Three new cyclobutanoid amides with trans-trans-trans configurations, piperarborenine C, piperarborenine D and piperarborenine E, and a new furanoid lignan, (+)-arborone, together with twelve known compounds, were isolated from the stems of Piper arborescens. The structures of these new compounds were determined by means of spectral analyses. Piperarborenine C, (+)-diayangambin, piplartine, piperolactam B, piperolactam C, aristolactam BIII, goniothalactam, and methyl trans-3,4,5-trimethoxycinnamate possessed anti-platelet aggregation activity in vitro. Among them, piplartine showed the most potent anti-platelet aggregation activity induced by collagen and showed an IC50 value of 21.5 microM. Piperarborenines A - E, piperarborenine, aristololactam BIII and goniothalactam showed significant cytotoxic activity (IC50 values < 4 microg/mL) against P-388, HT-29 and A549 cell lines in vitro.

Two new cyclobutanoid amides, piperarborenine A ( 1,1'-{ [(1a,2a,3b,4b)-2,4-bis(3,4-2) were isolated from the stem of Piper arborescens, besides two known cyclobutanoid amides, piperarboresine ( 1,1'-{[(1a,2a,3b,4b)-2-(7-methoxy-1,3-benzodioxol-5-yl)-4-(3,4,5-trimethoxyphenyl)cyclobutane-1,3-diyl]dicarbonyl}bis[5,6-dihydropyridin-2(1H)-one]; 3) and piplartine-dimer A ( 1,1'-{[(1a,2a,3b,4b)-2,4-bis(3,4,5-trimethoxyphenyl)cyclobutane-1,3-diyl]dicarbonyl}bis[5,6-dihydropyridin-2(1H)-one]; 4). The structures of the two new compounds were determined by spectral analyses.