De bepaling van foliumzuur - een evaluatie van de recente literatuur met speciale aandacht voor voedsel
[The determination of folate - an evaluation of recent literature with speciale emphasis on food.]
Melis PHAM, Vaessen HAMG
RIVM Rapport 389101005
The literature from 1985 up to 1994 has been studied for folic acid in biological substrates and for the group of compounds similar to folic acid in respect of chemical structure and biological activities ("folates"). Emphasis in the evaluation was on nomenclature, occurrence, physiology, dietary recommendations and in particular on the determination of folates in food. Data on the determination of these compounds in food are collected in Table 1, in Table 2 for body fluids and in Table 3 for other matrices. It was found that determination of folates in food is still predominantly done by microbiology in combination with the test organism Lactobacillus casei. However, from collaborative studies it is evident that there is an urgent need to much further standardize this procedure than achieved sofar, to improve the comparability of laboratory results. In addition, the advice is to discontinue the use of the term "free" folate since this is deceptive and ambiguous. HPLC methods fit best to the present and future needs of the folate determination. However these procedures also require further optimalization towards a method in which, after actraction with optional hog kidney deconjugase, the extracts are cleaned (anion exchange) and enriched (affinity chromatography) and subsequently assayed for folates by HPLC in combination with fluorescence- and UV-detection in series.