Metabolites of dietary atractyligenin glucoside in coffee drinkers' urine.

Arabica roast coffee contains a substantial amount of water soluble atractyligenin-2-O-β-d-glucoside, which is ingested by consumption of coffee brew. Metabolomics data suggest this coffee compound is excreted as glucuronides, but the structures of conjugates have not been elucidated so far. We collected coffee drinkers' urine and isolated four metabolites by MS-guided liquid chromatographic fractionation. The structures were investigated by nuclear magnetic resonance (NMR) and time-of-flight mass spectrometry (ToF-MS) and identified as atractyligenin-19-O-β-d-glucuronide (M1), 2β-hydroxy-15-oxoatractylan-4α-carboxy-19-O-β-d-glucuronide (M2), and 2β-hydroxy-15-oxoatractylan-4α-carboxylic acid-2-O-β-d-glucuronide (M3). An unconjugated metabolite (M4) was confirmed as atractyligenin. We analyzed spot urines from n = 6 coffee drinking individuals and detected the metabolites M1, M2 and M4 in every sample, and M3 in four out of six samples, suggesting interindividual differences in metabolism.