Anti-glycation study of hydro-alcohol and aqueous extracts of Moroccan plant species

Abstract

Inhibition of advanced glycation end products (AGEs) and free radicals generated during diabetes represents a major therapeutic target in the prevention and treatment of diabetic complications. Natural molecules present in fruits, vegetables and herbs and which are usually safe for human consumption, could represent a strong glycation inhibitor. Anti-glycation effect of nine plant species used in traditional medicine has been evaluated after extraction by hot (EAC) or cold (EAF) maceration and by ethanol (EE). Anti-glycation activity performed on a model system of bovine serum albumin, and methylglyoxal was measured by fluorescence and native electrophoresis. Total phenolic and flavonoid contents were assessed as well. Except for Sesamum indicum, all the species studied have an Anti-glycation effect. The highest effect was recorded in Laurus nobilis and was dose-dependent, inhibiting both formations of Amadori products and fluorescent AGEs. HPLC analysis revealed a richness of Laurus nobilis EE in phenolic compounds such as quercetin, vanillin and gallic acid. A strong correlation was registered between antioxidant power and phenolic/flavonoid content. In contrast, there was no correlation between antioxidant and anti-glycation power. Phenolic and flavonoid compounds were strongly involved in the observed anti-glycation effect. However, the anti-glycation activity obtained is probably attributed to non-antioxidant compounds.

Assessing the In Vitro Inhibitory Effects on Key Enzymes Linked to Type-2 Diabetes and Obesity and Protein Glycation by Phenolic Compounds of Lauraceae Plant Species Endemic to the Laurisilva Forest

“…Previously [ 23 ], our research group reported PACs (A- and B-types) and flavonol glycosides as the main components of Apollonias barbujana , Laurus novocanariensis (laurel), Ocotea foetens and Persea indica ( Figure 2 ), the most relevant Lauraceae species of Laurissilva. The anti-diabetic effects of similar plants ( Laurus nobilis , Persea americana and Ocotea bullata ) have been documented before [ 3 , 5 , 13 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], and similar properties were expected for targeted Lauraceae species. Therefore, this study was designed to evaluate for the first time the in vitro inhibitory effects of four Lauraceae plant extracts ( A. barbujana , L. novocanariensis , O. foetens and P. indica ) on digestive enzymes linked to the carbohydrates (α-amylase, and α-glucosidase) and lipids metabolism (pancreatic lipase), aldose reductase and protein glycation.…”

“…Previously [ 29 , 30 , 39 ], different extracts of L. nobilis prevented the formation of AGEs. Gallic acid was the main compound in the extract and its anti-glycation effect was partially attributed to this phenolic [ 30 ].…”

“…Previously [ 29 , 30 , 39 ], different extracts of L. nobilis prevented the formation of AGEs. Gallic acid was the main compound in the extract and its anti-glycation effect was partially attributed to this phenolic [ 30 ]. Gallic acid was absent in L. novocanariensis extract [ 23 ], therefore, we hypothesize that the activity of this species can be attributed to PACs.…”

“…Another consequence of the elevated blood glucose is an increase in non-enzymatic glycation of proteins such as hemoglobin A1c (HbA1c) and serum albumin [ 1 ]. Protein glycation, also known as Maillard reaction, occurs when the carbonyl group of a reducing carbohydrate reacts with an amino group of proteins to form a highly reversible Schiff base intermediate, which rearranges to form a more stable Amadori product (early phase) ( Figure 2 ) [ 30 , 35 , 39 ]. Then, Schiff bases or Amadori products go through a complex series of reactions (rearrangement, oxidation, dehydration, polymerization) to generate reactive dicarbonyl compounds, including methylglyoxal, glyoxal and 3-deoxyglucusone (middle phase), which further form adducts with proteins to generate AGEs (late phase) [ 15 , 38 , 40 ].…”

“…These ailments include nephropathy, neuropathy, retinopathy, coronary heart disease and atherosclerosis [ 18 , 29 , 35 ]. Hence, inhibition of AGEs formation has been frequently considered as an efficient target to slow down the progression of some diabetic complications [ 18 , 30 , 41 ]. To avoid the problems related to the synthetic molecules (like AMG), research has been directed to phytochemicals, such as phenolic compounds, which have proven effective anti-glycation properties with a reduced risk of adverse effects [ 18 , 30 , 41 ].…”