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.

Keywords: Scutellaria alpina; Scutellaria altissima; advanced glycation end products; antioxidants; flavonoids.

Figure 1

The inhibitory effect on advanced glycation end-products (AGE) formation of Scutellaria altissima shoot (A) and root (B) extracts and S. alpina shoot (C) and root (D) extracts at different concentrations. The results are mean values ± SE. IC₅₀, the concentration (µg/mL) required to reduce fluorescent AGE formation by 50% (n = 4–5).

Figure 2

Antiglycation activity (expressed as % inhibition of AGE formation) of S. altissima (shoot, root) extracts, S. alpina (shoot, root) extracts and the main compounds present in the analyzed extracts (verbascoside, baicalin, wogonoside, luteolin, luteolin-7-glucoside). BSA after glycation (100% AGE) was used as the negative and aminoguanidine as the positive control. All extracts and compounds were used at a concentration of 100 µg/mL. The results are the mean values ± SE.