Differential toxicity and teratogenic effects of the hot water and cold water extracts of Lignosus rhinocerus (Cooke) Ryvarden sclerotium on zebrafish (Danio rerio) embryos

Ethnopharmacological relevance: The sclerotium of Lignosus rhinocerus (Cooke) Ryvarden is highly valued for its purported medicinal properties. The decoction and macerated materials prepared from the sclerotium are used for treating cancer and other ailments based on extensive traditional knowledge. Scientific evidence from in vitro cytototoxicity, anti-inflammatory and immunomodulatory analyses showed the effectiveness of sclerotial water extracts but toxicity assessment of such preparations has not been reported. Aim of the study: This study aimed to compare the differential toxicity and teratogenicity (if any) of the hot water (HW) and cold water (CW) extracts of both wild and cultivated sclerotium on zebrafish (Danio rerio) embryos. Materials and methods: Zebrafish embryos were treated with varying concentrations of the sclerotial HW and CW extracts (0.3-500 mu g/mL) for 72 h until hatching. The hatching, mortality and heartbeat rate of the embryos as well as the potential teratogenic effect of the extracts were assessed in embryos post-treatment with the extracts. Results: While the sclerotial HW extracts were nontoxic (LC50 > 500 mu g/mL), the sclerotial CW extracts delayed the hatching of the embryos up to 48 h and showed slight toxicity with LC50 values of 398.4 mu g/mL and 428.3 mu g/ mL for the cultivated and wild sclerotium, respectively. The sclerotial CW extracts also induced minor tachycardia in zebrafish larvae. Phenotypic assessment revealed that, while yolk sac edema was observed at high concentrations (300 and 500 mu g/mL) of all extracts, curved trunk and bent tail were only observed in the embryos treated with CW extracts of wild sclerotium (300 and 500 mu g/mL) but not for CW extracts of cultivated sclerotium at similar concentrations. Conclusion: The sclerotial water extracts of L. rhinocerus prepared using different methods have varying degree of toxicity and teratogenicity in zebrafish embryos with the sclerotial CW extracts showed higher toxicity than the HW extracts.