Toxicity and antioxidant effects of the decoction of the leaf of guavira (Campomanesia guazumifolia) as a food additive for Geophagus pyrocephalus.

The use of plant-derived nutraceuticals in aquaculture has increased, including in ornamental species. Guavira (Campomanesia guazumifolia) is a native Cerrado plant with reported antioxidant and anti-inflammatory properties. This study evaluated the toxicity and functional effects of C. guazumifolia leaf decoction as a feed additive for Geophagus pyrocephalus. Acute toxicity assays were conducted using Artemia salina (1.5-1000 µg mL⁻¹) and juvenile fish (0.1-500 µg mL⁻¹), alongside a 30-day feeding trial with dietary inclusion levels of 0, 250, 500, 1000, and 2000 mg kg⁻¹. The decoction exhibited high toxicity, with LD₅₀ values of 23.29 µg mL⁻¹ for A. salina and 50.03 µg mL⁻¹ for G. pyrocephalus. In fish, mortality increased markedly at concentrations ≥ 100 µg mL⁻¹, accompanied by elevated plasma glucose and severe gill lesions, including epithelial hyperplasia, lamellar fusion, and necrosis. Despite this toxicity, dietary supplementation at 250 mg kg⁻¹ significantly enhanced muscle antioxidant activity, with superoxide dismutase (SOD) levels increasing by approximately 2.5-fold compared to the control (p < 0.05), without affecting growth performance or survival. In contrast, higher inclusion levels (≥ 1000 mg kg⁻¹) were associated with reduced condition factor and increased hepatic alanine aminotransferase (ALT), indicating metabolic stress. In conclusion, C. guazumifolia leaf decoction presents a narrow safety margin, combining pronounced toxicity at relatively low concentrations with beneficial antioxidant effects at low dietary inclusion. The dose of 250 mg kg⁻¹ is suggested as a safe and functional level for G. pyrocephalus, highlighting the importance of dose optimization for its application in ornamental aquaculture.