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Four new alkaloids, vibripyrrolidine A ( 1 ), vibripiperazine A ( 2 ), and vibridiazinane A, B ( 3 , 4 ), comprising one pyrrolidine, one piperazine, and two diazinane alkaloids, along with two known analogs ( 5 , 6 ), were isolated from the marine bacterium Vibrio ruber ZXR-93 cultured in ISP2 medium. Their chemical structures were elucidated by analysis of their 1D and 2D NMR, mass spectra, and electronic circular dichroism (ECD) calculations. Compounds 1 and 3 - 6 showed vigorous antibacterial activity against Staphylococcus aureus , with MIC values ranging from 0.96 to 7.81 μg/mL. Moreover, compound 1 exhibited robust anti-inflammatory activity in vitro using the LPS-induced RAW264.7 macrophage model. All compounds also showed moderate antineoplastic activity against cervical cancer cells (HeLa) and gastric cancer cells (SGC-7901).

Chetocochliodin M ( 5 ) containing a rare cage-ring and chetocochliodin N ( 6 ) featuring an unusual piperazine-2,3-dione ring system together with known analogues chetomin ( 1 ), chetoseminudin C ( 2 ), chetocochliodin I ( 3 ), and oidioperazine E ( 4 ) were targeted for purification from the fungus Chaetomium cochliodes using a UPLC-Q-TOF-MS/MS approach. The structures of the new compounds were elucidated using HR-ESI-MS, NMR, and ECD spectra. Compounds 1 , 3 , and 6 exhibited strong cytotoxic activities against A549 and HeLa cancer cell lines.

Two new indole diketopiperazine alkaloids (IDAs), (+)19-epi-sclerotiamide (1) and (-)19-epi-sclerotiamide (2), along with 13 known analogs (3-15), were isolated from a soft coral-associated epiphytic fungus Aspergillus versicolor CGF 9-1-2. The structures of two new compounds were established based on the combination of HR-ESI-MS, 1D and 2D NMR spectroscopy, optical rotation measurements and quantum chemical 13 C-NMR, the absolute configurations were determined by experimental and electronic circular dichroism (ECD) calculations. The results of molecular docking showed that all the compounds had a good binding with TDP1, TDP2, TOP1, TOP2, Ache, NLRP3, EGFR, EGFR L858R, EGFR T790M and EGFR T790/L858. Biological evaluation of compounds 3, 6, 8, 11 showed that 3 exerted a strong inhibitory effect on TDP2 with a rate of 81.72 %., (© 2023 Wiley-VHCA AG, Zurich, Switzerland.)

The biological screening of 44 marine sponge extracts for the research of bioactive molecules, with potential application in the treatment of age-related diseases (cancer and Alzheimer's disease) and skin aging, resulted in the selection of Scopalina hapalia extract for chemical study. As no reports of secondary metabolites of S. hapalia were found in the literature, we undertook this research to further extend current knowledge of Scopalina chemistry. The investigation of this species led to the discovery of four new compounds: two butenolides sinularone J ( 1 ) and sinularone K ( 2 ), one phospholipid 1- O -octadecyl-2-pentanoyl- sn -glycero-3-phosphocholine ( 3 ) and one lysophospholipid 1- O -(3-methoxy-tetradecanoyl)- sn -glycero-3-phosphocholine ( 4 ) alongside with known lysophospholipids ( 5 and 6 ), alkylglycerols ( 7 - 10 ), epidioxysterols ( 11 and 12 ) and diketopiperazines ( 13 and 14 ). The structure elucidation of the new metabolites ( 1 - 4 ) was determined by detailed spectroscopic analysis, including 1D and 2D NMR as well as mass spectrometry. Molecular networking was also explored to complement classical investigation and unravel the chemical classes within this species. GNPS analysis provided further information on potential metabolites with additional bioactive natural compounds predicted.

The COVID-19 pandemic and its continuing emerging variants emphasize the need to discover appropriate treatment, where vaccines alone have failed to show complete protection against the new variants of the virus. Therefore, treatment of the infected cases is critical. This paper discusses the bio-guided isolation of three indole diketopiperazine alkaloids, neoechinulin A ( 1 ), echinulin ( 2 ), and eurocristatine ( 3 ), from the Red Sea-derived Aspergillus fumigatus MR2012. Neoechinulin A ( 1 ) exhibited a potent inhibitory effect against SARS-CoV-2 M pro with IC 50 value of 0.47 μM, which is comparable to the reference standard GC376. Despite the structural similarity between the three compounds, only 1 showed a promising effect. The mechanism of inhibition is discussed in light of a series of extensive molecular docking, classical and steered molecular dynamics simulation experiments. This paper sheds light on indole diketopiperazine alkaloids as a potential structural motif against SARS-CoV-2 M pro . Additionally, it highlights the potential of different molecular docking and molecular dynamics simulation approaches in the discrimination between active and inactive structurally related M pro inhibitors.

