A new lignan from the flowers of Hibiscus sabdariffa L. (Malvaceae).

From MeOH-soluble fraction of the flowers of Hibiscus sabdariffa (Malvaceae), one new lignan, (+)-4-O-methyl-5'-methoxy-secoisolariciresinol (1), together with four known compounds (2-5) were isolated. The structures were elucidated based on NMR spectroscopic analysis. The absolute configuration of 1 was determined based on the Cotton effects in the CD spectrum. Compounds 1, 3 and 4 showed antioxidant activities with the SC50 values of 56.9, 19.3 and 22.7 µM, respectively.