methoxylated fatty acid isolated from the brown seaweed Ishige okamurae inhibits bacterial phospholipase A

A methoxylated fatty acid that inhibits phospholipase A₂ (PLA₂; EC 3.1.1.4) was purified from the brown seaweed Ishige okamurae. Approximately 8.1 mg of the inhibitory compound, 7-methoxy-9-methylhexadeca-4,8-dienoic acid, was isolated from 1 kg of I. okamurae powder. Recombinant PLA₂ derived from the pathogenic bacterium Vibrio mimicus was used as the target enzyme. The methoxylated fatty acid compound competitively inhibited PLA₂ with a Ki value of 3.9 μg/mL. The concentrations required for 50% inhibition of PLA₂, oedema and erythema were 1.0 μg/mL, 3.6 mg/mL and 4.6 mg/mL, respectively. The compound strongly inhibited PLA₂ activity in vitro and had potent antiinflammatory activity in vivo. Copyright © 2008 John Wiley & Sons, Ltd.