Stability of dietary 5-formyl-tetrahydrofolate and its determination by HPLC: a pilot study on impact of pH, temperature and antioxidants on analytical results

The Bioaccessibility of Folate in Breads and the Stability of Folate Vitamers during in vitro Digestion

Both the liberation and stability of endogenous folate are relevant to the bioaccessibility of folate. Since folates are unstable, in addition to studying the natural folate content in foods, bioaccessibility...

Partition and stability of folic acid and caffeic acid in hollow zein particles coated with chitosan

The carriers for hydrophobic bioactives have been extensively studied, while those for hydrophilic bioactives are still challenging. The partition of bioactives in the particles depends greatly on their solubility, interaction with carrier materials, as well as structure of carriers. In this study, chitosan-coated hollow zein particles using calcium phosphate as a sacrificing template (CS-HZ) were fabricated to co-encapsulate folic acid (FA) and caffeic acid (CA). Partition, photostability, and antioxidant capacity of bioactive compounds were also studied. The size, polydispersity index and ζ-potential of optimized CS-HZ were 176.3 nm, 0.14 and +39.3 mV, respectively, indicating their small and uniform dimension with excellent colloidal stability. FA interacted with chitosan to form complexes and then coated on the zein particles where CA was encapsulated. After co-encapsulation in CS-HZ, the photostability of both FA and CA was improved in comparison with encapsulation of single compound, with 85% of FA remaining after 240 min of UVA irradiation, and 90% of CA remaining after 80 min. Antioxidant activity of CA decreased upon encapsulation, but significantly increased after irradiation. Findings in this study shed some light on the design of carriers for co-delivery of hydrophilic compounds in acidic condition.

Mechanism for Inhibition of Folic Acid Photodecomposition by Various Antioxidants

Folic acid, a synthetic form of folate, is a water-soluble vitamin that is essential during periods of rapid cell division and growth. However, it decomposes upon ultraviolet irradiation to form inactive photoproducts. In this study, the protective effect and mechanisms of antioxidants, including cinnamic acids, flavonoids, catechol and its derivatives, stilbenes, p-benzoquinone and its derivatives, isoprenoids, curcumin, oleic acid, and linoleic acid, against folic acid photodecomposition were investigated by using fluorescence and absorbance spectroscopy, high-performance liquid chromatography, and antioxidant assay. It was found that antioxidants could inhibit or delay the folic acid decomposition in varying degrees, among which caffeic acid was the most effective. The increase in its remarkable antioxidant efficiency and absorbance in the UVA region during irradiation contributed to its effective protection. This finding could be useful for the protection of photolabile components in food and other uses.

The use of a plant enzyme for rapid and sensitive analysis of naturally-occurring folates in food by liquid chromatography-tandem mass spectrometry

A rapid, sensitive and reproducible method for analysis of naturally-occurring folates and folic acid in food has been developed and validated. A single-enzyme extraction step, in which a pure recombinant enzyme of plant origin (Arabidopsis thaliana) was used, enabled fast and reproducible deglutamylation during folate extraction within the incubation time of 1 h. Six commonly occurring folate forms (tetrahydrofolate, 5,10-methenyltetrahydrofolate, 10-formylfolic acid, 5-formyltetrahydrofolate, folic acid and 5-methyltetrahydrofolate) were detected and quantified in 9 min using liquid chromatography-tandem mass spectrometry (LC-MS/MS). ¹³C₅-labeled 5-formyltetrahydrofolate, ¹³C₅-labeled folic acid and ¹³C₅-labeled 5-methyltetrahydrofolate were used as internal standards for the quantification. The method is described by a calibration curve (R²>0.99 and trueness 85-115%), a limit of quantification at 0.1 μg/100 g, trueness at 80-120% in spiked samples and certified reference materials, and a precision <10%. However, the precision in quantification of tetrahydrofolate was not within the acceptable limits due to the lack of use of the corresponding internal standard. An interconversion study of unstable formyl forms was performed which showed that 50% of 5,10-methenyltetrahydrofolate is converted to 5-formyltetrahydrofolate during the analysis. The developed LC-MS/MS method is a candidate for a future standard method for folate analysis in food.

