Fermentation-induced changes in antioxidant activities and oxidative DNA damage protection of melinjo (Gnetum gnemon) flour

Abstract

The radical scavenging capacities and DNA damage protection of fermented melinjo (Gnetum gnemon) flour were investigated to determine its potential use as a nutraceutical ingredient. Fermented melinjo flour was prepared using a Lactobacillus fermentum starter culture. The fermented and unfermented melinjo flours were examined for antioxidant activities using different standard methods. The results indicated that fermented flour had significantly (p < .05) higher phenolic content (10.61 mg Galic acid equivalent (GAE)/g) than the unfermented flour (8.61 mg GAE/g). High-performance liquid chromatography-Diode Array Detector detection demonstrated that fermentation resulted in a loss of phenolic compounds, such as gnetifolin E, gnemonoside E, and resveratrol but not gnetin C. Subsequently, fermentation led to marked increases (significant, p < .05) in the radical scavenging abilities of DPPH, ABTS, hydroxyl, and hydrogen peroxide. In addition, fermented flour extract possessed superior resistance to oxidative damage of DNA by Fenton's reagent. Overall, the antioxidant enhanced melinjo flour was successfully produced and could be used as a functional food to promote the health and nutrition of consumer. Practical applications The Gnetum gnemon tree is popularly known in Indonesia as melinjo. Melinjo seeds are regularly consumed as crackers or cookies made from ground flour. These seeds are a suitable nutritional supplement with high bioavailability. In this study, the antioxidant activity of fermented melinjo flour was increased after Lactobacillus fermentum fermentation. In addition, some bioactive compounds were produced during fermentation. The fermented products can be used as nutritional supplements for the prevention and control of degenerative diseases. Therefore, this study provides a simple and effective strategy to improve the nutritional value of melinjo flour.