Anticholinesterase and antioxidative properties of water-extractable phytochemicals from some citrus peels.

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 properties of aqueous extracts from some citrus peels [orange (Citrus sinensis), grapefruit (Citrus paradisii), and shaddock (Citrus maxima)].

Methods: The effects of the extracts on acetylcholinesterase (AChE) activity, as well as Fe2+-induced malondialdehyde (MDA) production in vitro, were investigated. The total phenolic, flavonoid content, and antioxidant activities 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 inhibited AChE activity in a dose-dependent manner, although there is no significant difference (p>0.05) in their inhibitory abilities of the peels. The extracts exhibited antioxidant activities as typified by their radical (DPPH· and OH·) scavenging abilities as well as the inhibition of Fe2+-induced lipid peroxidation in rat's brain in vitro.

Conclusions: The anticholinesterase activity and inhibition 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.