Acute toxicity of hot aqueous extract from leaves of the Terminalia catappa in juvenile fish Colossoma macropomum

Phytoterapy has been used in aquaculture for disease control, especially the Terminalia catappa that demonstrated excellent antimicrobial potential. The aquaculture commonly uses the extract obtained at room temperature, but the hot aqueous extract (HAE) and its effects on the fish are still unknown. This study aimed to determine the lethal concentration (LC 50 ) of HAE from Terminalia catappa in juvenile fish Colossoma macropomum as well as to evaluate hematological and histological parameters. Two extracts were obtained in different temperatures and submitted to HPLC. Despite both extracts presented the similar chemical compounds, HAE showed higher levels of compounds and then it was selected. For acute toxicity test, six different extract concentrations (0.00, 0.10, 0.20, 0.30, 0.40, and 0.50 g/L) in triplicate was used. At the end of the experiment, all fishes were submitted to hematological and histological analysis. The LC 50 was determined using trimmed Spearman-Karber method, and water quality (pH, temperature, DO, electrical conductivity, and ammonia) were measured. The results were submitted to ANOVA followed by Tukey’s test ( p < 0.05). The HAE showed LC 50 of 0.41 g/L with changes on water parameters, such as pH and conductivity, as well as the fish behavior. HAE also altered hematologic parameters and showed histopathological changes on the gill and liver using high concentration of the extract or longtime exposure in low extract concentrations. Despite HAE showed higher concentration of compounds, it remains considered as a practically non-toxic product. Nonetheless, water quality, hematological, and histological alterations must be considered to determine concentrations and strategies of application in vivo.