Antimicrobial compounds from Ceanothus americanus against oral pathogens

During the search for antimicrobial compounds from higher plant sources, a methanol extract of Ceanothus americanus demonstrated antimicrobial activity against selected oral pathogens. Through further bioassay-guided fractionation and purification, three triterpenes (ceanothic acid, 27-hydroxy ceanothic acid and ceanothetric acid) and two flavonoids (maesopsin and maesopsin-6-O-glucoside) were identified. Among these, ceanothetric acid and maesopsin-6-O-glucoside were new compounds. Ceanothic acid and ceanothetric acid demonstrated growth inhibitory effect against Streptococcus mutans, Actinomyces viscosus, Porphyromonas gingivalis, and Prevotella intermedia with MICs ranging from 42 to 625 micrograms ml-1. Maesopsin, its glucoside, and 27-hydroxy ceanothic acid, were inactive below the concentration of 500 micrograms ml-1.