Peroxynitrite-scavenging constituents from the brown alga Sargassum thunbergii

Peroxynitrite formation in vivo is implicated in numerous human diseases and there is considerable interest in the use of antioxidants and natural products for their treatment. The three components (1-3) isolated from Sargassum thunbergii as well as the organic solvent-soluble fractions and the aqueous layer of S. thunbergii were evaluated for their potential to scavenge authentic ONOO- and ONOO- derived from 3-morpholinosydnonimine (SIN-1). The antioxidant activity of the individual fractions was in the order of 85% aqueous (aq.) MeOH > n-BuOH > n-hexane > H2O. The three known compounds, sargahydroquinoic acid (1), sargaquinoic acid (2) and sargachromenol (3) showed peroxynitrite-scavenging activities comparable to those of L-ascorbic acid and penicillamine. These results showed a possible antioxidant activity in major constituents of S. thunbergii.