Abstract
Flavonoids have the potential to modulate inflammation by inhibition of cyclooxygenase-2 (COX-2) transcription. In this study, we compared the effect of the human flavonold plasma metabolites (quercetin 3′-sulfate, quercetin 3-glucuronide and 3′-methylquercetin 3-glucuronide) on expression of COX-2 mRNA in human lymphocytes ex vivo using TaqMan real-time RT-PCR. We show that the flavonoid quercetin metabolites as detected in human plasma at physiologically significant concentrations inhibit COX-2 expression in human lymphocytes ex vivo. To examine the effect in vivo, we measured COX-2 mRNA levels in 8 subjects (5 men and 3 women) participating in a 3-way, single-blind, randomized crossover study after consumption of a single meal of white, low-quercetin onions, compared with yellow, high-quercetin onions. After consumption of high-quercetin onions, quercetin conjugates were detected in plasma (up to a maximum concentration of 4 μmol/L at ∼1 h). However, the expression of COX-2 mRNA in lymphocytes was unchanged by the consumption of high-quercetin onions compared with the low-quercetin group. The results show that a single high dose of the flavonold quercetin from onions does not change COX-2 mRNA expression in human lymphocytes in vivo even though this change occurred in vitro and ex vivo.
Original language | English |
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Pages (from-to) | 552-557 |
Number of pages | 6 |
Journal | The Journal of Nutrition |
Volume | 134 |
Issue number | 3 |
DOIs | |
Publication status | Published - 1 Mar 2004 |
Externally published | Yes |
Keywords
- Cyclooxgenase-2
- Flavonoids
- Gene expression
- Lymphocyte
- Quercetin metabolites