Cantleyoside-dimethyl-acetal and other iridoid glucosides from Pterocephalus perennis--antimicrobial activities.

Cantleyoside-dimethyl-acetal (6), was isolated from the endemic Greek plant Pterocephalus perennis subsp. perennis in addition to five other known iridoid glucosides, loganin, loganic acid, cantleyoside, secologanin, and secologanin-dimethyl-acetal. The structure of these compounds was determined by all spectroscopic means mainly by NMR and MS techniques. The above compounds as well as their acetyl derivatives were tested against six Gram positive and negative bacteria and three pathogenic fungi.