Antioxidant Activity of Melinjo Ketan (Gnetum gnemon L., ‘Ketan’) Seed Extract at Various Ripening Stages and Ethanol Solvent Concentration

Melinjo seeds ( Gnetum gnemon L.) have the potency as antioxidants due to their bioactive compounds such as polyphenols, flavonoids, tannins, and resveratrol. The study was conducted to determine the effect of the ripening stages of Melinjo ketan variety seeds and ethanol solvent concentration on total of phenolic , flavonoid also resveratrol content, and antioxidant activity of Melinjo seed extract. The ripening stages of Melinjo seeds used were immature, semi-mature and mature. The ethanol solvent concentrations were 20%, 50% and 80%. Samples of dried melinjo seeds were macerated in ethanol (1: 5) at room temperature for 2 days. The extract was filtrated, evaporated and freeze-dried. This study reported that the ripening stages of melinjo seeds and ethanol solvent concentrations had effect on the total of phenolic , flavonoid, resveratrol content, and antioxidant activity of melinjo seed extract significantly (p<0,05). Mature melinjo seeds macerated using 50% ethanol solvent produced extract with the highest antioxidant activity. It had the total phenolic content of 7.033 ± 0.06 mg GAE/g, total flavonoids content of 335.04 ± 1.32 mg CE/100 g, resveratrol content of 1.55 ± 0.3%, DPPH radical inhibition of 66.07 ± 0.38%, and reducing power (80.26 ± 0.06%). These studies showed that the antioxidant effect of Melinjo ketan extract is influenced by the level of maturity and solvent concentrations of ethanol that can be an alternative of antioxidant sources. It is recommended to use Melinjo ketan seeds macerated with 50% ethanol solvent.