RESUMO
The present study was designed to determine the chemical constituents of the stems and hooks of Uncaria rhynchophylla. The chemical constituents were isolated and purified from CH2Cl2 fraction by chromatography. Their structures were elucidated by spectroscopic analyses. Their cytotoxicity was tested using MTT method. Two new ortho benzoquinones, 3-diethylamino-5-methoxy-1, 2-benzoquinone (1) and 3-ethylamino-5-methoxy-1, 2-benzoquinone (2), together with a known compound isorhynchophyllic acid (3) were isolated from U. rhynchophylla. These compounds were evaluated for their cytotoxicity against cancer cells A549, HepG2 and A2780. Compounds 1 and 2 were new ortho benzoquinones and showed weak antiproliferative activities on A549, HepG2 and A2780 cells. Compound 3 significantly inhibited the proliferation of A549, HepG2 and A2780 cells with IC50 values being 5.8, 12.8 and 11.8 µmol·L(-1), respectively.