Screening of Selected Ghanaian Medicinal Plants for Anti-Prostate Cancer Activity

Abstract

Introduction: Prostate cancer is a major disease that affects adult males. The high cost of current drugs in use, treatment failure/drug resistance as well as toxic side effects warrants the development of more effective, less toxic and affordable anti-prostate cancer drugs. The aim of the study was to investigate the anti-prostate cancer properties of selected Ghanaian medicinal plants used for the management of prostate cancer. Method: The leaves, fruit and seeds of selected plants claimed to have anti-prostate cancer properties were collected, dried and crushed. Each sample was sequentially extracted with solvents of increasing polarity (petroleum ether, dichloromethane, ethyl acetate, ethanol and aqueous) using cold maceration. The phenolic substances in the plants were determined by the Folin-Ciocalteau method. Antioxidant and anti-proliferative activities were determined using DPPH and MTT assays, respectively. Results: Nine medicinal plants namely, Latuca sativa, Tetrapleura tetraptera, Jatropha curcas, Capparis erythrocarpus, Ficus asperifolia, Mentha piperita, Carica papaya, Moringa oleifera and Phyllanthus amarus were identified. Among them, the ethanolic extract of P. amarus recorded the highest (92.71g GAE/100g) level of phenolic substances. The aqueous and ethanolic extracts of P. amarus showed the strongest antioxidant activities (EC50values of 19.32 ± 1.13μg/ml and 60.03 ±1.07μg/ml, respectively). Ethyl acetate extract of Latuca sativa and Mintha piperita also showed significant (p<0.05) antioxidant activities (EC50=121.4± 1.07 μg/ml, 91.13% and EC50=129.7± 1.07 μg/ml, 88.37%, respectively) but did not meet the 100 μg/ml limit cut off for consideration as strong antioxidants. Most of the plant extracts significantly inhibited proliferation of LNCaP and PC3 prostate cancer cell lines compared to normal prostate (PNT2) cells. The ethyl acetate extract of whole Tetrapleura tetraptera fruit showed the highest cytotoxic activity and was selective to PC3 (IC50 =5.39 ± 1.24 μg/ml, SI=7.72)and LNCaP (IC50=8.38±1.27μg/ml, SI=4.97) Conclusion: All the plants contained phenolic substances and had antioxidant activities. All the samples demonstrated anti-proliferative activities with ethyl acetate extract ofwhole Tetrapleura tetraptera exhibiting the strongest anti-proliferative activity against LNCaP and PC3 prostate cancer cell lines. Recommendation: Future studies should focus on investigating the phytochemical profile of Tetrapleura tetraptera, isolating the bioactive compounds responsible for the anti-prostate cancer activity and understanding the mechanisms involved in their anti-proliferative activity against LNCaP and PC3 cancer cells. Keywords: Medicinal plants, Secondary metabolites, DPPH, Antioxidants, Total phenolic content.