Growth stimulation/inhibition effect of medicinal plants on human intestinal microbiota

This experiment was carried out to determine the growth stimulation/inhibition effect of popular herbal extracts on intestinal microbiota and pathogenic bacteria. A paper disc agar diffusion method was employed for preliminary data. All extracts failed to promote intestinal microbiota growth around the discs. Green tea (Camellia sinensis) and Eleutherine americana did not produce inhibition zones against all intestinal microbiota, but inhibited Gram-positive pathogenic bacteria. All pure compounds, except eleutherin demonstrated antibacterial activity against all bacteria. Growth response of the substances on intestinal microbiota were further investigated by viable counts. Eleutherin from E. americana did not produce antibacterial antagonism against important groups of intestinal microbiota. In contrast, E. americana extract and eleutherin at minimal inhibitory concentration (MIC) and 4 MIC showed significant inhibition on growth of Grampositive pathogenic bacteria. The results indicated that both E. americana extract and eleutherin exerted dual beneficial effects to the host by regulating beneficial bacteria and inhibiting pathogenic bacteria.