Amides with anti-platelet aggregation activity from Piper taiwanense

Three new amides, taiwanamides A-C (1-3), and two known amides, 1-cinnamoylpyrrolidine (4) and 1-(m-methoxycinnamoyl)pyrrolide (5), have been isolated from the stem of Piper taiwanense. The structures of the new amides were determined by spectral analyses. These five amides exhibited inhibitory activity of platelet aggregation in vitro. Taiwanamide C (3) owned the most potent inhibition activity of platelet aggregation induced by collagen showing IC50 value as 8.9 μM. Taiwanamide B (2) and 1-(m-methoxycinnamoyl)pyrrolide (5) exhibited IC50 values of 17.3 and 17.4 μM, respectively.