Study on Antioxidant and Toxicity Evaluation of Xanthone Crude Extract on Hypoxic Human Hepatocellular Carcinoma and Zebrafish (Danio rerio) Embryos

In this study, we evaluated the effects of xanthone crude extract (XCE) and α-mangostin (α-MG) on
normoxic and hypoxic human hepatocellular carcinoma (HepG2) cells and their toxicity towards
zebrafish embryos. XCE was isolated using a mixture of acetone and water (80:20) and verified via
high performance liquid chromatography (HPLC). The antioxidant activities of both XCE and α-MG
compounds were determined where α-MG had the lowest antioxidant activities followed by XCE and
ascorbic acid, (IC50 = >50 μg/mL, 8.25 ± 0.2, and 2.88 ± 0.02 μg/mL, respectively). XCE and α-MG
showed higher anti-proliferation effects on normoxic HepG2 cells compared to the control drug, 5-
fluorouracil (IC50 = 50.23 ± 1.38, 8.39 ± 0.14, and 143.75 ± 15.31 μg/mL, respectively). In hypoxic
conditions, HepG2 cells were two times less sensitive towards XCE compared to normoxic HepG2
cells (IC50 = 109.38 ± 1.80 μg/mL) and three times less sensitive when treated with >500 μg/mL 5-
fluorouracil (5-FU). A similar trend was seen with the α-MG treatment on hypoxic HepG2 cells (IC50 =
10.11 ± 0.05 μg/mL) compared to normoxic HepG2 cells. The effect of XCE and α-MG extracts on
normal cell migration were determined. The highest and lowest percentage of migration ability for
XCE was found to be 66.80% (25 μg/mL) and 15.91% (100 μg/mL), respectively. Similar trend was
also observed with the highest percentage of migration ability for α-MG was found to be 85.73%
(3.13 μg/mL) while the lowest at 12.08% (25 μg/mL). At a concentration of 12.5 μg/mL, the α-MG
treatment caused tail-bend deformities in surviving zebrafish embryos, while no malformation was
observed when embryos were exposed to XCE and 5-FU treatments. Our study suggests that both
XCE and α-MG are capable of inhibiting HepG2 cell proliferation during normoxic and hypoxic
conditions, more effectively than 5-FU. Both XCE and α-MG treatments showed similar reduction in
the percentage of inflammation response towards Reactive Oxygen Species (ROS) in zebrafish
embryos as compared to ascorbic acid at predetermined dose of 87.42±0.54% for 15.63 μg/mL,
88.12±0.86% for 3.13 μg/mL and 85.57±0.44% for 8μg/mL, respectively. In conclusion, XCE is more
preferable compared to α-MG as it was observed to not caused teratogenicity, while similarly
performed to inhibit cancer cells, promote normal cell migration at lower concentration and reduces
radical molecules.