Tissue distribution of Ocimum basilicum essential oil in Nile tilapia Oreochromis niloticus after anesthesia

This study evaluated how the levels of methyl chavicol and linalool behave in tissues of juvenile Nile tilapia after anesthesia with the essential oil (EO) of Ocimum basilicum at different temperatures. The EO was diluted in ethanol (1:9), and the fish (64.99 ± 13.90 g) were immersed in the anesthetic solution (250 mg L^-1) at 23 and 27 ºC for 10 min. After anesthesia, the fish were placed in tanks free of anesthetic solution for recovery. Tissues (gill, brain, liver and muscle) were collected at 0, 0.5, 3, 6, and 12 h after anesthesia. The compounds were quantified in the gills, brain and liver up to 6 h, and in the muscle up to 12 h at both temperatures. The maximum concentration (C_max) of both compounds was highest in the liver at 23 ºC and lowest in the muscle at 27 ºC. In the gills, the C_max of methyl chavicol and linalool was highest at 23 ºC with half-lives of 0.78 h and 0.70 h, respectively. The levels of methyl chavicol and linalool in the brain were similar at 23 and 27 ºC. In the liver, elimination of the compounds was more efficient at 27 ºC, with a significant interaction between temperature and depletion. In the muscle, the compounds showed greater retention, with slower elimination compared to the other tissues. The temperature of 23 ºC favored greater absorption of the compounds in the gills and liver, while 27 ºC accelerated their elimination. The brain and muscle, on the other hand, were not influenced by temperature. The liver was identified as the main organ for metabolizing the compounds, with less elimination in the muscle. The results highlight the impact of temperature on the metabolism of anesthetics in fish.