In Vitro Growth-inhibiting Effects of Leaf Extracts from Pinus Species on Human Intestinal Bacteria

Methanol extracts of leaves from 15 Pinus species belonging to the family Pinaceae were tested for their in vitro growth-inhibiting activities against 10 bacteria commonly found in the gastrointestinal tracts of human, using impregnated paper disk methods. The inhibitory activities varied with both bacterial strain and Pinus species used. At a concentration of 10 mg/disk, a clear growth inhibition was produced from the extracts of Pinus armandii, P. banksiana, P. bungeana, P. densiflora, P. rigida, and P. thunbergii against Clostridium perfringens, whereas all Pinus samples revealed weak or little growth-inhibiting activity against Escherichia coli, Bacteroides fragilis, and Staphylococcus aureus. At 5 mg/disk, the extracts of P. banksiana and P. thunbergii exhibited potent growth inhibition toward C. perfringens. All the extracts except the one from P. densiflora did not adversely affect growth of Bifidobacterium adolescentis, B. longum, B. bifidum, B. breve, B. animalis, and Lactobacillus casei. The growth-inhibiting activity was more pronounced in C. perfringens, as compared to the lactic acid-producing bacteria. These results may be an indication of at least one of the pharmacological activities of these Pinus species.