Inhibition of Protein Glycation by Combined Antioxidant and Antiglycation Constituents from a Phenolic Fraction of Sage (Salvia officinalis L.)

Disturbed advanced glycation end products (AGEs)-oxidative stress axis is strongly linked to vascular complications observed in diabetes and other metabolic conditions. Salvia officinalis L. (sage) is a medicinal plant used as an ingredient in foods and beverages and displays a wide range of biological and pharmacological activities including anti-diabetic effects. However, no study has assessed its anti-glycative potential. The aim of this study is to determine the phenolic compounds associated with the anti-glycation and antioxidant potential of sage methanol extract (SME). SME shows similar effects to aminoguanidine on fluorescent AGEs inhibition. It protects albumin damage from glycation (52.9 vs. 50.3%, respectively) by preventing the loss of protein thiol groups (50.0 vs. 44.3%, respectively) and by reducing protein carbonyl accumulation (67.4 vs. 70.5%, respectively). Moreover, linear regression and multivariate analysis support the efficient contribution of SME antioxidant capacity, as judged by DPPH, TBARS and iron chelating tests, in AGEs suppression. Furthermore, HPLC analysis revealed the presence of verbascoside as a novel phenolic constituent identified in sage leaves and suggests that the protective activity is mostly assigned to the presence of rosmarinic acid, resveratrol, quercetin, rutin and luteolin-7-O-glucoside. Likewise, the screening of SME phenolic content supports the contribution of various antioxidant substances to the observed effects. Therefore, a polyphenol enriched sage extract was able to inhibit the formation of AGEs and protein glycation. Our data unveils the promising properties of sage and its bioactive principles in the management of AGEs-mediated vascular complications observed in diabetes and other metabolic disorders.

Keywords: Glycation; Oxidative stress; Salvia officinalis; phenolic compounds.