α-Glucosidase inhibitory activity and antioxidant capacity in the peel and pulp of mixed-species blueberry hybrids
2015
Ehlenfeldt, Mark K. | Camp, Mary J. | Wang, Shiow Y.
Inhibition of α-glucosidase activity is considered an effective means for controlling diabetes by regulating glucose uptake, and blueberries have been shown to possess high levels of inhibitory activity. In the present study, we examined the variations in α-glucosidase inhibition, phenolic and anthocyanin levels, and antioxidant capacity in the peel and pulp of 16 mixed-species rabbiteye hybrids (Vaccinium ashei Reade × Vaccinium spp.), one rabbiteye cultivar (V. ashei) and two highbush hybrids (Vaccinium corymbosum). Peel tissue had, on average, about four times higher levels of α-glucosidase inhibitory activity than pulp, and exhibited significantly higher levels of all other measured activities, even though the peel comprised only a small portion of the fruit. Significant variations in the levels of antioxidant activity were observed; however, no consistent differences were observed between the hybrids with various species composition. Significant positive correlations (r≥ 0.84) were found among α-glucosidase inhibitory activity, total anthocyanin (TA) and phenolic levels, and scavenging activity against ROO∙, ∙OH, ¹O₂ and H₂O₂ radicals in the extracts from the peel and pulp. There was a high correlation observed between α-glucosidase inhibitory activity levels and ROO∙(ORAC)ₚₑₑₗ (r= 0.95). A similarly high correlation with TAₚₑₑₗ (r= 0.93) suggests that TA would be a suitable assay proxy if a broader genotypic evaluation of blueberry genotypes is desired.
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