Small amounts of ethanol attenuate folic acid stability in acidic beverages during storage

Folic acid (FA) is an essential compound involved in important biochemical processes and is used to fortify various food products. FA in fortified acidic beverages decomposes during storage due to H+ attack. FA stability in acidic beverages is a serious problem as food fortification should guarantee labeled FA concentrations until the expiry date. In this study, we investigated the influence of ethanol (EtOH) on FA depletion using a model acidic beverage and observed that small amounts of EtOH, derived from added flavor, promoted FA depletion. FA depletion was promoted by only small amounts of EtOH, but not by acetonitrile. This suggested that FA decomposition might be accelerated by EtOH, which surrounds FA molecules in solution due to selective solvation. In the development of FA-fortified beverages, EtOH content should be decreased or removed altogether, to prevent accelerating FA decomposition.

Protection of folic acid through encapsulation in mesoporous silica particles included in fruit juices

Folic acid (FA) is a synthetic vitamin commonly used for food fortification. However, its vulnerability to processing and storage implies loss of efficiency, which would induce over-fortification by processors to obtain a minimum dose upon consumption. Recent studies have indicated potential adverse effects of FA overdoses, and FA protection during processing and storage could lead to more accurate fortification. In addition, sustained vitamin release after consumption would help improve its metabolism. The objective of this work was to study controlled FA delivery and stability in fruit juices to reduce potential over-fortification risks by using gated mesoporous silica particles (MSPs). The obtained results indicated that FA encapsulation in MSPs significantly improved its stability and contributed to controlled release after consumption by modifying vitamin bioaccessibility. These results confirmed the suitability of MSPs as support for controlled release and protection of bioactive molecules in food matrices in different food production and storage stages.

Folates in Fruits and Vegetables: Contents, Processing, and Stability

Folates play a key role in human one-carbon metabolism and are provided by food. It is well established that folates are beneficial in the prevention of neural tube defects and cardiovascular and neurodegenerative diseases. Fruits and vegetables, and especially green vegetables, are the main sources of folates. In parallel, fruits and vegetables, with high contents of folates, are mostly consumed after processing, such as, canning, freezing, or home-cooking, which involve folate losses during their preparation. Hence, it is important to know the percentage of folate losses during processing and, moreover, the mechanisms underlying those losses. The current knowledge on folate losses from fruit and vegetables are presented in this review. They depend on the nature of the respective fruit or vegetable and the respective treatment. For example, steaming involves almost no folate losses in contrast to boiling. Two main mechanisms are involved in folate losses: (i) leaching into the surrounding liquid and (ii) oxidation during heat treatment, the latter of which depending on the nature of the vitamer considered. In this respect, a vitamer stability decreases in the order starting from folic acid followed by 5-HCO-H₄ folate, 5-CH₃ -H₄ folate, and, finally, H₄ folate. Further studies are required, especially on the diffusion of the vitamers in real foods and on the determination of folate degradation products.

Occurrence, stability, and determination of formyl folates in foods

The B-vitamin folate has specific tasks as a one-carbon (C1) group supplier in the building and repair of DNA and RNA as well as in the methylation of homocysteine to methionine. Folate occurs in all living cells as a dynamic pool of several interconvertible forms carrying different C1 groups. Along the food chain, this dynamic pool of folates constantly changes due to either enzymatic or chemical interconversions during food processing and storage. These interconversions make it difficult to determine individual folate forms in foods. The formyl folates, the second most predominant forms of food folates, after 5-methyltetrahydrofolate, are particularly prone to interconvert at low pH. Today, this knowledge is often neglected, leading to risks for analytical underestimation of formyl folates. The purpose of the review is to explore the stability and interconversions of formyl folates in foods as well as to analyze the pitfalls in the determination of formyl folates.