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Extracts, subfractions, isolated anthocyanins and isolated procyanidins B2, B5 and C1 from the berries and bark of Aronia melanocarpa were investigated for their antioxidant and enzyme inhibitory activities. Four different bioassays were used, namely scavenging of the diphenylpicrylhydrazyl (DPPH) radical, inhibition of 15-lipoxygenase (15-LO), inhibition of xanthine oxidase (XO) and inhibition of α-glucosidase. Among the anthocyanins, cyanidin 3-arabinoside possessed the strongest and cyanidin 3-xyloside the weakest radical scavenging and enzyme inhibitory activity. These effects seem to be influenced by the sugar units linked to the anthocyanidin. Subfractions enriched in procyanidins were found to be potent α-glucosidase inhibitors; they possessed high radical scavenging properties, strong inhibitory activity towards 15-LO and moderate inhibitory activity towards XO. Trimeric procyanidin C1 showed higher activity in the biological assays compared to the dimeric procyanidins B2 and B5. This study suggests that different polyphenolic compounds of A. melanocarpa can have beneficial effects in reducing blood glucose levels due to inhibition of α-glucosidase and may have a potential to alleviate oxidative stress.

Uptake of glucose and fatty acids in skeletal muscle is of interest for type 2 diabetes treatment. The aim was to study glucose and fatty acid uptake in skeletal muscle cells, antioxidant effects, and inhibition of carbohydrate-hydrolyzing enzymes by elderberries. Enhanced glucose and oleic acid uptake in human skeletal muscle cells were observed after treatment with phenolic elderberry extracts, anthocyanins, procyanidins, and their metabolites. The 96% EtOH and the acidified MeOH extracts were highly active. Of the isolated substances, cyanidin-3-glucoside and cyanidin-3-sambubioside showed highest stimulation of uptake. Phloroglucinol aldehyde was most active among the metabolites. Isolated anthocyanins and procyanidins are strong radical scavengers and are good inhibitors of 15-lipoxygenase and moderate inhibitors of xanthine oxidase. As α-amylase and α-glucosidase inhibitors, they are considerably better than the positive control acarbose. The antidiabetic property of elderberry phenolics increases the nutritional value of this plant and indicates potential as functional food against diabetes.

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