Polyphenols composition and anti-diabetic properties in vitro of haskap (Lonicera caerulea L.) berries in relation to cultivar and harvesting date

Abstract

Haskap (Lonicera caerulea L.) is a recently commercialized fruit crop in Canada. Berries of four cultivars, Aurora, Rebecca, Larissa, and Evie, were harvested at five harvesting dates (H1-H5) and assessed for their polyphenol composition and anti-diabetic potential in vitro. The analyses revealed that the interaction effect of cultivar and harvesting date influenced the concentration of anthocyanins. Cyanidin-3-O-glucoside represents about 79 % of total anthocyanins present in ripened haskap berries. Total anthocyanins estimated by a non-destructive method showed a strong correlation for quantified anthocyanin by liquid chromatography-mass spectrometry (UPLC-ESI-MS), indicating the potential application of the non-destructive method for deciding the berry maturity for mechanical harvesting of haskap berry for value-added processing. Extracts derived from five maturity stages of four cultivars showed anti-diabetic properties including inhibition of activities of alpha-amylase (IC50 ranges from 2380 to 5080 μg/mL), alpha-glucosidase (IC50 ranges from 1130 to 2120 μg/mL), dipeptidyl peptidase-4 (DPP-4, IC50 ranges from 2150 to 11,600 μg/mL), and formation of advanced glycation end-products (AGE, IC50 ranges from 1200 to 4790 μg/mL) in vitro. Though the impact of harvesting date on polyphenol composition is very distinct, the extracts of late harvesting date (H5) reduced the anti-diabetic activities in vitro only in Aurora and Larisa cultivars. Inhibition of DPP-4 and AGE formation dependent on cultivar and harvesting date. Haskap berry warrants further investigation as a dietary therapeutic to manage type 2 diabetes.