Growth-inhibiting effects of Coptis japonica root-derived isoquinoline alkaloids on human intestinal bacteria

The growth-inhibiting activity of Coptis japonica (Makino) root-derived mat erials toward eight human intestinal bacteria was examined using an impregn ated paper disk method and compared to that of four commercially available isoquinoline alkaloids [berberine sulfate (BS), berberine iodide (BI), palm atine chloride (PC), and palmatine sulfate(PS)], as well as that of Thea si nensis leaf-derived epigallocatechin gallate (EGCG). The biologically activ e constituents of the Coptis extract were characterized as the isoquinoline alkaloids berberine chloride (BC), palmatine iodide (PI), and coptisine ch loride (CC) by spectral analysis. The growth responses varied with both che mical and bacterial strain used. In a test using 500 mu g/disk, BC and PI p roduced a clear inhibitory effect against Bifidobacterium longum, Bifidobac terium bifidum, Clostridium perfringens, and Clostridium paraputrificum, wh ereas weak or no inhibition was observed in Bifidobacterium adolescentis, L actobacillus acidophilus, Lactobacillus casei, and Escherichia coli. At 100 0 mu g/disk, CC revealed weak or no growth inhibition toward all test bacte ria, whereas EGCG exhibited weak growth inhibition against only C. perfring ens and C. paraputrificum. Among various isoquinoline alkaloids, BC exhibit ed more potent-inhibitory activity toward C. perfringens than BI and BS, wh ereas the inhibitory effect was more pronounced in PI compared to PC and PS . The Coptis root-derived materials did not promote growth of B. longum and C. perfringens.