Comparative Fatty Acids Profiling and Antioxidant Potential of Pawpaw and Watermelon Seed Oils

Abstract

Seed oils of watermelon, unripe and ripe pawpaw were extracted and analyzed for their fatty acid composition using GC/EIMS, phenolic content and antioxidant potential using free radical scavenging effect on 2, 2-diphenyl-2-picrylhydrazyl (DPPH) radical. Watermelon seed oil has eight fatty acids ranging from C16– C21, unripe pawpaw seed oil has nine fatty acids also ranging from C16 – C21 and ripe pawpaw seed oil has twelve fatty acids ranging from C15-C27. The major chemical component identified in both watermelon seed oil (49.41%) and unripe pawpaw seed oils (39.07%) was 11-Octadecenoic acid methyl ester while 14-Octadecenoic acid methyl ester (40.25%) was the major component identified in ripe pawpaw seed oil. Only watermelon seed oil contained an essential fatty acid; linoleic acid (17.23%) in contrast to previous literatures values (60%). The fatty acids present in these oils are mixtures of saturated and unsaturated homologues. Ripe pawpaw seed oil showed more chemical compounds than the unripe pawpaw seed oil and this may be due to ripening. The phenolic contents of the oils ranged from 1.41-1.55 mg gallic acid equivalent per gram. The three oils showed significant DDPH free radical scavenging potential. The order of inhibition are; watermelon > ripe pawpaw > unripe pawpaw seed oil. The IC50 values of these oils were are, 36 mg/ml, 44 mg/ml and 56 mg/ml for watermelon, ripe pawpaw and unripe pawpaw seed oils respectively. This study however did not show a positive correlation between the phenolic contents and antioxidant activity. We recommend further studies into the use of these oils for treating various specific diseases.