Abstract
As a result of screening the medicinal herbs which selectively control human intestinal microflora, water extract of Akebia quinata Decaisne was proved to have a strong inhibitory activity against the growth of Clostridium pefringens, a major harmful intestinal bacterium. The anti-bacte-rial activity was stable under the thermal treatment at 100$\circ$C for 120 min and in a range of pH 1 to 11. In addition, the water extract of Akebia quinata Decaisne showed the antibacterial activities against five different strains of Clostridia including C. perfringens. On the contrary, the extract did not inhibit the growths of Bifidobacterium, Lactobacillus, Escherichia coli, Enterococcus faecalis. The extract, however, suppressed markedly the growth of Bacteroides fragilis and Staphylococcus aureus in vitro. Alike in the mixed culture inoculated with human feces as starter, in vivo tests using rats showed that the extract tends to increase the numbers of Bifidobacteria and Lactobacilli in the intestinal microflora of rats, whereas those of Clostridia were attenuated.