APPLICATION OF AN HPLC ASSAY FOR THE DETERMINATION OF FOLATE DERIVATIVES IN SOME VEGETABLES, FRUITS AND BERRIES CONSUMED IN FINLAND

The folate content of 30 commodities of vegetables, fruits and berries , including a few processed products, was determined by high-performan ce liquid chromatography (HPLC). HPLC was used with a combination with fluorescence and ultraviolet detectors to analyze folate monoglutamat e derivatives and their distribution after extraction at pH 6.0 and de conjugation with hog kidney deconjugase at pH 4.9. 5-Methyltetrahydrof olate was the main derivative in all foods studied, but tetrahydrofola te, 5-formyltetrahydrofolate and 10-formylfolic acid were also detecte d. The sum of the monitored folate derivatives (as mu g folic acid) in vegetables ranged from 9 to 114 mu g per 100 g and that of berries an d fruits from 3 to 36 mu g per 100 g. The variation in folate content, which was studied by analyzing raw potato, carrot and cabbage bought from retail shops three times a year, was small. Some of the studied p rocessed vegetable foods were also reasonably good sources of folate. The results obtained with HPLC are rather similar to the previously re ported values for vegetables determined by a microbiological method. S everal measures for method improvement and quality control of the anal ysis allowed reliable determination of the main folate forms, particul arly 5-methyltetrahydrofolate, in a wide range of plant-derived foods. (C) 1997 Elsevier Science Ltd.