Ethanol extract of mango (Mangifera indica L.) peel inhibits α-amylase and α-glucosidase activities, and ameliorates diabetes related biochemical parameters in streptozotocin (STZ)-induced diabetic rats.

Peel is a major by-product during processing of
mango fruit into pulp. Recent report indicates that the whole
peel powder ameliorated diabetes. In the present study,
ethanolic extract of mango peel was analysed for its bioactive
compounds, evaluated for α-amylase and α-glucosidase inhibitory
properties, oral glucose tolerance test, antioxidant
properties, plasma insulin level and biochemical parameters
related to diabetes. In addition to gallic and protocatechuic
acids, the extract also had chlorogenic and ferulic acids, which
were not reported earlier in mango peel extracts. The peel
extract inhibited α-amylase and α-glucosidase activities, with
IC50 values of 4.0 and 3.5 μg/ml. Ethanolic extract of peel
showed better glucose utilization in oral glucose tolerance test.
Treatment of streptozotocin-induced diabetic rats with the extract
decreased fasting blood glucose, fructosamine and
glycated hemoglobin levels, and increased plasma insulin level.
Peel extract treatment decreased malondialdehyde level,
but increased the activities of antioxidant enzymes significantly
in liver and kidney compared to diabetic rats. These beneficial
effects were comparable to metformin, but better than
gallic acid treated diabetic rats. The beneficial effects of peel
extract may be through different mechanism like increased
plasma insulin levels, decreased oxidative stress and inhibition
of carbohydrate hydrolyzing enzyme activities by its bioactive
compounds. Thus, results suggest that the peel extract can
be a potential source of nutraceutical or can be used in functional
foods and this is the first report on antidiabetic properties
of mango peel extract.