Chemopreventive and anti-breast cancer activity of compounds isolated from leaves of Abrus precatorius L.

The present study focuses on isolation and evaluation of the anti-cancer activity of compounds from the leaves of Abrus precatorius. The bioassay-directed strategy was adopted using chromatographic, gas chromatographic-mass spectrum analysis, nuclear magnetic resonance and X-ray crystallography techniques for purification and characterization of active cytotoxic compounds. Further, MDA-MB-231 breast cancer cell lines and 7,12-dimethylbenz (a) anthracene (DMBA) induced virgin female Sprague Dawley (SD) rats were used for in vitro and in vivo cytotoxicity evaluation. Stigmasterol hemihydrate and 9,12-Octadecadienoic acid (Z,Z)-2-hydroxy-1-(hydroxymethyl)ethyl ester or (β-monolinolein) were the two main cytotoxic constituents of leaf extract of A. precatorius, with an IC50 value of 74.2 and 13.2 µg/ml, respectively, in MDA-MB-231 cells. Additionally, the treatment with the stigmasterol and β-monolinolein as a combinatorial drug therapy in DMBA-induced female SD rats led to recovery of body weight, decreased tumor weight and volume, without any toxic side effects. Immunohistochemical examination showed extensive cell death and low proliferation in the treated tumor tissues that was confirmed by results from H and E staining, TUNEL assay and Ki-67 index as compared to control animal group. The reversion of glycoprotein, lysosomal and tumor marker enzyme levels back to near-normal levels after treatment with the plant compounds clearly demonstrated the reduction of tumor burden in these animals. This is the first report on isolation and characterization of the two active cytotoxic components from leaves of A. precatorius. Additionally, the profound cytotoxic and tumor-suppressive effect of these two compounds as a combinatorial therapy provide an alternative option for breast cancer treatment.