Growth-inhibitory Responses of Human Intestinal Bacteria to Extracts of Oriental Medicinal Plants

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Abstract
Methanol extracts from 50 species of oriental medicinal plants were prepared and subjected to an in vitro screening test for their growth-inhibitory activity towards Bifidobacterium adolescentis, Clostridium perfringens and Escherichia coli, using a paper disc agar diffusion method under O2-free conditions. The inhibitory activity was both bacteria and plant-species dependent. Extracts from Pueraria thunbergiana, Astragalus membranaceus, Eucommia ulmoides, Coptis japonica, Akebia quinata and Rhus chinensis strongly inhibited growth of C. perfringens, A growth-inhibitory effect against E. coli was observed from extracts of C. japonica. These plant extracts did not affect the growth of B. adolescentis. It is concluded that intake of these oriental medicinal plants may be important in the prevention of human diseases caused by intestinal microorganisms by altering the growth and composition of intestinal bacteria and modulating the genesis of potentially harmful metabolites.