No abstract

No abstract

The molecular structures of the radical scavenging compounds present in extracts of Potentilla fruticosa blossoms were elucidated and the antioxidant activities of various extracts were determined. The activities of the different fractions were monitored by off-line and on-line RP-HPLC DPPH • and ABTS •+ scavenging methods. Twelve compounds were isolated and identified, namely ellagic acid, catechin, quercetin-3-β-glucopyranoside, quercetin-3-β-galactopyranoside, quercetin-3-β-rutinoside, quercetin-3-β-glucuronopyranoside, quercetin-3-α-arabinofuranoside, kaempferol-3-β-rutinoside, kaempferol-3-O-β-(6 -O-(E)-p-coumaroyl)glucopyranoside, rhamnetin-3-β-glucopyranoside and rhamnetin-3-β-galactopyranoside. The radical scavenging activity of each isolated compound was measured using DPPH • and ABTS • + assays and compared with the activity of rosmarinic acid. Catechin and ellagic acid were found to be the most active radical scavengers. The antioxidant properties of plant fractions were assessed in model systems by measuring superoxide anion and hydrogen peroxide scavenging, β-carotene bleaching, hexanal production in edible oil, peroxide formation, and the increase in UV absorbance in the course of oxidation.

A hyphenated LC-DAD-SPE-NMR setup in combination with on-line radical scavenging detection has been applied for the identification of radical scavenging compounds in extracts of Rhaponticumcarthamoides. After NMR measurements, the pure compounds were infused into a mass spectrometer. The technique enabled selective detection and identification of individual radical scavenging compounds without any prior off-line chromatographic steps. Seven compounds, namely, quercetagetin-7-beta-glucopyranoside (1), quercetagetin-7-(6"-acetyl-beta-glucopyranoside) (3), 6-hydroxykaempferol-7-beta-glucopyranoside (2), 6-methoxykaempferol-3-beta-glucopyranoside (4), 6-hydroxykaempferol-7-(6"-acetyl-beta-glucopyranoside) (5), chlorogenic acid (6), and beta-ecdysone (7), were identified in ethanol or aqueous extracts. Compound 5 is a new natural compound. Its radical scavenging activity was tested against DPPH radical and was found to be weaker than that of the reference antioxidants rosmarinic acid and Trolox.