Mohd Sajid Khan

Glycoxidation of biological macromolecules: A critical approach to halt the menace of glycation

Glycation is the result of covalent bonding of a free amino group of biological macromolecules with a reducing sugar, which results in the formation of a Schiff base that undergoes rearrangement, dehydration and cyclization to form a more stable Amadori product. The final products of nonenzymatic glycation of biomacromolecules like DNA, proteins and lipids are known as advanced glycation end products (AGEs). AGEs may be generated rapidly or over long times stimulated by distinct triggering mechanisms, thereby accounting for their roles in multiple settings and disease states. Both Schiff base and Amadori glycation products generate free radicals resulting in decline of antioxidant defense mechanisms and can damage cellular organelles and enzymes. This critical review primarily focuses on the mechanistic insight of glycation and the most probable route for the formation of glycation products and their therapeutic interventions. Furthermore, the prevention of glycation reaction using therapeutic drugs such as metformin, pyridoxamine and aminoguanidine (AG) are discussed with special emphasis on the novel concept of the bioconjugation of these drugs like, AG with gold nanoparticles (GNPs). At or above 10 mM concentration, AG is found to be toxic and therefore has serious health concerns, and the study warrants doing this novel bioconjugation of AG with GNPs. This approach might increase the efficacy of the AG at a reduced concentration with low or no toxicity. Using the concept of synthesis of GNPs with abovementioned drugs, it is assumed that toxicity of various drugs which are used at high doses can be minimized more effectively.

Inhibitory Effect of Metformin and Pyridoxamine in the Formation of Early, Intermediate and Advanced Glycation End-Products

Background Non-enzymatic glycation is the addition of free carbonyl group of reducing sugar to the free amino groups of proteins, resulting in the formation of a Schiff base and an Amadori product. Dihydroxyacetone (DHA) is one of the carbonyl species which reacts rapidly with the free amino groups of proteins to form advanced glycation end products (AGEs). The highly reactive dihydroxyacetone phosphate is a derivative of dihydroxyacetone (DHA), and a product of glycolysis, having potential glycating effects to form AGEs. The formation of AGEs results in the generation of free radicals which play an important role in the pathophysiology of aging and diabetic complications. While the formation of DHA-AGEs has been demonstrated previously, no extensive studies have been performed to assess the inhibition of AGE inhibitors at all the three stages of glycation (early, intermediate and late) using metformin (MF) and pyridoxamine (PM) as a novel inhibitor. Methodology/Principal Findings In this study we report glycation of human serum albumin (HSA) & its characterization by various spectroscopic techniques. Furthermore, inhibition of glycation products at all the stages of glycation was also studied. Spectroscopic analysis suggests structural perturbations in the HSA as a result of modification which might be due to generation of free radicals and formation of AGEs. Conclusion The inhibition in the formation of glycation reaction reveals that Pyridoxamine is a better antiglycating agent than Metformin at all stages of the glycation (early, intermediate and late stages).

Immunogenicity of DNA-advanced glycation end product fashioned through glyoxal and arginine in the presence of Fe3+: Its potential role in prompt recognition of diabetes mellitus auto-antibodies

Glyoxal, methylglyoxal and 3-deoxyglucosones are reactive dicarbonyl compounds, which transform free amino groups of proteins and lipoproteins macromolecule into advanced glycation end-products (AGEs). AGEs play a significant role in the pathophysiology of aging and diabetic complications because of their genotoxic effect. Glyoxal also reacts with free amino group of nucleic acids resulting in the formation of DNA-AGEs. The present study reports the genotoxicity and immunogenicity of AGEs formed by Glyoxal-Arginine-Fe(3+) (G-Arg-Fe(3+)) system as a glycating agent. Immunogenicity of native and G-Arg-Fe(3+)-DNA was probed in female rabbits. Immunofluorescence suggests the presence of immune complex deposition in the kidney section of immunized rabbits. Spectroscopic analysis and melting temperature indicates the structural modification in the human DNA. The modified human DNA is found to be highly immunogenic, whereas unmodified form was simply non-immunogenic. This study shows the presence of auto-antibodies against G-Arg-Fe(3+) modified human DNA in the sera of diabetes type 1 and in few cases type 2 patients due to secondary complications of nephropathy. The glyco-oxidative lesions have also been detected in the lymphocyte DNA isolated from patients having type 1 and type 2 diabetes. The results show structural perturbations generating new epitopes in G-Arg-Fe(3+)-DNA rendering it pretty immunogenic.

