Phenolic compounds, tocochromanols profile and antioxidant properties of winter melon [Benincasa hispida (Thunb.) Cogn.] seed oils

The seed oils from two different cultivars of winter melon were evaluated for their phenolics, tocochromanols and antioxidant properties. The oils contained 961.8 to 1027.6 µg/g of total tocochromanols, including α-tocopherol (2–3%), β-tocopherol (46.6–61.7%), γ-tocopherol (23–24.9%), γ-tocotrienol (6.8–8.2%), and δ-tocopherol (4.6–19.2%). Gallic acid, protocatechuic acid, 3,4-dihydroxybenzaldehyde, vanillic acid, vanillin, para-coumaric acid, trans-cinnamic acid and ferulic acid were found to be in the range between 12.27 and 17.25 µg/g oil. As far as antioxidant properties is concerned, 80% ethanol seed oil extract (SOE) from cultivar 1 (round) and 100% methanol SOE from cultivar 2 (hybrid round) showed the highest DPPH radical scavenging activity (IC50 value 7.03 and 6.88 mg/mL, respectively) while 80% methanol SOE from cultivar 2 exhibited the least (IC50 value 64.71 mg/mL). Trolox equivalent antioxidant capacity of the SOE ranged from 9.82 to 24.61 µg TE/g (cultivar 1) and 12.17–26.83 TE/g (cultivar 2), with 80% ethanol extract having the highest antioxidant potential. The extracted total phenolic compounds were 19.37 to 203.93 µg GAE/g oil for cultivar 1, whereas 30.77 to 190.07 µg GAE/g oil for cultivar 2, with 80% isopropanol recovering the maximum amounts. These results conclude that aqueous alcoholic solvents were a better choice for extraction of potent antioxidants from winter melon seed oils, nevertheless, the antioxidant properties considerably (p < 0.05) varied in relation to extraction solvents and cultivars selected. Data of this study support that the seed oils of the tested cultivars of winter melon are potential dietary source of tocochromanol, phenolic compounds, and natural antioxidants.