Total phenolic content, in vitro antioxidant activity and type II diabetes relevant enzyme inhibition properties of methanolic extract of traditionally processed underutilized food legume, Acacia nilotica (L.) Willd ex. Delile

The methanolic extract of Acacia nilotica (L.) Willd ex. Delile (black thorn tree) seed materials, an underutilized food legume collected from India was found to contain total free phenolic content of 14.57 ± 1.69 g catechin equivalent/100 g extract DM. Encouraging levels of ferric reducing/antioxidant power (FRAP, 1840 mmol Fe[II]/mg extract), inhibition of ß-carotene degradation (53.26%) and radical scavenging activity against DPPH (64.91%) and superoxide (53.23%) radicals were noticed. Further, it also recorded 72.91% of α-amylase and 65.13% of α-glucosidase enzyme inhibition characteristics. Sprouting + oil-frying caused a apparent increase on the total free phenolic content and also significant improvement on the antioxidant and free radical scavenging capacity of methanolic extract of A. nilotica seeds, while soaking + cooking as well as open-pan roasting treatments showed diminishing effects. Moreover, inhibition of α-amylase and α-glucosidase enzyme activities was declined to 22.47 and 46.13%, respectively during sprouting + oil-frying treatment, which are more desirable for the dietary management of type II diabetes.