Glucitol-core containing gallotannins inhibit the formation of advanced glycation end-products mediated by their antioxidant potential.
Glucitol-core containing gallotannins (GCGs) are polyphenols containing galloyl groups attached to a 1,5-anhydro-d-glucitol core, which is uncommon among naturally occurring plant gallotannins. GCGs have only been isolated from maple (Acer) species, including the red maple (Acer rubrum), a medicinal plant which along with the sugar maple (Acer saccharum), are the major sources of the natural sweetener, maple syrup. GCGs are reported to show antioxidant, α-glucosidase inhibitory, and antidiabetic effects, but their antiglycating potential is unknown. Herein, the inhibitory effects of five GCGs (containing 1-4 galloyls) on the formation of advanced glycation end-products (AGEs) were evaluated by MALDI-TOF mass spectroscopy, and BSA-fructose, and G.K. peptide-ribose assays. The GCGs showed superior activities compared to the synthetic antiglycating agent, aminoguanidine (IC50 15.8-151.3 vs. >300 μM) at the early, middle, and late stages of glycation. Circular dichroism data revealed that the GCGs were able to protect the secondary structure of BSA protein from glycation. The GCGs did not inhibit AGE formation by the trapping of reactive carbonyl species, namely, methylglyoxal, but showed free radical scavenging activities in the DPPH assay. The free radical quenching properties of the GCGs were further confirmed by electron paramagnetic resonance spectroscopy using ginnalin A (contains 2 galloyls) as a representative GCG. In addition, this GCG chelated ferrous iron, an oxidative catalyst of AGE formation, supported a potential antioxidant mechanism of antiglycating activity for these polyphenols. Therefore, GCGs should be further investigated for their antidiabetic potential given their antioxidant, α-glucosidase inhibitory, and antiglycating properties.
Bioactive Botanical Research Laboratory, Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA. nseeram@uri.edu.
Hang
H
Ma
Weixi
W
Liu
Leslie
L
Frost
Louis J
LJ
Kirschenbaum
Joel A
JA
Dain
Navindra P
NP
Seeram
D031002:Acer / Q000737:chemistry; D000975:Antioxidants / Q000494:pharmacology*; D002942:Circular Dichroism / Q000379:methods; D003847:Deoxyglucose / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000737:chemistry; D004077:Digoxin / Q000037:antagonists & inhibitors / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D016166:Free Radical Scavengers; D005609:Free Radicals / Q000032:analysis; D005632:Fructose / Q000378:metabolism; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000737:chemistry; D005959:Glucosidases / Q000187:drug effects*; D017127:Glycation End Products, Advanced / Q000378:metabolism; D065089:Glycoside Hydrolase Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D006031:Glycosylation / Q000187:drug effects; D006146:Guanidines; D047348:Hydrolyzable Tannins / Q000037:antagonists & inhibitors* / Q000737:chemistry; D007004:Hypoglycemic Agents / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D007501:Iron; D007502:Iron Chelating Agents / Q000032:analysis; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D059808:Polyphenols / Q000494:pharmacology; D017433:Protein Structure, Secondary; D011765:Pyruvaldehyde / Q000032:analysis / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000187:drug effects; D013012:Sorbitol / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors* / Q000737:chemistry
C559718:2-O-galloyl-1,5-anhydroglucitol; C559717:6-O-galloyl-1,5-anhydroglucitol; D000975:Antioxidants; D016166:Free Radical Scavengers; D005609:Free Radicals; D017127:Glycation End Products, Advanced; D065089:Glycoside Hydrolase Inhibitors; D006146:Guanidines; D047348:Hydrolyzable Tannins; D007004:Hypoglycemic Agents; D007502:Iron Chelating Agents; D010936:Plant Extracts; D059808:Polyphenols; C575803:ginnalin A; D012710:Serum Albumin, Bovine; D005632:Fructose; D013012:Sorbitol; D005707:Gallic Acid; D011765:Pyruvaldehyde; D004077:Digoxin; D003847:Deoxyglucose; D007501:Iron; D005959:Glucosidases; C004479:pimagedine