title: Antiradical and reductant activities of anthocyanidins and anthocyanins, structure-activity relationship and synthesis.
abstract: Eight anthocyanidins, seven anthocyanins and two synthesized 4'-hydroxy flavyliums were examined as hydrogen donors to DPPH, ABTS and hydroxyl radicals, and as electron donors in the FRAP assay. Most compounds gave better activities than trolox and catechol. A structure-activity relationship (SAR) study showed that, in the absence of the 3-OH group, radicals of the 4, 5 or 7-OH groups can only be stabilized by resonance through pyrylium oxygen, while 3-OH group improved hydrogen atom donation because of the stabilization by anthocyanidin semiquinone-like resonance. Electron donation was also enhanced by the 3-OH group. Both anthocyanidins and their respective anthocyanins showed similar trends and close activities. Different types of sugar unit bonded to the 3-OH group or counter ion had minor effect on activities. The catechol structure improved both hydrogen and electron donation. Compounds lacking the catechol structure had a decreasing order of H-atom and electron donation (Mv>Pn>Pg>Ap>4'-OH-flavylium) consistent with the decreasing number of their hydroxyl and/or methoxy groups.
authors.affiliation: Agricultural Biochemistry Department, Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, Cairo, Egypt. Electronic address: Hussein_galaleldeen@agr.asu.edu.eg.
authors.forename: Hussein M
authors.initials: HM
authors.lastname: Ali
authors.affiliation: Chemistry Department, Faculty of Science for Girls, Dammam University, Dammam, Saudi Arabia.
authors.forename: Wafaa
authors.initials: W
authors.lastname: Almagribi
authors.affiliation: Chemistry Department, Faculty of Science for Girls, Dammam University, Dammam, Saudi Arabia.
authors.forename: Mona N
authors.initials: MN
authors.lastname: Al-Rashidi
mesh_terms: D000872:Anthocyanins / Q000138:chemical synthesis / Q000737:chemistry*; D000975:Antioxidants / Q000138:chemical synthesis / Q000737:chemistry*; D019163:Reducing Agents / Q000138:chemical synthesis / Q000737:chemistry*; D013329:Structure-Activity Relationship
chemical_list: D000872:Anthocyanins; D000975:Antioxidants; D019163:Reducing Agents
keywords: Anthocyanins; Antioxidants; Radical stabilization; SAR; Semiquinone resonance