ACETYLCHOLINESTERASE INHIBITION AND ANTIOXIDANT EVALUATION OF POLYPHENOLIC FRACTIONS AND OIL FROM FOUR MELON SEEDS USED AS CONDIMENTS IN NIGERIA

Species of different melon seeds i.e. Citrullus lanatus (Thunb),Cucumeropsis mannii, Lagenaria siceraria (Mol.) Standl. and Citrullus colocynthis (L.) Schrad. are used mostly for culinary and health purposes in Nigeria, West Africa. Their health promoting potential may be connected to the antioxidant properties of their chemical constituents i.e. polyphenolic. Antioxidant evaluation was carried out on polyphenolic fractions and oils from the melon seeds’ species using the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging and 2, 2′-azino-bis-(3-ethyl) benzothiazoline-6-sulfonic acid (ABTS) radical cation scavenging activities under in vitro conditions. Acetylcholinesterase inhibition effect of the polyphenolic fractions and oils were also investigated. The result of the antioxidant activity of the polyphenolic extracts and oils obtained by different in vitro methods varied remarkably on the basis of method used. Nevertheless, the oil from Citrullus colocynthis gave the best IC50 value of 3.88 µg/mL and the polyphenolic fraction from Cucumeropsis mannii gave the best result with IC50 values of 1.89 µg/mL and 22.49 µg/mL against DPPH and ABTS respectively. Polyphenolic fraction from seeds of Lagenaria siceraria and oil from seeds of Citrullus lanatus gave the best acetylcholinesterase inhibition activity with IC50 value of 47.40 µg/mL and 19.50 µg/mL. This study’s results indicated that the different seeds of melon species are sources of natural antioxidants preventing oxidative damage and a good source of acetylcholinesterase inhibition preventing old-age related and neurodegenerative diseases i.e. Parkinson and Alzheimer’s diseases.