Identification of 2,5-dimethyl-4-hydroxy-3[2H]-furanone beta-D-glucuronide as the major metabolite of a strawberry flavour constituent in humans.

2,5-Dimethyl-4-hydroxy-3[2H]furanone (Furaneol, DMHF) [3658-77-3], an important flavour constituent of strawberry fruit, was administered to four male and two female volunteers using fresh strawberries as a natural DMHF source. The amount excreted was determined by measuring urinary levels of DMHF and DMHF glucuronide. DMHF glucuronide was synthesized and the structure elucidated by mens of 1H, 13C and two dimensional nuclear magnetic resonance, as well as mass spectral data. Identification and quantification of DMHF glucuronide in human urine were achieved after solid phase extraction on XAD-2 using reverse-phase reverse-phase HPLC with either on-line UV/VIS or electrospray tandem mass spectrometry detection. Male and female volunteers excreted 59-69% and 81-94%, respectively, of the DMHF dose (total of free and glycosidically bound DMHF in strawberries) as DMHF glucuronide in urine within 24 hr. The amount of DMHF excretion was independent of the dose size and the ratio of free to glycosidically bound forms of DMHF in strawberry fruit. DMHF, DMHF glucoside and its 6'-O-malonyl derivative, naturally occurring in strawberries, were not detected in human urine.