The transport of more than 90% of the drugs viz. anticoagulants, analgesics, and general anesthetics in the blood takes place by albumin. Hence, albumin is the prime protein needs to be investigated to find out the nature of drug binding. Serum albumin molecules are prone to glycation at elevated blood glucose levels as observed in diabetics. In this piece of work, glycation of bovine serum albumin (BSA) was carried out with glyceraldehyde and characterized by molecular docking and fluorometry techniques. Glycation of BSA showed 25% loss of free amino groups and decreased protein fluorescence (60%) with blue shift of 6 nm. The present study was also designed to evaluate the binding of colchicine (an anti-inflammatory drug) to native and glycated BSA and its ability to displace 8-analino-1-nephthalene sulfonic acid (ANS), from the BSA-ANS complex. Binding of ANS to BSA showed strong binding (K = 4.4 μM) with native conformation in comparison to glycated state (K = 8.4 μM). On the other hand, colchicine was able to quench the fluorescence of native BSA better than glycated BSA and also showed weaker affinity (K = 23 μM) for glycated albumin compared with native state (K = 16 μM). Molecular docking study showed that both glyceraldehyde and colchicine bind to common residues located near Sudlow's site I that explain the lower binding of colchicine in the glycated BSA. Based on our results, we believe that reduced drugs-binding affinity to glycated albumin may lead to drugs accumulation and precipitation in diabetic patients.

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The non-enzymatic reaction between reducing sugars and proteins has received increased attention in nutritional and medical research recently. In the current manuscript, effect of glycation in structural changes of human serum albumin (HSA) by the metabolites of glucose such as glyoxal, methylglyoxal and glyceraldehyde was studied using different spectroscopy techniques. Glycation of HSA was monitored by following advanced glycation end-products (AGEs) fluorescence changes, HSA intrinsic fluorescence measurement, extrinsic fluorescence using 8-analino 1-nephthlene sulfonic acid (ANS) dye, and circular dichroism (CD) studies. AGEs were formed within 7 days of incubation with glyoxal, methylglyoxal and glyceraldehyde. However, methylglyoxal induced significant structural changes in HSA compared with glyoxal and glyceraldehydes. Moreover, ANS binding to native and glycated-HSA showed difference in binding pattern of these metabolites to HSA. The CD spectrum revealed changes in the secondary structure of HSA upon glycation when compared to native HSA. Furthermore, the MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide) assay established the cytotoxicity of the glycated- HSA towards human liver carcinoma (HepG2) cell lines via the production of reactive oxygen species.

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