Isolation of Onosmins A and B, Lipoxygenase Inhibitors from Onosma hispida

• Published in: Chemical & Pharmaceutical Bulletin Vol. 53; no. 8; pp. 907 - 910
• Main Authors: Ahmad, Ijaz, Nawaz, Sarfraz Ahmad, Afza, Nighat, Malik, Abdul, Fatima, Itrat, Khan, Sher Bahadar, Ahmad, Manzoor, Choudhary, Muhammad Iqbal
• Format: Journal Article
• Language: English; Japanese
• Published: TOKYO The Pharmaceutical Society of Japan 01.08.2005; Pharmaceutical Society of Japan; Pharmaceutical Soc Japan; Japan Science and Technology Agency
• Subjects: Benzoates - chemistry; Benzoates - isolation & purification; Benzyl Compounds - chemistry; Benzyl Compounds - isolation & purification; Boraginaceae; Boraginaceae - chemistry; Chemistry; Chemistry, Medicinal; Chemistry, Multidisciplinary; kinetics; Life Sciences & Biomedicine; lipoxygenase inhibiting constituent; Lipoxygenase Inhibitors - pharmacology; Onosma hispida; Pharmacology & Pharmacy; Physical Sciences; Science & Technology; Spectrum Analysis - methods; Onosma hispida; ROOTS; kinetics; Boraginaceae; lipoxygenase inhibiting constituent; CONSTITUENTS
• ISSN: 0009-2363; 1347-5223
• DOI: 10.1248/cpb.53.907

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-β-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 μM, 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 Ki values 22.0 μM and 31.1, respectively.