Properties of two plant extractives as anaesthetics and antioxidants for juvenile tambaqui Colossoma macropomum

The aim of this study was to evaluate the anaesthetic activities of the extractives of Nectandra grandiflora and Spilanthes acmella in juvenile tambaqui fish, Colossoma macropomum as well as to investigate their effects on oxidative stress status of fish submitted to transport in hyperoxia. Fish were placed in aquaria containing five different concentrations of essential oil (EO) of N. grandiflora (25; 50; 100; 200; and 300μLL−1) or waxy extract of S. acmella (5; 10; 15; 20; and 25mgL−1), and the times of anaesthetic induction and recovery were determined by concentration-response trials. Fish transported inside plastic bags in hyperoxic conditions for 2, 6 and 10h with or without anaesthetics were investigated for the occurrence of oxidative stress through the assessment of total antioxidant capacity against peroxyl radicals (ACAP), glutathione S-transferase (GST) activity and lipid peroxidation levels (TBARS) in muscle, gills, liver and brain. Both extractives of S. acmella and N. grandiflora induced deep anaesthesia in juvenile C. macropomum. Although transient changes occurred in ACAP and GST activity after transport, irrespective of transport time or anaesthetic used, antioxidant components in these extractives reduced or maintained lipid peroxidation within basal levels in the assessed organs. The use of 10mgL−1 of extract of S. acmella was suitable to induce fast anaesthesia (<3min) and safe recovery (<5min). Sedation concentrations at 1mgL−1 and 30μLL−1 of the extractives of S. acmella and N. grandiflora respectively, enhanced protection against oxidative damage mainly in muscle and gills of juvenile tambaqui and therefore have the potential to be used as chemoprotectants for transport purposes.This study presents novel products to be used as anaesthetics/sedatives for fish.