br Introduction Anthocyanidins and anthocyanins

Introduction Anthocyanidins and anthocyanins (glycosides of anthocyanidins) are flavonoid phenolic compounds that are among the most common types of plant pigments [1]. They typically are responsible for the red, orange, blue, and violet colors in flowers, fruits, and vegetative tissues [1], [2]. They are water soluble, with various biological activities, including antioxidant, anti-inflammatory, anti-cancer, and anti-diabetic activities [3], and they have been used as colorants in food and cosmetic products [4]. Among the various anthocyanins, cyanidin-3-O-glucoside has been shown to suppress reproductive toxicity induced by acrylamide and glycidamide in leydig cell [5]. Cyanidin was reported to down-regulate superoxide anion and hydroxyl radical generation in a lysine/methylglycoxal system [6]. Furthermore, anthocyanin derivatives are characterized by their different forms depending on the pH value of the solution. With a pH > 7, cyanidins are degraded to aldehydes and phenolic acids or changed with diketone [7]. α-Glucosidase (EC 3.2.1.20), which is located on the epithelium of the small intestine, is a hydrolase that converts starch and tetraethylammonium to glucose by reacting with 1,4-α linkages during digestion [8], [9]. Free monosaccharides absorbed in the bloodstream can result in hyperglycemia caused by type-2 diabetes [9]. Therefore, the development of α-glucosidase inhibitors, such as acarbose, voglibose, and miglitol, has been critical treatments for type-2 diabetes by reducing postprandial hyperglycemia [8], [9]. In 2014, there were 422 million diabetics, and in 2015, there were 1.6 million reported deaths directly from this disease [10]. In a 2012 report, type-2 diabetes is found in 90% of all diabetics [11]. By 2030, the World Health Organization predicts that diabetes will be the seventh leading cause of death [10]. Therefore, additional treatments will be necessary to combat the growing incidence of this disease. Recently, anti-diabetic inhibitors have been developed flavonoids from natural plants [12]. Kaempferol, quercetin, luteolin, quercetin 3-O-(6-O˝-galloyl)-β-glucopyranoside and 3,7,8,3′,4′-pentahydroxyflavone has showed potential inhibitory activities to prevent the catalytic reaction of α-glucosidase [12], [13]. These inhibitors are similar to the anthocyanin structure except for the difference in the positive charge of oxygen of the C-ring of flavonoids [14].
Results and discussion
Conclusion This study evaluated the inhibitory activity of anthocyanin derivatives 1–8 on α-glucosidase. Delphinidin (4) and petunidin-3-O- β-glucoside (8) showed the greatest potential inhibitory activity, with IC50 values of 14.4 ± 0.1 and 29.7 ± 1.2 μM, respectively. Furthermore, these compounds are mixed with noncompetitive inhibitors that bind more with greater affinity to allosteric sites, with ki values of 18.5 ± 1.4 and 24.3 ± 2.1 μM, respectively. Fluorescence quenching of α-glucosidase by anthocyanins was supported by the binding information of Ksv, Kb, and n values between their complexes. Molecular docking simulations allowed us to find predicted binding positions on the receptor. Inhibitors 4 and 8 have been suggested to have hydrogen bonds within 3.5 Å distance of Gly155, Thr227, Lys231, Leu232 and Asn309, (compound 4) and Gln61, Met64, Glu397 and Trp460 (compound 8). The potential inhibitor (4) influenced the structure of α-glucosidase, while the complex of ligand with receptor was calculated as GROMOS force field by molecular simulation. Therefore, delphinidin (4) and petunidin-3-O-β-glucoside (8) may be excellent potential inhibitors of α-glucosidase as targets for treating diabetes.
Materials and methods
Introduction The β-glucosidase enzyme catalyzes the specific hydrolysis of β-D-1,4-glycosidic bonds in oligosaccharides, disaccharides, and conjugated glycosides [1,2], consequently finding many applications in different industrial sectors. In the lignocellulosic biomass conversion process, β-glucosidase acts together with other specialized cellulase enzymes in the hydrolysis of cellulose to glucose, which can be used to obtain biofuels and other bioproducts, according to the biorefinery concept [3,4]. β-Glucosidase plays a key role in these biomass-to-sugar platforms, releasing glucose from cellobiose and preventing inhibition of the enzymes endoglucanase and cellobiohydrolase [5,6]. β-Glucosidase enzymes are also important in the food and beverage sectors, where they are used to enhance the quality of wines, teas, and juices [7,8]. In the pharmaceutical sector, β-glucosidase is employed for the hydrolysis of isoflavone glycosides, found in soybean agro-industrial residues, generating aglycone molecules that have estrogenic properties [9,10]. Therefore, finding an effective strategy to allow the recovery of β-glucosidase for reuse would be of great interest to these industrial sectors, given the high cost of the enzyme [11,12].