Safety assessment of the standardized aqueous extract from solid-state cultured Xylaria nigripes (Wuling Shen) in rats

Background Xylaria nigripes (Koltz.) Cooke, also known as Wuling Shen, is a high-value medicinal mushroom. It is a herbal medicine traditionally used for treating insomnia, trauma and depression. However, its toxicity has never been systematically evaluated. This study aimed to evaluate the safety of a standardized aqueous extract (XNE), an ingredient of commercial products, prepared from solid-state cultured X. nigripes in rats. Methods A 90-day subchronic toxicity study was conducted by oral administration of XNE at daily doses of 20, 1000 and 2000 mg/kg body weight to Sprague-Dawley rats of both sexes, and the control group was given distilled water (vehicle). All animals were checked daily for general behavior, body weight changes and signs of toxicity. At the end of the treatment period, hematological analysis, biochemical analysis and histopathological examination of organs were conducted. Results At tested concentrations, oral XNE administration caused no treatment-induced adverse effects on general health, body weight gain, relative organ weights, and hematological and biochemical parameters. Histopathological results also showed no significant structural changes in organs even in high-dose XNE-treated animals. Conclusion This study suggests that treatment with XNE for 90 days does not produce significant toxicity, even up to 100 fold (2000 mg/kg body weight/day) of the recommended daily intakes. Therefore, the use of XNE as herbal medicines is considered to be relatively safe.