Cytotoxicity of Lapachol and Derivatized Analogues from Kigelia africana (Lam.) Benth. on Cancer Cell Lines

Lapachol, a naphthoquinone, was obtained from the methanol extract of the root of Kigelia africana (sausage tree) (Lam.) Benth. and structurally modified to improve anticancer specificity. The structures of the lapachol and derivatives were elucidated following the consideration of spectra data which included mass spectrometry and nuclear magnetic resonance (NMR) techniques. The in vitro cytotoxic activities of the lapachol and its derivatives were evaluated on healthy human prostate (PC-3), human cervical cancer (Hela) and mouse fibroblast (3T3) cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Lapachol exhibited higher cytotoxicity on the Hela cells (IC₅₀ = 6.15 μg mL⁻¹) compared to the derivative molecules. The lapachol was cytotoxic to both cancer and normal cell, while the derivatized conjugates lost the cytotoxic potency to cancer cell. This work provides evidence that supports lapachol as one of the major cytotoxic compounds present in the root of K. africana of Nigerian origin and it is recommended that the extract of the plant should be consumed with caution owing to general cellular toxicity of the major phytoconstituent.