Search

The search for potent antimicrobial compounds is critical in the face of growing antibiotic resistance. This study explores Acalypha arvensis Poepp. (A. arvensis), a Caribbean plant traditionally used for disease treatment. The dried plant powder was subjected to successive extractions using different solvents: hexane (F1), dichloromethane (F2), methanol (F3), a 50:50 mixture of methanol and water (F4), and water (F5). Additionally, a parallel extraction was conducted using a 50:50 mixture of methanol and chloroform (F6). All the fractions were evaluated for their antimicrobial activity, and the F6 fraction was characterized using untargeted metabolomics using SPME-GC×GC-TOFMS. The extracts of A. arvensis F3, F4, and F5 showed antibacterial activity against Staphylococcus aureus ATCC 25923 (5 mg/mL), MRSA BA22038 (5 mg/mL), and Pseudomonas aeruginosa ATCC 27853 (10 mg/mL), and fraction F6 showed antibacterial activity against Staphylococcus aureus ATCC 29213 (2 mg/mL), Escherichia coli ATCC 25922 (20 mg/mL), Pseudomonas aeruginosa ATCC 27853 (10 mg/mL), Enterococcus faecalis ATCC 29212 (10 mg/mL), Staphylococcus aureus 024 (2 mg/mL), and Staphylococcus aureus 003 (2 mg/mL). Metabolomic analysis of F6 revealed 2861 peaks with 58 identified compounds through SPME and 3654 peaks with 29 identified compounds through derivatization. The compounds included methyl ester fatty acids, ethyl ester fatty acids, terpenes, ketones, sugars, amino acids, and fatty acids. This study represents the first exploration of A. arvensis metabolomics and its antimicrobial potential, providing valuable insights for plant classification, phytochemical research, and drug discovery.

Infections caused by drug-resistant bacteria are a serious threat to human and global public health. Moreover, in recent years, very few antibiotics have been discovered and developed by pharmaceutical companies. Therefore, there is an urgent need to discover and develop new antibacterial agents to combat multidrug-resistant bacteria. In this study, two novel series of juglone/naphthazarin derivatives (43 compounds) were synthesized and evaluated for their antibacterial properties against various clinical and reference Gram-positive MSSA, clinical Gram-positive MRSA, and clinical and reference Gram-negative bacteria E. coli and P. aeruginosa. These strains are of clinical importance because they belong to ESKAPE pathogens. Compounds 3al, 5ag, and 3bg showed promising activity against clinical and reference MSSA (MIC: 1–8 µg/ml) and good efficacy against clinical MRSA (MIC: 2–8 µg/ml) strains. 5am and 3bm demonstrated better activity on both MSSA (MIC: 0.5 µg/ml) and MRSA (MIC: 2 µg/ml) strains. Their MICs were similar to those of cloxacillin against clinical MRSA strains. The synergistic effects of active compounds 3al, 5ag, 5am, 3bg, and 3bm were evaluated with reference antibiotics, and it was found that the antibiotic combination with 3bm efficiently enhanced the antimicrobial activity. Compound 3bm was found to restore the sensitivity of clinical MRSA to cloxacillin and enhanced the antibacterial activity of vancomycin when they were added together. In the presence of 3bm, the MIC values of vancomycin and cloxacillin were lowered up to 1/16th of the original MIC with an FIC index of 0.313. Moreover, compounds 3al, 5ag, 5am, 3bg, and 3bm did not present hemolytic activity on sheep red blood cells. In silico prediction of ADME profile parameter results for 3bm is promising and encouraging for further development.

VOCs emitted by flowers play an important role in plant ecology. In the past few years, the Tillandsia genus has been scarcely studied according to the VOCs emitted by flowers. Hence, we decided to enlarge the VOCs composition study already undergone in our laboratory on fragrant 3 Tillandsia species to 12 unscented and 2 faint-scented Tillandsia species and hybrids. The headspace solid phase microextraction (HS-SPME) coupled with gas chromatography combined with the mass spectrometry (GC-MS) method was used to explore the chemical diversity of the VOCs. This study allowed the identification of 65 VOCs among the 14 species and between 6 to 25 compounds were identified in each of the species. The aromatic profile of 10 of the species and hybrids are similar to each other’s and show 8 predominant compounds: benzaldehyde, benzacetaldehyde, hexanol, hexanal, heptanal, octanal, nonanal, and furan-2-pentyl. Some specific compounds are present only in some unique species such as trans-calamenene, α-muurolene, and α-guaiene trans-β-bergamotene. The two faint-scented species studied present an original aromatic profile with a high number of monoterpenes or phenylpropanoids/benzenoids. Our studies allow a better understanding of the ecological role and function of these VOCs in the interactions between these plants with their environment.

An original and effective approach for achieving trifluoromethyl hydroxyalkylation of 5-phenylthiophen-2-amine using α-trifluoromethyl ketones is described. In the last few years, reaction of Friedel-Crafts had been widely used to realize hydroxyalkylation on heterocycles such as indoles or thiophenes by means of Lewis acid as catalyst. Additionally, amine functions are rarely free when carbonyl reagents are used because of their tendency to form imines. This is the first time that a site-selective electrophilic aromatic substitution on C3 atom of an unprotected 5-phenylthiophen-2-amine moiety is reported. The liberty to allow reaction in neutral conditions between free amine is valuable in a synthesis pathway. The reaction proceeds smoothly using an atom-economical metal-and catalyst-free methodology in good to excellent yields. A mechanism similar to an electrophilic aromatic substitution has been proposed.

Numerous volatile organic compounds (VOCs) with a large chemical diversity are emitted by plant flowers. They play an important role in the ecology of plants, such as pollination, defense, adaptation to their environment, and communication with other organisms. The Tillandsia genus belongs to the Bromeliaceae family, and most of them are epiphytes. The aromatic profile of the Tillandsia genus is scarcely described. In this study, we use the headspace solid phase microextraction (HS-SPME) coupled with gas chromatography combined with mass spectrometry (GC-MS) method developed in our laboratory to explore the chemical diversity of the VOCs of fragrant flowers of three species of the genus Tillandsia. We were able to identify, for the first time, 66 volatile compounds (monoterpenes, sesquiterpenes, phenylpropanoids, and other compounds). We identified 30 compounds in T. xiphioides, 47 compounds in T. crocata, and 43 compounds in T. caliginosa. Only seven compounds are present in all the species studied. Comparison of the volatile compounds profiles by principal component analysis (PCA) between T. xiphoides, T. crocata, and T. caliginosa species showed a clear difference in the floral emissions of the studied species. Moreover, floral VOCs profiles allowed to differentiate two forms of T. xiphioides and of T. crocata.