Diversity-oriented synthesis of α-aminophosphonates: a new class of potential anticancer agents.

A small library of structurally diverse α-aminophosphonates has been synthesized by reacting alkyl/aryl aldehydes, alkyl/aryl amines and alkyl/aryl phosphites in one-pot catalyzed by Amberlite-IR 120 resin (acidic). All the synthesized α-aminophosphonates were assayed for their in vitro cytotoxic activities against a panel of five human cancer cell lines including A-549, NCI-H23 (Lung), Colo 320DM (Colon), MG-63 (Bone marrow) and Jurkat (Blood T lymphocytes). Compound 4n having (R)-1-phenylethanamine was found to be the most active amongst all the synthesized α-aminophosphonates against all the five cancer cell lines, most prominent being against Jurkat cell line with an IC50 value of 4 μM. Surprisingly, compound 4o having (S)-1-phenylethanamine was found to be devoid of any cytotoxicity. Our finding suggests that these chemical entities could further serve as interesting template for the design of potential anticancer agents.

Antioxidant and α -amylase inhibitory property of phyllanthus virgatus L.: an in vitro and molecular interaction study.

The present study on Phyllanthus virgatus, known traditionally for its remedial potential, for the first time provides descriptions of the antioxidant and inhibition of α-amylase enzyme activity first by in vitro analyses, followed by a confirmatory in silico study to create a stronger biochemical rationale. Our results illustrated that P. virgatus methanol extract exhibited strong antioxidant and oxidative DNA damage protective activity than other extracts, which was well correlated with its total phenolic content. In addition, P. virgatus methanol extract strongly inhibited the α-amylase activity (IC50 33.20 ± 0.556 μg/mL), in a noncompetitive manner, than acarbose (IC50 76.88 ± 0.277 μg/mL), which showed competitive inhibition. Moreover, this extract stimulated the glucose uptake activity in 3T3-L1 cells and also showed a good correlation between antioxidant and α-amylase activities. The molecular docking studies of the major bioactive compounds (9,12-octadecadienoic acid, asarone, 11-octadecenoic acid, and acrylic acid) revealed via GC-MS analysis from this extract mechanistically suggested that the inhibitory property may be due to the synergistic effect of these bioactive compounds. These results provide substantial basis for the future use of P. virgatus methanol extract and its bioactive compound in in vivo system for the treatment and management of diabetes as well as in the related condition of oxidative stress.

Evaluation of antihepatotoxic potential of Solanum xanthocarpum fruit extract against antitubercular drugs induced hepatopathy in experimental rodents.

OBJECTIVE To assess the hepatoprotective effect of Solanum xanthocarpum (S. xanthocarpum) fruit extract against antitubercular drug-induced liver toxicity in experimental animals. METHODS Ethanolic (50%) fruit extract of S. xanthocarpum (100, 200 and 400 mg/kg bw) was administered daily for 35 days in experimental animals. Liver toxicity was induced by combination of three antitubercular drugs [isoniazid (I) 7.5 mg/kg, rifampicin (R) 10 mg/kg and pyrazinamide (P) 35 mg/kg] given orally as suspension for 35 days in rats. The hepatoprotective activity was assessed using various biochemical parameters like aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatise (ALP), total bilirubin (TBL), albumin (ALB), total protein (TP), lactate dehydroginase (LDH), and serum cholesterol (CHL). Meanwhile, in vivo antioxidant activities as lipid peroxidation (LPO), reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) were measured in rat liver homogenate. The biochemical observations were supplemented by histopathological examination. RESULTS The results demonstrated that treatment with S. xanthocarpum significantly (P<0.05-P<0.001) and dose-dependently prevented drug induced increase in serum levels of hepatic enzymes. Furthermore, S. xanthocarpum significantly (up to P<0.001) reduced the LPO in the liver tissue and restored activities of defence antioxidant enzymes GSH, SOD and CAT towards normal levels. Histopathology of the liver tissue showed that S. xanthocarpum attenuated the hepatocellular necrosis and led to reduction in inflammatory cells infiltration. CONCLUSIONS The results of this study strongly indicate the protective effect of S. xanthocarpum against liver injury which may be attributed to its hepatoprotective activity, and thereby scientifically support its traditional use.

Glycation-assisted synthesized gold nanoparticles inhibit growth of bone cancer cells.

