Phytochemical composition and radical scavenging activities of watermelon (Citrullus lanatus) seed constituents

It is a known fact that antioxidant phytochemicals in foods have many health benefits including prevention of various diseases associated with oxidative stress such as cancer, cardiovascular disease, neuro-degeneration and diabetes. Watermelon seed constituents (whole meal, shelled and shells flours) were evaluated for phytochemical components and in vitro antioxidant activity to determine the potential practical applications in food and other related areas. Antioxidant activity was investigated by measuring its DPPH (2,2-diphenyl-2-picryl hydrazyl) and ABTS (2, 2’-azinobis-3-ethylbenzothiozoline- 6-sulphonic acid) radical scavenging ability as well as FRAP method (ferric reducing power). Quantitative estimation of the constituents showed cardiac glycosides (9.94-14.35 mg/g) and saponins (11.62-32.48 mg/g) as the most concentrated phytochemicals in the constituents, while alkaloids (47.2-95.8 mg/g), total phenol (5.63-8.40 mg GAE/g), flavonoids 3.51-7.76 mg QE/g. A positive radical scavenging ability of the constituents against ABTS and DPPH free radicals ranged from 0.02 to 0.04 mg Trolox equivalent /g seed flour and 39.89 to 61.11 mg ascorbic acid equivalent /g seed flour respectively. There was a considerable ferric reducing power and higher activity was observed in whole meal than shelled seeds and shells. The significant antioxidant capacities of the seed constituents underline the potential source of natural antioxidants and bioactive compounds for therapeutic purposes