Food Research Institute

SKRBEK, S. – RÜFER, C. E. – MARKO, D. – ESSELEN, M.
Quercetin and its microbial degradation product 3,4-dihydroxyphenylacetic acid generate hydrogen peroxide modulating their stability under in vitro conditions
Journal of Food and Nutrition Research, 48, 2009, No. 3, s. 129-140

Melanie Esselen, Institute of Applied Biosciences, Section of Food Toxicology, University of Karlsruhe (TH), Adenauerring 20, D – 76131 Karlsruhe, Germany. Tel.: +49(721)608-7645, fax: +49(721)608-7255, e-mail: melanie.esselen@lmc.uni-karlsruhe.de

Summary: In contrast to the microbial degradation of quercetin (QUE), little is known about its degradation under cell culture conditions and the contribution of potential degradation products to the observed cellular effects of QUE. In a cell culture medium, the concentration of QUE was found to decrease rapidly in a time-dependent manner. The presence of catalase substantially affected the stability of QUE but not of the microbial degradation product, 3,4-dihydroxyphenyl¬acetic acid (HPA). Within human colon carcinoma cells (HT29), formation of a QUE glucuronide, the only metabolite, was observed with a maximum at 3 h, whereas no free QUE was detected under the chosen experimental conditions. From the putative degradation products, only the microbial QUE-metabolite HPA, which was not generated under cell culture conditions, exhibited substantial growth-inhibitory properties in HT29 cells. Both QUE and HPA led to the formation of hydrogen peroxide in the cell culture medium. The presence of catalase or ascorbic acid was found to diminish the growth-inhibitory effect of HPA in cell culture, but also under these conditions, still substantial growth inhibition was observed. However, HPA and phloroglucinol lacked the effectiveness of QUE against the epidermal growth factor receptor and cAMP-hydrolysing phosphodiesterases, indicating a different pattern of cellular activities.

Keywords: microbial degradation products; quercetin; 3,4-dihydroxyphenylacetic acid; phloroglucinol; epidermal growth factor receptor; 3’,5’-cAMP- phosphodiesterase; HT29 cells

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