The Antiglycoxidative Ability of Selected Phenolic Compounds-An In Vitro Study

Abstract

Hyperglycemia and oxidative stress may be observed in different diseases as important factors connected with their development. They often occur simultaneously and are considered together as one process: Glycoxidation. This can influence the function or structure of many macromolecules, for example albumin, by changing their physiological properties. This disturbs the homeostasis of the organism, so the search for natural compounds able to inhibit the glycoxidation process is a current and important issue. The aim of this study was the examination of the antiglycoxidative capacity of 16 selected phenolic compounds, belonging to three phenolic groups, as potential therapeutic agents. Their antiglycoxidative ability, in two concentrations (2 and 20 µM), were examined by in vitro study. The inhibition of the formation of both glycoxidative products (advanced glycation end products (AGEs) and advanced oxidation protein products (AOPPs)) were assayed. Stronger antiglycoxidative action toward the formation of both AOPPs and AGEs was observed for homoprotocatechuic and ferulic acids in lower concentrations, as well as catechin, quercetin, and 8-O-methylurolithin A in higher concentrations. Homoprotocatechuic acid demonstrated the highest antiglycoxidative capacity in both examined concentrations and amongst all of them. A strong, significant correlation between the percentage of AOPPs and AGEs inhibition by compounds from all phenolic groups, in both examined concentrations, was observed. The obtained results give an insight into the antiglycoxidative potential of phenolic compounds and indicate homoprotocatechuic acid to be the most promising antiglycoxidative agent, but further biological and pharmacological studies are needed.

Keywords: AGEs; AOPPs; antiglycoxidative potential; glycoxidation; phenolic compounds.

Figure 1

Percentage of advanced oxidation protein products (AOPPs) (1A) and advanced glycation end products (AGEs) (1B) formation during the glycoxidation process in samples incubated with 2 and 20 µM of tested phenolic acids and their esters (group 1.). Significant differences in comparison to (ctrl), as well as between both used concentrations, were expressed as: (*) p < 0.001, (•) p < 0.01, (#) p < 0.05.

Figure 2

Percentage of AOPPs (2A) and AGEs (2B) formation during the glycoxidation process in samples incubated with 2 and 20 µM of tested ellagic acids and other ellagitannins metabolites (group 2.). Significant differences in comparison to (ctrl), as well as between both used concentrations were expressed as: (*) p < 0.001, (•) p < 0.01, (#) p < 0.05.

Figure 2

Percentage of AOPPs (2A) and AGEs (2B) formation during the glycoxidation process in samples incubated with 2 and 20 µM of tested ellagic acids and other ellagitannins metabolites (group 2.). Significant differences in comparison to (ctrl), as well as between both used concentrations were expressed as: (*) p < 0.001, (•) p < 0.01, (#) p < 0.05.

Figure 3

Percentage of AOPPs (3A) and AGEs (3B) formation during the glycoxidation process in samples incubated with 2 and 20 µM of tested flavan derivatives (group 3.). Significant differences in comparison to (ctrl), as well as between both used concentrations, were expressed as: (*) p < 0.001, (•) p < 0.01, (#) p < 0.05.

Figure 4

Possible chelating and trapping sites of quercetin, and exemplary structures of reaction products.

Figure 4

Possible chelating and trapping sites of quercetin, and exemplary structures of reaction products.