ANTIOXIDANT PROPERTIES AND EFFECTS OF ESSENTIAL OILS FROM SOME CITRUS PEELS ON IN VITRO ACETYLCHOLINESTERASE AND BUTYRYLCHOLINESTERASE ACTIVITIES

Abstract

This study sought to investigate the antioxidant properties and effects of essential oils from some citrus peels (Citrus sinensis and Citrus limon) on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities in vitro. Essential oils from the peels were extracted by hydrodistillation, dried with anhydrous Na2SO4 and characterized using gas chromatography. Antioxidant properties of the oils and its effects on some pro-oxidant (Fe2+ and quinolinic acid) induced malondialdehyde (MDA) production in rats brain homogenate as well as their interaction with key enzymes linked with neurodegenerative condition (AChE and BChE) were assessed. There was no significant difference in the AChE [Orange peels (EC50=172.32μl/L), Lemon peels (EC50=164.35μl/L)] and BChE [Orange peels EC50=165.31μl/L, Lemon peels (EC50=169.63μl/L)] inhibitory activities. Furthermore, the essential oils inhibited Fe2+ and quinolinic acid-induced MDA production and further exhibited antioxidant activities as typified by ferric reducing antioxidant property, Fe2+-chelation and radicals(NO*, DPPH*, OH*, ABTS*) scavenging abilities. The result revealed that essential oil from lemon peels has higher antioxidant properties than the oil from orange peels. There was no significant difference in the phenolic content [Orange peels (8.23mg/100g) and Lemon peels (7.42mg/100g)] and flavonoid content of the [orange peels (3.93mg/100g) and lemon peels (3.56mg/100g) essential oils. Furthermore, the GC analysis revealed the presence of sabinene, limonene, α-pinene, β-pinene, neral, geranial, 1,8-cineole, linalool, borneol, α-terpineol, terpinen-4-ol, linalyl acetate and β-caryophyllene in significant amounts. The inhibition of AChE and BChE activities, inhibition of pro-oxidant induced lipid peroxidation in rats’ brain and antioxidant activities could be possible mechanisms for the use of the essential oil in the management and prevention of oxidative stress-induced neurodegeneration. However, lemon essential oil is more effective than that of orange peels