Developmental toxicity of the anthraquinone dye alizarin to zebrafish: Effects on development and behaviour

There is a push for development of more ecologically friendly alternatives to synthetic dyes, with the natural anthraquinone dye alizarin (1,2-dihydroxyanthraquionone) representing a promising alternative. However, the toxicity of alizarin is not well characterized. The present study investigated the effects of alizarin on zebrafish (Danio rerio) embryos, including potential mechanisms of toxicity. Alizarin caused dose-dependent increases in mortality, developmental malformations, and altered behavioural responses to photokinetic stimuli. Zebrafish exposed to alizarin had increased transcript abundance of genes important for the response to oxidative stress, suggesting oxidative stress contributes to toxicity. Additionally, alizarin activated the aryl hydrocarbon receptor (AhR) in an in vitro AhR transactivation assay, and in vivo, suggesting that the toxicity could be partly AhR-mediated. These results highlight a need for further investigation into the contribution of AhR-mediated and oxidative stress mediated toxicities following exposure to alizarin and highlight the potential adverse effects on biota despite being a natural dye.