Evaluation of the structure-activity relationship of flavonoids as antioxidants and toxicants of zebrafish larvae

The antioxidant ability of an array of commercially available flavonoids was evaluated on the larvae of the zebrafish model organism, in order to find flavonoids with lower toxicities and higher radical oxygen-scavenging properties than flavone. Among the flavonoids tested, chrysin and morin possessed higher reactive oxygen species (ROS)-scavenging rates (-99% and -101%, respectively) and lower toxicity (LD₅₀ > 100 ppm). Zebrafish fins in the UVB + chrysin group were 6.30 times more likely to grow to normal fin size than those in the UVB-only control group, while zebrafish fins in the UVB + morin group were 11.9 times more likely to grow to normal fin size than those in the UVB-only control group. These results were analysed by the QSAR method and were in accordance with predicted values. A new 4′-fluoroflavone was synthesised. The ROS-scavenging rate of 4′-fluoroflavone was -54%, which corresponds well with the predicted value (-48%). We propose that a combination of QSAR prediction and the zebrafish model organism is efficient for evaluating new flavonoids.