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 IC(50) value as 8.9 microM. Taiwanamide B (2) and 1-(m-methoxycinnamoyl)pyrrolide (5) exhibited IC(50) values of 17.3 and 17.4 microM, respectively.