Comparative study of the antioxidant and cytotoxicity activities of organs of Kigelia africana and their topoisomerase I inhibitory activities

Abstract

Kigelia africana (Lam.) Benth. is a Bignoniaceae African tree that has diverse medicinal uses. This work aimed to examine the cytotoxicity, antioxidant, and topoisomerase inhibitory effects, as well as the total phenolic and flavonoid contents of four main organs of K. africana. The cytotoxicity of leaves, flowers, fruits and bark extracts was evaluated against two cancer cell lines; human prostate cancer (PC-3) and human cervical carcinoma (Hela), and a normal cell line; normal fibroblasts of baby hamster kidney (BHK-21). Of the ethanol extracts tested, total phenolic content was the highest in K. africana leaves followed by fruits, whereas total flavonoid content was the highest in fruits followed by leaves. Fruits and leaves ethanolic extracts displayed the best antioxidant activity (IC50 1.8 and 3.59 µg/ml, respectively) followed by bark extract (IC50 5.39 µg/ml). Leaves and bark ethanol extracts demonstrated an interesting safety profile with reasonable selectivity index values on both PC-3 and Hela cell lines, and were then subjected to fractionation. The leaves methylene chloride fraction showed the best cytotoxic activity against PC-3 and Hela cells with IC50 values of 27.41 and 42.40 μg/ml, respectively, the same fraction also displayed the highest inhibitory activity against Topo I with an IC50 value of 10.71 μg/ml. Furthermore, the phytochemical profile of the same extracts and fractions of K. africana was explored using liquid chromatography-mass spectrometry (LC-MS) revealing the presence of phenolic acids, iridoid glycosides, phenylpropanoid glycoside and fatty acids. More in-depth investigations are recommended to define the cytotoxic potential of pure isolated compounds from K. africana.