Antimicrobial activities of stearidonic and gamma-linolenic acids from the green seaweed Enteromorpha linza against several oral pathogenic bacteria

Background: We found that the edible green seaweed Enteromorpha linza displayed potent antimicrobial activity against Prevotella intermedia and Porphyromonas gingivalis. To elucidate the active component of E. linza, isolation procedures were performed. Results: The main active compound was isolated by polarity fractionation, Sephadex LH-20 gel chromatography, and reverse-phase high-performance liquid chromatography (RP-HPLC). The active compounds were eluted at isocratic 95% acetonitrile by RP-HPLC and identified as unsaturated fatty acids, stearidonic acid (SA, C18:4 n-3) and gamma-linolenic acid (GLA, C18:3 n-6) by gas chromatography-mass spectrometry, H-1 nuclear magnetic resonance (NMR) spectroscopy, and C-13 NMR spectroscopy. The yields of SA and GLA from dried seaweed tissue were 6.33 x 10(-3)% and 6.47 x 10(-3)%, respectively. The minimal inhibitory concentration values of SA and GLA were 39.06 mu g/mL against P. intermedia and 9.76 mu g/mL against P. gingivalis, respectively. SA and GLA were also active against several other oral pathogens, including Aggregatibacter actinomycetemcomitans, Candida albicans, Fusobacterium nucleatum subsp. vincenti, and Streptococcus mutans, at micromolar concentrations. Conclusions: These data suggest that the E. linza extracts SA and GLA are useful antimicrobial agents for the prevention and/or treatment of periodontitis.