Trapping reactions of reactive carbonyl species with tea polyphenols in simulated physiological conditions

Abstract

The carbonyl stress that leads to the formation of advanced glycation end products (AGEs) in diabetes mellitus has drawn much attention recently. Reactive alpha-dicarbonyl compounds, such as glyoxal (GO) and methylglyoxal (MGO), have been shown to be a high potential glycation agent in vitro and in vivo. In this study, epicatechins in green tea and theaflavins in black tea were found to be able to reduce the concentration of MGO in physiological phosphate buffer conditions. Modified MGO derivatization for GC/flame ionization detector (FID) method in quantification was systematically conducted. In molar ratio of 3 (MGO/polyphenol), theaflavin-3,3'-digallate (TF3) in theaflavins and (-)-epigallocatechin (EGC) in epicatechins showed the highest MGO reduction at 66.65 and 45.74%, respectively, after 1 h of incubation. In kinetic study (molar ratio of MGO/polyphenol = 1:1), rapid MGO reduction occurred within 10 min. Identities of primary adducts between (-)-epigallocatechin gallate (EGCG) and MGO were determined. Newly generated stereoisomers at the C8 position of EGCG A-ring were isolated with a chiral column, and structurally confirmed by 2-D NMR analyses.

The Mechanisms of Inhibition of Advanced Glycation End Products Formation through Polyphenols in Hyperglycemic Condition

“…Inhibition of Amadori products formation, α-dicarbonyl compounds and glycation of amino group [51] Astragalus membranaceus (Milk Vetch) Astragaloside IV (AGS-IV) Lowering glucose level and aldose reductase pathway increasing plasma insulin levels and glutathione peroxidase activity [67] Camellia sinesis (Green and Black tea) Epicatechins, theaflavins, EGCG Trapping of α-dicarbonyl compounds [54,97] Chrysanthemum morifolium and C. indicum (Chrysanthemum) Chlorogenic acid, flavonoid glucoside, apigenin, caffeic acid, luteolin, kaempferol Free radical and metal scavenging [49] Cinnamomum zeylacnicum (Cinnamon) Cinnamtannin B1, catechin, epicatechin, procyanidin B2…”

“…Epicatechins and theaflavins found in green and black tea, respectively, lowered the amount of MGO to the physiological levels [97]. Active components of guava [Psidium guajava L.…”

Investigations on the effect of antioxidant type and concentration and model system matrix on acrylamide formation in model Maillard reaction systems

“…Significant reductions in Maillard reaction products in model systems with added epicatechin and hydroxycinnamic acids were attributed to similar trapping reactions between phenolics and reactive carbonyl intermediates (Jiang, Chiaro, Maddali, Prabhu, & Peterson, 2009;Lo, et al, 2006;Totlani & Peterson, 2006). However, when examining the effect of phenolics on acrylamide, positive, negative or no effects were reported, highlighting the antioxidants' ambiguous role on acrylamide formation (Bassama, Brat, Bohuon, Boulanger, & Günata, 2010;Ou, et al, 2010;Zhang, et al, 2008;Zhu, Cai, Ke, & Corke, 2009).…”

“…Their observed inhibitory effect on acrylamide formation could be attributed to a direct carbonyl-trapping property; it was reported that epicatechin may directly react with glyoxal and methylglyoxal to form adducts (Lo et al, 2006;Totlani & Peterson, 2006) in aqueous model systems, whereas under low moisture conditions epicatechin was found to form adducts primarily with C 6 sugar moieties, i.e., 3-deoxyglucosone (Totlani & Peterson, 2007). The acetaldehyde-induced oligomerisation of epicatechin and formation of ethylbridged adducts has also been shown (Doco, Es-Safi, Cheynier, & Moutounet, 1996).…”

“…They have also been studied extensively for their health-promoting properties (Crozier, Jaganath, & Clifford, 2009) which has been partly attributed to their ability to scavenge reactive oxygen species (ROS), thus inhibiting the formation of advanced glycation end-products (AGEs). For example, flavan-3-ols from green tea were found to scavenge methylglyoxal (MGO) under simulated physiological conditions (Lo et al, 2006) whereas procyanidins from cinnamon were shown to inhibit protein glycation (Peng et al, 2008). The reactivity of electron-rich phenols towards electrophilic carbonyls was also observed in food systems; condensation reactions between polyphenols and carbonyls, leading to the formation of various phenolic oligomers, polymers and adducts, have been examined in connection to reduced astringency and colour development in wine during ageing (Pissarra, Mateus, Rivas-Gonzalo, Santos Buelga, & Freitas, 2003;).…”