Relaxant Effects of Quercetin Methyl Ether Derivatives in Isolated Guinea Pig Trachea and their Structure-Activity Relationships

Abstract

In the present study, we attempted to compare quercetin methyl ethers and to look for the structure-activity relationships, which may be helpful for synthesizing more active compounds for the treatment of asthma. Four present and two previously studied quercetin methyl ethers concentration-dependently relaxed histamine (30 µM), carbachol (0.2 µM) and KCI (30 mM) induced precontraction. According to their IC₂₅ values to histamine-induced precontraction, the potency order was quercetin 3,3′,4′,5,7-pentamethyl ether (QPME), quercetin 3-methyl ether > quercetin, quercetin 3,4′,7-trimethyl ether (ayanin) > quercetin 4′-methyl ether (tamarixetin), quercetin 3,3′,4′,7,-tetramethyl ether (QTME). Therefore, the methylation at 3, at 5, and at both 3 and 7 positions of the A or/and C ring of quercetin nucleus may increase their tracheal relaxant activity. However, the methylation at the 3′ and at the 4′ position of the B ring of quercetin nucleus may decrease their tracheal relaxant activity.