethyl acetate), and 1.236 μg/mL (methanol extract). The results of the antioxidant activity test showed that the inhibitory activity of usnic acid isolate was very active with an IC50 value of 11.696 μg/mL. Meanwhile, methanol extracts and ethyl acetate showed antioxidant activity with IC50 values of 18.098 and 26.917 μg/mL, respectively. [ABSTRACT FROM AUTHOR]

Usnic acid is a well-known secondary lichen metabolite exhibiting a broad spectrum of biological activity. Previously it was shown that the reaction of usnic acid with various amines resulted in enamine-bond formation instead of the C(11)=O carbonyl group. Enamines obtained have a pronounced biological activity. In this work, we have shown that the reaction of usnic acid with ammonia can be regioselective if the solvent is replaced by water. The regioselectivity of that reaction depends on temperature and ammonia quantity. The C-1 enamine as only product formation has been obtained by the usnic acid reaction with an excess of ammonia (20 eq.) in water with cooling (+9 °C).

Background: Lichens are complex symbiotic associations between a fungus and an alga or cyanobacterium. Due to their great adaptability to the environment, they have managed to colonize many terrestrial habitats, presenting a worldwide distribution from the poles to the tropical regions and from the plains to the highest mountains. In the flora of the Antarctic region, lichens stand out due to their variety and development and are a potential source of new bioactive compounds. Methods: A phytochemical study of the Antarctic lichen Usnea aurantiaco-atra (Jacq) Bory was conducted with the intention of determining the most important metabolites. In addition, the cytotoxic and antioxidant activities of its extracts were determined. Results: Cytotoxicity studies revealed that the hexane extract contains usnic acid as a majority metabolite, in addition to linoleic acid, ergosterols and terpenes, and demonstrates cytotoxic activity against an A375 melanoma cell line. On the other hand, the presence of total phenols in the extracts did not influence their antioxidant activity. Conclusions: U. aurantiaco-atra contains mainly usnic acid, although there are terpenes and ergosta compounds that could be responsible for its cytotoxic activity. The presence of phenols did not confer antioxidant properties.

Tyrosyl-DNA phosphodiesterase 1 and 2 (Tdp1 and Tdp2) are DNA repair enzymes that repair DNA damage caused by various agents, including anticancer drugs. Thus, these enzymes resist anticancer therapy and could be the reason for resistance to such widely used drugs such as topotecan and etoposide. In the present work, we found compounds capable of inhibiting both enzymes among derivatives of (−)-usnic acid. Both (+)- and (−)-enantiomers of compounds act equally effectively against Tdp1 with IC50 values in the range of 0.02–0.2 μM; only (−)-enantiomers inhibited Tdp2 with IC50 values in the range of 6–9 μM. Surprisingly, the compounds protect HEK293FT wild type cells from the cytotoxic effect of etoposide (CC50 3.0–3.9 μM in the presence of compounds and 2.4 μM the presence of DMSO) but potentiate it against Tdp2 knockout cells (CC50 1.2–1.6 μM in the presence of compounds against 2.3 μM in the presence of DMSO). We assume that the sensitizing effect of the compounds in the absence of Tdp2 is associated with the effective inhibition of Tdp1, which could take over the functions of Tdp2.

Lichens are important sources of versatile bioactive compounds. Two new dibenzofurans (1–2), a multi-substituted single benzene ring (3), and two organic acid compounds (4–5) along with 25 known compounds (6–30) were isolated from the lichen Usnea diffracta Vain. Their structures were identified by physicochemical properties and spectral analyses. Compounds 1–30 were tested for inhibitory activities against Staphylococcus aureus, Escherichia coli, and Candida albicans by the disk diffusion method and microdilution assay respectively. Compound 3 showed moderate inhibitory activities against S. aureus and E. coli with the inhibition zone (IZ) of 6.2 mm and 6.3 mm, respectively. Depside 10 exhibited good activity against S.aureus and C. albicans with 6.6 mm and 32 μg/ml, respectively. The acetylcholinesterase inhibitory activities of compounds 1, 2, and 6–8 with the characteristic dibenzofuran scaffold were evaluated var anti-AChE assay and a molecular docking study. Compound 2 could better inhibit AChE at the concentration of 0.3 μmol/ml with a value of 61.07 ± 0.85%. The molecular docking study also demonstrated that compound 2 had the strongest binding affinity among the five dibenzofurans, and the “-CDOCKER Energy” value was 14.4513 kcal/mol.