Contribution of phenolic compounds to the antioxidant potential and type II diabetes related enzyme inhibition properties of Pongamia pinnata L. Pierre seeds

The methanolic extract of Pongamia pinnata L. Pierre (locally called as karanja) seed materials, an underutilized food legume collected from India was analyzed for antioxidant and type II diabetes related enzyme inhibition properties. The methanolic extract of raw seeds contained total free phenolic content of 14.85 ± 0.32 g catechin equivalent/100 g extract DM. Encouraging levels of ferric reducing/antioxidant power (FRAP, 1179 mmol Fe[II]/mg extract), inhibition of β-carotene degradation (41.13%) and radical scavenging activity against DPPH (54.64%) and superoxide (54.53%) were exhibited by the raw sample. Further, it also recorded 77.92% of α-amylase and 86.50% of α-glucosidase enzyme inhibition characteristics under in vitro starch digestion bioassay. 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 P. pinnata 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 24.24 and 45.14%, respectively during sprouting + oil-frying treatment, which are more desirable for the dietary management of type II diabetic patients.