Three new antioxidant C-glucosylanthrones from Aloe nobilis

Three new C-glucosylanthrones, 3'-O-acetyl-5-hydroxylaloin A (2), 2',6'-O-diacetyl-5-hydroxylaloin A (4), and 4',6'-O-diacetyl-5-hydroxylaloin A (5), along with three known compounds, 5-hydroxyaloin A (1), 6'-acetyl-5-hydroxylaloin A (3), and 4-methoxy-6-(2',4'-dihydroxy-6'-methylphenyl)-pyran-2-one (6), were isolated from the leaves of Aloe nobilis, and their structures were elucidated on the basis of spectroscopic evidences. Compounds 1, 2, 4 and 5 showed antioxidant activity with inhibitory rates of 31.0, 34.0, 34.0, and 42.0%, respectively, at 10(-5) M.