The Korean Society of Applied Pharmacology 2011; 19(1): 27-32  
Quercetin Derivatives from Siegesbeckia glabrescens Inhibit the Expression of COX-2 Through the Suppression of NF-κB Activation in Microglia
Hyo Jin Lim1, Hua Li1, Jae Yeon Kim1 and Jae-Ha Ryu1,*
1College of Pharmacy, Sookmyung Women' University, Seoul 140-742, Republic of Korea
Jae-Ha Ryu
Received: October 11, 2010; Revised: November 9, 2010; Accepted: November 9, 2010; Published online: January 31, 2011.
© The Korean Society of Applied Pharmacology. All rights reserved.

Open Access
Abstract
The activation of microglia induces the overproduction of infl ammatory mediators that are responsible for the neurodegenerative disorders including Alzheimer' disease and Parkinson' disease. The large amounts of prostaglandin E2 (PGE2) produced by inducible cyclooxygenase (COX-2) is one of the main infl ammatory mediators that can contribute to neurodegeneration. The inhibition of COX-2 thus may provide therapeutic strategy for the treatment of neurodegenerative diseases. From the activityguided purifi cation of EtOAc soluble fraction of Siegesbeckia glabrescens, four compounds were isolated as inhibitors of PGE2 production in LPS-activated microglia. Their structures were determined as 3, 4'dimethylquercetin (1), 3, 7-dimethylquercetin (2), 3-methylquercetin (3) and 3, 7, 4'trimethylquercetin (4) by the mass and NMR spectral data analysis. The compounds 1-4 showed dose-dependent inhibition of PGE2 production in LPS-activated microglia with their IC50 values of 7.1, 4.9, 4.4, 12.4 ?M respectively. They reduced the expression of protein and mRNA of COX-2 through the inhibition of I-κBα degradation and NF-κB activity that were correlated with the inactivation of p38 and ERK. Therefore the active compounds from Siegesbeckia glabrescens may have therapeutic effects on neuro-infl ammatory diseases through the inhibition of overproduction of PGE2 and suppression of COX-2 overexpression.
Keywords: Siegesbeckia glabrescens, Quercetin, Cyclooxygenase, Nuclear factor kappa B, Microglia

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