Many vegetables are excellent folate sources occurring as polyglutamyl 5-methyltetrahydrofolate (5MTHF). Quantitative determination of the intact folate is difficult due to lengthy extraction and clean-up procedures as well as limited detection sensitivity. Here we report a rapid extraction and UPLC-MS/MS method for the determination of folate in vegetables and vegetable juice. Samples (14 different vegetable species from Brassicaaceae, Asteraceae, Amaranthaceae and Apiaceae families) were extracted in boiling reducing buffer with 13C5-5MTHF added as internal standard. The folate species were separated by reversed phase UPLC in 9 min and eluate was interfaced with a triple quadrupole mass spectrometer operated in positive electrospray mode. The respective pseudo-molecular cation of each 5MTHF species was fragmented for selective MS/MS detection. 5MTHF polyglutamyls predominated in vegetables but during juicing converted to monoglutamyl 5MTHF and degraded enzymatically. Pre-steaming of the vegetables preserved folate and various polyglutamyl folate profiles and could be achieved by combining specific vegetable juices.

Quantitative UPLC-MS/MS method for the determination of native 5-methyl-tetrahydrofolate and polyglutamyl derivatives in raw vegetables and vegetable juice

239th National Meeting (2010)

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