title: Antioxidant activity of the dihydrochalcones Aspalathin and Nothofagin and their corresponding flavones in relation to other Rooibos ( Aspalathus linearis ) Flavonoids, Epigallocatechin Gallate, and Trolox.
abstract: The antioxidant activity of rooibos flavonoids, including the dihydrochalcones aspalathin and nothofagin and their corresponding flavone glycosides, was evaluated using the ABTS radical cation, metal chelating, and Fe(II)-induced microsomal lipid peroxidation assays. Epigallocatechin gallate (EGCG) and Trolox were used as reference standards. Optimized geometric conformers of aspalathin and nothofagin, in addition to calculated physicochemical properties, were considered to explain interaction with the microsomal membrane structure and thus relative potency of the dihydrochalcones. The most potent radical scavengers were aspalathin (IC50 = 3.33 microM) and EGCG (IC50 = 3.46 microM), followed by quercetin (IC50 = 3.60 microM) and nothofagin (IC50 = 4.04 microM). The least effective radical scavengers were isovitexin (IC50 = 1224 microM) and vitexin (IC50 > 2131 microM). Quercetin (IC50 = 17.5 microM) and EGCG (IC50 = 22.3 microM) were the most effective inhibitors of lipid peroxidation. Aspalathin (IC50 = 50.2 microM) and catechin (IC50 = 53.3 microM) displayed similar potencies. Nothofagin (IC50 = 1388 microM) was almost as ineffective as its flavone glycoside analogues.
authors.affiliation: Departments of Chemistry, Stellenbosch University, Private Bag X1, Matieland (Stellenbosch) 7602, South Africa.
authors.forename: Petra W
authors.initials: PW
authors.lastname: Snijman
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Joubert
authors.forename: Daneel
authors.initials: D
authors.lastname: Ferreira
authors.forename: Xing-Cong
authors.initials: XC
authors.lastname: Li
authors.forename: Yuanqing
authors.initials: Y
authors.lastname: Ding
authors.forename: Ivan R
authors.initials: IR
authors.lastname: Green
authors.forename: Wentzel C A
authors.initials: WC
authors.lastname: Gelderblom
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000737:chemistry* / Q000494:pharmacology; D036903:Aspalathus / Q000737:chemistry*; D002839:Chromans / Q000737:chemistry* / Q000494:pharmacology; D005419:Flavonoids / Q000737:chemistry* / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D008862:Microsomes, Liver; D008968:Molecular Conformation; D051381:Rats
chemical_list: D000975:Antioxidants; D002839:Chromans; D005419:Flavonoids; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid