Collinin, which was isolated from the leaves of Zanthoxylum schinifolium, could exert cytotoxic effect on various human tumor cells with IC50 values in the range of 38.1-111.6 mu M, whereas the IC50 value for human normal mammary epithelial MCF-10A cells was 124.4 mu M. To examine the contribution of apoptosis to the cytotoxicity of collinin toward tumor cells, collinin-induced apoptotic events of Jurkat T cells transfected with vector (JT/Neo) were compared with those of Jurkat T cells transfected with Bcl-2 gene (JT/Bcl-2). Treatment of JT/Neo cells with collinin (30-60 mu M) resulted in induction of sub-G(1) peak representing apoptotic cells along with activation of Bak and Bax, mitochondrial membrane potential (Delta psi(m)) loss, activation of caspase-9, -3, -8, and -7, degradation of PARP, and DNA fragmentation dose-dependently, but these apoptotic events were abrogated by overexpression of Bcl-2, which could prevent the induced activation of Bak and Bax, and subsequent mitochondrial damage. Under these conditions, necrosis was not accompanied. Pretreatment of JT/Neo cells with the pan-caspase inhibitor z-VAD-fmk completely blocked collinin-induced apoptotic sub-G(1) cells and caspase cascade activation, whereas it failed to suppress Bak activation and Delta psi(m) loss. Neither FADD-deficiency nor caspase-8-deficiency affected the susceptibility of Jurkat T cells to collinin-induced cytotoxicity and apoptotic cell death. These results demonstrate that the apoptogenic activity of collinin was mediated by the intrinsic mitochondrial apoptotic pathway which was preceded by activation of pro-apoptotic multidomain Bcl-2 family members Bak and Bax, mitochondrial damage, and resultant activation of caspase cascade, leading to PARP degradation, which could be regulated by Bcl-2. (C) 2013 Elsevier Ltd. All rights reserved.