Magnone A and B, novel anti-PAF tetrahydrofuran lignans from the flower buds of Magnolia fargesii

In a search for platelet-activating-factor (PAF) antagonists, two new lignan compounds were isolated from the Chinese crude drug shin-i, the flower buds of Magnolia fargesii. Their structures were elucidated as (2S,3R,4R)-tetrahydro-2-(3,4-dimethoxyphenyl)-4-(3,4-dimethoxybenzoyl)-3-(hydroxymethyl)furan (magnone A, 1) and (2S,3R,4R)-tetrahydro-2-(3,4,5-trimethoxyphenyl)-4-(3,4-dimethoxybenzoyl)-3-(hydroxymethyl)furan (magnone B, 2). Magnones A and B showed antagonistic activity against PAF in the [H-3]PAF receptor binding assay with the IC50 values of 3.8 x 10(-5) M and 2.7 x 10(-5) M, respectively.