Growth-Inhibiting Effects of Vegetable Extracts on Beneficial and Harmful Human Intestinal Bacteria

Ethanol extracts of 38 vegetables were subjected to an in vitro screening for their growth-inhibitory activities towards Bifidobacterium bifidum, B. longum, Clostridium perfringens, Lactobacillus acidophilus, L. casei, and Escherichia coli using paper disc agar diffusion methods under anaerobic conditions. The responses varied with both bacterial strain and vegetable species. In a test with 20 mg/disc, Zingiber officinale extracts showed significant growth-inhibitory responses against B. bifidum, and strong inhibitions against L. casei were detected in the extracts of Chrysanthemum coronarium var. spatiosum and Lactuca sativa. The extracts of Allium sativum, Capsicum annuum, L. esculentum, L. esculentum var. cerasiforme, and Z. officinale showed strong inhibitory activities against C. perfringens, while moderate growth-inhibitory responses were observed in the extracts of C. ffutescens, Cucurbita moschata, Daucus carota var. sativa, and Rubus coreanus. However, all vegetable extracts showed no inhibitions against B. longum, L. acidophilus, and E. coli. In tests with 5 mg/disc, moderate inhibitions were observed in the extracts of C. coronarium var. spatiosum and L. sativa against L. casei and Z. officinale against B. bifidum. Vegetables extracts, except for C. coronarium var. spatiosum, L. sativa, and Z. officinale, did not affect the growth of beneficial bacteria. Strong inhibitory responses against C. perfringens were detected in the extracts of C. annuum and L. esculentum var. cerasiforme. Daily intake of vegetables may be important in the prevention of human diseases caused by the intestinal bacteria.