title: Thermal Degradation Kinetics Modeling of Benzophenones and Xanthones during High-Temperature Oxidation of Cyclopia genistoides (L.) Vent. Plant Material.
abstract: Degradation of the major benzophenones, iriflophenone-3-C-glucoside-4-O-glucoside and iriflophenone-3-C-glucoside, and the major xanthones, mangiferin and isomangiferin, of Cyclopia genistoides followed first-order reaction kinetics during high-temperature oxidation of the plant material at 80 and 90 °C. Iriflophenone-3-C-glucoside-4-O-glucoside was shown to be the most thermally stable compound. Isomangiferin was the second most stable compound at 80 °C, while its degradation rate constant was influenced the most by increased temperature. Mangiferin and iriflophenone-3-C-glucoside had comparable degradation rate constants at 80 °C. The thermal degradation kinetic model was subsequently evaluated by subjecting different batches of plant material to oxidative conditions (90 °C/16 h). The model accurately predicted the individual contents of three of the compounds in aqueous extracts prepared from oxidized plant material. The impact of benzophenone and xanthone degradation was reflected in the decreased total antioxidant capacity of the aqueous extracts, as determined using the oxygen radical absorbance capacity and DPPH(•) scavenging assays.
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 7602, South Africa.
authors.forename: Theresa
authors.initials: T
authors.lastname: Beelders
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: †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 7602, South Africa.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Joubert
mesh_terms: D001577:Benzophenones / Q000737:chemistry*; D053998:Cyclopia Plant / Q000737:chemistry*; D005960:Glucosides / Q000737:chemistry*; D006358:Hot Temperature; D007700:Kinetics; D010084:Oxidation-Reduction; D010936:Plant Extracts / Q000737:chemistry*; D013696:Temperature; D044004:Xanthones / Q000737:chemistry*
chemical_list: D001577:Benzophenones; D005960:Glucosides; D010936:Plant Extracts; D044004:Xanthones
keywords: antioxidant capacity; high-temperature processing; honeybush herbal tea; oxidation; thermal degradation kinetics modeling