Afr. J. Biomed. Res. Vol. 24 (May, 2021); 257- 263 Research Article Protective Effect of Alkaloid-rich Extract of Brimstone Tree (Morinda lucida) on Neurotoxicity in the Fruit-fly (Drosophila melanogaster) Model Nwanna E.E. Functional Food, Nutraceutical and Phytomedicine unit Department of Biochemistry, Federal University of Technology Akure PMB 704, Nigeria ABSTRACT Brimstone plant is one of the medicinal plants found in Nigeria used in fore-lore medicine with little scientific information on its alkaloid constituents. This study was aimed at investigating the effect of alkaloid-rich compounds from the plant in manganese- induced (MgCl2) neurotoxicity in the fruit fly. In addition, alkaloid compounds will be characterized using gas chromatograph coupled with flame ionization detector (GC-FID). Alkaloid-rich extract was prepared by solvent extraction method, fruit flies were pre-treated with the extract (0.5 – 1.0mg/ml) in a fortified diet before induction with MgCl2. The survival rate and negative geotaxis were observed. Thereafter, the activity of acetylcholinesterase (AChE) enzyme, antioxidantive potentials in in -vivo reactive oxygen species (ROS) thiobarbituric acid reactive species (TBARS), total thiol content, nitric oxide (NO*), hydroxyl oxide (OH*) scavenging ability, ferric reducing antioxidant property (FRAP) and 2, 2’-azino-bis (3-ethylbenzthiazoline-6- sulphonic acid) (ABTs*) radical scavenging ability were carried out on the flies’ homogenate. Results obtained revealed that the alkaloid-rich extract regulated the neuro-protective activity of AchE, reduced the reactive oxygen species level in the induced flies with an increased in antioxidantive potential, higher survival rate and increases in the life span of the flies with 50% reduction in the mortality rate. The GC-MS showed a total of (1.55/100mg) of different plant-derived alkaloids such as dicentrine, atropine, aporphine. These alkaloids-rich compounds were found to have anti-oxidative, anti-nociceptive, anti-inflammatory and anti- cholinergic activities. In conclusion, this study suggests that alkaloids from brimstone plant could be the reason for the observed biological activities for the prevention of neuronal related complications.