This study presents a novel approach to synthesize glycogenic gold nanoparticles (glycogenic GNps) capped with glycated products (Schiffs base, Heyns products, fructosylamine etc.). These glycogenic GNps have been found to be active against human osteosarcoma cell line (Saos-2) with an IC50 of 0.187 mM, while the normal human embryonic lung cell line (L-132) remained unaffected up to 1mM concentration. The size of glycogenic GNps can also be controlled by varying the time of incubation of gold solution. Glycation reactions involving a combination of fructose and HSA (Human Serum Albumin) were found to be effective in the reduction of gold to glycogenic GNps whereas glucose in combination with HSA did not result in the reduction of gold. The progress of the reaction was followed using UV-visible spectroscopy and NBT (Nitroblue tetrazolium) assay. The glycogenic GNps were found to be spherical in shape with an average size of 24.3 nm, in a stable emulsion. These GNps were characterized using UV-visible spectroscopy, zeta potential analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

Antimicrobial potential of bacteriocins: in therapy, agriculture and food preservation.

Due to the appearance of antibiotic resistance and the toxicity associated with currently used antibiotics, peptide antibiotics are the need of the hour. Thus, demand for new antimicrobial agents has brought great interest in new technologies to enhance safety. One such antimicrobial molecule is bacteriocin, synthesised by various micro-organisms. Bacteriocins are widely used in agriculture, veterinary medicine as a therapeutic, and as a food preservative agent to control various infectious and food-borne pathogens. In this review, we highlight the potential therapeutic and food preservative applications of bacteriocin.

An in vitro and molecular informatics study to evaluate the antioxidative and β-hydroxy-β-methylglutaryl-CoA reductase inhibitory property of Ficus virens Ait.

The present study is initially intended to evaluate antioxidant and β‐hydroxy‐β‐methylglutaryl‐CoA reductase (HMGR) inhibitory property of Ficus virens Ait., first by in vitro analyses followed by a corroboratory molecular informatics study. Our results show that of all the sequentially extracted fraction of F. virens bark and leaves extract, F. virens bark methanol extract exhibits strong radical scavenging, antioxidant and oxidative DNA damage protective activity, which is well correlated with its total phenolic content. In addition, F. virens bark methanol extract, which is non‐cytotoxic, significantly and non‐covalently inhibit the HMGR activity (IC50 = 3.45 ± 0.45 µg/ml) in comparison with other extracts. The mechanistic aspect of this inhibition activity is authenticated by molecular docking study of bioactive compounds as revealed from gas chromatography–mass spectrometry data, with HMGR. The analysis for the first time indicates that quinic acid (ΔG: −8.11 kcal/mol) and paravastatin (ΔG: −8.22 kcal/mol) exhibit almost same binding energy, while other compounds also showed good binding energy, suggesting that quinic acid alone or in combination with other major bioactive compound is probably responsible for HMGR inhibitory property of the extract and plausibly can be used in in vivo system for the management, prevention, and alleviation of hypercholesterolemia as well as hypercholesterolemia‐induced oxidative stress. Copyright

In vitro screening for β-hydroxy-β-methylglutaryl-CoA reductase inhibitory and antioxidant activity of sequentially extracted fractions of Ficus palmata Forsk.

Hypercholesterolemia-induced oxidative stress has been strongly implicated in the pathogenesis of atherosclerosis, which is one of the major causes of mortality worldwide. The current work, for the first time, accounts the antioxidant, genoprotective, antilipoperoxidative, and HMG-CoA reductase (EC 1.1.1.34) inhibitory properties of traditional medicinal plant, Ficus palmata Forsk. Our result showed that among sequentially extracted fractions of Ficus palmata Forsk, FPBA (F. palmata bark aqueous extract) and FPLM (F. palmata leaves methanolic extract) extracts have higher phenolic content and also exhibited significantly more radical scavenging (DPPH and Superoxide) and antioxidant (FRAP) capacity. Moreover, FPBA extract also exhibited significantly higher inhibition of lipid peroxidation assay. Additionally, results showed almost complete and partial protection of oxidatively damaged DNA by these plant extracts when compared to mannitol. Furthermore, our results showed that FPBA extract (IC50 = 9.1 ± 0.61 µg/mL) exhibited noteworthy inhibition of HMG-CoA reductase activity as compared to other extracts, which might suggest its role as cardioprotective agent. In conclusion, results showed that FPBA extract not only possess significant antioxidant and genoprotective property but also is able to attenuate the enzymatic activity of HMG-CoA reductase, which might suggest its role in combating various oxidative stress-related diseases, including atherosclerosis.