ANTIBACTERIAL ACTIVITY OF THE PHLOROTANNINS DIECKOL AND PHLOROFUCOFUROECKOL-A FROM ECKLONIA CAVA AGAINST PROPIONIBACTERIUM ACNES

Methanol extract of the marine brown alga Ecklonia cava has been shown to exhibit antimicrobial activity against Propionibacterium acnes. To identify the compounds conferring this antimicrobial activity, methanol extract was fractionated using silica-gel column chromatography by increasing solvent polarity, and the antimicrobial activities of each fraction were determined in terms of the minimum inhibitory concentration. Hexane, diethyl ether, acetone, ethyl acetate, acetonitrile, methanol, and water fractions were generated, with the acetone fraction exhibiting the greatest antibacterial activity (minimum inhibitory concentration = 156 mu g/mL). The acetone fraction was further purified by Sephadex LH-20 column chromatography and reverse-phase HPLC using an Alltima C18 column with an H2O-MeOH linear gradient from 30 to 100%. Two peaks were eluted at 18.1 (P1) and 23.8 (P2) mm, both of which exhibited marked antibacterial activity (minimum inhibitory concentration = 39 mu g/mL for both). The structures of these compounds were determined on the basis of H-1 and C-13 nuclear magnetic resonance data and, through comparison with published data, can be phloroglucinol derivatives dieckol (P1) and phlorofucofuroeckol-A (P2). These results suggest that phlorotannins derived from E. cava have antimicrobial activity against P. acnes, and so may be useful as natural additives in antiacne cosmetics and pharmaceutical products.