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Abstract: Arctiin, an important lignan compound in Fructus Arctii, has been reported to possess various kinds of bioactivities. Previous studies on the pharmacokinetic of arctiin after oral administration showed that it had a rapid absorption phase followed by a sharp but lasting disappearance. To gain deep insight into the action mechanism of arctiin, the excretion and metabolism of arctiin in vivo should be further studied. In this paper, three metabolites were isolated and identified in rat feces as (−)-enterolactone (M-1), (−)-arctigenin (M-2) and [(2R,3R)-2-(3′-hydroxybenzyl)-3-(3″,4″-dimethoxybenzyl)-butyrolactone] (M-3). Based on the structures of three metabolites, possible metabolic pathways of arctiin in rats are proposed. At the same time, the cumulative excretion rate of arctiin and its metabolites in rat urine and feces were determined, indicating that arctiin was excreted 19.84% in urine and 1.80% in feces, respectively, enterolactone, the most main metabolite, was excreted 35.80% in feces. These results provide very important information for understanding the metabolism and excretion of arctiin in vivo and speculating its action mechanism, they can provide useful information and reference for further metabolic investigations on arctiin in humans. [Copyright &y& Elsevier]

The dietary supply of folates and their measurement are both affected, potentially, by the instability of some folates. Labile folates appear to be stabilized by binding to folate-binding protein (FBP); this paper reports measurements of that stabilization. The degradation rates of the very labile tetrahydrofolate (H(4)folate) and moderately labile 5-methyltetrahydrofolate (5-CH(3)H(4)folate) were measured with the compounds free or bound to either soluble or immobilized bovine milk FBP. Complexation increased stability from 2- to > 1000-fold, depending on buffer and temperature conditions. H(4)folate at 4 degrees C and pH 6.7 appeared to be quite stable for > 100 d when bound to soluble FBP but had a half-life of < 1 h when free. Stabilization of milk folates may be a role of FBP and would improve the bioavailability of milk folate to newborns and other consumers. [ABSTRACT FROM AUTHOR]