Influence of postharvest gamma irradiation treatment on the content of bioactive compounds and antioxidant activity of fenugreek (Trigonella foenum-graceum L.) and spinach (Spinacia oleracea L.) leaves

Fenugreek and spinach leaves after irradiation in the dose range of 0.25-1.5 kGy were evaluated for the content of bioactive compounds and antioxidant activity using DPPH radical scavenging, ferric reducing ability power (FRAP), hydroxyl radical scavenging and ferrous ion chelating assays. Results of the study revealed that bioactive content except total ascorbic acid was significantly (p <= 0.05) higher in fenugreek compared to spinach. Data analysis revealed that gamma irradiation treatment significantly (p <= 0.05) enhanced the content of individual as well as total bioactive components of both vegetables. Positive correlation (r = 0.92) existed between gamma irradiation and total phenolics. The results of the antioxidant activity as determined by above mentioned assays revealed a significant (p <= 0.05) decrease in EC50 values and a corresponding increase in antioxidant content and activity due to irradiation. Comparison of the increase in inhibition percentage, reducing power and chelating efficiency revealed that treatment of irradiation was significantly (p <= 0.05) effective in enhancing the ferric reducing power of both the vegetables (3.1-37.5% for fenugreek, 4.1-42.8% for spinach) and OH radical scavenging for spinach (1.5-22.4%) compared to fenugreek (0.78-13.1%). The present investigation suggested that postharvest radiation treatment to fenugreek and spinach has a potential to enhance their antioxidant content and activities, besides acting as a photo-sanitary treatment. Industrial relevance: The increasing demand of convenience, wholesome and health promoting foods has resulted in search of new technologies to improve the shelf-life and at the same time preserve the nutritional quality. Prolonging postharvest storage, while enhancing the content of bioactive compounds will have a positive impact on both the industry and consumers. The present study demonstrated that postharvest radiation treatment of fenugreek and spinach can be used a novel approach to enhance their bioactive composition and antioxidant activity. (C) 2015 Elsevier Ltd. All rights reserved.