title: In vitro inhibitory effect of rubraxanthone isolated from Garcinia parvifolia on platelet-activating factor receptor binding.
abstract: Rubraxanthone and isocowanol isolated from Garcinia parvifolia Miq. were investigated for their inhibitory effects on platelet-activating factor (PAF) binding to rabbit platelets using 3H-PAF as a ligand. Rubraxanthone showed a strong inhibition with IC 50 value of 18.2 microM. The IC 50 values of macluraxanthone, 6-deoxyjacareubin, 2-(3-methylbut-2-enyl)-1,3,5-trihydroxyxanthone, 2-(3-methylbut-2-enyl)-1,3,5,6-tetrahydroxyxanthone and 1,3,5-trihydroxy-6,6'-dimethylpyrano(2',3':6,7)-4-(1,1-dimethylprop-2-enyl)-xanthone were also determined for comparison. In the course of our study on structure-activity relationship of xanthones, the results revealed that a geranyl group substituted at C-8 was beneficial to the binding while a hydroxylated prenyl group at C-4 resulted in a significant loss in binding to the PAF receptor.
authors.affiliation: Department of Pharmacy, Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia. ibj@medic.ukm.my
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Jantan
authors.forename: Mazura Md
authors.initials: MM
authors.lastname: Pisar
authors.forename: Muhammad Sum
authors.initials: MS
authors.lastname: Idris
authors.forename: M
authors.initials: M
authors.lastname: Taher
authors.forename: Rasadah Mat
authors.initials: RM
authors.lastname: Ali
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D001792:Blood Platelets / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D029760:Garcinia; D015394:Molecular Structure; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D010980:Platelet Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled; D013329:Structure-Activity Relationship; D014966:Xanthenes / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D044004:Xanthones
chemical_list: D010936:Plant Extracts; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D014966:Xanthenes; D044004:Xanthones; C039351:platelet activating factor receptor; C472156:isocowanol; C472155:rubraxanthone