title: Isolation and structure elucidation of highly antioxidative 3,8″-linked biflavanones and flavanone-C-glycosides from Garcinia buchananii bark.
abstract: The aim of this study was to identify antioxidants from Garcinia buchananii bark extract using hydrogen peroxide scavenging and oxygen radical absorbance capacity (ORAC) assays. LC-MS/MS analysis, 1D- and 2D-NMR, and circular dichroism (CD) spectroscopy led to the unequivocal identification of the major antioxidative molecules as a series of three 3,8″-linked biflavanones and two flavanone-C-glycosides. Besides the previously reported (2R,3R,2″R,3″R)-naringenin-C-3/C-8″ dihydroquercetin linked biflavanone (GB-2; 4) and (2R,3S,2″R,3″R)-manniflavanone (3), whose stereochemistry has been revised, the antioxidants identified for the first time in Garcinia buchananii were (2R,3R)-taxifolin-6-C-β-D-glucopyranoside (1), (2R,3R)-aromadendrin-6-C-β-D-glucopyranoside (2), and the new compound (2R,3S,2″S)-buchananiflavanone (5). The H₂O₂ scavenging and the ORAC assays demonstrated that these natural products have an extraordinarily high antioxidative power, especially (2R,3S,2″R,3″R)-manniflavanone (3) and GB-2 (4), with EC₅₀ values of 2.8 and 2.2 μM, respectively, and 13.73 and 12.10 μmol TE/ μmol. These findings demonstrate that G. buchananii bark extract is a rich natural source of antioxidants.
authors.affiliation: Lehrstuhl für Lebensmittelchemie und Molekulare Sensorik, Technische Universität München, Lise-Meitner Str. 34, D-85354 Freising, Germany. timo.stark@tum.de
authors.forename: Timo D
authors.initials: TD
authors.lastname: Stark
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Matsutomo
authors.forename: Sofie
authors.initials: S
authors.lastname: Lösch
authors.forename: Paul A
authors.initials: PA
authors.lastname: Boakye
authors.forename: Onesmo B
authors.initials: OB
authors.lastname: Balemba
authors.forename: Sofie P
authors.initials: SP
authors.lastname: Pasilis
authors.forename: Thomas
authors.initials: T
authors.lastname: Hofmann
mesh_terms: D000975:Antioxidants / Q000737:chemistry* / Q000302:isolation & purification; D044946:Biflavonoids / Q000737:chemistry* / Q000302:isolation & purification; D055808:Drug Discovery; D044950:Flavanones / Q000737:chemistry* / Q000302:isolation & purification; D029760:Garcinia / Q000737:chemistry*; D006027:Glycosides / Q000737:chemistry* / Q000302:isolation & purification; D024301:Plant Bark / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D013636:Tanzania
chemical_list: D000975:Antioxidants; D044946:Biflavonoids; D044950:Flavanones; D006027:Glycosides; D010936:Plant Extracts