Cinnamon Bark Proanthocyanidins as Reactive Carbonyl Scavengers To Prevent the Formation of Advanced Glycation Endproducts

Abstract

Cinnamon bark has been reported to be effective in the alleviation of diabetes through its antioxidant and insulin-potentiating activities. In this study, the inhibitory effect of cinnamon bark on the formation of advanced glycation endproducts (AGEs) was investigated in a bovine serum albumin (BSA)-glucose model. Several phenolic compounds, such as catechin, epicatechin, and procyanidin B2, and phenol polymers were identified from the subfractions of aqueous cinnamon extract. These compounds showed significant inhibitory effects on the formation of AGEs. Their antiglycation activities were not only brought about by their antioxidant activities but also related to their trapping abilities of reactive carbonyl species such as methylglyoxal (MGO), an intermediate reactive carbonyl of AGE formation. Preliminary study on the reaction between MGO and procyanidin B2 revealed that MGO-procyanidin B2 adducts are primary products which are supposed to be stereoisomers. This is the first report that proanthocyanidins can effectively scavenge reactive carbonyl species and thus inhibit the formation of AGEs. As proanthocyanidins behave in a similar fashion as aminoguanidine (AG), the first AGE inhibitor explored in clinical trials, they show great potential to be developed as agents to alleviate diabetic complications.

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

“…Multidisciplinary studies have demonstrated that the composition of a polyphenol has an outstanding relationship to its antioxidant properties. On the other hand, the antioxidant activity of a natural compound shows strong linking with its molecular structures [45]. Therefore, it is an important matter to assess the antioxidant activity of a polyphenolic compound not only quantity but also by quality (which is decided by chemical structure).…”

“…Mimicking insulin activity [45] Curcuma longa (Turmeric) Curcumin Preventing free radicals and glycosylated haemoglobin (HbA) formation, protecting non-enzymatic antioxidants pools, preventing of lipid peroxidation, lowering blood glucose level [59,61,62,66] Cyperus rotundus (Nut sedge) Gallic acid, p-coumaric acid, epicatechin Reduction of protein carbonyl and thiol oxidation…”

“…Alteration in polyphenol levels during the harvesting period has been shown for some compounds, such as such as chlorogenic acid, rutin, quercetin3-arabinoside, (+)-catechin, and (−)-epicatechin [48]. In a comparative antiglycation study among some bean species, alcoholic extract of mung bean, Vigna radiate (L.) R.Wilczek (Fabaceae), displayed the highest inhibitory activity on AGEs formation due to its higher amount of phenolic compounds known as vitexin and isovitexin [45]. Vitexin contains a 4′-hydroxyl group in the B ring of its structure [43].…”

“…Cinnamtannin B1 from Cinnamomum zeylanicum Blume (Lauraceae) helped glucose uptake by stimulating the phosphorylation of insulin receptors on 3T3-L1 cell line [56]. Cinnamon also contains catechin, epicatechin, and procyanidin B2, which all possess antiglycation activity [45]. According to Zhao et al berberine isolated from some plants improved diabetic complications in diabetic rats through attenuation of insulin resistance and activation of insulin-like growth factor-binding protein signaling pathways [57].…”

Plant-Derived Agents with Anti-Glycation Activity

“…Catechin and epicatechin procyanidin B2 (a dimer-type proanthocyanidin) isolated from cinnamon bark extract have been shown to possess a significant MGO trapping activitiy, with procyanidin B2 demonstrating the strongest inhibition of AGE formation among proanthocyanidins isolated from cinnamon bark [146]. All these flavonoids potently inhibited (more than 50%) the formation of pentosidine and CML [147] with procyanidin B2 showing the highest inhibition capacity (almost 80%) on the CML formation.…”