Neoechinulins are fungal and plant-derived chemicals extracted from Microsporum sp., Eurotium rubrum, Aspergillus sp., etc. Two analogues of neoechinulin, i.e., A and B, exerted extensive pharmacological properties described in this review. Neoechinulin is an indole alkaloid and has a double bond between C8/C9, which tends to contribute to its cytoprotective nature. Neoechinulin A exhibits protection to PC12 cells against nitrosative stress via increasing NAD(P)H reserve capacity and decreasing cellular GSH levels. It also confers protection via rescuing PC12 cells from rotenone-induced stress by lowering LDH leakage. This compound has great positive potential against neurodegenerative diseases by inhibiting SIN-1 induced cell death in neuronal cells. Together with these, neoechinulin A tends to inhibit Aβ42-induced microglial activation and confers protection against neuroinflammation. Alongside, it also inhibits cervical cancer cells by caspase-dependent apoptosis and via upregulation of apoptosis inducing genes like Bax, it suppresses LPS-induced inflammation in RAW264.7 macrophages and acts as an antidepressant. Whereas, another analogue, Neoechinulin B tends to interfere with the cellular mechanism thereby, inhibiting the entry of influenza A virus and it targets Liver X receptor (LXR) and decreases the infection rate of Hepatitis C. The present review describes the pharmaceutical properties of neoechinulins with notes on their molecular, cellular, and functional basis and their therapeutic properties., (Copyright © 2021 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Context: Streptomyces species are prolific sources of bioactive secondary metabolites known especially for their antimicrobial and anticancer activities., Objective: This study sought to isolate and characterize antioxidant molecules biosynthesized by Streptomyces sp. KTM18. The antioxidant potential of an isolated compound and its toxicity were accessed., Materials and Methods: The compound was purified using bioassay-guided chromatography techniques. Nuclear magnetic resonance (NMR) experiments were carried out for structure elucidation. The antioxidant potential of the isolated compound was determined using DPPH free radical scavenging assay. The toxicity of the isolated compound was measured using a brine shrimp lethality (BSL) assay., Results: Ethyl acetate extract of Streptomyces sp. KTM18 showed more than 90% inhibition of DPPH free radical at 50 µg/mL of the test concentration. These data were the strongest among 13 Streptomyces isolates (KTM12-KTM24). The active molecule was isolated and characterized as maculosin (molecular formula, C 14 H 16 N 2 O 3 as determined by the [M + H] + peak at 261.1259). The DPPH free radical scavenging activity of pure maculosin was higher (IC 50 , 2.16 ± 0.05 µg/mL) than that of commercial butylated hydroxyanisole (BHA) (IC 50 , 4.8 ± 0.05 µg/mL). No toxicity was observed for maculosin (LD 50 , <128 µg/mL) in brine shrimp lethality assay (BSLA) up to the compound's antioxidant activity (IC 50 ) concentration range. The commercial standard, berberine chloride, showed toxicity in BSLA with an LD 50 value of 8.63 ± 0.15 µg/mL., Conclusions: Maculosin may be a leading drug candidate in various cosmetic and therapeutic applications owing to its strong antioxidant and non-toxic properties.

Thaxtomin A (TA) is a phytotoxin secreted by Streptomyces scabies that causes common scab in potatoes. However, the mechanism of potato proteomic changes in response to TA is barely known. In this study, the proteomic changes in potato leaves treated with TA were determined using the Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) technique. A total of 693 proteins were considered as differentially expressed proteins (DEPs) following a comparison of leaves treated with TA and sterile water (as a control). Among the identified DEPs, 460 and 233 were upregulated and downregulated, respectively. Based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, many DEPs were found to be involved in defense and stress responses. Most DEPs were grouped in carbohydrate metabolism, amino acid metabolism, energy metabolism, and secondary metabolism including oxidation-reduction process, response to stress, plant-pathogen interaction, and plant hormone signal transduction. In this study, we analyzed the changes in proteins to elucidate the mechanism of potato response to TA, and we provided a molecular basis to further study the interaction between plant and TA. These results also offer the option for potato breeding through analysis of the resistant common scab.

Probiotic lactobacilli have been implicated in the production of many low molecular weight bioactive molecules with tremendous potential to kill multidrug resistant human pathogens. The aim of the present study is to purify, characterise and evaluate a novel compound produced by a probiotic Lactobacillus plantarum LJR13 strain. The compound was purified employing silica gel column chromatography followed by RP-HPLC technique. The compound was identified as tert-butyl-4-(4-oxo-(2-((2-oxo-1- (p-tolyl) -2- (p-tolyloxy) ethyl) carbamoyl) pyrrolidin-1-yl) butanoyl) piperazine-carboxylate (BPBP) through various spectral techniques. Exhaustive literature search has revealed that the compound BPBP has not been reported from Lactobacillus species so far and ours is the first report describing its spectrum of activities against multidrug resistant human pathogens together with the morphological and physiological manifestations it brings about in the normal as well as human colon carcinoma cells. The MIC of BPBP for Listeria monocytogenes and Staphylococcus aureus was 15.62 μg/mL and 62.50 μg/mL respectively; however, for Acinetobacter baumannii the MIC was determined to be 31.25 μg/mL. Scanning electron microscopic studies of BPBP treated L. monocytogenes, S. aureus, and A. baumannii revealed the presence of blebs on the cell wall which represents the compromise in the cell wall integrity. While BPBP showed no significant cytotoxicity on mouse embryonic fibroblast cells, (NIH-3T3), marked discernible cytotoxic effect was observed on colorectal carcinoma cells, HCT-116, suggesting potential anti-cancer activity. Molecular docking studies displayed the interaction of BPBP with appropriate drug resistance associated proteins such as Penicillin binding proteins in gram positive L. monocytogenes and S. aureus and beta-lactamase in gram negative A. baumannii., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

The cancer cells that are adapted to the hypoxic and nutrient-starved conditions of the tumor microenvironment have become a key target for anticancer therapies. In the course of search for selective cytotoxic substances against cancer cells adapted to nutrient starvation, (3S,6S)-3,6-dibenzylpiperazine-2,5-dione (1) was isolated from culture extract of marine-derived Paecilomyces formous 17D47-2. Compound 1 showed cytotoxic activity on the human pancreatic carcinoma PANC-1 cells adapted to glucose-starved conditions with IC 50 value of 28 µM, whereas no effect was observed against PANC-1 cells under general culture conditions up to 1000 µM. Further studies on the mechanism of the selective cytotoxicity of 1 against the glucose-starved PANC-1 cells suggest that it may function via uncoupling of mitochondrial oxidative phosphorylation.

Two new antibacterial thiodiketopiperazine derivatives (TDKPs), 7-dehydroxyepicoccin H and 7-hydroxyeutypellazine F, along with seven known TDKP analogs, were isolated and identified from Epicoccum nigrum SD-388, a deep-sea-sediment-derived fungus. The structures of these compounds were elucidated on the basis of detailed spectroscopic analysis. The absolute configuration of 7-dehydroxyepicoccin H was established by X-ray crystallographic analysis, while 7-hydroxyeutypellazine F was determined by ECD experiment and TDDFT-ECD calculation. The antibacterial activities against human and aquatic pathogens were evaluated. 7-Dehydroxyepicoccin H and 7-hydroxyeutypellazine F displayed inhibitory activities against aquatic pathogens Vibrio vulnificus, V. alginolyticus, and Edwardsiella tarda, with MIC values ranging from 4.0 to 8.0 μg/mL., (© 2020 Wiley-VHCA AG, Zurich, Switzerland.)

