title: Redox reactivity in propolis: direct detection of free radicals in basic medium and interaction with hemoglobin.
abstract: Propolis is one of many natural products with known antioxidant properties. The present work aims to investigate the intimate molecular-level mechanisms of this antioxidant reactivity. Electron paramagnetic resonance (EPR)-detectable free radical signals are described here for the first time in propolis extracts. The shape of these signals and the conditions in which they were obtained, point to polyphenolic flavonoids as the sites of the radicals. An inverse correlation between antioxidant capacity and free radical signal intensity is shown. The free radical reactivity of propolis is also illustrated by the effect it exerts on the biologically-relevant peroxide reactivity of hemoglobin. A new test of antioxidant ability in natural extracts such as propolis is proposed, based on modulation of the ascorbate peroxidase activity of hemoglobin (HAPX). Results of this test correlate well with those obtained via traditional methods such as those based on DPPH (2,2-diphenyl-1-picrylhydrazyl), or on ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid).
authors.affiliation: Department of Chemistry and Chemical Engineering, 'Babes-Bolyai' University, Cluj-Napoca, Romania.
authors.forename: Augustin-Catalin
authors.initials: AC
authors.lastname: Mot
authors.forename: Grigore
authors.initials: G
authors.lastname: Damian
authors.forename: Costel
authors.initials: C
authors.lastname: Sarbu
authors.forename: Radu
authors.initials: R
authors.lastname: Silaghi-Dumitrescu
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry*; D060387:Ascorbate Peroxidases; D002855:Chromatography, Thin Layer / Q000379:methods; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry*; D006454:Hemoglobins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism; D011429:Propolis / Q000737:chemistry*
chemical_list: D000890:Anti-Infective Agents; D005609:Free Radicals; D006454:Hemoglobins; D011429:Propolis; D010544:Peroxidases; D060387:Ascorbate Peroxidases