Comprehensive analysis of Leonotis nepetifolia flower extracts: phytochemical composition and toxicity in zebrafish embryos

Abstract

Leonotis nepetifolia (L.) R. Br., a plant used in traditional medicine, has underexplored phytochemical and toxicological profiles. This study investigates the metabolite profile of L. nepetifolia flowers and assesses their toxicity using zebrafish (ZF) embryos. The main active compounds were characterised using metabolomic approaches. ZF embryos were exposed to methanol extract (CEF), n-hexane (FHF) and ethyl acetate (FAF) fractions at different concentrations for 96 h. Toxicological effects were assessed including acetylcholinesterase activity, lipid peroxidation, cardiotoxicity, as well as hatching delay, developmental defects and morphological malformations. Phytochemical analysis revealed diverse metabolites, including phytosterols, terpenoids, flavonoids and phenylpropanoids. Verbascoside, a major compound, was isolated from the flowers for the first time. Toxicological assessments showed that CEF and FAF caused various toxic effects, with FAF showing pronounced embryotoxic and teratogenic effects. This study highlights the chemical diversity and potential toxicological risks of L. nepetifolia, emphasising the need for thorough evaluations of herbal medicines.