Bromophenols from the Marine Red Alga Symphyocladia latiuscula and Their Radical Scavenging Activity

A new (1) and five known (2-6) bromophenols were isolated from the organic extract of the marine red alga Symphyocladia latiuscula.  Their structures were assigned by interpretation of NMR and MS data, and these compounds were determined as 2,3,5′-tribromo-3′,4,4′,5-tetrahydroxy-diphenylmethane (1), 2-methoxy-3-bromo-5-hydroxymethylphenol (2), 5-(2,3-dihydroxybenzyl)-3,4-dibromobenzene-1,2-diol (3), 5-(2-bromo-3,4-dihydroxy-6-(methoxymethyl)benzyl)-3,4-dibromobenzene-1,2-diol(4), methyl 2-(3,5-dibromo-4-hydroxybenyl) acetate (5), and 3,4-dibromo-5-(methoxymethyl)benzene-1,2-diol (6). All these compounds were evaluated for DPPH radical scavenging activity, and they displayed potent antioxidant activity with IC50 values ranging from 9.6 to 31.5 μM. These compounds also showed moderate ABTS radical scavenging activity with TEAC value ranging from 2.1 to 3.0 mM. The results suggested that these bromophenols or the marine red alga S. latiuscula may have potential application in food as natural antioxidants.