title: Aged garlic extract and S-allyl cysteine prevent formation of advanced glycation endproducts.
abstract: Hyperglycaemia causes increased protein glycation and the formation of advanced glycation endproducts which underlie the complications of diabetes and ageing. Glycation is accompanied by metal-catalysed oxidation of glucose and Amadori products to form free radicals capable of protein fragmentation. Aged garlic extract is a potent antioxidant with established lipid-lowering effects attributed largely to a key ingredient called S-allyl cysteine. This study investigated the ability of aged garlic extract and S-allyl cysteine to inhibit advanced glycation in vitro. Bovine serum albumin (BSA) was glycated in the presence of Cu(2+) ions and different concentrations of aged garlic extract and protein fragmentation was examined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Lysozyme was glycated by glucose or methylglyoxal in the presence of different concentrations of aged garlic extract or S-allyl cysteine with subsequent analysis of glycation-derived crosslinking using SDS-PAGE. Amadori-rich protein was prepared by dialysing lysozyme that had been glycated by ribose for 24 h. This ribated lysozyme was reincubated and the effects of aged garlic extract, S-allyl cysteine and pyridoxamine on glycation-induced crosslinking was monitored. Aged garlic extract inhibited metal-catalysed protein fragmentation. Both aged garlic extract and S-allyl cysteine inhibited formation of glucose and methylglyoxal derived advanced glycation endproducts and showed potent Amadorin activity when compared to pyridoxamine. S-allyl cysteine inhibited formation of carboxymethyllysine (CML), a non-crosslinked advanced glycation endproduct derived from oxidative processes. Further studies are required to assess whether aged garlic extract and S-allyl cysteine can protect against the harmful effects of glycation and free radicals in diabetes and ageing.
authors.affiliation: School of Biology, Chemistry and Health Science, Manchester Metropolitan University, Oxford Road, Manchester M1 5GD, UK.
authors.forename: Muhammad Saeed
authors.initials: MS
authors.lastname: Ahmad
authors.forename: Monika
authors.initials: M
authors.lastname: Pischetsrieder
authors.forename: Nessar
authors.initials: N
authors.lastname: Ahmed
mesh_terms: D000375:Aging / Q000473:pathology; D000975:Antioxidants / Q000008:administration & dosage / Q000494:pharmacology*; D003545:Cysteine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D048909:Diabetes Complications / Q000473:pathology / Q000517:prevention & control; D004591:Electrophoresis, Polyacrylamide Gel; D005609:Free Radicals / Q000378:metabolism; D005737:Garlic / Q000737:chemistry*; D005947:Glucose / Q000378:metabolism; D017127:Glycation End Products, Advanced / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D006943:Hyperglycemia / Q000503:physiopathology; D009113:Muramidase / Q000378:metabolism; D010446:Peptide Fragments / Q000187:drug effects / Q000378:metabolism; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology*; D011733:Pyridoxamine / Q000378:metabolism; D011765:Pyruvaldehyde / Q000378:metabolism; D012266:Ribose / Q000378:metabolism
chemical_list: D000975:Antioxidants; D005609:Free Radicals; D017127:Glycation End Products, Advanced; D010446:Peptide Fragments; D010936:Plant Extracts; D011733:Pyridoxamine; D012266:Ribose; D011765:Pyruvaldehyde; C065299:S-allylcysteine; D009113:Muramidase; D005947:Glucose; D003545:Cysteine