Estimation of Safe and Effective Sedative Concentration of Ground Clove (Syzygium aromaticum) Buds Using 96-hour Lethal Concentration 50 (LC50) Test in the Zebrafish, Danio rerio (F. Hamilton, 1822) (Cypriniformes: Cyprinidae)

A 96-hour lethal concentration 50 (LC50) test was performed in 210 sexually immature zebrafish (Danio rerio) to determine the safe and effective sedative concentration of ground clove (Syzygium aromaticum) buds (GCB). Fish exposed to 0 and 10 ppm GCB (w/v) did not exhibit signs of sedation and irritation and appeared to be swimming normally throughout the experiment. Fish exposed to 20 and 50 ppm GCB showed mild sedation with no signs of irritation and recovery was observed at 48 hours of exposure. Fish exposed to 100, 200 and 400 ppm GCB exhibited irritation, narcosis and subsequent loss of balance and swimming ability. Deep sedation occurred instantaneously in fish exposed to 400 ppm with signs similar to anesthetic induction. Histopathologic changes were dose-dependent. Exposure to higher GCB concentrations resulted to gill lesions which range from congestion of the primary lamellae (100 to 400 ppm) to lifting of lamellar epithelia (100 ppm). LC50 was identified at 198.23 ppm while effective and safe sedative concentration was estimated at 19.52 ppm using linear regression analysis (P<0.05). This indicates that at this concentration, fish were in mild sedation for at least 48 hours without any signs of neither irritation nor histopathological lesions and without causing any mortality within 96 hours of exposure to GCB.