Activity-Guided Fractionation of Red Fruit Extracts for the Identification of Compounds Influencing Glucose Metabolism

Abstract

An activity-guided search for compounds influencing glucose metabolism in extracts from aronia (Aronia melanocarpa, A.), pomegranate (Punica granatum L., P.), and red grape (Vitis vinifera, RG) was carried out. The three extracts were fractionated by means of membrane chromatography to separate the anthocyanins from other noncolored phenolic compounds (copigments). In addition, precipitation with hexane was performed to isolate the polymers (PF). The anthocyanin and copigment fractions (AF, CF) of aronia, pomegranate, and red grape were furthermore fractionated with high-performance countercurrent chromatography (HPCCC) and the subfractions were characterized by HPLC-PDA-MS/MS analyses. Each of the (sub-)fractions was examined by in vitro-tests, i.e., the inhibition of the activity of α-amylase and α-glucosidase. On the basis of this screening, several potent inhibitors of the two enzymes could be identified, which included flavonols (e.g., quercetin), ellagitannins (e.g., pedunculagin), and anthocyanins (e.g., delphinidin-3-glucoside and petunidin-3-glucoside). In the α-glucosidase assay all of the examined fractions and subfractions of the fruit extracts were more active than the positive control acarbose.

In Vitro Bioaccessibility of Extractable Compounds from Tannat Grape Skin Possessing Health Promoting Properties with Potential to Reduce the Risk of Diabetes

“…Tannins (proanthocyanidins and ellagitannins) from grape extracts showed inhibition of α-amylase enzymatic activity [30], being in accordance with the results of the present work. Anthocyanins delphinidin-3-glucoside and petunidin-3-glucoside present in the extract according to UHPLC-MS/MS results, were found to inhibit α-amylase and α-glucosidase activities, as well as a red grape extract anthocyanin fraction that showed an IC 50 value of 589 ± 57 µg/mL for α-amylase inhibition and 80.9 ± 3.6 µg/mL for α-glucosidase inhibition [31]. Non-anthocyanins flavonoids, such as rutin and quercetin, are also potent inhibitors of α-glucosidase finding increased inhibition by the number of hydroxyl groups on the B-ring and glycosylation at both 3-OH and 5-OH [32], being quercetin present in the extract as well, according to UHPLC-MS/MS results.…”

Impact of B-Ring Substitution and Acylation with Hydroxy Cinnamic Acids on the Inhibition of Porcine α-Amylase by Anthocyanin-3-Glycosides

“…As anthocyanins are also promising glucosidase inhibitors [15], an increased inhibitory effect for acylated anthocyanins is conceivable. Based on plant extracts containing acylated anthocyanins, Matsui et al propose that acetylated anthocyanins are better inhibitors for α-glucosidases than the non-acylated representatives [35].…”

“…Acarbose (ACA) is a commercially available drug to inhibit enzymes of the carbohydrate metabolism and to reduce the absorption of glucose into the body [10], hence lowering postprandial glucose levels and preventing hyperglycemia. Inhibitory effects of anthocyanins [11][12][13] and anthocyanin-rich plant extracts [12,14,15] on the intestinal α-amylase in in vitro experiments, thus reducing starch degradation and glucose formation by α-glucosidase, have also been proposed. However, systematic studies of the impact of their B-ring substitution and the effect of an additional acylation do not exist.…”

Anthocyanins as Antidiabetic Agents—In Vitro and In Silico Approaches of Preventive and Therapeutic Effects

“…A study of the influence of the red fruit components on α-amylase and α-glucosidase activities have identified some anthocyanins (D3G > petunidin-3-glucoside (Pet3G) > Peo3G) as potential inhibitors (even better than acarbose in the α-glucosidase assays) [ 92 ]. The obtained inhibition order, as well as many other studies, proposed that a high amount of hydroxyl groups on ring B is advantageous for the inhibition, whilst the methylation and methoxylation reduces the inhibitory activity [ 79 , 80 ].…”