Antioxidant and α-glucosidase inhibitory phenolics isolated from highbush blueberry flowers

Blueberries have been extensively researched, but there are limited studies on other parts of the plant. Here we report the first phytochemical examination of highbush blueberry (Vaccinium corymbosum) flowers, which yielded 21 phenolics. The compounds were identified from extensive NMR and mass spectral analyses and included five caffeic acid (1–5), three coumaric acid (6–8), and two cinnamyl alcohol (9–10) derivatives, eight flavonol glycosides (11–18), and three phenylpropanoid-substituted catechins (19–21). The isolates were evaluated for antioxidant and α-glucosidase inhibitory activities. Overall, the flavonol glycosides and phenylpropanoid-substituted catechins showed superior antioxidant activities compared to the positive controls, vitamin C (IC50 = 63 μM) and butylated hydroxytoluene (IC50 = 1548 μM). Similarly, these phenolic sub-classes were more potent α-glucosidase inhibitors than the clinical drug, acarbose (IC50 = 200 μM). Thus, non-consumed parts of food plants may be exploited as sources of bioactive compounds beyond their edible parts alone for nutraceutical and functional food applications.