EFFECTS OF SOME SELECTED CITRUS SPECIES PEELS ON Drosophila melanogaster MODEL OF ALZHEIMER’S DISEASE

Abstract

Citrus peel, a major by-product of citrus juice processing industry, is used as a source of phytochemicals by the food, pharmaceutical and nutraceutical industries. This studyseeks to determine the effect of orange (Citrus sinensis), tangerine (Citrus maxima) and grapefruit (Citrus paradisi) peels on Drosophila melanogastermodel of Alzheimer’s disease. Flies (both gender, 3-5 days old) were divided into 8 groups with 40 flies per vial. Group I (flies expressing human microtubule associated protein) and group II (wild flies) were placed on normal diet while groups III and IV were placed on normal diet with dietary inclusions of 0.1 and 1.0 % of tangerine peels respectively, groups V and VI were placed on normal diet with dietary inclusions of 0.1 and 1.0 % orange peels, groups VII -VIII were placed on normal diet with dietary inclusions of0.1 and 1.0% grapefruit peels respectively for 14 days. After 14 days, lethality response, negative geotaxis and aversive phototaxis assay were carried out to assess the behaviour of the flies. The flies were anesthetized on ice and homogenized for biochemical assays which includes reactive oxygen species (ROS), lipid peroxidation, total thiol content, glutathione transferase and catalase activities, acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and monoamine oxidase (MAO) activities. The results revealed that transgenic flies expressing human microtubule associated protein induced neurobehavioural and neurochemical alterations which was ameliorated by dietary inclusions of the selected citrus peels as evident by the significant improment in the behavioural profiles and antioxidant status; decreased ROS, lipid peroxidation, AChE, BChE and MAO activities, increased GSH as well as increased catalase and glutathione peroxidase activities in the treated flies when compared to the tau-untreated flies. The result obtained implies that the peels can be considered dietary or nutraceutical source for the prevention / management of multifactorial AD and other neurodegenerative diseases and further validates D. melanogaster as a viable invertebrate alternative model for the study of neurodegenerative diseases.