Determination of folic acid in fortified foods and folate in some Philippine indigenous vegetables based on the developed and validated method of analyses

A reversed-phase high-performance liquid chromatography (RP-HPLC) method with ultraviolet detection at 280 nm was validated to determine the folic acid (FA) content of fortified foods. The analytical method involves FA extraction with phosphate buffer (pH 8) or amylase treatment after buffer extraction (for samples with carbohydrate bound-FA) and detection through HPLC using a Supelcosil LC-18 column. Validation of the method was based on AOAC 2002 and Eurachem/CITAC (2003) with limit of detection of 0.0524ppm , limit of quantitation of about 0.1747ppm and an average correlation coefficient (r) of 0.998. The repeatability and reproducibility of the method were also evaluated based on Horrat acceptance criteria and found to be considerably good. Recovery of the test results were established at 81% to 97% while the accuracy of the method was verified using SRM 1849 (Infant Nutritional Formula). The fully validated method was used to analyze fifteen (15) fortified food samples available in the market which included breakfast cereals, milk, breads and powdered juice drinks. The study revealed that the folic acid contents of most of the samples tested were lower than those indicated in their nutritional labels. RP-HPLC with UV-Vis detection at 280 nm was also used to evaluate the 5- methyltetrahydrofolate (5-CH3-THF), 5-formyltetrahydrofolate (5-CHO-THF) and tetrahydrofolate (THFA) in seven (7) green leafy vegetables extracted by triple-enzyme digestion with amylase, protease and conjugase although only 5-CHO-THFA and THFA were successfully quantified. Extracts of LC-MS alugbati, malunggay and swamp cabbage were also subjected to LC-MS analysis for the determination of folate profiles. Several peaks were detected but none of these corresponded to those of the available standards