Phytochemical Analysis, Antioxidant Activity, and Anticancer Potential of Afzelia quanzensis Welw—Bark Extract: A Traditional Remedy Utilized by Indigenous Communities in KwaZulu-Natal and Eastern Cape Provinces of South Africa

Despite the significant advancements in treatment and prevention, the fight against cancer is ongoing worldwide. This study evaluated the pharmacological properties and anticancer activity of Afzelia quanzensis bark, traditionally used by the indigenous communities of KwaZulu Natal and Eastern Cape Provinces of South Africa to treat cancer and related illnesses. Phytochemical screening, high-performance liquid chromatography–diode array detection (HPLC-DAD), and Fourier-transform infrared spectroscopy (FTIR) analyses were carried out using established protocols. The antioxidant activity was assessed via the 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging capacity and nitric oxide radicals. The anticancer activity was evaluated using the MTT assay (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide). Phytochemical analysis revealed the presence of saponins, flavonoids, terpenoids, alkaloids, steroids, cardiac glycosides, and phlobatannins. The HPLC-DAD analysis detected seven distinctive peaks in the aqueous extract and three distinctive peaks in the methanolic extract. The FTIR spectra of the aqueous extract displayed characteristic peaks corresponding to O-H, C=O, C=C, and =C–H functional groups. Among the tested extracts, the methanol extract exhibited the strongest antioxidant activity, followed by the ethanolic extract, in both DPPH and nitric oxide. The methanol extract showed a higher cell proliferation inhibition against the DU-145 cancer cell line with the percentage of inhibition of 37.8%, followed by the aqueous extract with 36.3%. In contrast, limited activity was observed against PC-3, SK-UT-1, and AGS cell lines. The results demonstrated notable dose-dependent antioxidant and antiproliferative activities supporting the ethnomedicinal use of Afzelia quanzensis bark in cancer management. These findings warrant further investigation into its bioactive constituents and mechanisms of action.