Avaliação da embriotoxicidade e atividade melanogênica dos extratos de Sonchus oleraceus: um estudo em modelo zebrafish (Danio rerio)

Abstract

Vitiligo is a skin pigmentation disorder caused by the destruction of melanocytes. It is considered an aesthetic pathology, but it is often neglected. Its pathogenesis includes several metabolic and inflammatory causes, and conventional treatment is still a challenge for patients and health professionals. Sonchus oleraceus is an unconventional vegetable that was once widely used in human nutrition. It has recently become the target of researchers due to its medicinal properties. It has been indicated in folk medicine for the control of vitiligo. However, studies on its toxicological effects and safe rational use are still scarce, as are studies on the potential use of this plant in the melanogenesis process. In this context, the objective of this study was to evaluate the effects of extracts (ethanolic and aqueous) of S. oleraceus leaves obtained in an agroecological cultivation system and at different phenological stages (vegetative and reproductive) on the melanogenic activity and toxicity in zebrafish embryos and larvae. Initially, the chemical composition of the extracts was determined by HPLC. Embryotoxicity tests were based on OECD guidelines No. 236 of 2013 and were performed on embryos up to 5 days post-fertilization (5 dpf). The doses used to evaluate teratogenic effects and lethality were: 2.5; 1.25; 0.625; 0.312; 0.156; 0.078; 0.039; 0.020; and 0.010 mg/mL. The results demonstrated that chicoric acid is present in all extracts at different concentrations. Regardless of the extraction solvent, doses of 0.312 mg/mL and lower did not show teratogenic effects, and embryo survival was above 90%. It was observed that the extract that presented the greatest lethality and deformity at lower doses was C1ET (hydroethanolic extract in the vegetative phase) at 5 dpf, presenting LC50 = 0.689 mg/mL and EC50 = 0.386 mg/mL, consequently higher IT = 1.785. The main teratogenic effects found were delayed development, yolk sac and pericardial edema and lordosis, evidenced at the dose of 0.625 mg/mL. The results of this study indicated that the toxicological effects are dose-dependent and that the biological activities can be influenced by the phenological stage of the plant, as well as by the extraction solvent. The melanogenic activity tests were performed up to 7 dpf. The doses used were: 0.312; 0.156; 0.078; 0.039; and 0.020 mg/mL. Our findings did not demonstrate significant differences in the activity of CAT, SOD and GPx enzymes for extracts C1AQ (aqueous extract, vegetative phase), C1ET (hydroethanolic extract, vegetative phase) and C2ET (hydroethanolic extract, reproductive phase) (p > 0.05); however, these extracts demonstrated an increase in the number of pigments in a dose-dependent manner (p < 0.05). A significant reduction in GST was demonstrated in the C2ET extract at doses below 0.020 mg/mL. For the C2AQ extract (aqueous extract, vegetative phase), this same effect was found at higher doses (p < 0.05). All extracts were able to stimulate melanogenesis by increasing the number of pigment fragments, pigmented area and relative intensity in a dose-dependent manner. Therefore, the results of this study indicate that S. oleraceus extracts are capable of stimulating melanogenesis depending on the extraction solvent, plant phenological stage and dose-response.