Antibacterial, Antifungal, and Antiviral Bioactive Compounds from Natural Products, 2nd Edition

Background: The viral main protease (M^pro) of SARS-CoV-2 has been recently proposed as a key target to inhibit virus replication in the host. Therefore, molecules that can bind the catalytic site of M^pro could be considered as potential drug candidates in the treatment of SARS-CoV-2 infections. Here we proposed the application of a state-of-the-art analytical platform which combines metabolomics and protein structure analysis to fish-out potential active compounds deriving from a natural matrix, i.e., a blueberry extract. Methods: The experiments focus on finding MS covalent inhibitors of M^pro that contain in their structure a catechol/pyrogallol moiety capable of binding to the nucleophilic amino acids of the enzyme’s catalytic site. Results: Among the potential candidates identified, the delphinidin-3-glucoside showed the most promising results. Its antiviral activity has been confirmed in vitro on Vero E6 cells infected with SARS-CoV-2, showing a dose-dependent inhibitory effect almost comparable to the known M^pro inhibitor baicalin. The interaction of delphinidin-3-glucoside with the M^pro pocket observed was also evaluated by computational studies. Conclusions: The HRMS analytical platform described proved to be effective in identifying compounds that covalently bind M^pro and are active in the inhibition of SARS-CoV-2 replication, such as delphinidin-3-glucoside. Full article

The green synthesis of zinc oxide nanoparticles (ZnO NPs) using plants has grown in significance in recent years. ZnO NPs were synthesized in this work via a chemical precipitation method with Jasminum sambac (JS) leaf extract serving as a capping agent. These NPs were characterized using UV-vis spectroscopy, FT-IR, XRD, SEM, TEM, TGA, and DTA. The results from UV-vis and FT-IR confirmed the band gap energies (3.37 eV and 3.50 eV) and the presence of the following functional groups: CN, OH, C=O, and NH. A spherical structure and an average grain size of 26 nm were confirmed via XRD. The size and surface morphology of the ZnO NPs were confirmed through the use of SEM analysis. According to the TEM images, the ZnO NPs had an average mean size of 26 nm and were spherical in shape. The TGA curve indicated that the weight loss starts at 100 °C, rising to 900 °C, as a result of the evaporation of water molecules. An exothermic peak was seen during the DTA analysis at 480 °C. Effective antibacterial activity was found at 7.32 ± 0.44 mm in Gram-positive bacteria (S. aureus) and at 15.54 ± 0.031 mm in Gram-negative (E. coli) bacteria against the ZnO NPs. Antispasmodic activity: the 0.3 mL/mL sample solution demonstrated significant reductions in stimulant effects induced by histamine (at a concentration of 1 µg/mL) by (78.19%), acetylcholine (at a concentration of 1 µM) by (67.57%), and nicotine (at a concentration of 2 µg/mL) by (84.35%). The antipyretic activity was identified using the specific Shodhan vidhi method, and their anti-inflammatory properties were effectively evaluated with a denaturation test. A 0.3 mL/mL sample solution demonstrated significant reductions in stimulant effects induced by histamine (at a concentration of 1 µg/mL) by 78.19%, acetylcholine (at a concentration of 1 µM) by 67.57%, and nicotine (at a concentration of 2 µg/mL) by 84.35%. These results underscore the sample solution’s potential as an effective therapeutic agent, showcasing its notable antispasmodic activity. Among the administered doses, the 150 mg/kg sample dose exhibited the most potent antipyretic effects. The anti-inflammatory activity of the synthesized NPs showed a remarkable inhibition percentage of (97.14 ± 0.005) at higher concentrations (250 µg/mL). Furthermore, a cytotoxic effect was noted when the biologically synthesized ZnO NPs were introduced to treated cells. Full article

Synthesis of the natural product prattinin A and some new derivatives has been achieved using abietic acid. The final products and a selection of intermediates were evaluated for their antibacterial activity against three human pathogenic bacteria: E. coli, P. aeruginosa, and S. aureus. The results showed that the antibacterial activity varies depending on the chemical structure of the compounds. Notably, compound 27 exhibited the most potent activity against E. coli and P. aeruginosa, with a minimal inhibitory concentration (MIC) of 11.7 µg/mL, comparable to that of the standard antibiotic ciprofloxacin, and strong activity against S. aureus, with an MIC of 23.4 µg/mL. Furthermore, we assessed the stability of these derivative compounds as potential antimicrobial agents and determined their interactions with the crystal structure of the protein receptor mutant TEM-12 from E. coli (pdb:1ESU) using molecular docking via UCSF Chimera software 1.17.3. The results suggest that 27 has potential as a natural antibiotic agent. Full article