Safety and anti-proliferative activity of Prunus africana, Warburgia stuhlmannii and Maytenus senegalensis extracts in breast and colon cancer cell lines

Abstract

Cancer is the leading cause of death worldwide. In Kenya, different cancer cases have been witnessed all over the country. The emphasis of diseases like malaria, Human Immunodeficiency Virus (HIV) and tuberculosis has resulted in the neglect of non-communicable diseases like cancer. This is characterized by lack of awareness, inadequate facilities, qualified personnel and financial shortages. Locally, majority of the population relies on traditional medicine as an alternative treatment since the conventional health system provides for only 30% of the population. Although medicinal plants in Kenya have been used for treatment of cancer by the traditional healers, there are no reports of studies carried out to verify their healing claims as well as their safety. The objective of this study was to determine the safety and anti-proliferative activity of Prunus africana, Warburgia stulhamannii and Maytenus senegalensis extracts in breast (4T1 ATCC®CRL-2539TM) and colon (ATCC® CRL-2638TM) cancer cell lines. The in vitro assays involved determination of the cytotoxic concentration levels (CC50) of the plant extracts on Vero cells as well as calculating the inhibitory concentration (IC50) of the plant extracts on breast and colon cancer cell lines.The extracts with the highest selectivity index (SI) to have low IC50 in the breast and colon cancer cell lines and high CC50 in Vero cells were used in the in vivo assays which involved acute oral toxicity studies, conducted on 8 weeks old Swiss albino mice to calculate the median lethal dose (LD50). The safest effective extracts were of leaf methanol extracts of leaves from Prunus africana whose triplicate results showed an average IC50 of 164.64±4.14 (n=3) µg/ml in the breast cancer cell lines and 21.33±0.5 (n=3) µg/ml in the colon cancer cell lines, as well as the stem bark water extracts from Warburgia Stuhlmanniiwhose triplicate results showed an average IC50 of 332.79±7.53 (n=3) µg/ml in the breast cancer cell lines and 107.20±2.50(n=3) µg/ml in the colon cancer cell lines.

Both extracts had an average CC50 of >1000 (n=3) µg/ml in Vero cells. Based on positive cytotoxicity results on the two extracts, acute oral toxicity studies were conducted on 8 weeks old female Swiss albino mice. This revealed no signs of acute toxicity after administration with LD50 of >5000mg/kg body weight, therefore the extracts were considered to be practically non-toxic. The findings of this study may form basis for the development of a candidate drug that is effective, less toxic and more affordable.