Inspired by the distinct chemical and physical properties of nanoparticles, here a novel open-tubular capillary electrochromatography column was prepared by electrostatic assembly of poly(diallydimethylammonium chloride) onto the inner surface of a fused-silica capillary, followed by self-adsorption of negatively charged SH-β-cyclodextrin/gold nanoparticles. The formation of the SH-β-cyclodextrin/gold nanoparticles coated capillary was confirmed and characterized by scanning electron microscopy and energy dispersive spectrometry. The results of scanning electron microscopy and energy dispersive spectrometry studies indicated that SH-β-cyclodextrin/gold nanoparticles were successfully coated on the inner wall of the capillary column. The performance of the SH-β-cyclodextrin/gold nanoparticles coated capillary was validated by the analysis of six pairs of chiral drugs, namely zopiclone, carvedilol, salbutamol, terbutaline sulfate, phenoxybenzamine hydrochloride, and ibuprofen. Satisfactory enantioseparation results were achieved, confirming the use of gold nanoparticles as the support could enhance the phase ratio of the open-tubular capillary column. Additionally, the stability and reproducibility of the SH-β-cyclodextrin/gold nanoparticles coated capillary column were also investigated. Then, this proposed method was well validated with good linearity (≥0.999), recovery (90.0-93.5%) and repeatability, and was successfully used for enantioseparation of ibuprofen in spiked plasma samples, which indicated the new column's potential usage in biological analysis., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nine new epipoly(thiodioxopiperazine) (ETP) analogues, chetocochliodins A - I ( 1 - 9 ), along with two known ones, chetoseminudins E and C ( 10 and 11 ), were purified from the fungus Chaetomium cochliodes . The planar structures and absolute configurations of these new compounds were determined by extensive NMR spectroscopic analysis, CD spectra, and chemical reactions. Shielding effects from the indole on the 3-SCH 3 /3-OCH 3 /3-OCH 2 - groups facilitated the determination of relative configuration of the analogues. Compound 9 was cytotoxic, suggesting the importance of the sulfide bridge for the diketopiperazine bioactivities.

Enantioselective open tubular capillary electrochromatography with carboxymethyl-β-cyclodextrin conjugated gold nanoparticles as stationary phase was developed. This novel open tubular column was fabricated through layer-by-layer self-assembly of gold nanoparticles on a 3-mercaptopropyl-trimethoxysilane-modified fused-silica capillary and subsequent surface functionalization of the gold nanoparticles through self-assembly of 6-mercapto-β-cyclodextrin. The 6-mercapto-β-cyclodextrin was firstly synthesized and determined by extensive spectroscopic data. Scanning electron microscopy, energy dispersive X-ray analysis spectroscopy, and electroosmotic flow experiments were carried out to characterize the prepared open tubular column. Then, the separation effectiveness of the open tubular column was verified by two pairs of ɑ-tetralones derivatives enantiomers and two pairs of basic drug enantiomers (tramadol hydrochloride and zopiclone) as mode analytes. Factors that influence the enantioseparation were optimized, and under the optimized conditions, satisfactory separation results were obtained for the four enantiomers: compound A, compound B, tramadol hydrochloride, and zopiclone with resolutions of 3.79, 1.56, 1.03, 1.60, respectively. For the combination of gold nanoparticles and negatively charged carboxymethyl-β-cyclodextrin, the open tubular column exhibited wider separation range for neutral and basic drugs. Moreover, the repeatability and stability of the column were studied through the run-to-run and day-to-day investigations., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Ten new epipolythiodioxopiperazines (ETPs), namely, amphiepicoccins A-J ( 1 - 10 ), were isolated from the fish-gill-derived fungus Epicoccum nigrum HDN17-88. Their structures were deduced from extensive spectroscopic data and electronic circular dichroism (ECD) calculations. Amphiepicoccin A ( 1 ) which contains an aromatic indole motif is unprecedented among the epicoccin type of ETPs. Compounds 1 , 3 , and 6 displayed anti-HSV-2 activities, with IC 50 values of 70, 64, and 29 μM, respectively (acyclovir as positive control with an IC 50 value of 31 μM), while 5 and 6 also revealed inhibitory activity against Bacillus subtilis with minimum inhibitory concentration (MIC) values of 13 and 25 μM, respectively.

A new xanthoquinodin B9 ( 1 ), together with two known xanthoquinodins, xanthoquinodin A1 ( 2 ) and xanthoquinodin A3 ( 3 ), three epipolythiodioxopiperazines, chetomin ( 4 ), chaetocochin C ( 5 ) and dethio-tetra(methylthio)chetomin ( 6 ), and four other compounds, chrysophanol ( 7 ), emodin ( 8 ), alatinone ( 9 ), and ergosterol ( 10 ) were isolated from the endophytic fungus Chaetomium globosum 7s-1, isolated from Rhapis cochinchinensis (Lour.) Mart. All isolated structures were established based on their spectroscopic data analyses. Compounds 1-6 showed antibacterial activity against Gram positive bacteria with MICs ranging from 0.02 pM to 10.81 µM. Compounds 1-6 also exhibited cytotoxicity against KB, MCF-7 and NCI-H187 cancer cell lines (IC 50 0.04-18.40 µM). However, they were cytotoxic towards a normal cell line ( Vero cell) with IC 50 values ranging from 0.04 to 3.86 µM.

Two new decalin/tetramic acid hybrid metabolites, hyalodendrins A (1) and B (2) were isolated from plant endophytic fungus Hyalodendriella sp. Ponipodef12. The structures of the new compounds were elucidated by analysis of the spectroscopic data, including NMR, HRMS and ECD, and by chemical conversion. Compounds 1 and 2 were phomasetin analogues, and both showed potent larvicidal activity against the fourth-instar larvae of Aedes aegypti with the median lethal dose (LC 50 ) values of 10.31 and 5.93 μg/mL, respectively., Competing Interests: The authors declare no conflict of interest.

Chemical analysis of Chrysosporium sp. CMB-F214, yielded five new piperazines, chrysosporazines A-E ( 1 - 5 ), with structures assigned by spectroscopic and X-ray analyses and biosynthetic considerations. The chrysosporazines 2 - 5 exist as an equilibrium of major and minor N -acyl rotamers, while 1 - 3 incorporate an unprecedented hexahydro-6 H -pyrazino[1,2- b ]isoquinolin-6-one scaffold. The noncytotoxic chrysosporazines reverse doxorubicin drug resistance in P-glycoprotein overexpressing colon carcinoma cells (SW620 Ad300), with 2 delivering a comparable gain in sensitivity to the positive control, verapamil.

