Impact of extraction methodology on microbiological screening of Coptis chinensis Franch for antimicrobial activity

Coptis chinensis Franch (CCF) is commonly used in herbal remedies in Traditional Chinese Medicine (TCM) owing to its observed antimicrobial and anticancer effects in clinical medicine [1]. As an individual herb, CCF has exhibited potent inhibition on a number of bacteria including Escherichia coli in vitro conditions. The alkaloid components in CCF have been suggested to be the bioactive ingredients. The aim of our study was to investigate: 1) if there is any inhibitory effect on food and animal pathogens such as E. coli, Listeria and Mycobacterium smegmatis, 2) the efficiency of our routine extraction procedures for removal of the known maker alkaloids from CCF.

Coptis chinensis Franch (10g) were extracted using a successive Soxhlet procedure (a) with a series of solvents (Hexane, Dichloromethane, Methanol and water) or a successive solvent and water procedure (b) in a beaker at room temperature. Crude extracts were tested by microbiological procedure (broth or plate), for possible antimicrobial effect on the three selected microorganisms and their growth inhibition effects were compared with the conventional antibiotics. No inhibitory effect on E. coli was observed from extracts of Soxhlet procedure except the methanol extract showed weak effect. The hexane extract (Soxhlet) and acetone extract from procedure (b) also exhibited weak effect on Listeria monocytogenes. Interestingly, none of the water extracts from two procedures demonstrated inhibition on neither E. coli nor Listeria monocytogenes. However, the water extract of Soxhlet was found to partially inhibit the growth of M. smegmatis. These results suggest that synergistic effect of different components of Coptis chinensis Franch may be important for its antimicrobial effect.

References: [1] Birdsall, T.C. et al. (1997) Altern. Med. Rev. 2:94.

[2] Lin, S. et al. (2006) Food Chem. Toxicol. 44:2078–2085.