title: A dimeric triterpenoid glycoside and flavonoid glycosides with free radical-scavenging activity isolated from Rubus rigidus var. camerunensis.
abstract: The aerial part of Rubus rigidus var. camerunensis (Rosaceae) is used to treat respiratory and cardiovascular disorders in the Cameroonian traditional medicine. The ethanol extract exhibited more potent antioxidant activity (E(max)s of 119% and 229% activity on DPPH and β-carotene test) than aqueous extract. Bioactivity-guided fractionation of the ethanol extract based on free radical-scavenging assay (DPPH assay) afforded five flavonoid glycosides (four flavonol glycosides and an anthocyanin) and three glucosides of 19α-hydroxyursane-type triterpenoid (two monomeric and one dimeric triterpenoids). The flavonoids were identified as kaempferol 3-O-(2″-O-E-p-coumaroyl)-β-D-glucopyranoside (1), kaempferol-3-O-β-D-glucopyranoside (astragalin, 2), kaempferol-3-O-α-L-arabinofuranoside (juglanin, 3), quercetin-3-O-β-D-glucopyranoside (isoquercitrin, 4), pelargonidin-3-O-β-D-glucopyranoside (callistephin, 5). The three triterpenoids were 2α, 3β, 19α, 23-tetrahydroxyurs-12-ene-28-O-β-D-glucopyranosyl ester (nigaichigoside F(1), 6), 2α, 3β, 19α-trihydroxyurs-12-ene-23-carboxyl-28-O-β-D-glucopyranosyl ester (suavissimoside R(1), 7) as monomeric triterpenoids and coreanoside F(1) (8) as a dimeric triterpenoid. The flavonoids exhibited potent antioxidant activities (66 to 93.56% against DPPH radical) and they were also active on β-carotene test. Coreanoside F(1) exhibited a 63% antioxidant activity, meanwhile the other two triterpenoids showed a weak activity. Three important facts on structure-activity relationship were observed: Compound 8, a dimeric triterpenoid glycoside, strongly enhanced antioxidant activity of its monomers, compound 3 with 3-O-α-L-arabinofuranyl has much more potent activity than compound 2 with 3-O-β-D-glucopyranosyl, and antocyanin (5) is more potent than its corresponding flavonol glycosides.
authors.affiliation: Laboratory of Animal Physiology and Phytopharmacology, Faculty of Science, University of Dschang, Dschang, Cameroon.
authors.forename: Télesphore Benoît
authors.initials: TB
authors.lastname: Nguelefack
authors.forename: Félicité Hermine Kamga
authors.initials: FH
authors.lastname: Mbakam
authors.forename: Léon Azéfack
authors.initials: LA
authors.lastname: Tapondjou
authors.forename: Pierre
authors.initials: P
authors.lastname: Watcho
authors.forename: Elvine Pami
authors.initials: EP
authors.lastname: Nguelefack-Mbuyo
authors.forename: Beaudelaire Kemvoufo
authors.initials: BK
authors.lastname: Ponou
authors.forename: Albert
authors.initials: A
authors.lastname: Kamanyi
authors.forename: Hee-Juhn
authors.initials: HJ
authors.lastname: Park
mesh_terms: D001713:Biphenyl Compounds / Q000737:chemistry; D019281:Dimerization; D005419:Flavonoids / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D005609:Free Radicals / Q000737:chemistry; D006027:Glycosides / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D015394:Molecular Structure; D010851:Picrates / Q000737:chemistry; D035261:Plant Components, Aerial / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D027824:Rosaceae / Q000737:chemistry*; D014315:Triterpenes / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology
chemical_list: D001713:Biphenyl Compounds; D005419:Flavonoids; D016166:Free Radical Scavengers; D005609:Free Radicals; D006027:Glycosides; D010851:Picrates; D010936:Plant Extracts; D014315:Triterpenes; C004931:1,1-diphenyl-2-picrylhydrazyl