inhibition of monoamine oxidase by stilbenes from rheum palmatum

seven stilbenes and one catechin were bioactivity-guidedly isolated from the rhizomes of rheum palmatem. their structures were identified as piceatannol(1), resveratrol(2), piceid(3), rhapontigenin(4), piceatannol-3'-o-β-d-glucopyranoside(5), rhaponticin(6), catechin(7) and desoxyrhapontigenin(8). anti-monoamine oxidase (mao) activities of compounds 1–8 were tested. compounds 1 and 8 showed significant mao inhibitory activities with ic50 values 16.4±1.5 μm and 11.5±.1.1, respectively, when the ic50 value of iproniazid as a standard was 6.5 ±0.5 μm. the selectivity of compounds 1-8 against mao-a and mao-b were also evaluated. the results showed that compounds 4、6、8 preferred to inhibit mao-a rather than mao-b with selectivity values ([ic50 of mao-b]/ [ic50 of mao-a]) of 4.74, 10.01 and 9.42, respectively . the preliminary structure–activity relationships (sars) of these compounds were discussed and the molecular modeling was also performed to explore the binding mode of inhibitors at the active site of mao-a and mao-b.