Antibacterial Effects of Unripe Cephalotaxus harringtonia Fruit Extract on Gram-positive Bacteria

Methanol extracts of 105 plant parts from 101 different edible plants were screened against three food-borne microorganisms, Bacillus cereus, Leuconostoc mesenteroides, and Saccharomyces cerevisiae. As the extract from unripe Japanese plum yew fruit (Cephalotaxus harringtonia) was the most efficient at inhibiting the growth of B. cereus and L. mesenteroides, its antibacterial activity was evaluated against 22 species of Gram-positive bacteria, 7 species of Gram-negatives bacteria, and 13 species of fungi, using the broth dilution method. The extract exhibited antibacterial activity against Gram-positive bacteria with minimum inhibitory concentrations (MIC) of 25 to 200 mu g/ml in agar broth and 5 to 40 mu g/ml in liquid broth. Moreover, the antimicrobial effect was stronger under acidic and basic conditions than neutral condition. In contrast, no antibacterial activity was observed for Gram-negative bacteria and fungi (MIC, > 1000 mu g/ml). (Received Mar. 26, 2009; Accepted Jul. 14, 2009)