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Naturally occurring flavonoids as inhibitors of purified cytosolic glutathione S-transferase

Naturally occurring flavonoids as inhibitors of purified cytosolic glutathione S-transferase Flavonoids are known to modulate catalytic activity and expression of various enzymes. Glutathione S-transferases (GSTs) are the important biotransformation enzymes defending cells against potentially toxic xenobiotics. Therefore, the modulation of GST activity may influence detoxification of xenobiotics. The aim of this study was to evaluate the in vitro inhibitory activity of several dietary flavonoids towards purified equine liver cytosolic GST.Pure GST was incubated in the presence or absence of flavonoids (10 nM–100 µM), its activity was assayed using 1-chloro-2,4-dinitrobenzene (CDNB) as a substrate, and half maximal inhibitory concentrations (IC50) were determined. The obtained results were confirmed by GST activity staining of native polyacrylamide gel electrophoresis (PAGE) gels. For the most potent inhibitor, the inhibition kinetics study was performed.From 24 flavonoids tested, the most potent GST inhibitor was gallocatechin gallate (IC50 = 1.26 µM). The inhibition kinetics of this compound followed noncompetitive mechanism versus both glutathione (Ki = 35.9 µM) and CDNB (Ki = 34.1 µM).The inhibitory potency of different flavonoids for GST activity depended mainly on the pattern of hydroxylation and number of hydroxyl groups in the ring B. Especially, pyrogallol-type catechins with 3-OH group esterified with gallic acid showed strong potential to inhibit GST in vitro. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Xenobiotica Taylor & Francis

Naturally occurring flavonoids as inhibitors of purified cytosolic glutathione S-transferase

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References (34)

Publisher
Taylor & Francis
Copyright
© 2012 Informa UK, Ltd.
ISSN
1366-5928
eISSN
0049-8254
DOI
10.3109/00498254.2012.670737
pmid
22458346
Publisher site
See Article on Publisher Site

Abstract

Flavonoids are known to modulate catalytic activity and expression of various enzymes. Glutathione S-transferases (GSTs) are the important biotransformation enzymes defending cells against potentially toxic xenobiotics. Therefore, the modulation of GST activity may influence detoxification of xenobiotics. The aim of this study was to evaluate the in vitro inhibitory activity of several dietary flavonoids towards purified equine liver cytosolic GST.Pure GST was incubated in the presence or absence of flavonoids (10 nM–100 µM), its activity was assayed using 1-chloro-2,4-dinitrobenzene (CDNB) as a substrate, and half maximal inhibitory concentrations (IC50) were determined. The obtained results were confirmed by GST activity staining of native polyacrylamide gel electrophoresis (PAGE) gels. For the most potent inhibitor, the inhibition kinetics study was performed.From 24 flavonoids tested, the most potent GST inhibitor was gallocatechin gallate (IC50 = 1.26 µM). The inhibition kinetics of this compound followed noncompetitive mechanism versus both glutathione (Ki = 35.9 µM) and CDNB (Ki = 34.1 µM).The inhibitory potency of different flavonoids for GST activity depended mainly on the pattern of hydroxylation and number of hydroxyl groups in the ring B. Especially, pyrogallol-type catechins with 3-OH group esterified with gallic acid showed strong potential to inhibit GST in vitro.

Journal

XenobioticaTaylor & Francis

Published: Sep 1, 2012

Keywords: Glutathione S -transferase; flavonoids; gallocatechin gallate; IC 50′ inhibition kinetics; structure-activity relationship; GST activity staining

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