In vitro Antioxidant and Antitumor Activity of Rooibos (Aspalathus linearis) Extract on Colon, Prostate, and Liver Cancer Cells

Rooibos tea (Aspalathus linearis) is recognized for its antioxidant properties, due to distinctive compounds such as aspalathin. This study examined the antioxidant potential of rooibos extract on three cancer cell lines (PC-3, HCT-116, and HepG2) to assess its overall antioxidant potential. Additionally, the inhibitory effect of aqueous rooibos extract at a concentration of 1,000 µg/ml was assessed on the three cancer cell lines. The cytotoxic effects of aqueous rooibos extract and cisplatin were compared for the cancer cell lines, with HepG2 cells showing the highest sensitivity to rooibos extract (IC50 = 1,399.41 ± 62.73 µg/ml) and PC-3 cells displaying the highest resistance (IC50 = 2,431.51 ± 98.71 µg/ml). Cisplatin consistently exhibited lower IC50 values across all cell lines, indicating a stronger inhibitory effect on cancer cell proliferation, notably for HCT-116 (IC50 = 2.53 ± 0.21 µg/ml) and HepG2 cells (IC50 = 3.67 ± 0.25 µg/ml). However, the total antioxidant capacity of rooibos extract (68.91 ± 4.07 mg GAE/g) is comparable to that of the ascorbic acid standard (74.19 ± 3.97 mg GAE/g), showing no statistically significant difference. Moreover, rooibos extract is a potent antioxidant, with lower IC50 values in the DPPH (3.62 ± 0.10 µg/ml), ABTS (2.13 ± 0.13 µg/ml), and H2O2 assays (4.97 ± 0.01 µg/ml) compared to ascorbic acid and EDTA. However, in the metal chelating activity assay, rooibos extract showed a similar performance (IC50 20.89 ± 0.09 µg/ml) to EDTA (IC50 21.16 ± 1.67 µg/ml), suggesting comparable efficacy in this measure. These results demonstrate the strong antioxidant and anticancer potential of rooibos extract, suggesting it as a promising complement in cancer treatment.