Improvements in the analysis of reduced folate monoglutamates and folic acid in food by high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic method with fluorescence and ultraviolet detection was used to evaluate the different steps in folate analysis to detect and quantify the most abundant folate forms naturally present in foods. Rapid heat extraction by microwave heating and an enzymatic deconjugation with hog kidney conjugase and chicken pancreas is presented. The extracts were purified with strong anion-exchange cartridges before injection. The combined use of ascorbic acid and mercaptoethanol in the extraction step noticeably improved the stability of tetrahydrofolate, making it also possible to analyze some of the most labile folate vitamers. Tetrahydrofolate was also shown to be easily degraded during the deconjugation step. The compounds 5-methyltetrahydrofolate and, to a lesser extent, 5-formyltetrahydrofolates were also found as important vitamers in foods. In addition, folic acid and 10-formylfolic acid could be determined with the described method. Keywords: Folates; folic a...