Antioxidant metabolites from the tunicate Amaroucium multiplicatum.

The antioxidant activity-directed analysis of the extract of the colonial tunicate Amaroucium multiplicatum enabled isolation of one novel chromene 2 and two novel hydroquinones 4 and 5, as well as previously reported compounds, as active compounds. Their structures were determined by spectroscopic data (1H nmr, 13C nmr, ms, uv, and ir) and confirmed by chemical synthesis. The isolated compounds were more potent than two standard antioxidants on the inhibitory effects on lipid peroxide formation in rat liver microsomes and on soybean 15-lipoxygenase.