Four undescribed amide alkaloids hongkongensines A -C and 1-(1-oxo-6-hydroxy-2 E ,4 E -dodecadienyl)-piperi- dine, five known amide alkaloids, and three known neolignans were isolated from the aerial part of Piper hongkongense . The planar structures of these compounds were determined by detailed analyses of HR-ESI-MS and NMR data. The absolute configurations of hongkongensines A -C were elucidated by single-crystal X-ray diffraction analysis and ECD calculations. Moreover, the inhibitory activities of PCSK9 expression in vitro for all compounds were assessed by PCSK9 AlphaLISA screening. Kadsurenone ( 10 ) displayed a significant inhibitory activity at 5 mu M with an inhibition rate of 51.98%, compared with 55.55% of berberine (BBR 5 mu M).