Antimicrobial and cytotoxic isopimarane diterpenoid glycosides from Microlepia pilosissima Ching

A phytochemical investigation of the EtOH extract of the dry fronds of Microlepia pilosissima Ching afforded four new isopimarane diterpene glycosides, 3α-O-α-L-rhamnopyranosyl-7β-O-β-D-fucopyranosyl-ent-iospimara-8(14),15-diene (1), 3α-O-[2-O-acetyl-α-L-rhamnopyranosyl]-7β-O-β-D-fucopyranosyl-ent-iospimara-8(14),15-diene (2), 3α-O-[β-D-glucopyranosyl-(1→2)-α-L-rhamnopyranosyl]-7β-O-β-D-fucopyranosyl-ent-iospimara-8(14),15-diene (3) and 3α-O-[β-D-fucopyranosyl-(1→2)-α-L-rhamnopyranosyl]-7β-O-β-D-fucopyranosyl-ent-iospimara-8(14),15-diene (4) as well as their aglycone, 3α,7β-dihydroxy-ent-iospimara-8(14),15-diene (5). Their structures were characterized by spectroscopic methods, including 1D-NMR, 2D-NMR, and HR-ESI-MS. The isolated compounds were evaluated in vitro for antimicrobial properties against three pathogen fungi and two oral pathogens and cytotoxicities against eight tumor cell lines. As a result, compounds 1-4 appeared to be promising antimicrobial potential and possessed moderate cytotoxic activities against the tested tumor cell lines.