Antitumour and Apoptotic Effects of a Plant Extract Mixture Containing Rhus verniciflua and Other Herbs in Human Leukaemia Cells.

The apoptotic effects of a novel antitumour agent (Rv-PEM01) prepared from 6 kinds of herbs, including Rhus verniciflua were investigated using flow cytometry and western blot analysis. Rv-PEM01 induced apoptosis but not necrosis in MOLT-3, KG-1, and K562 human leukaemia cell lines. Further, Rv-PEM01-treated cells showed significantly upregulated expression of caspase-3 and 9 and cleaved caspase-3 and 9 compared to the control cells. Taken together, the results suggest that Rv-PEM01 induced apoptosis via the mitochondrial-mediated pathway, and is a potential natural anticancer agent and/or a functional food material.

Novel urushiols with human immunodeficiency virus type 1 reverse transcriptase inhibitory activity from the leaves of Rhus verniciflua.

Two novel urushiols, 1 and 2, and two known urushiols, 3 and 4, were isolated from the leaves of Rhus verniciflua and were examined for their human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) inhibitory activity. The novel urushiols were found to be 1,2-dihydroxyphenyl-3-[7'(E),9'(Z),11'(Z)-pentadecatrienyl]-14'-ol (1) and 1,2-dihydroxyphenyl-3-[8'(Z),10'(E),12'(E)-pentadecatrienyl]-14'-ol (2) by spectroscopic analyses. The absolute configuration at C-14' in 1 and 2 was determined to be a racemic mixture of (R) and (S) isomers by ozonolysis. Compound 2 (IC50: 12.6 µM) showed the highest HIV-1 RT inhibitory activity among the four urushiols, being 2.5-fold more potent than the positive control, adriamycin (IC50: 31.9 µM). Although the known urushiols were isolated from the sap and leaves of R. verniciflua, 1 was exclusively present in the leaves, and higher amounts of 2 were found in the leaves than in the sap. Present findings indicate that the leaves of R. verniciflua represent a new biological resource from which novel and known urushiols may be prepared, and the possible use of novel urushiols as bioactive products.

[Antitumor effects of a plant extract mixture].

Cancer is the most common cause of death in Japan. Fundamental and clinical studies on cancer were conducted from the viewpoint of Western medicine so far. However, a sustained complete remission has not been achieved yet. In order to alleviate the side effects of anticancer drugs, some traditional herbal medicines (Kampo medicines) have been prescribed to cancer patients. We have been studying on antitumor substances in medicinal herbs and found an antitumor medicinal herb named Rhus verniciflua (lacquer, Urushi in Japanese). To investigate the antitumor effect in vitro, a plant extract mixture was prepared from six medicinal herbs containing lacquer. The plant extract mixture containing lacquer (Rv-PEM) inhibited the proliferation of several mouse and human tumor cell lines. Rv-PEM had more potent inhibitory effect on the proliferation of human leukemia cell lines (MOLT-3, KG-1) than on other tumor cell lines. The IC50 values of Rv-PEM on MOLT-3 and KG-1 cells were 0.208 and 0.293 mg/mL, respectively. After treating Rv-PEM to the tumor cells, DNA fragmentation and Caspase-3 and -9 activity increased in the treated cells. The mechanisms of the inhibitory proliferation activity of Rv-PEM would involve apoptosis of human leukemia cells (MOLT-3, KG-1, K-562) by the mitochondrial pathway.