Antibacterial activities of Coptis chinensis and Glycyrrhiza glabra against seven bacteria associated with human gastrointestinal infections

Minimum inhibitory concentration (MIC) of crude extracts of the rhizome of huang lian (Coptis chinensis) and the root of licorice (Glycyrrhiza glabra) were determined in vitro by a modified agar dilution method, at concentration levels of 0.4–6.5 mgml^-1, according to Clinical and Laboratory Standards Institute (CLSI) 2005 (1,2) against seven bacteria frequently involved in gastrointestinal infections. Tested bacteria were Escherichia coli, Klebsiella pnuemoniae, Salmonella typhi, Serratia marcescens, Vibrio cholerae non 01, non 0139, Vibrio parahaemolyticus, and Enterococcus faecalis. Most bacteria were susceptible to the extract of Glycyrrhiza glabra with the MIC values >6.5 mgml^-1. MIC values of Coptis chinensis extract within the group of bacteria range from 3.25 to >6.5 mgml^-1 which did not much differ from those of Glycyrrhiza glabra extract. However, the crude extract of Coptis chinensis which contained berberine showed the best antibacterial activity against Vibrio cholerae non 01, non 0139. The results indicated that both natural products showed antimicrobial activity which may be useful for treating gastrointestinal infections.

Berberine

Acknowledgements: National Research council of Thailand, Faculty of Medicine and Faculty of Pharmacy, Srinakharinwirot University.

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