Antioxidant Hispidin Derivatives from Medicinal Mushroom Inonotus hispidus

Two natural antioxidants, named inonotusin A (1) and B (2), were isolated from the methanolic extract of the fruit bodies of Inonotus hispidus, together with (E)-4-(3,4-dihydroxyphenyl)but-3-en-2-one (3), hispidin (4) and 3,4-dihydroxybenzaldehyde (5). Their structures were identified by means of extensive NMR and MS data analysis. Compounds 1, 2 and 4 exhibited significant scavenging activity against the 2,20-azinobis(3-ethylbenzhiazoline-6-sulfonate) (ABTS) radical cation. Compound 1 also showed moderate cytotoxicity against a human breast carcinoma cell line (MCF-7) with IC50 values of 19.6 μM.