title: Benzophenone O-glucoside, a biogenic precursor of 1,3,7-trioxygenated xanthones in Hypericum annulatum.
abstract: Two benzophenones, hypericophenonoside (1) and annulatophenone (2) were isolated from the methanol extract of the herb of Hypericum annulatum. The structures of the benzophenones were established as 2'-O-beta-D-glucopyranosyl-2,4,5',6-tetrahydroxy benzophenone (1) and 2,3',5',6-tetrahydroxy-4-methoxybenzophenone (2) based on spectral and chemical evidence. Hypericophenonside is the second benzophenone O-glycoside found in nature. Acid and enzymatic hydrolysis of (1) led directly to the formation of 1,3,7-trihydroxyxanthone (gentisein). This fact confirmed the hypothesis that some xanthones could be formed in plants by dehydration of 2,2'-dihydroxybenzophenones, and the intermediate precursors appear to be benzophenone O-glycosides ortho to the carbonyl function.
authors.affiliation: Department of Pharmacognosy, Faculty of Pharmacy, Medical University of Sofia, Dunav str. 2, 1000, Sofia, Bulgaria. gkitanov@mbox.pharmfac.acad.bg
authors.forename: G M
authors.initials: GM
authors.lastname: Kitanov
authors.forename: P T
authors.initials: PT
authors.lastname: Nedialkov
mesh_terms: D001577:Benzophenones / Q000737:chemistry / Q000302:isolation & purification*; D005960:Glucosides / Q000737:chemistry / Q000302:isolation & purification*; D006027:Glycosides / Q000737:chemistry / Q000302:isolation & purification*; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D010944:Plants / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D014966:Xanthenes / Q000737:chemistry*; D044004:Xanthones
chemical_list: D001577:Benzophenones; D005960:Glucosides; D006027:Glycosides; D014966:Xanthenes; D044004:Xanthones; C436832:annulatophenone; C436831:hypericophenonoside; C436833:gentisein