The enantioseparation of chiral drugs via CE was first investigated using β-CD as chiral additive and deep eutectic solvents (DESs) as auxiliary additive. The results showed that improved separation of tested chiral drugs was obtained in the presence of DESs and β-CD compared to the single β-CD separation system. With the optimized condition, resolutions of DESs applied β-CD separation system for rac-Zopiclone, rac-Salbutamol, and rac-Amlodipine increased 3-4.2 times as single β-CD separation system. The resolutions reached 4.74, 6.37, and 9.67, respectively. The results demonstrate that DESs are viable additives to CD system in CE for the separation of the chiral drugs., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Eight new diketopiperazine-type alkaloids including four oxepin-containing diketopiperazine-type alkaloids, oxepinamides H-K (1-4), and four 4-quinazolinone alkaloids, puniceloids A-D (5-8), together with two known analogues (9 and 10), were isolated from the culture broth extracts of the deep-sea-derived fungus Aspergillus puniceus SCSIO z021. Their structures were elucidated by spectroscopic analyses, and their absolute configurations were determined by Marfey's method along with comparison of their specific rotations and ECD spectra. The absolute configurations of 4 and 5 were further confirmed by a single-crystal X-ray diffraction analysis. Compounds 1-8 showed significant transcriptional activation of liver X receptor α with EC 50 values of 1.7-50 μM, and 7 and 8 were the most potent agonists.

The fungus Chaetomium sp. is a causative agent of infections in humans and is ubiquitous in the natural environment. The secondary metabolites of this genus exhibit many biological activities, including antifungal activity and toxicity in mitochondria. In this study, we isolated cristazine from the fungus C. cristatum, which has the potential to inhibit the growth of human epidermoid carcinoma (A431) cells in a dose- and time-dependent manner. Its inhibitory activity was examined using a cell viability assay and cell death was elucidated by western blot analysis. Cristazine triggered apoptotic cell death via the Type I death receptor pathway including the activation of caspases and other target proteins. However, cristazine did not have any effect on mitochondrial apoptotic proteins such as Bid, cytochrome c, and apoptosis-inducing factor. Cristazine inhibited the cell cycle progression by arresting the G 1 /S phase and up-regulating the inhibitory proteins of cyclin-dependent kinases. Thus, cristazine has great potential for inducing apoptosis in A431 cells via both cell cycle arrest and the inhibition of cell growth., (© 2019 Wiley Periodicals, Inc.)

In recent years, drug-abuse problem is growing by leaps and bounds all over the world. The master minds spearheading its proliferation among the youth are difficult to identify, so drug-abuse case has become a hard nut to crack even with the help of best international experts in forensic science and criminology. Because most nations have tightened their controls on traditional drugs, the younger generation is now hooked onto new-type drugs: 1-(3- trifluoromethylphenyl) piperazine (TFMPP), 1-(3-chlorophenyl) piperazine (mCPP) and other new piperazine-drugs, acting as hallucinogens like 'ecstasy', are being consumed by vulnerable masses all over the world. However, only few research studies have focused on developing highly effective detection methods for TFMPP and mCPP in biological fluids; the number of detection methods for these new-type drugs is almost nil in China. Therefore, it is difficult to detect and prevent drug abuse cases related to piperazine drugs in China. There is an urgent need to develop some simple, fast, and reliable methods for detecting piperazine-drugs in vulnerable masses. Thus, the development of novel detection methods with high sensitivity and selectivity is a difficult task for the officials working in the department of forensic science in China. In this work, a new method was developed for the detection of piperazine derivatives: it was performed under the various specific conditions required for conducting chromatography and mass spectrometry analysis. With this novel method, TFMPP and mCPP was successfully detected with high accuracy in various biological samples. By comparing the purification effect of different solid-phase extraction columns for TFMPP and mCPP in biological fluids (urine and blood), we confirmed the validity of the novel method. In addition, this method has good linear relationship and a low detection line when GC/MS was performed for detecting TFMPP, mCPP in the biological fluids (urine and blood). It is a simple, reproducible method that is highly specific in the detection of piperazine-drugs. Thus, it is indeed a reliable method in forensic science.

A new piperazine derivative designated helvamide was isolated as a pair of rotamers (1 and 2) from the culture broth of the fungus Aspergillus nidulans BF-0142 along with a known helvafuranone (3). The structures of 1 and 2 were elucidated based on spectroscopic analyses by the interpretation of one-dimensional and two-dimensional nuclear magnetic resonance data, ROESY (rotational Overhauser effect spectroscopy) correlations, and a chemical method. Helvamide existed as a rotameric mixture (1 and 2) in dimethyl sulfoxide. Helvamide inhibited sterol O-acyltransferases 1 and 2 (SOAT1 and SOAT2) in enzyme-based and cell-based assays using SOAT1-expressing and SOAT2-expressing Chinese hamster ovary (CHO) cells.

Three new thiodiketopiperazines, geospallins A⁻C ( 1 ⁻ 3 ), together with nine known analogues ( 4 ⁻ 12 ), were isolated from the culture of the deep-sea sediment-derived fungus Geosmithia pallida FS140. Among them, geospallins A and B ( 1 and 2 ) represent rare examples of thiodiketopiperazines featuring an S-methyl group at C-10 and a tertiary hydroxyl group at C-11. Their structures were determined by high-resolution electrospray mass spectrometry (HRESIMS), spectroscopic analyses, and electronic circular dichroism (ECD) calculations. Their angiotensin-converting enzyme (ACE) inhibitory activity was reported, and geospallins A⁻C ( 1 ⁻ 3 ) showed inhibitory activity with IC 50 values of 29⁻35 µM.

Two new diketopiperazine alkaloids, named protuboxepin C (1) and protuboxepin D (2), which contain D-Phe residue and oxepin ring, were isolated from EtOAc extract of sponge-derived fungus Aspergillus sp SCSIO XWS02F40. Their structures were elucidated by 1D, 2D NMR and HRESIMS dates, and their absolute configurations were confirmed by single crystal X-ray diffraction experiments and CD analyses. The in vitro cytotoxicity of these two new compounds was further evaluated using A549 and Hela cell lines.

