The Antidiabetic Effect of Grape Pomace Polysaccharide-Polyphenol Complexes

Abstract

Type 2 diabetes mellitus (T2DM) is one of the most prevalent chronic metabolic diseases of the 21st century. Nevertheless, its prevalence might be attenuated by taking advantage of bioactive compounds commonly found in fruits and vegetables. This work is focused on the recovery of polyphenols and polysaccharide–polyphenol conjugates from grape pomace for T2DM management and prevention. Bioactives were extracted by solid–liquid extraction and by pressurized hot water extraction (PHWE). Polyphenolic fraction recovered by PHWE showed the highest value for total phenolic content (427 μg GAE.mg−1), mainly anthocyanins and proanthocyanidins, and higher antioxidant activity compared to the fraction recovered by solid–liquid extraction. Polysaccharide–polyphenol conjugates comprehended pectic polysaccharides to which approximately 108 μg GAE of phenolic compounds (per mg fraction) were estimated to be bound. Polyphenols and polysaccharide–polyphenol conjugates exhibited distinct antidiabetic effects, depending on the extraction methodologies employed. Extracts were particularly relevant in the inhibition of a-glucosidase activity, with free polyphenols showing an IC50 of 0.47 μg.mL−1 while conjugates showed an IC50 of 2.7, 4.0 and 5.2 μg.mL−1 (solid–liquid extraction, PHWE at 95 and 120 °C, respectively). Antiglycation effect was more pronounced for free polyphenols recovered by PHWE, while the attenuation of glucose uptake by Caco-2 monolayers was more efficient for conjugates obtained by PHWE. The antidiabetic effect of grape pomace bioactives opens new opportunities for the exploitation of these agri-food wastes in food nutrition, the next step towards reaching a circular economy in grape products.

The Role of Nutraceutical Containing Polyphenols in Diabetes Prevention

“…Importantly, phenolic compounds are used to slow starch digestion and in the transport of simple sugars across the intestinal epithelia, thereby reducing the plasma blood glucose spike after a meal. These effects are achieved through the inhibition of amylases, glucosidases, and glucose transporters present in the gastrointestinal tract and the brush boarder membranes [74]. The extent of inhibition by phenolic compounds is dependent on their molecular structure, intake doses, and the food matrix.…”

Tempranillo Grape Extract in Transfersomes: A Nanoproduct with Antioxidant Activity

“…These findings were in accordance with previously reported work, where anthocyanins were also the main compounds found in red grape skin extracts, and among them, Mv-3- O -glc was the most important [ 29 , 30 ]. As for the other compounds, the most abundant were reported to be phenolic acids, flavan-3-ols, and flavonols [ 31 ]. In addition, oligomers and polymers of flavan-3-ols, such as (-)-epicatechin and (+)-catechin, have also been found in grape seeds [ 32 ].…”

Polymeric Compounds of Lingonberry Waste: Characterization of Antioxidant and Hypolipidemic Polysaccharides and Polyphenol-Polysaccharide Conjugates from Vaccinium vitis-idaea Press Cake

“…Antioxidant and hypolipidemic potential of polysaccharides and polyphenol–polysaccharide conjugates are markedly linked with structural specifics as molecular weight, elemental and monosaccharide composition, glycosidic linkage, and nature of conjugated polyphenolics [ 55 , 83 ]. The value of phenolic content in carbohydrate polymers is a crucial marker of radical-scavenging ability, nitric oxide (II) and hydrogen peroxide inactivating potential [ 94 ], as well as pancreatic lipase inhibition [ 95 ]. Additionally, high uronic content is an important factor of metal-chelating activity [ 96 ] and binding of bile, fat and cholesterol [ 83 ].…”