Antioxidant and Antiproliferative Activities of Plant Derived Extracts against Cervical and Prostate Cancer Cell Lines

Abstract

Cancer is the third largest cause of mortality in Kenya. Treatment options available for cancer include chemotherapy, radiation and surgical procedures but none presents with minimal side effects and high cure rates. Therefore there is a need to explore new therapies for cancer. For a long time, plants have been used to manage tumor and related ailments in Kenya. The aim of this study was to determine the antioxidant, antiproliferative, acute toxicity and phytochemical composition of organic and aqueous extracts of Azadirachta indica, Vernonia amygdalina and Galium aparinoides. The in vitro antioxidant activity was determined using DPPH (1, 1- diphenyl-2-picrylhydrazyl) radical scavenging assay. Antiproliferative activity was determined against cervical (Hela), prostate (DU145) and Vero (L6) cancer cells lines using MTT (3-(4, 5-Dimethylthiazol-2-yl)-2, 5-Diphenyltetrazolium Bromide) assay method and the IC50 (Inhibitory concentration) values reported. Cytotoxicity was determined using L6 and CC50 (Cytotoxicity concentration) values calculated. Further, the active extracts were combined and assayed in vitro using the checkerboard method. Acute oral toxicity was evaluated using (OECD) Organisation of economic cooperation and development guidelines and the lethal dose (LD50) determined. The acute toxicity was carried out on bioactive plant extracts with the highest selectivity index (SI). A. indica exhibited the greatest antioxidant activity with the methanol extracts of the stem bark having an IC50 value of 69.31 µg/ml, comparable to the positive control of ascorbic acid which had an IC50 value of 42.74 µg/ml. V. amygdalina highest antioxidant activity was observed in methanol stem parts with an IC50 value of 430.8 µg/ml and all G. aparinoides extracts had IC50 value >500 µg/ml. In the antiproliferative assay, methanol root bark and stem bark extracts of A. indica reported IC50 values of 1.85 ± 0.01 µg/ml and 2.59 ± 0.29 µg/ml respectively, against Hela cancer cell line and IC50 values of 1.53± 0.07µg/ml and 3.26±0.28µg/ml respectively, against DU145 cancer cell line. The results were comparable with the untreated cells (negative control) and 5-Fluorouracil (5-FU), (positive control) with IC50 values of 2.04 ± 0.87µg/ml and 5.06± 0.28 µg/ml against Hela and DU145 cell lines, respectively. Methanol extract of V. amygdalina aerial parts had IC50 values of 430.67 ± 1.17µg/ml and 301.8± 0.93µg/ml 7 µg/ml in Hela and DU145 cell lines, respectively. Notably, the methanol stem bark extract of A. indica had a high SI index of 436.52, an indication that the cytotoxic effect of this extract was selective to cancerous cells. In combination assay, all combinations showed synergistic activity except for ethylacetate stem and root bark extracts of A. indica against DU 145 cell line. Oral administration of methanol root bark extracts of A. indica in mice at the highest dose of 2000 mg/kg body weight demonstrated no mortalities and no adverse effects suggesting that these extracts were non-toxic. Methanol stem bark extracts of A. indica on the other hand revealed acute toxicity. All the three plants contained alkaloids, phenolics, flavonoids tannins and terpenoids. The findings of the study demonstrate the potential of A. indica in management of cancer and particularly the methanol extracts from the root bark of A. indica have great potential as a valuable alternative source for anticancer agent