Abstract
We isolated a substance inhibiting the growth of lactic acid bacteria from duhat bark, which is added to “basi”, a sugar cane wine in the Philippines, and investigated its structure. By adding gelatin to the aqueous extract of duhat bark (AEDB), 63.2% of the polyphenol components in AEDB were precipitated, and the resulting supernatant lost its inhibitory activity on the growth of lactic acid bacteria. This result indicates that the inhibitory substance was the polyphenol component combining to protein. In addition, we fractionated AEDB into two fractions by ultrafiltration and investigated their inhibitory activities on the growth of lactic acid bacteria. A strong inhibitory activity was found in the fraction having molecular weight (MW) above 1× 104 containing about 53% of the polyphenol components in AEDB, indicating that the main inhibitory substance is a polyphenol component with high MW. We then separated the polyphenol components with MW above 1× 104 by ion-exclusion chromatography using CMSepharose CL-6B, and obtained a polyphenol component with inhibitory activity on the growth of lactic acid bacteria. The polyphenol component produced gallic acid, anthocyanidins of delphinidin and cyanidin, and glucose by hydrolysis with HCl, and was assumed to be condensed tannin comprised of gallic acid and leucoanthocyanin.
