Records of Natural Products

Gymnema sylvestre is a commonly used herb in Ayurvedic medicine. The demand for its extracts in the commercial and pharmaceutical fields has been steadily increasing in recent years. Its extracts are used to treat various ailments as well as for their antimicrobial properties. This study has evaluated the antimicrobial effects of different G. sylvestre extracts and of eight triterpenes isolated from the most active extract on six bacterial poultry pathogens i.e. Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterobacter aerogenes. In particular, it has been evaluated the minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of all extracts and isolated triterpenes. Finally, the cytotoxicity activity of triterpenes was evaluated by MTT assay and their antioxidant activity in basal and oxidant conditions by DCFH-DA assay.

Salvia pichinchensis Benth was collected in the South of Ecuador and the essential oil (EO) was distilled from aerial parts and analyzed by GC-MS and GC-FID. The physical properties, chemical composition, and cholinesterase inhibitory activity were determined. Six major components, all sesquiterpenes, were identified: cis-cadina-1(6),4-diene (17.11%) (1),γ-curcumene (13.75%) (2), (E)-caryophyllene (12.58%) (3), (E,E)-α-farnesene (10.00%) (4), α-gurjunene (9.46%) (5) and allo-aromadendrene (6.96%) (6). The EO showed an interesting selective inhibitory activity against the enzyme butyrylcholinesterase (50.70 μg/mL) and only low inhibitory activity against acetylcholinesterase (117.60 μg/mL). The chemical composition and butyrylcholinesterase activity of the EO of S. pichinchensis Benth was reported for first time.

From the extract of lichen Dirinaria applanata, two hopane derivatives including 1b-acetoxy-3b-hydroxy-21a-hopan-29-oic acid (1), hopane-3b, 6b, 21a-triol (2) and a depside namely 2-O¢-methylnordivaricatic acid (3) were isolated and identified by extensive analyzing 1D-NMR, 2D-NMR, HRESI-MS, and FT-IR. Notably, compound 1 and 3 were novel compounds while compound 2 was isolated from this lichen species for the first time.

Chemical examination of a fraction of the EtOAc extract of a marine-derived fungus Aspergillus sp. YPGA8 resulted in the isolation of two new compounds, namely aspertriols A-B (1-2). Compounds 1-2 possess an identical 2,3,4-trihydroxybutoxy moiety, which is rarely found in natural products. Their structures were determined by extensive analyses of spectroscopic data (1D and 2D NMR, HRESIMS). The bioassay study revealed that compounds 1 and 2 were inactive toward a-glucosidase.