Known diketopiperazine WIN 64821 and its asymmetric stereoisomers (1-3) had been isolated from the culture broth of a marine gut fungus Aspergillus sp. DX4H. The planar and stereochemistry for new compounds were determined by a suite of techniques including mass, NMR and CD spectra together with Marfey's method. Their inhibitory activity against PC3 cell line had been tested.

A simple, rapid, and robust RP-HPLC method have been developed and validated to measure palbociclib (PB) and letrozole (LT) at single wavelength (254 nm). A isocratic elution of samples performed on Intersil C 8 (4.6 mm × 250 mm particle size 5 μm) column with mobile phase consisting 0.02 M sodium dihydrogen phosphate buffer (pH 5.5): acetonitrile: methanol (80:10:10 v/v/v) delivered at flow rate 1.0 mL min -1 . A good linear response was achieved over the range of 5-50 μg mL -1 . The LODs for PB and LT were found to be 0.098 and 0.0821 µg mL -1 , while the LOQs for PB and LT were 0.381-0.315 µg mL -1 , respectively. The method was quantitatively evaluated in terms of system suitability test, linearity, precision, accuracy (recovery) and robustness as per standard guidelines. The method is simple, convenient and suitable for the analysis of PB and LT in bulk drug.

Endophytic Streptomyces strains are potential sources for novel bioactive molecules. In this study, the diketopiperazine gancidin W (GW) was isolated from the endophytic actinobacterial genus Streptomyces , SUK10, obtained from the bark of Shorea ovalis tree, and it was tested in vivo against Plasmodium berghei PZZ1/100. GW exhibited an inhibition rate of nearly 80% at 6.25 and 3.125 μg kg -1 body weight on day four using the 4-day suppression test method on male ICR strain mice. Comparing GW at both concentrations with quinine hydrochloride and normal saline as positive and negative controls, respectively, 50% of the mice treated with 3.125 μg kg -1 body weight managed to survive for more than 11 months after infection, which almost reached the life span of normal mice. Biochemical tests of selected enzymes and proteins in blood samples of mice treated with GW were also within normal levels; in addition, no abnormalities or injuries were found on internal vital organs. These findings indicated that this isolated bioactive compound from Streptomyces SUK10 exhibits very low toxicity and is a good candidate for potential use as an antimalarial agent in an animal model., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Six new epipolythiodioxopiperazine (ETP) alkaloids, penicisulfuranols A-F (1-6), were isolated from the mangrove endophytic fungus Penicillium janthinellum HDN13-309. All structures including absolute configurations were elucidated on the basis of comprehensive spectroscopic data and ECD calculations. They belong to the unusual family of ETPs containing sulfur atoms on both α- and β-positions of amino acid residues and a rare 1,2-oxazadecaline core moiety. In addition, compounds 1-6 also possess a rare spiro-furan ring and 1-3 showed cytotoxicity with IC 50 values ranging from 0.1 to 3.9 μM.

Unlabelled: Cell culture systems reproducing virus replication can serve as unique models for the discovery of novel bioactive molecules. Here, using a hepatitis C virus (HCV) cell culture system, we identified neoechinulin B (NeoB), a fungus-derived compound, as an inhibitor of the liver X receptor (LXR). NeoB was initially identified by chemical screening as a compound that impeded the production of infectious HCV. Genome-wide transcriptome analysis and reporter assays revealed that NeoB specifically inhibits LXR-mediated transcription. NeoB was also shown to interact directly with LXRs. Analysis of structural analogs suggested that the molecular interaction of NeoB with LXR correlated with the capacity to inactivate LXR-mediated transcription and to modulate lipid metabolism in hepatocytes. Our data strongly suggested that NeoB is a novel LXR antagonist. Analysis using NeoB as a bioprobe revealed that LXRs support HCV replication: LXR inactivation resulted in dispersion of double-membrane vesicles, putative viral replication sites. Indeed, cells treated with NeoB showed decreased replicative permissiveness for poliovirus, which also replicates in double-membrane vesicles, but not for dengue virus, which replicates via a distinct membrane compartment. Together, our data suggest that LXR-mediated transcription regulates the formation of virus-associated membrane compartments. Significantly, inhibition of LXRs by NeoB enhanced the activity of all known classes of anti-HCV agents, and NeoB showed especially strong synergy when combined with interferon or an HCV NS5A inhibitor. Thus, our chemical genetics analysis demonstrates the utility of the HCV cell culture system for identifying novel bioactive molecules and characterizing the virus-host interaction machinery., Importance: Hepatitis C virus (HCV) is highly dependent on host factors for efficient replication. In the present study, we used an HCV cell culture system to screen an uncharacterized chemical library. Our results identified neoechinulin B (NeoB) as a novel inhibitor of the liver X receptor (LXR). NeoB inhibited the induction of LXR-regulated genes and altered lipid metabolism. Intriguingly, our results indicated that LXRs are critical to the process of HCV replication: LXR inactivation by NeoB disrupted double-membrane vesicles, putative sites of viral replication. Moreover, NeoB augmented the antiviral activity of all known classes of currently approved anti-HCV agents without increasing cytotoxicity. Thus, our strategy directly links the identification of novel bioactive compounds to basic virology and the development of new antiviral agents., (Copyright © 2016, American Society for Microbiology. All Rights Reserved.)

Eleven emestrin-type epipolythiodioxopiperazines, including four new compounds, emestrins H-K (1-4), were isolated from the crude extracts of two strains of the coprophilous fungus Podospora australis. The structures of 1-4 were established primarily by analysis of NMR data, and the absolute configuration of C-6 in 1 was independently assigned using the modified Mosher method. Four of the known emestrins obtained (emestrins C-E and MPC1001C) were found to selectively inhibit the growth of Cryptococcus neoformans. These results also represent the first report of chemistry from any strain of P. australis.

