title: Free radical scavenging activity of Kielmeyera variabilis (Clusiaceae).
abstract: As part of our ongoing research on antioxidant agents from Brazilian flora, we screened the free radical scavenging activity of two extracts and eight fractions of Kielmeyera variabilis (Clusiaceae) using DPPH· (2,2-diphenyl-1-picrylhydrazyl-hydrate) and ABTS·+ [2,2'-azinobis(3-ethylenebenzothiazoline-6-sulfonic acid)] colorimetric assays. The ethyl acetate and n-butanol fractions of the leaves of K. variabilis displayed the strongest activity (IC₅₀ of 3.5 ± 0.3 and 4.4 ± 0.2 μg mL⁻¹ for DPPH· and 6.6 ± 0.4 and 3.1 ± 0.1 μg mL⁻¹ for ABTS·+, respectively). Chromatographic fractionation of the most potent fractions led to identification of three flavonols with previously described antioxidant activity, quercitrin (1), quercetin-3-O-β-glucoside (3), and quercetin-3-O-β-galactoside (4), and of one biflavone, podocarpusflavone A (2). This is the first time that the presence of these flavonoids in Kielmeyera variabilis has been reported.
authors: Department of Organic Chemistry, Institute of Chemistry, São Paulo State University, Araraquara 14800-900, Brazil.
authors: Aline
authors: A
authors: Coqueiro
authors: Luis Octávio
authors: LO
authors: Regasini
authors: Scheila Cristina Gutkoski
authors: SC
authors: Skrzek
authors: Marcos Marçal Ferreira
authors: MM
authors: Queiroz
authors: Dulce Helena Siqueira
authors: DH
authors: Silva
authors: Vanderlan
authors: V
authors: da Silva Bolzani
mesh_terms: D052160:Benzothiazoles / Q000378:metabolism; D001713:Biphenyl Compounds / Q000378:metabolism; D028084:Clusiaceae / Q000737:chemistry*; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000737:chemistry / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D010851:Picrates / Q000378:metabolism; D013451:Sulfonic Acids / Q000378:metabolism
chemical_list: D052160:Benzothiazoles; D001713:Biphenyl Compounds; D005419:Flavonoids; D016166:Free Radical Scavengers; D010851:Picrates; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; C004931:1,1-diphenyl-2-picrylhydrazyl