Composição química e efeito anestésico de óleos essenciais derivados de plantas em tilápia do Nilo (Oreochromis niloticus)

Abstract

The use of plant-derived essential oils in aquaculture has aroused interest due to their bioactive properties, including anesthetic effects. This study investigated the chemical composition and anesthetic effect of six plant-derived essential oils (EOs) (Eucalyptus globulus - EGEO, E. citriodora - ECEO, Thymus vulgaris - TVEO, Mentha piperita - MPEO, Melaleuca alternifolia - MAEO and Ocimum basilicum - OBEO) on juvenile Nile tilapia (Oreochromis niloticus), a species of global economic importance. The chemical composition of EOs was determined through high-resolution gas chromatography coupled with mass spectrometry (GC/MS), and the anesthetic effect was assessed by the induction time to anesthesia and recovery after exposing healthy tilapia (5±2 g) to 100 mg/L of EO or lidocaine (positive control). The in vivo experiment with tilapia was performed in triplicate. Forty-five compounds were identified. 1,8 cineole, ρ - cymene, citronellal, thymol, menthol, 1-terpinen- 4-ol and estragole were the major components of EGEO, ECEO, TVEO, MPEO, MAEO and OBOE, respectively. All tested oils demonstrated anesthetic properties for juvenile Nile tilapia. Lidocaine, EGEO and MAEO had similar anesthesia times (~30 min), TVEO presented the shortest time (~4 min), followed by OBEO (~6 min). ECEO and MPEO had intermediate times (~9 and ~23 min, respectively). Recovery time was very similar among the experimental groups, except of the OEOB which had a longer time (p ≤ 0.003) and mortality was observed. TVEO was the most effective anesthetic and can be recommended for use in juvenile Nile tilapia. This study highlights the potential of using EOs as anesthetics in aquaculture or aquaculture research.