Study of the Metabolism of Estragole in Humans Consuming Fennel Tea

Abstract

The metabolism of the potent carcinogen estragole was investigated in humans after consumption of fennel tea by analyses of its metabolites in blood plasma and urine. Stable isotope dilution assays based on LC-MS/MS detection revealed that 1'-hydroxylation of estragole happened very fast as the concentration of conjugated 1'-hydroxyestragole in urine peaked after 1.5 h, whereas it was no longer detectable after 10 h. Besides the formation of less than 0.41% conjugated 1'-hydroxyestragole of the estragole dose administered, the further metabolite p-allylphenol was generated from estragole in a higher percentage (17%). Both metabolites were also detected in blood plasma in less than 0.75-2.5 h after consumption of fennel tea. In contrast to this, no estragole was present in these samples above its detection limit. From the results, it can be concluded that an excess of the major fennel odorant trans-anethole principally does not interfere with estragole metabolism, whereas influences on the quantitative composition of metabolites cannot be excluded. The presence of a sulfuric acid conjugate of estragole could not be confirmed, possibly due to its high reactivity and lability.

Quantification of 1,8‐cineole and of its metabolites in humans using stable isotope dilution assays

“…The mixture was allowed to stir for 15 min at room temperature and then hydrolyzed with 300 mL ice-cold water. The precipitate was dissolved by adding saturated aqueous NH 4 Cl solution. After separating the organic layer the aqueous solution was extracted with dichloromethane (2 Â 5 mL).…”

“…After separating the organic layer the aqueous solution was extracted with dichloromethane (2 Â 5 mL). The combined organic extracts were washed with water, dried over Na 2 SO 4 and concentrated in a stream of nitrogen. Filtration over Florisil with pentane/diethylether (3/1, v/v) gave pure [9- …”

“…The latter was dissolved in toluene (20 mL), extracted with water and the combined aqueous extracts were re-extracted with dichloromethane. The dichloromethane phases were combined, dried over Na 2 SO 4 (13).…”

“…Metabolism of odorants is an actual topic in toxicology and pharmacology, as important herbal compounds such as pulegone from pennyroyal [3], estragole from fennel [4] and coumarin from cinnamon [5] have been shown to undergo bioactivation by metabolizing enzymes. Fig.…”

Determination of Estragole in Pharmaceutical Products, Herbal Teas and Herbal Extracts Using GC-FID

“…Solvent extraction using dichloromethane has been reported for extraction of estragole in Fennel tea followed by GC-MS analysis (Zeller and Rychlik 2006). The effect of using different internal standards on the analytical method performance for estragole has been studied, results have concluded that using p-propyl anisole as an internal standard provided accurate results comparable to those obtained from other methods using stable isotopically labeled internal standard (Zeller et al, 2009). HPLC method using different microextraction procedures have been applied for extraction of estragole and other bioactive compounds from different plant extracts and human urine (Rajabi et al, 2014).…”