One undescribed amide, pipermullesine A, two undescribed isoquinoline alkaloids, pipermullesines B and C, and six undescribed dipeptides, pipermullamides A-F, along with 28 known compounds, were isolated from the aerial parts of Piper mullesua. The structures of the undescribed compounds were elucidated based on the analysis of 1D and 2D NMR and MS data. Furthermore, the structures of pipermullesines A-C were confirmed by single crystal X-ray diffraction analysis. All isolates were evaluated for inhibitory activity against platelet aggregation induced by thrombin (IIa) or platelet-activating factor (PAF). (-)-Mangochinine, pellitorine, and (2E,4E)-N-isobutyl-2,4-dodecadienamide showed weak inhibitory activity against rabbit platelet aggregation induced by PAF, with IC50 values of 470.3 µg/mL, 614.9 µg/mL, and 579.7 µg/mL, respectively.
Keywords: Amides; Antiplatelet; Isoquinoline alkaloids; Piper mullesua; Piperaceae.