DOI 10.1515/jbcpp-2013-0027 J Basic Clin Physiol Pharmacol 2014; 25(2): 199–204 Ayokunle Olubode Ademosun and Ganiyu Oboh* Anticholinesterase and antioxidative properties of water-extractable phytochemicals from some citrus peels Abstract Background: Aqueous extracts from citrus peels are used in many rural communities in Nigeria in treating various degenerative conditions, although the scientific basis for its use has not been well established. This study sought to investigate the anticholinesterase and antioxidant pro- perties of aqueous extracts from some citrus peels [orange (Citrus sinensis), grapefruit (Citrus paradisii), and shad- dock (Citrus maxima)]. Methods: The effects of the extracts on acetylcholinest- erase (AChE) activity, as well as Fe 2+ -induced malondial- dehyde (MDA) production in vitro, were investigated. The total phenolic, flavonoid content, and antioxidant activi- ties as typified by 1,1-diphenyl-2 picrylhydrazyl (DPPH) free radical scavenging ability and hydroxyl (OH) radicals scavenging abilities were also investigated. Results: The results revealed that orange peels had the highest total phenol content followed by grapefruit peels, whereas shaddock peels had the least. The extracts inhib- ited AChE activity in a dose-dependent manner, although there is no significant difference (p> 0.05) in their inhi- bitory abilities of the peels. The extracts exhibited anti- oxidant activities as typified by their radical (DPPH · and OH ·) scavenging abilities as well as the inhibition of Fe 2+ - induced lipid peroxidation in rat’s brain in vitro. Conclusions: The anticholinesterase activity and inhibi- tion of MDA production by the aqueous extracts of the peels, as well as other antioxidant activities, could make the peels a good dietary means for the management of oxidative-mediated neurodegenerative disorders. Keywords: acetylcholinesterase; antioxidant; brain; citrus; peels. *Corresponding author: Ganiyu Oboh, Functional Foods and Nutraceuticals Unit, Department of Biochemistry, Federal University of Technology, Akure, Ondo-State, Nigeria, Phone: +234 703 138 8644, E-mail: goboh2001@yahoo.com Ayokunle Olubode Ademosun: Functional Foods and Nutraceuticals Unit, Department of Biochemistry, Federal University of Technology, Akure, Ondo-State, Nigeria Introduction Certain neurodegenerative disorders have been linked to a deficiency in the neurotransmitter acetylcholine, which is broken down by the enzyme acetylcholinesterase (AChE) into inactive choline and acetate. AChE-inhibiting drugs are the only effective treatment for Alzheimer’s disease; however, these drugs are limited in use due to their adverse side-effects such as gastrointestinal disturbances [1]. Oxi- dative damage caused by free radicals has been implicated in the pathogenesis of Alzheimer’s disease [2]. The central nervous system, especially the brain, is susceptible to free radical damage due to high oxygen consumption (∼20%), presence of high levels of iron, abundance of readily oxi- dizable fatty acids, and relatively low antioxidant enzymes and antioxidants [3, 4]. This high amount of free radicals in the brain has been linked to Alzheimer’s disease, as evi- dence for oxidative damage-induced dementia has been obtained from brain tissues of patients with Alzheimer’s disease [5]. Furthermore, free radical damage in the brain increases the malondialdehyde (MDA) content and levels of thiobarbituric acid (TBA)-reactive substances (TBARS) in the brain. Elevated hydroxynonenal (HNE) levels have been observed in the brains of patients with Alzheimer’s disease, which is a pointer to lipid peroxidation [6]. Citrus peels, which are byproducts of the citrus indus- try, are an excellent source of many nutrients and phyto- chemicals that contribute to a healthy diet, and they are good sources of antioxidants such as phenolics [7, 8]. Citrus peels have also been considered as dietary intervention in the management of neurodegenerative disorders, as Citrus reticulata peels have been accepted in Japan as dietary management for Alzheimer’s disease [9]. Furthermore, citrus peel flavonoids can cross the blood-brain barrier [10] and they have been shown to exert neuroprotection in several animal models through induction of antioxidant enzymes and anti-inflammatory and signaling properties [11–13]. Citrus peels are consumed as infusion drinks in parts of Asia and sub-Saharan Africa, although there is dearth of information on the possible mechanism by which the Brought to you by | University of Ottawa OCUL Authenticated Download Date | 8/4/15 10:00 AM