title: Iriflophenone-3-C-glucoside from Cyclopia genistoides: isolation and quantitative comparison of antioxidant capacity with mangiferin and isomangiferin using on-line HPLC antioxidant assays.
abstract: The benzophenone, iriflophenone-3-C-glucoside, was isolated from Cyclopia genistoides using a combination of fluid-fluid extraction, high performance counter-current chromatography (HPCCC) and semi-preparative high performance liquid chromatography (HPLC). The microplate oxygen radical absorbance capacity (ORAC) assay, with fluorescein as probe, was adapted for use in an on-line HPLC configuration. The method was validated using a mixture of authentic standards including iriflophenone-3-C-glucoside, and the xanthones, mangiferin and isomangiferin. Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) was included in the mixture for calculation of Trolox equivalent antioxidant capacity (TEAC) values. Using the on-line HPLC-ORAC assay, as well as 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(+)) on-line assays, the antioxidant activity of iriflophenone-3-C-glucoside and isomangiferin was demonstrated for the first time. Iriflophenone-3-C-glucoside presented no radical scavenging ability against DPPH, but scavenged ABTS(+) and peroxyl radicals (TEACABTS of 1.04 and TEACORAC of 3.61). Isomangiferin showed slightly lower antioxidant capacity than mangiferin against DPPH (TEACDPPH of 0.57 vs. 0.62), but higher capacity against ABTS(+) (TEACABTS of 1.82 vs. 1.67) and peroxyl radical (TEACORAC of 4.14 vs. 3.69) than mangiferin. The on-line HPLC-ORAC assay was shown to be more sensitive for radical scavengers, but at the same time less selective for rapid radical scavengers than the DPPH assay.
authors.affiliation: Post-Harvest and Wine Technology Division, Agricultural Research Council (ARC) Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch 7599, South Africa. Electronic address: MalherbeCh@arc.agric.za.
authors.forename: Christiaan J
authors.initials: CJ
authors.lastname: Malherbe
authors.affiliation: Post-Harvest and Wine Technology Division, Agricultural Research Council (ARC) Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch 7599, South Africa.
authors.forename: Elize
authors.initials: E
authors.lastname: Willenburg
authors.affiliation: Post-Harvest and Wine Technology Division, Agricultural Research Council (ARC) Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch 7599, South Africa.
authors.forename: Dalene
authors.initials: D
authors.lastname: de Beer
authors.affiliation: Department of Chemistry, University of Free State, P.O. Box 339, Bloemfontein 9300, South Africa.
authors.forename: Susan L
authors.initials: SL
authors.lastname: Bonnet
authors.affiliation: Directorate Research Development, University of the Free State, P.O. Box 339, Bloemfontein, 9300, South Africa.
authors.forename: Jan H
authors.initials: JH
authors.lastname: van der Westhuizen
authors.affiliation: Post-Harvest and Wine Technology Division, Agricultural Research Council (ARC) Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch 7599, South Africa; Department of Food Science, Stellenbosch University, Private Bag X1, Matieland Stellenbosch 7602, South Africa.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Joubert
mesh_terms: D000975:Antioxidants / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D001577:Benzophenones / Q000737:chemistry / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D053998:Cyclopia Plant / Q000737:chemistry*; D005419:Flavonoids / Q000737:chemistry / Q000378:metabolism; D005960:Glucosides / Q000737:chemistry / Q000378:metabolism; D012680:Sensitivity and Specificity; D013662:Tea / Q000737:chemistry; D044004:Xanthones / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D001577:Benzophenones; D005419:Flavonoids; D005960:Glucosides; D013662:Tea; D044004:Xanthones; C013592:mangiferin; C061492:isomangiferin; C047723:benzophenone
keywords: (Bio)chemical detection; Benzophenone; HPCCC; Herbal tea; Honeybush; Peroxyl radical