title: Isolation of onosmins A and B, lipoxygenase inhibitors from Onosma hispida.
abstract: Onosmins A (1) and B (2), lipoxygenase inhibitors, have been isolated from Onosma hispida. Their structures were established as 2-[(4-methylbenzyl)amino]benzoic acid (1) and methyl 2-[(4-methylbenzyl)amino]benzoate (2) through spectroscopic studies, including 2D-NMR. The known compounds apigenin (3), 6,4'-dimethoxy-3,5,7-trihydroxyflavone (4), 6,7-dimethoxy-3,5,4'-trihydroxyflavone (5) and apigenin 7-O-beta-D-glucoside (6) are also reported for the first time from this species. Compounds (1) and (2) inhibited lipoxygenase (LOX, EC 1.13.11.12) enzyme in a concentration-dependent fashion with IC50 values of 24.0 and 36.2 microM, respectively. Lineweaver-Burk as well as Dixon plots and their secondary replots indicated that the nature of inhibition was purely a non-competitive type, with K(i) values 22.0 microM and 31.1, respectively.
authors.affiliation: International Center for Chemical Sciences, HEJ Research Institute of Chemistry, University of Karachi, Karachi-75270, Pakistan.
authors.forename: Ijaz
authors.initials: I
authors.lastname: Ahmad
authors.forename: Sarfraz Ahmad
authors.initials: SA
authors.lastname: Nawaz
authors.forename: Nighat
authors.initials: N
authors.lastname: Afza
authors.forename: Abdul
authors.initials: A
authors.lastname: Malik
authors.forename: Itrat
authors.initials: I
authors.lastname: Fatima
authors.forename: Sher Bahadar
authors.initials: SB
authors.lastname: Khan
authors.forename: Manzoor
authors.initials: M
authors.lastname: Ahmad
authors.forename: Muhammad Iqbal
authors.initials: MI
authors.lastname: Choudhary
mesh_terms: D001565:Benzoates / Q000737:chemistry / Q000302:isolation & purification*; D001593:Benzyl Compounds / Q000737:chemistry / Q000302:isolation & purification*; D028082:Boraginaceae / Q000737:chemistry*; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D001565:Benzoates; D001593:Benzyl Compounds; D016859:Lipoxygenase Inhibitors; C504486:onosmin A; C504487:onosmin B