Antioxidant Activity and Anxiolytic Effect of Cnidoscolus quercifolius Pohl Stem Bark Extract in Zebrafish

Background: Cnidoscolus quercifolius, popularly known as “favela”, is used in traditional medicine to treat various conditions, such as infections and inflammations. However, its therapeutic potentials remain underexplored in scientific research. The present study aimed to evaluate the anxiolytic effect, toxicity, and antioxidant activity of methanolic (EMCq) and ethyl acetate (EAECq) extracts of C. quercifolius bark, as well as determine their chemical composition by HPLC/DAD and their levels of phenolic compounds and flavonoids. Methods: Anxiolytic effect and acute toxicity tests were conducted using the zebrafish model, while antioxidant activity was assessed using the DPPH• and ABTS+ methods. The chemical composition was obtained by HPLC/DAD, and phenolic compounds and flavonoids were quantified with the Folin–Ciocalteu reagents and the aluminum chloride colorimetric method, respectively. Results: Caffeic acid, p-coumaric acid, cinnamic acid, pinocembrin, and apigenin were identified and quantified. The results indicated that both extracts exhibited low antioxidant activity, possibly due to their low levels of phenols (0.187 and 0.293 mg GAE/g) and flavonoids (0.84 and 0.64 mg QE/g). However, the extracts did not show acute toxicity (>400 mg/kg) and reduced the locomotor activity of zebrafish at all the doses tested (40 to 400 mg/kg), while increasing the time the animals remained in the light zone, indicating an anxiolytic effect. Conclusions: These findings suggest for the first time that C. quercifolius has anxiolytic properties, warranting further investigation into specific bioactive compounds and their mechanisms of action. Future studies may explore molecular analysis techniques to identify the responsible compounds, as well as investigate safety and clinical efficacy in mammalian models.