Sources and relative stabilities of acylated and nonacylated anthocyanins in beverage systems.

Anthocyanins are considered as the largest group of water-soluble pigments found in the vacuole of plant cells, displaying range of colors from pink, orange, red, purple and blue. They belong to flavonoids, a polyphenolic subgroup. Application of anthocyanins in food systems as natural food colourants is limited due to the lack of stability under different environmental conditions such as light, pH, heat etc. Anthocyanins esterified with one or more acid groups are referred as acylated anthocyanins. Based on the presence or absence of acyl group, anthocyanins are categorized as acylated and nonacylated anthocyanins. Acylated anthocyanins are further classified as mono, di, tri, tetra acylated anthocyanins according to the number of acyl groups present in the anthocyanin. This review classifies common anthocyanin sources into non-acylated, mono-, di-, tri- and tetra-acylated anthocyanins based on the major anthocyanins present in these sources. The relative stabilities of these anthocyanins with respect to thermal, pH and photo stress in beverage systems are specifically discussed. Common anthocyanin sources such as elderberry, blackberry, and blackcurrant mainly contain nonacylated anthocyanins. Red radish, purple corn, black carrot also mainly contain mono acylated anthocyanins. Red cabbage and purple sweet potato have both mono and diacylated anthocyanins. Poly acylated anthocyanins show relatively higher stability compared with nonacylated and monoacylated anthocyanins. Several techniques such as addition of sweeteners, co-pigmentation and acylation techniques could enhance the stability of nonacylated anthocyanins. Flowers are main sources of polyacylated anthocyanins having higher stability, yet they have not been commercially exploited for their anthocyanins.

Diacylated anthocyanins from purple sweet potato (Ipomoeabatatas L.) attenuate hyperglycemia and hyperuricemia in mice induced by a high-fructose/high-fat diet. / ç´«è–¯åŒé °åŸºèŠ±è‰²è‹·å¯¹é«˜æžœç³–/é«˜è„‚è‚ªé¥®é£Ÿè¯±å¯¼çš„å°é¼ é«˜è¡€ç³–å’Œé«˜å°¿é ¸è¡€ç—‡çš„è°ƒèŠ‚ä½œç”¨.

Studies have shown that targeting xanthine oxidase (XO) can be a feasible treatment for fructose-induced hyperuricemia and hyperglycemia. This study aimed to evaluate the dual regulatory effects and molecular mechanisms of diacylated anthocyanins from purple sweet potato (diacylated AF-PSPs) on hyperglycemia and hyperuricemia induced by a high-fructose/high-fat diet. The body weight, organ index, serum biochemical indexes, and liver antioxidant indexes of mice were measured, and the kidneys were observed in pathological sections. The relative expression levels of messenger RNAs (mRNAs) of fructose metabolism pathway enzymes in kidney were detected by fluorescent real-time quantitative polymerase chain (qPCR) reaction technique, and the expression of renal transporter protein and inflammatory factor pathway protein was determined by immunohistochemistry (IHC) technique. Results showed that diacylated AF-PSPs alleviated hyperuricemia in mice, and that this effect might be related to the regulation of liver XO activity, lipid accumulation, and relevant renal transporters. Diacylated AF-PSPs reduced body weight and relieved lipid metabolism disorder, liver lipid accumulation, and liver oxidative stress, thereby enhancing insulin utilization and sensitivity, lowering blood sugar, and reducing hyperglycemia in mice. Also, diacylated AF-PSPs restored mRNA levels related to renal fructose metabolism, and reduced kidney injury and inflammation. This study provided experimental evidence for the mechanisms of dual regulation of blood glucose and uric acid (UA) by diacylated AF-PSPs and their utilization as functional foods in the management of metabolic syndrome.

Inhibition mechanism of diacylated anthocyanins from purple sweet potato (Ipomoea batatas L.) against α-amylase and α-glucosidase.

This study aimed to evaluate inhibitory activity of anthocyanins from purple sweet potato and blueberries against α-amylase and α-glucosidase, as well as investigate the inhibition mechanism of diacylated anthocyanins (Diacylated AF-PSP). Diacylated AF-PSP better inhibited α-amylase (IC50 = 0.078 mg mL-1) and α-glucosidase (IC50 = 1.56 mg mL-1) than other anthocyanin fractions, which was a mixed-type inhibitor. Fluorescence analysis indicated that Diacylated AF-PSP bound to the enzymes mainly through hydrogen bonds and influenced the microenvironments of proteins. Additionally, surface hydrophobicity and circular dichroism spectra results confirmed conformational changes in the enzymes induced by Diacylated AF-PSP. Molecular docking further demonstrated the interaction of Diacylated AF-PSP with enzyme active site, which might be stabilized by its acyl groups. Finally, 160 mg kg-1 Diacylated AF-PSP significantly decreased (p < 0.01) blood glucose level peak by 20.52% after starch administration in SD rats. This study provided theoretical evidences for utilization of diacylated anthocyanins in hyperglycemia-management functional foods.