Phenolic compounds from Baseonema acuminatum leaves: isolation and antimicrobial activity

Three new phenolic compounds, 1-galloyl-beta-D-glucopyranosyl-(1-->4)-beta-D-galactopyranoside (1), 2-methoxy-5-(1 '2 3'-trihydroxypropyl)-phenyl- 1-0-(6"-galloyl)-beta-D-glucopyranoside (2),and 2-methoxy-5-hydroxymethyl-phenyl-1-O-(6"-galloyl)-beta-D-glucopyranoside (3), together with the known compounds benzyl 6'-O-galloyl-beta-D-glucopyranoside (4), 1,6-di-O-galloyl-beta-D-glucopyranose (5), myrciaphenone B (6), kaempferol 3-0-(6"-galloyl)-beta-D-glucopyranoside (7), quercetin 3-0-(6"-galloyl)-beta-D-glucopyranoside (8), vomifoliol 9-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside, 2,3-dihydrobenzofuran-2-(4'-hydroxy-3'-methoxyphenyl)-3-alpha-L-rhamnopyranosyloxymethyl-7-methoxy-5-propanol, and benzyl-O-alpha-L-rhamnopyranosyl-(1-->6)-Beta-D-glucopyranoside were isolated from the leaves of Baseonema acuminatum P. Choux (Asclepiadaceae). Their structures were determined by 1D- and 2D-NMR spectroscopy and by ESI-MS analysis. The antimicrobial activity of all compounds was evaluated in vitro against bacteria (Staphylococcus aureus two strains, Bacillus cereus, Bacillus subtilis, Escherichia coli, Salmonella thyphimurium) and three strains of Candida albicans. The new compounds 2 and 3, together with the known compound 4, showed antifungal activity against two clinically isolated Candida albicans strains and against C. albicans ATCC 2091; MIC values were in the range of 25-100 microg/mL. Compound 5 was active against the two clinically isolated strains of C. albicans with MICs of 12.5 microg/mL and 25 microg/mL. Compounds 1, 6, 7, and 8 inhibited only one strain of C albicans at the maximum concentration used. None of the phenolic compounds tested was active against the bacteria studied.