In vitro antimicrobial activities of anethole, carvacrol, cinnamon bark oil, eugenol, guaiazulene and thymol against G streptococci

Abstract

The present study describes the antimicrobial activity of various natural substances against group G streptococci. A total of 50 strains of group G streptococci was included in this study. The minimum bactericidal concentrations of 6 substances — anethole, eugenol, guaiazulene, carvacrol, cinnamon bark oil from Cinnamomum zeylanicum and thymol were obtained by the broth microdilution method. The substances were extended either directly in brain heart infusion broth or in 24 % ethanol. Carvacrol was found to be the most effective substance with the highest antimicrobial activity, which inhibited the growth of 90 % of group G streptococci strains at the concentration of 236.7 :g ml–1. The minimum bactericidal concentrations of eugenol, oil from the bark of Cinnamomum zeylanicum, and thymol were 1000 :g ml–1. Anethole and guaiazulene were the least effective natural substances in our study.