Inhibition of Advanced Glycation End-Product Formation and Antioxidant Activity by Extracts and Polyphenols from Scutellaria alpina L. and S. altissima L.

Abstract

Methanolic extracts from the aerial parts and roots of two Scutellaria species, S. alpina and S. altissima, and five polyphenols from these plants demonstrated a significant ability to inhibit the formation of advanced glycation end-products (AGE) in vitro. S. alpina, which is richer in polyphenolic compounds, had strong antiglycation properties. These extracts demonstrated also high activity in the FRAP (ferric-reducing antioxidant power), antiradical (DPPH) and lipid peroxidation inhibition assays. Among the pure compounds, baicalin was the strongest glycation inhibitor (90.4% inhibition at 100 µg/mL), followed by luteolin (85.4%). Two other flavone glycosides had about half of this activity. Verbascoside was similar to the reference drug aminoguanidine (71.2% and 75.9%, respectively). The strong correlation observed between AGE inhibition and total flavonoid content indicated that flavonoids contribute significantly to antiglycation properties. A positive correlation was also observed between antiglycative and antioxidant activities. The studied skullcap species can be considered as a potential source of therapeutic agents for hyperglycemia-related disorders.

Zinc against advanced glycation end products

“…AGE generation can be accelerated beyond normal levels under certain pathologic conditions such as decreased antioxidant capacity, increased oxidative stress, overproduction of AGE precursors including ROS and protein carbonyl levels . Numerous in vitro and experimental evidences indicate that zinc deficiency induces formation of AGE precursors and creation of oxidative stress condition (Table ).…”

Secondary metabolites from lichen as potent inhibitors of advanced glycation end products and vasodilative agents

“…Overall, seventeen natural and one semisynthetically modified compound exhibited notable inhibition of AGEs formation IC 50 < 1.0 mM, fold activity of aminoguanidine (FAA)  2.0. Best activities (IC 50 < 0.1 mM, FAA  25) were observed for variolaric acid (36), pannaric acid (22) and leprapinic acid (14), which are in the range of previously tested flavonoids such as pinobanksin, pinobanksin-5methyl ether and pinobanksin-3-acetate as well as cinnamic acid derivatives 2-acetyl-1,3-dicoumaroylglycerol and prenyl caffeate (IC 50 : 0.05-0.09 mM) [31]. In terms of potential structure-activity relationships, it was interesting to observe that the entire group of tested depsidones (compounds 11, 16, 25, 31 (38)(39)(40)(41) was quite interesting to study.…”

“…Therefore a compilation of reported cytotoxicity for all lichen compounds that inhibited AGEs formation was added to the supplementary section of the manuscript (Table S3). In this regard β-Collatolic (4), leprapinic (14) and pannaric acid as well as (22) thamnolic acid (33) and 2,3,4-trihydroxy-6-propylbenzoic acid methyl ester (34) represent most interesting candidates for follow up studies. They all show notable anti-AGEs effects (IC 50 0.06-0.5 mM) but no reported cytotoxicity.…”

“…With this in mind, the present study evaluated thirty-seven secondary lichen metabolites as well as five semisynthetic derivatives of usnic acid (a major metabolite found in many lichen species) for their potential anti-AGE effects in a fluorescence-based Maillard reaction assay [20]. According to previous reports, anti-AGE, antioxidant, and radical scavenging effects are often related, so all compounds were additionally tested in an 1,1-diphenyl-2picrylhydrazyl (DPPH) assay [14,21,22]. Considering that both AGEs but also hypertension are known important risk factors for age-and lifestyle related diseases, some compounds, that were available in sufficient quantities, were further evaluated in a vasodilation assay.…”

Protection against Advanced Glycation End Products and the Mode of Action of Lemon Balm on Hemoglobin Fructose-Mediated Glycation

“…Melissa officinalis L., commonly known as lemon balm (LB), is a folk medicine characterized by unique high polyphenolic content [7,8] with medicinal properties such as, anti-inflammatory, antiviral, memory enhancer, cardiac tonic, anti-depressant, sleeping aid, and antioxidant activity [9][10][11][12][13][14]. Phenolic acids, the main active ingredients present in the extract of LB are reported for anti-oxidative [15], anti-proliferative [16], antiinflammatory [17], anti-angiogenic [18] and anti-cancer properties [19,20]. The traditional use of LB extract has been proven in lowering blood glucose levels [21,22].…”