Identification and evaluation of apoptotic compounds from Garcinia oligantha

Four new compounds, oliganthins A-D (1-4), and one known caged xanthone gaudichaudione H (5) were isolated from the stems of Garcinia oligantha. The structures of the new compounds were elucidated by spectroscopic evidences. All of the five compounds were evaluated for their apoptosis-inducing effects using HeLa-C3 cells which have been genetically engineered to produce a fluorescent biosensor capable of detecting caspase-3 activation. All of them induced cell apoptosis at 10 mu M or lower concentrations. The apoptotic activity of oliganthins A, B and gaudichaudione H were further confirmed by detecting the cleavage of PARP, which is the substrate of activated caspase-3, in these compounds-treated cells using the method of Western blot. Moreover, the values of IC50 were measured for all five compounds on HeLa cells using the MTT assay. Among them, gaudichaudione H had the lowest IC50 value of 0.90 mu M, while the other four new compounds had IC50 values of 1.58, 1.52, 4.15, and 7.82 mu M, respectively. These results show that gaudichaudione H has the strongest apoptosis-inducing effect and cell growth inhibition effect among these xanthones and it may have the potential to be developed into a new anticancer agent. (C) 2012 Elsevier Ltd. All rights reserved.