Piperine exhibits preventive and curative effect on erythrocytes membrane modifications and oxidative stress against in vitro albumin glycation.

Inhibition of non-enzymatic glycation processes is an essential aspect of treating type 2 diabetes and related complications. In this study, piperine's preventative, simultaneous and curative effect in glucose-induced albumin glycation was examined by analyzing the structural and functional markers of albumin. The protective and antioxidant influence of piperine on erythrocytes was assessed by examining cellular membrane modifications with antioxidant status. Albumin glycation was performed in three different experimental sets of 21 days at 37°C in dark conditions-using different piperine concentrations (250, 500, and 1,000 µM) and time of addition of glucose (30 mM)/piperine (1,000 µM) in a respective solution at 10th day. Piperine with glycated albumin leads to decreased fructosamine, carbonyl group, and protein-bound glucose. It had protected free amino groups, thiol group, and reduced beta-amyloid, protein aggregates formation. The presence of piperine with glycated albumin prevented erythrocytes hemolysis, membrane modifications, and maintained the antioxidant status. Piperine showed the antiglycation effects in a dose-dependent manner, additionally, its pre-treatment exhibited maximum attenuation by manifesting its primarily preventive role. PRACTICAL APPLICATIONS: Piperine is a natural alkaloid compound found in pepper, has been reported to possess anti-cancer, anti-microbial, and anti-inflammatory properties. The present study evaluated the antiglycation potential of piperine in albumin's glycation and it displayed preventive action, protected erythrocytes from oxidative damage induced by glycated albumin. We concluded that the daily intake of piperine can be adequate to prevent glycation-induced diabetic complications development in hyperglycemic conditions.

Zinc inhibits glycation induced structural, functional modifications in albumin and protects erythrocytes from glycated albumin toxicity.

The present work aims to investigate the concentration and time dependant effect of zinc on the in vitro non enzymatic modifications of albumin by diabetic levels of glucose. Further, preventive and curative effect of zinc was studied by adding zinc before and after initiation of glycation respectively. Glycation of albumin was done at different concentrations of zinc (125, 250 and 500 µM) at different time intervals (21, 28 and 35 days) with appropriate controls. The antiglycation potential of zinc was assessed by estimating different markers of albumin glycation (fructosamines, carbonyls, bound sugar, AGEs), structural modifications (free amino, thiol group, ß amyloid, native PAGE, ANS binding, fluorescence lifetime decay and CD analysis) and functional properties (antioxidant activity, hemolysis). Zinc at highest concentration (500 µM) significantly reduced modifications of albumin which was comparable to aminoguanidine and also protected secondary and tertiary structure of albumin after 28 days of incubation. Zinc exhibited significant protective effect on erythrocytes by inhibiting hemolysis. Thus the present study indicate preventive mode of albumin glycation inhibition by zinc.

Aqueous extract of some indigenous medicinal plants inhibits glycation at multiple stages and protects erythrocytes from oxidative damage-an in vitro study.

Azadirachta indica, Emblica officinalis, Syzygium cumini and Terminalia bellirica are common in Indian system of traditional medicine for the prevention of diabetes and its complications. The aim of the present study was to comprehensively and comparatively investigate the antiglycation potential of these plant extracts at multiple stages and their possible protective effect against glycated albumin mediated toxicity to erythrocytes. Antiglycation activities of these plant extracts was measured by co-incubation of plant extract with bovine serum albumin-fructose glycation model. The multistage glycation markers- fructosamines (early stage), protein carbonyls (intermediate stage) and AGEs (late stage) are investigated along with measurement of thiols and ß aggregation of albumin using amyloid-specific dyes-Congo red and Th T. Protection of erythrocytes from glycated albumin induced toxicity by these plant extracts was assessed by measuring erythrocytes hemolysis, lipid peroxidation, reduced glutathione and intracellular antioxidant capacity. Total phenolics, reducing power and antioxidant activities of the plant extracts were also measured. In vitro glycation assays showed that plant extracts exerted site specific inhibitory effects at multiple stages, with T. bellirica showing maximum attenuation. In erythrocytes, along with the retardation of glycated albumin induced hemolysis and lipid-peroxidation, T. bellirica considerably maintained cellular antioxidant potential. Significant positive correlations were observed between erythrocyte protection parameters with total phenolics. These plant extracts especially T. bellirica prevents glycation induced albumin modifications and subsequent toxicity to erythrocytes which might offer additional protection against diabetic vascular complications.

Nutraceutical properties of dietary plants extracts: prevention of diabetic nephropathy through inhibition of glycation and toxicity to erythrocytes and HEK293 cells.

CONTEXT: Glycated albumin is reported to elicit pathobiologic effects in diabetic nephropathy and abrogating its biologic effects has novel therapeutic potential. OBJECTIVE: This study examines the effects of dietary plants extracts (Laurus nobilis, Carum carvi, Coccinia grandis, Mentha arvensis, Phaseolus vulgaris) against albumin glycation and its toxicity to erythrocytes and HEK293 cells. MATERIALS AND METHODS: Albumin (10 mg/ml) was incubated with fructose (250 mM) in PBS along with aqueous plant extracts (1% w/v) for 4 d. After incubation, the antiglycation potential of extracts was estimated by measuring AGEs, fructosamine, amyloids, carbonyls, free amino groups, and antioxidant potential of albumin. The glycation extent of the treated samples was determined by boronate affinity chromatography. Effect of extracts against glycation induced cytotoxicity in erythrocytes and HEK 293 cells was assessed by estimating viability, glutathione, and antioxidant capacity. Plant extracts were tested for their phenolic content and antioxidant potential (reducing potential, DPPH, ABTS, NO, and H2O2 radical scavenging activities). RESULTS: Plant extracts significantly decreased the AGEs formation and amyloid aggregation in glycated BSA (p < 0.001). Further, fructosamine and carbonyls were reduced to 55-72% and 83-89%, respectively. Free amino group and antioxidant activity of albumin were also preserved by 1.25-1.40-fold and 1.75-1.8-fold, respectively. Further, co-incubation of extracts with glycated albumin, protected erythrocytes, and HEK293 cells as they inhibited cellular hemolysis/toxicity (p < 0.001) by upregulating cellular antioxidants. DISCUSSION AND CONCLUSION: Plant co-incubation reversed many modifications in albumin glycation, cellular dysfunction indicating that dietary sources with antiglycating and antioxidant potential could be considered for the effective management of diabetic nephropathy.