Phytochemical and biological evaluation of Preskia bleo (Kunth) DC, a plant species used in traditional medicine for the treatment of diabetes

The leaves of Pereskia bleo (pokok jarum tujuh), are being used in Malaysian traditional medicine for the prevention and treatment of breast cancer. In order to validate the use of this plant in breast cancer treatment we have prepared crude extracts of the leaves and assessed them for activity against several breast cancer cell lines such as the MCF-7, MDA-MB231 and against non-tumour 3T3 cells. The crude extracts were also subjected to toxicity test using brine shrimp lethality assay. Dried and milled Pereskia bleo leaves were extracted successively with petroleum ether, chloroform, methanol and distilled water. Extracts of the organic solvent were filtered and the supernatant were concentrated using the rotary evaporator. The aqueous extract was lyophilized. The extracts were screened for the presence of alkaloids, terpenoids, flavanoids and saponins. Activity against Artemia salina was determined using a 96-well microplate method (Solis et al., 1993). Inhibition of growth of cultured cancer cell lines were measured using a standard MTT assay. Cytotoxic drugs, tamoxifen, was used as a positive control against the brine shrimps and cell lines, respectively. All the non-polar extracts of the leaves were found to exhibit significant cytotoxic activities against both the ER positive (MCF7) and ER negative (MDA-MB231) breast cancer cell-lines but. All the extracts were found to be not cytotoxic against the non-tumour (3T3) cells. The non-polar extracts were found to be 2 to 3 times more cytotoxic than the more polar methanol extracts against the ER positive, MCF-7 cells. The strongest cytotoxic activity was observed with petroleum extract with IC50 values of 6.5 μg/ml and 11.5 μg/ml towards MCF-7 and MDA-MB cell lines, respectively. The cytotoxic activities of the petroleum ether and chloroform extracts against the ER negative, MDA-MB231 cell-line are about the same (IC50 19.3 to 26.3 μg/ml ). The cytotoxic activities of the anticancer drug, tamoxifen, against the ER positive and ER negative breast cancer cell lines were found to be 1.3 and 3.5 μg/ml, respectively. The aqueous extract was found to be non-cytotoxic. All the extracts tested were also found to be non-toxic against the brine shrimps up to 2,000 μg/ml of the extracts. This study demonstrated that the non-aqueous extracts of the leaves of Pereskia bleo (Kunth) D.C exhibited a non-selective mode of action against breast cancer cells proliferation in-vitro. Their non-cytotoxic activities toward the non-tumour 3T3 mouse fibroblasts indicates that the extracts exhibited selective mode of inhibition between tumour and non-tumour cells. The results obtained support the reputation of the above species as anticancer plant. Further work to isolate the cytotoxic compounds and to investigate the in vivo antitumour activity in rat is in progress. (Author)