Antioxidant Flavonoids from Asteriscus Maritimus
One new flavonol glycoside, patuletin-7- O-[6- O-caffeoyl-2- O-[(S)-3-hydroxyisobutanoyl]glucopyranoside] (astermaritimoside) (1) and four known flavonoids, patuletin-7- O-β-[-6- O-[( S)-3-hydroxyisobutanoyl]glucopyranoside] (2), patuletin-7- O-[6- O-caffeoylglucopyranoside] (3), patuletin-7- O-β-D-glucopyranoside (4) and quercetin-3- O-β-rutinoside (5) have been isolated from Asteriscus maritimus (L.) Less. Chemical structures were elucidated by mass spectrometric, and 1H NMR, 13C NMR, COSY, HMQC and HMBC spectroscopic techniques. The antioxidative effect was evaluated using an electronic spin resonance (ESR) method in order to visualize the inhibition of the DPPH radical. The n-butanol fraction was found to possess a remarkable antioxidant activity that was correlated with the total amount of phenolics. The isolated compounds exhibited good antioxidant activity.