Two bioactive cyclic dipeptides, cyclo(L-Pro-L-Tyr) and cyclo(D-Pro-L-Tyr), were isolated from the culture broth of Streptomyces sp. strain 22-4 and tested against three economically important plant pathogens, Xanthomonas axonopodis pv. citri, Ralstonia solanacearum and Clavibacter michiganensis. Both cyclic dipeptides were active against X. axonopodis pv. citri and R. Solanacearum with MIC of 31.25 μg/mL. No activity could be observed against C. michiganensis.

Context Oxidative stress plays a key role in neurodegenerative disorders, including Parkinson's disease (PD). Rice fermented with Monascus purpureus Went (Monascaceae) NTU 568 (red mould rice) was found to contain antioxidants, including dimerumic acid (DMA) and deferricoprogen (DFC). Objective The effects of DMA and DFC on 6-hydroxydopamine (6-OHDA)-induced cytotoxicity and potential protective mechanisms in differentiated PC-12 pheochromocytoma cells were investigated. Materials and methods DMA (0-60 μM) or DFC (0-10 μM) was co-treated with 6-OHDA (200 μM, 24 h exposure) in differentiated PC-12 cells. Cell viability and intercellular reactive oxygen species (ROS) were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and 2',7'-dichlorofluorescein-diacetate (DCFH-DA) assays, respectively. Cell apoptosis was determined by DNA fragmentation analysis and propidium iodide staining by flow cytometry. Western blot analysis was used to measure the levels of cell protein expression. Results DMA and DFC significantly increased cell viability to 72% and 81% in 6-OHDA-induced differentiated PC-12 cell cultures, respectively. Furthermore, DMA and DFC reduced 6-OHDA-induced formation of extracellular and intercellular ROS by 25% and 20%, respectively, and decreased NADPH oxidase-2 expression in differentiated PC-12 cells. DMA and DFC inhibited 6-OHDA-induced apoptosis and decreased activation of caspase-3 via regulation of Bcl-2-associated X protein (Bax) and Bcl-2 protein expression in differentiated PC-12 cells. Conclusion DMA and DFC may protect against 6-OHDA toxicity by inhibiting ROS formation and apoptosis. These results showed that the metabolites from M. purpureus NTU 568 fermentation were potential therapeutic agents for PD induced by oxidative damage and should be encouraged for further research.

The performances of three neutral static coatings (hydroxypropyl cellulose, polyethylene oxide and poly(N,N-dimethylacrylamide) have been evaluated in order to determine the binding constants of the complexes formed between four polycationic compounds (piperazine derivatives) and four cyclodextrins of pharmaceutical interest (β-CD, HP-β-CD, Me-β-CD and sulfobutyl ether-β-CD) by affinity capillary electrophoresis. The physically-adsorbed poly(N,N-dimethylacrylamide) coating proves to be the more efficient to mask the silanol groups of the capillary wall since the lowest electroosmotic flow was measured for this coating. Moreover, it drastically reduces the adsorption of the compounds since it allows a correct repeatability of their migration time, higher efficiencies of the peaks and no baseline shift. Then, it was verified for four complexes that this coating allows a correct determination of the binding constants avoiding the CD adsorption which is responsible of an undervaluation of binding constants. The highest binding constants are obtained using the anionic sulfobutyl ether-β-CD (SBE-β-CD). The structure of the complex formed between the tacrine derivative and the SBE-β-CD was further investigated through 2D ROESY NMR experiments and structure-binding constant relationships. Results suggest that the inclusion in the SBE-β-CD cavity occurs through the aliphatic ring portion of the tacrine moiety., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Date-rape drugs have the potential to be used in drug-facilitated sexual assault, organ theft and property theft. Since they are colorless, tasteless and odorless, victims can drink without noticing, when added to the beverages. These drugs must be detected in time, before they are cleared up from the biofluids. A simultaneous extraction and determination method in urine for GHB, ketamine, norketamine, phenobarbital, thiopental, zolpidem, zopiclone and phenytoin (an anticonvulsant and antiepileptic drug) with LC-MS/MS was developed for the first time with analytically acceptable recoveries and validated. A 4 steps liquid-liquid extraction was applied, using only 1.000mL urine. A new age commercial C18 poroshell column with high column efficiency was used for LC-MS/MS analysis with a fast isocratic elution as 5.5min. A new MS transition were introduced for barbital. 222.7>179.8 with the effect of acetonitrile. Recoveries (%) were between 80.98-99.27 for all analytes, except for GHB which was 71.46. LOD and LOQ values were found in the ranges of 0.59-49.50 and 9.20-80.80ngmL(-1) for all the analytes (except for GHB:3.44 and 6.00μgmL(-1)). HorRat values calculated (between 0.25-1.21), revealed that the inter-day and interanalist precisions (RSD%≤14.54%) acceptable. The simultaneous extraction and determination of these 8 analytes in urine is challenging because of the difficulty arising from the different chemical properties of some. Since the procedure can extract drugs from a wide range of polarity and pKa, it increases the window of detection. Group representatives from barbiturates, z-drugs, ketamine, phenytoin and polar acidic drugs (GHB) have been successfully analyzed in this study with low detection limits. The method is important from the point of determining the combined or single use of these drugs in crimes and finding out the reasons of deaths related to these drugs., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Polyhedral oligomeric silsesquioxane (POSS) was successfully applied, for the first time, to prepare imprinted monolithic coating for capillary electrochromatography. The imprinted monolithic coating was synthesized with a mixture of PSS-(1-Propylmethacrylate)-heptaisobutyl substituted (MA 0702), S-amlodipine (template), methacrylic acid (functional monomer), and 2-methacrylamidopropyl methacrylate (crosslinker), in a porogenic mixture of toluene-isooctane. The influence of synthesis parameters on the imprinting effect and separation performance, including the amount of MA 0702, the ratio of template to monomer, and the ratio of monomer to crosslinker, was investigated. The greatest resolution for enantiomers separation on the imprinted monolithic column prepared with MA 0702 was up to 22.3, about 2 times higher than that prepared in absence of the POSS. Column efficiency on the POSS-based MIP coatings was beyond 30,000 plate m(-1). The comparisons between MIP coating synthesized with the POSS and without the POSS were made in terms of selectivity, column efficiency, and resolution. POSS-based MIP capillaries with naproxen or zopiclone was also prepared and separation of enantiomers can be achieved., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Three new epithiodiketopiperazine natural products [outovirin A (1), outovirin B (2), and outovirin C (3)] resembling the antifungal natural product gliovirin have been identified in extracts of Penicillium raciborskii, an endophytic fungus isolated from Rhododendron tomentosum. The compounds are unusual for their class in that they possess sulfide bridges between α- and β-carbons rather than the typical α-α bridging. To our knowledge, outovirin A represents the first reported naturally produced epimonothiodiketopiperazine, and antifungal outovirin C is the first reported trisulfide gliovirin-like compound. This report describes the identification and structural elucidation of the compounds by LC-MS/MS and NMR.

