Toxicological and Histopathological Effects of Psidium guajava Leaf Extract on African Catfish (Clarias gariepinus): Implications for Aquaculture

Abstract

Psidium guajava (guava) leaves are rich in bioactive compounds, including flavonoids, tannins, and saponins, known for their antimicrobial and antioxidant properties. These attributes have led to their incorporation in fish diets to enhance growth performance and health status. This study assessed the toxicological impact of ethanolic leaf extract of Psidium guajava on African catfish (Clarias gariepinus) fingerlings. Fish were exposed to varying concentration of the extract 0–10 mg/L for 96 h, with mortality, behavior, water quality, and histopathology evaluated. Results showed a concentration-dependent mortality (96-h LC₅₀ = 4 mg/L), significant declines in dissolved oxygen and pH, and abnormal behaviors including erratic swimming and respiratory distress. Gill lesions ranged from epithelial lifting to lamellar degeneration, while liver tissues exhibited steatosis, vacuolation, and necrosis at higher concentrations. The water temperature exhibited slight fluctuations throughout the 96-hour experimental period. The lowest temperature (26.1 °C) was recorded at the 8mg/l concentration of the extract after 96 hours, whereas the highest temperature (28.6 °C) was observed in the control group (0mg/l) after 24 hours. Statistical analysis revealed significant variations (p<0.05) at 48 and 72 hours, while no significant differences were observed at 24 and 96 hours across the various concentrations.  These effects may relate to phytochemicals such as tannins, flavonoids, and saponins, which act as antioxidants at low levels but induce oxidative stress and cellular injury at higher doses. While P. guajava is valued for its antimicrobial and immunostimulatory properties, excessive concentrations impair organ function, reduce survival, and may compromise nutrient utilization and fillet quality, raising aquaculture and food safety concerns. Defining safe exposure thresholds and integrating biomarker assays in future work are essential to balance its potential benefits with toxicological risks.