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[摘要]：Seven proanthocyanidins (2-8) together with epicatechin (1) were isolated from the EtOH extract of the leaves of Machilus philippinensis. Of these, machiphilitannins A (7) and B (8) are new natural products, with respective IC50 values of 31.3 (7) and 18.4 mu M (8) against alpha-glucosidase type IV from Bacillus stearothermophilus. Their structures were elucidated mainly on the basis of CD and 2D NMR analyses. In addition, aesculitannin B (2) showed inhibitory activity against alpha-glucosidase with an IC50 value of 3.5 mu M. This work demonstrates for the first time that the purified proanthocyanidins possess inhibitory activity against alpha-glucosidase type IV. |
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