Natural compounds are increasingly explored for their ability to modulate multiple molecular pathways involved in inflammation and oxidative stress and for their therapeutic potential. Among these, Opuntia ficus-indica (L.) Mill. has attracted growing interest due to its rich phytochemical profile; however, the biological properties of unripe fruits remain largely unexplored. In this study, a hydroalcoholic extract obtained from unripe O. ficus-indica fruits was characterized for its chemical composition, antioxidant capacity, and concentration-dependent embryotoxic profile and subsequently investigated in a zebrafish model of spinal cord injury (SCI). UHPLC-HRMS/MS analysis identified 14 secondary metabolites, mainly flavonoids and phenylpropanoid acids. Antioxidant activity was confirmed by DPPH and ABTS assays. An embryotoxicity assessment conducted according to OECD Test Guideline 236 revealed no mortality at concentrations below 100 µg mL⁻¹ and an LC₅₀ of 323.59 µg mL⁻¹ at 96 h post-fertilization, allowing the identification of non-toxic concentrations for subsequent in vivo experiments. Based on these results, the extract was tested in a larval zebrafish SCI transection model. Treated larvae showed improved locomotor recovery, particularly under continuous exposure, accompanied by modulation of molecular pathways involved in inflammation, neurotrophic support, and neurogenesis, including reduced pro-inflammatory cytokine expression and increased BDNF and Sonic Hedgehog signaling markers. Overall, these findings expand current knowledge on unripe O. ficus-indica and highlight its potential to modulate molecular pathways involved in SCI-induced damage and repair.

Flavonoids are a diverse group of natural polyphenolic compounds, recognized for their ability to modulate cellular pathways and mitigate the pathological processes of many neurodegenerative diseases. This study investigates the neurotrophic potential of a polyphenolic-rich lemon peel extract (Lpe) in a Zebrafish larvae spinal cord injury (SCI) model. To evaluate its potential effects, embryos were divided into six experimental groups: a baseline control group in which larvae were neither subjected to spinal cord injury nor treated (Ctrl Group); a group with larvae subjected to spinal cord injury at 3 dpf without treatment (SCI Group); a group treated continuously with Lpe (25 µg/mL) from 0 to 5 dpf without injury (Continuous Group); a group treated continuously with Lpe and injured at 3 dpf (Continuous SCI Group); a group treated with Lpe starting at 3 dpf without injury (Curative Group); and finally, a group injured at 3 dpf and treated simultaneously with Lpe (Curative SCI Group). Lpe treatment significantly downregulated proinflammatory cytokines (tnfa, il1b, and xcl8), and modulated the neuroregenerative pathways Wnt/β catenin, and neurotrophic factor Bdnf. Immunohistochemical analysis further revealed Sox2-positive cells localized around the central canal, consistent with activation of ependymal progenitor populations involved in injury-induced repair processes. These findings support the exploration of Lpe for mitigating SCI-induced damage.