Deterioration of Antioxidant and Antidiabetic Activity of Seven Taruls Through Boiling

Abstract

The underground edible rhizomes and tubers are commonly known as "Taruls' in Darjeeling Himalaya and are mostly available during winter season. These vegetables are consumed as raw or processed through boiling for making them more palatable by local people of Darjeeling Himalaya. The methanolic extracts of raw and boiled (ten minutes) taruls were screened for their in vitro antioxidant potential by DPPH and ABTS' free-radicals, reducing power, metal chelating. nitric oxide, superoxide, hydroxyl radical scavenging capacity and anti-lipid peroxidation assays along with measuring in vitro antidiabetic activity by a-glucosidase and a-amylase inhibition. Our present study demonstrated that in majority of experimental assays, the performance of Dioscorea alata (ghar tarul) was best followed by Ipomoea batatas (red and white cultivar of sakarkanda) and D. hamiltonii (ban tarul), which showed stronger free-radical scavenging activity, high degree of different polyphenol content as well as antidiabetic capacity except for the iron-induced metal chelation where Sechium edule (squash-jara) was excellent performer. Therefore it can be stated that the extracts of different taruls might help in preventing or slowing the progress of various oxidative stress induced diseases. Our study also showed that in every antioxidant assays the scavenging activity reduced with boiling. As boiling decreases bioactive potency, it can be suggested that some alternative strategies should be developed during post-processing through which valuable phytochemicals of taruls might be preserved.