Anti-microbial properties of Scutellaria baicalensis and Coptis chinensis, two traditional Chinese medicines

High incidence of resistance to pharmaceutical antibiotics among microbes in hospital environments prompts the search for alternative sources of anti-microbial chemicals. A largely underexploited resource in this regard is plants used in traditional Chinese medicine (TCM). In this investigation, anti-microbial properties of water extracts of two herbs used in TCM—Scutellaria baicalensis Georgi (Huang Qin) and Coptis chinensis Franch (Huang Lian)—against Escherichia coli B, coagulase-negative staphylococcus and Saccharomyces cerevisiae were examined using the disc diffusion method with water as a negative control and vancomycin as the positive control for coagulase-negative staphylococcus. Coptis chinensis appeared more potent than S. baicalensis against the three microbes used in the main experiments. Against E. coli B, the mean width and standard error of the kill zone was 3.9 ± 0.6 and 13.3 ± 0.7 mm for S. baicalensis and C. chinensis, respectively. Against coagulase-negative staphylococcus, the mean kill zone widths were 6.6 ± 1.1 and 11.0 ± 1.0 mm for S. baicalensis and C. chinensis, respectively. Against S. cerevisiae, the mean kill zone widths were 8.4 ± 1.0 and 12.6 ± 1.4 mm for S. baicalensis and C. chinensis, respectively. When compared with the positive control, C. chinensis was comparable in effect to vancomycin against coagulase-negative staphylococcus, whereas S. baicalensis was less effective than vancomycin. Further experiments investigated the use of herbs in combination and minimum inhibitory concentration. A limited number of further tests were conducted with other bacteria; E. coli 8879 (NCIMB 8879), Staphylococcus aureus (NCIMB 9518), Micrococcus luteus and Bacillus megaterium; both herbs killed all of the other bacteria, but C. chinensis appeared more potent than S. baicalensis. Diffusion disc technique provided a useful method to evaluate the anti-microbial effects of the two herbs, both of which showed promise as new anti-microbial agents.