An open-tubular capillary electrochromatography column was prepared by chemically immobilized β-cyclodextrin modified gold nanoparticles onto new surface with the prederivatization of (3-mercaptopropyl)-trimethoxysilane. The synthesized nanoparticles and the prepared column were characterized by transmission electron microscopy, scanning electron microscopy, infrared spectroscopy and ultraviolet visible spectroscopy. When the column was employed as the chiral stationary phase, no enantioselectivity was observed for ten model basic drugs. So β-cyclodextrin was added to the background electrolyte as chiral additive to expect a possible synergistic effect occurring and resulting in a better separation. Fortunately, significant improvement in enantioselectivity was obtained for ten pairs of drug enantiomers. Then, the effects of β-cyclodextrin concentration and background electrolyte pH on the chiral separation were investigated. With the developed separation mode, all the enantiomers (except for venlafaxine) were baseline separated in resolutions of 4.49, 1.68, 1.88, 1.57, 2.52, 2.33, 3.24, 1.63 and 3.90 for zopiclone, chlorphenamine maleate, brompheniramine maleate, dioxopromethazine hydrochloride, carvedilol, homatropine hydrobromide, homatropine methylbromide, venlafaxine, sibutramine hydrochloride and terbutaline sulfate, respectively. Further, the possible separation mechanism involved was discussed.

Cristazine (1), a new class of dioxopiperazine alkaloid, along with previously isolated chetomin (2), neoechinulin A (3), and golmaenone (4), were isolated from the mudflat-sediment-derived fungus Chaetomium cristatum. The structure and absolute stereochemistry of 1 was assigned on the basis of NMR, electron impact (EI)-MS, tandem FAB-MS/MS, and circular dichroism (CD) experiments. Compounds 1-4 displayed potent radical-scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH), with IC50 values of 19, 15, 24, and 20 µM, respectively, which were similar to that of the positive control, ascorbic acid (IC50, 20 µM). Compound 1 also displayed cytotoxic activity against human cervical carcinoma (HeLa) cells, with an IC50 value of 0.5 µM.

Objectives: The main objective was analysis and assessment of toxinogenic capabilities of fungi isolated from moldy surfaces in residential rooms in an urban agglomeration situated far from flooded areas in moderate climate zone., Material and Methods: The assessment of environmental exposure to mycotoxins was carried out in samples collected from moldy surfaces in form of scrapings and airborne dust from 22 moldy dwellings in winter season. In each sample 2 mycotoxins were analyzed: sterigmatocystin and roquefortine C produced by Aspergillus versicolor and Penicillium chrysogenum, respectively. Mycotoxins were analyzed by high-performance liquid chromatography (HPLC) in: scrapings from moldy surfaces, mixture of all species of fungi cultured from scrapings on microbiological medium (malt extract agar), pure cultures of Aspergillus versicolor and Penicillium chrysogenum cultured from scrapings on microbiological medium; mycotoxins in the indoor air dust were also analyzed., Results: The production of sterigmatocystin by individual strains of Aspergillus versicolor cultured on medium was confirmed for 8 of 13 isolated strains ranging 2.1-235.9 μg/g and production of roquefortine C by Penicillium chrysogenum for 4 of 10 strains ranging 12.9-27.6 μg/g. In 11 of 13 samples of the mixture of fungi cultured from scrapings, in which Aspergillus versicolor was found, sterigmatocystin production was at the level of 3.1-1683.2 μg/g, whereas in 3 of 10 samples in which Penicillium chrysogenum occurred, the production of roquefortine C was 0.9-618.9 μg/g. The analysis did not show in any of the tested air dust and scrapings samples the presence of analyzed mycotoxins in the amount exceeding the determination limit., Conclusions: The capability of synthesis of sterigmatocystin by Aspergillus versicolor and roquefortine C by Penicillium chrysogenum growing in mixtures of fungi from scrapings and pure cultures in laboratory conditions was confirmed. The absence of mycotoxins in scrapings and air dust samples indicates an insignificant inhalatory exposure to mycotoxins among inhabitants in moldy flats of urban agglomeration situated far from flooded territories. Int J Occup Med Environ Health 2016;29(5):823-836., (This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.)

In this study, molecularly imprinting technology and stir bar absorption technology were combined to develop a microextraction approach based on a molecularly imprinted polymeric stir bar. The molecularly imprinted polymer stir bar has a high performance, is specific, economical, and simple to prepare. The obtained naftopidil-imprinted polymer-coated bars could simultaneously agitate and adsorb naftopidil in the sample solution. The ratio of template/monomer/cross-linker and conditions of template removal were optimized to prepare a stir bar with highly efficient adsorption. Fourier transform infrared spectroscopy, scanning electron microscopy, selectivity, and extraction capacity experiments showed that the molecularly imprinted polymer stir bar was prepared successfully. To utilize the molecularly imprinted polymer stir bar for the determination of naftopidil in complex body fluid matrices, the extraction time, stirring speed, eluent, and elution time were optimized. The limits of detection of naftopidil in plasma and urine sample were 7.5 and 4.0 ng/mL, respectively, and the recoveries were in the range of 90-112%. The within-run precision and between-run precision were acceptable (relative standard deviation <7%). These data demonstrated that the molecularly imprinted polymeric stir bar based microextraction with high-performance liquid chromatography was a convenient, rapid, efficient, and specific method for the precise determination of trace naftopidil in clinical analysis., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new diketopiperazine (DKP) derivative, (6R,3Z)-3-benzylidene-6-isobutyl-1-methyl piperazine-2,5-dione (1), as well as five known DKPs 2-6 was isolated from a deep sea-derived Streptomyces sp. SCSIO 04496. The structure of 1 was elucidated using a combination of 1D and 2D NMR, HR-ESI-MS and chiral-phase HPLC techniques. Compounds 1-6 did not show cytotoxic activity at a concentration of 100 μM in bioactivity assay.

