Anti-proliferative Activity of Prunus africana, Warburgia stuhlmannii and Maytenus senegalensis Extracts in Breast and Colon Cancer Cell Lines

Abstract

Aims: To determine the anti-proliferative activity of Prunus africana, Warburgia stuhlmannii and Maytenus senegalensis in breast and colon cancer cell lines and to assess their toxicity levels based on responses against Vero cells and the Swiss albino mice. Study Design:  Experimental laboratory-based study. Place and Duration of Study: Centre for Traditional Medicine and Drug Research, Kenya Medical Research Institute, between May 2013 and May 2014. Methodology: 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 drugs 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). Results: The safest and effective drugs were methanol extracts of leaves from Prunus africana whose results showed an average IC50 of 164.64±4.14 µg/ml in the breast cancer cell lines and 21.33±0.5 µg/ml in the colon cancer cell lines, as well as the stem bark water extracts from Warburgia stuhlmannii, whose results showed an average IC50 of 332.79±7.53 µg/ml in the breast cancer cell lines and 107.20±2.50 µg/ml in the colon cancer cell lines. Both extracts had an average CC50 of >1000 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 drug administration with LD50 of >5000 mg/kg body weight, therefore the extracts were considered to be safe. Conclusion: The methanol extract from the leaves of Prunus africana and the water extracts from the stem bark of Maytenus senegalensis were safe for use in the murine model. These extracts also showed a level of anti-proliferative activity in both breast and colon cancer cells without being toxic to Vero cells. This information forms a basis for the development of the extracts as safer alternative therapies for the management of cancer.