Isolation of onosmins A and B, lipoxygenase inhibitors from Onosma hispida.
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.
Ahmad
Ijaz
I
International Center for Chemical Sciences, HEJ Research Institute of Chemistry, University of Karachi, Karachi-75270, Pakistan.
Nawaz
Sarfraz Ahmad
SA
Afza
Nighat
N
Malik
Abdul
A
Fatima
Itrat
I
Khan
Sher Bahadar
SB
Ahmad
Manzoor
M
Choudhary
Muhammad Iqbal
MI
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
D001565:Benzoates; D001593:Benzyl Compounds; D016859:Lipoxygenase Inhibitors; C504486:onosmin A; C504487:onosmin B