One new cyclic tetrapeptide cyclic-(Tyr-Ala-Leu-Ser) (1) along with four natural compounds firstly obtained 3H-imidazole-4-carboxylic acid (2), 2-methyl-3H-imidazole-4-carboxylic acid (3), 3-ethylidene-6-isopropyl-piperazine-2,5-dione (4), and 3-isobutylidene-6-methyl piperazine-2,5-dione (5) have been isolated from the coral derived endophytic bacteria Brevibacterium sp. L-4 collected from the South China Sea. Their structures were elucidated through spectroscopic techniques including NMR (1D and 2D), MS, and EA, and their relative configurations were also assigned by NMR analysis.

An approach to the dihydrooxepino[4,3-b]pyrrole core of diketopiperazine natural products which utilizes a vinyl pyrrole epoxide Cope rearrangement was investigated. It was found that an ester substituent on the epoxide was essential for the [3,3]-rearrangement to occur. Density functional calculations with M06-2X provided explanations for the effects of the pyrrole and ester groups on these rearrangements.

Marine-derived Trichoderma sp. TPU199 (cf. T. brevicompactum) produced gliovirin (1), pretrichodermamide A (2), and trichodermamide A (3) in a freshwater medium. Compounds 1 and 2 are rare epidithiodiketopiperazines possessing an unusual disulfide linkage. In the seawater medium, the strain biosynthesized the 5-chloro-5-deoxy derivatives (4 and 5) of 3 and 2. The production of 5 was proportional to the concentration of seawater (NaCl). Therefore, 5-bromo-5-deoxy (6) and 5-deoxy-5-iodo (7) derivatives were biosynthesized in the freshwater media supplemented with NaBr and NaI, respectively. The structure of a new iodo derivative (7) was elucidated on the basis of its spectroscopic data.

A pair of new enantiomeric alkaloid dimers, (+)- and (-)-pestaloxazine A (1), with an unprecedented symmetric spiro[oxazinane-piperazinedione] skeleton, consisting of 22 carbons and 12 heteroatoms, were isolated from a Pestalotiopsis sp. fungus derived from a soft coral. Separation of the enantiomeric alkaloid dimers was achieved by chiral HPLC. Their structures including absolute configurations were elucidated on the basis of a comprehensive analysis of their spectroscopic and X-ray diffraction data and CD calculations. (+)-Pestaloxazine A exhibited potent antiviral activity against EV71 with an IC50 value of 14.2 ± 1.3 μM, which was stronger than that of the positive control ribavirin (IC50 = 256.1 ± 15.1 μM).

This study was designed to establish, optimize and validate a sensitive, selective and accurate high-performance thin layer chromatographic (HPTLC) method for determination of zopiclone (ZPC) and its main impurity, 2-amino-5-chloropyridine, one of its degradation products, in raw material and pharmaceutical formulation. The proposed method was applied for analysis of ZPC and its impurity over the concentration range of 0.3-1.4 and 0.05-0.8 µg/band with accuracy of mean percentage recovery 99.92% ± 1.521 and 99.28% ± 2.296, respectively. The method is based on the separation of two components followed by densitometric measurement of the separated peaks at 305 nm. The separation was carried out on silica gel HPTLC F254 plates, using chloroform-methanol-glacial acetic acid (9:1:0.1, by volume) as a developing system. The suggested method was validated according to International Conference on Harmonization guidelines and can be applied for routine analysis in quality control laboratories. The results obtained by the proposed method were statistically compared with the reported method revealing high accuracy and good precision., (© The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Brasilamides K-N (1-4), four new bergamotane sesquiterpenoids; with 4-oxatricyclo (3.3.1.0 (2,7))nonane (1)and 9-oxatricyclo(4.3.0.0 (4,7))nonane (2-4) skeletons; were isolated from the scale-up fermentation cultures of the plant endophytic fungus Paraconiothynium brasiliense Verkley. The previously identified sesquiterpenoids brasilamides A and C (5 and 6) were also reisolated in the current work. The structures of 1-4 were elucidated primarily by interpretation of NMR spectroscopic data. The absolute configurations of 1-3 were deduced by analogy to the co-isolated metabolites 5 and 6; whereas that of C-12 in 4 was assigned using the modified Mosher method. The cytotoxicity of all compounds against a panel of eight human tumor cell lines were assayed.

Unlabelled: A high-throughput phenotypic screen based on a Citrobacter freundii AmpC reporter expressed in Escherichia coli was executed to discover novel inhibitors of bacterial cell wall synthesis, an attractive, well-validated target for antibiotic intervention. Here we describe the discovery and characterization of sulfonyl piperazine and pyrazole compounds, each with novel mechanisms of action. E. coli mutants resistant to these compounds display no cross-resistance to antibiotics of other classes. Resistance to the sulfonyl piperazine maps to LpxH, which catalyzes the fourth step in the synthesis of lipid A, the outer membrane anchor of lipopolysaccharide (LPS). To our knowledge, this compound is the first reported inhibitor of LpxH. Resistance to the pyrazole compound mapped to mutations in either LolC or LolE, components of the essential LolCDE transporter complex, which is required for trafficking of lipoproteins to the outer membrane. Biochemical experiments with E. coli spheroplasts showed that the pyrazole compound is capable of inhibiting the release of lipoproteins from the inner membrane. Both of these compounds have significant promise as chemical probes to further interrogate the potential of these novel cell wall components for antimicrobial therapy., Importance: The prevalence of antibacterial resistance, particularly among Gram-negative organisms, signals a need for novel antibacterial agents. A phenotypic screen using AmpC as a sensor for compounds that inhibit processes involved in Gram-negative envelope biogenesis led to the identification of two novel inhibitors with unique mechanisms of action targeting Escherichia coli outer membrane biogenesis. One compound inhibits the transport system for lipoprotein transport to the outer membrane, while the other compound inhibits synthesis of lipopolysaccharide. These results indicate that it is still possible to uncover new compounds with intrinsic antibacterial activity that inhibit novel targets related to the cell envelope, suggesting that the Gram-negative cell envelope still has untapped potential for therapeutic intervention., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)