Metabolites of dietary atractyligenin glucoside in coffee drinkers' urine

Arabica roast coffee contains a substantial amount of water soluble atractyligenin-2-O-beta-D-glucoside, which is ingested by consumption of coffee brew. Metabolomics data suggest this coffee compound is excreted as glu-curonides, 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 investi-gated by nuclear magnetic resonance (NMR) and time-of-flight mass spectrometry (ToF-MS) and identified as atractyligenin-19-O-beta-D-glucuronide (M1), 2 beta-hydroxy-15-oxoatractylan-4 alpha-carboxy-19-O-beta-D-glucuronide (M2), and 2 beta-hydroxy-15-oxoatractylan-4 alpha-carboxylic acid-2-O-beta-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.