New antioxidant polyphenols from the medicinal mushroom Inonotus obliquus

Three new free radical scavengers, inonoblins A ( 1), B ( 2), and C ( 3), were isolated from the methanolic extract of the fruiting body of the medicinal mushroom Inonotus obliquus, along with the known compounds phelligridins D ( 4), E ( 5), and G ( 6). Their structures were established by extensive spectroscopic analyses. These compounds exhibited significant scavenging activity against the ABTS radical cation and DPPH radicals, and showed moderate activity against the superoxide radical anion. The fruiting body of Inonotus obliquus, a medicinal mushroom called chaga, has been used as a traditional medicine for cancer treatment. Although this mushroom has been known to exhibit potent antioxidant activity, the mechanisms responsible for this activity remain unknown. In our investigation for free radical scavengers from the methanolic extract of this mushroom, inonoblins A ( 1), B ( 2), and C ( 3) were isolated along with the known compounds, phelligridins D ( 4), E ( 5), and G ( 6). Their structures were established by extensive spectroscopic analyses. These compounds exhibited significant scavenging activity against the ABTS radical cation and DPPH radical, and showed moderate activity against the superoxide radical anion.