Thermal and irradiation resistance of folic acid encapsulated in zein ultrafine fibers or nanocapsules produced by electrospinning and electrospraying.

The objectives of this study were to characterize zein fibers and capsules prepared by electrospinning and electrospraying techniques, respectively, and then use them to encapsulate folic acid. Folic acid containing fibers and capsules (0.5, 1.0, and 1.5%, w/v) were submitted to thermal treatment (100, 140, and 180 °C) and ultraviolet A light (UVA) irradiation to evaluate the resistance of folic acid. Zein fibers and capsules containing folic acid showed high encapsulation efficiency (>80%). Unencapsulated folic acid showed a reduction in folic acid content from 17.17 µg/mL to 5.44 µg/mL (approximately 70%) when exposed to 180 °C. Photodegradation of unencapsulated folic acid lowered its concentration from 17.17 µg/mL to 12.58 µg/mL (~26% of reduction), when exposed for 1 h to UVA irradiation. However, folic acid concentration when encapsulated in fibers (1.5%) was maintained or only slightly reduced from 9.73 µg/mg to 8.88 µg/mg after thermal treatment at 180 °C. The capsules containing 1.5% of folic acid also presented a slight reduction in folic acid concentration from 8.84 µg/mg to 7.88 µg/mg when exposed to 24 h of UVA irradiation. Zein fibers and capsules containing folic acid present promising characteristics for application in foods that require thermal processing or exposure to irradiation.

Association between seasonal serum folate levels and ultraviolet radiation.

UV radiation has been consistently reported to cause folate photodegradation in vitro and in human skin. Seasonal variations in UV radiation might explain seasonal changes in folate levels in blood. Yet, few studies have addressed this phenomenon. The main objective of this study was to investigate whether a relationship exists between seasonal variations in serum folate levels in a population of Spain (Latitude: 36° 41' 6.88″; Longitude: 4° 30' 0.64″) and the annual variations of solar ultraviolet reached in the localization. From a sample of 118,831 serum folate determinations, two studies were performed. The first one, which included all subjects, showed a decreased in mean folate concentrations in all seasons with respect to winter with lower values in summer. The risk of folate deficiency was 1.37 times greater in summer than in winter (95%CI: 1.29-1.46). In the second study, subjects with a first folate determination in winter and a second one in summer were 3.32 more likely to develop folate deficiency than those with a first folate determination in summer and a second one in winter (95%CI: 1.55 to 7.11). Folate levels showed a seasonal variation inversely related to solar total UV radiation reached in our location, with maximum daily doses of 5000 J m-2 reached in June. A gradual increase in percentage of folate deficiency is observed since spring. So, patients with folate levels close to deficiency are at a higher risk of having folate deficiency in summer.

Protection of resveratrol against the photodecomposition of folic acid and photodecomposition-induced structural change of beta-lactoglobulin.

Folic acid is a synthetic form of the B-group vitamin known as folate and essential for a variety of physiological processes. However, it decomposes under UV irradiation, causing indirect oxidation and structural change of protein. In this study, the protective effect of resveratrol against the photodecomposition of folic acid and its caused protein structural change was investigated by using fluorescence and absorbance spectroscopy, high performance liquid chromatography and ABTS assay. It was found that resveratrol could inhibit the folic acid decomposition and control the decomposition process, depending on the polyphenol concentration and addition time. Transformation of resveratrol was accelerated by photodecomposition of folic acid. Antioxidant activity of resveratrol was important for the protective effect. Moreover, resveratrol could also inhibit the unfolding of beta-lactoglobulin caused by the folic acid decomposition by using circular dichroism.

Folate and phototherapy: What should we inform our patients?

BACKGROUND: Ultraviolet (UV) degradation of folate has been studied in vitro and in vivo, but comprehensive reviews of the subject and recommendations for supplementing folate are lacking, especially for women of childbearing age, in whom decreases in folate predisposes newborns to neural tube defects. OBJECTIVE: We reviewed the effects of phototherapy on folate and provide a recommendation for women of childbearing age on phototherapy. METHODS: PubMed was searched for in vivo studies comparing folate levels before and after phototherapy. RESULTS: There is no evidence of decreased folate levels after UVA exposure. Decreased folate levels after sun exposure were limited to subjects taking folate supplements. Studies using narrowband UVB showed mixed results, potentially explained by dose-dependent degradation of folate; exposure >40 J/cm2 cumulatively and >2 J/cm2 per treatment were associated with 19%-27% decreases in serum folate levels, while lower doses did not affect folate levels. LIMITATIONS: Extensive variability in results from studies and lack of considering confounders. CONCLUSIONS: We recommend all women of childbearing age on phototherapy take 0.8 mg/day of folate supplements, as suggested by current guidelines for women of childbearing age, to reduce the risk of neural tube defects in unplanned pregnancy.

UV-associated decline in systemic folate: implications for human nutrigenetics, health, and evolutionary processes.

OBJECTIVES: The purpose of this study was to examine whether UV exposure alters folate status according to C677T-MTHFR genotype, and to consider the relevance of this to human health and the evolutionary model of skin pigmentation. METHODS: Total Ozone Mapping Spectrometer (TOMS) satellite data were used to examine surface UV-irradiance, as a marker of UV exposure, in a large (n = 649) Australian cross-sectional study population. PCR/RFLP analysis was used to genotype C677T-MTHFR. RESULTS: Overall, cumulative UV-irradiance (42 and 120 days pre-clinic) was significantly negatively related to red cell folate (RCF) levels. When the cohort was stratified by MTHFR-C677T genotype, the relationship between UV-irradiance (42 days pre-clinic) and RCF remained significant only in the cohorts containing carriers of the T allele. Statistically significant z-score statistics and interaction terms from genotype and UV-irradiance (p-interaction) demonstrated that genotype did modify the effect of UV-irradiance on RCF, with the largest effect of UV being demonstrated in the 677TT-MTHFR subjects. CONCLUSIONS: Data provide strong evidence that surface UV-irradiance reduces long-term systemic folate levels, and that this is influenced by the C677T-MTHFR gene variant. We speculate this effect may be due to 677TT-MTHFR individuals containing more 5,10CH2 -H4 PteGlu, and that this folate form may be particularly UV labile. Since UV-irradiance lowers RCF in an MTHFR genotype-specific way, there are likely implications for human health and the evolution of skin pigmentation.

Stability of folic acid under several parameters.

Folic acid is a small molecule, also known as vitamin B9. It is an essential compound involved in important biochemical processes. It is widely used as a vector for targeted treatment and diagnosis especially in cancer therapeutics. Nevertheless, not many authors address the problem of folic acid degradation. Several researchers reported their observations concerning its denaturation, but they generally only took into account one parameter (pH, temperature, light or O2etc.). In this review, we will focus on five main parameters (assessed individually or in conjunction with one or several others) that have to be taken into account to avoid the degradation of folic acid: light, temperature, concentration, oxygen and pH, which are the most cited in the literature. Scrupulous bibliographic research enabled us to determine two additional degradation factors that are the influence of singlet oxygen and electron beam on folic acid stability, which are not considered as among the prime factors. Although these two factors are not commonly present as compared to the others, singlet oxygen and electron beams intervene in new therapeutic technologies and must be taken in consideration for further applications such photodynamic or X-rays therapies.

Overview of the in vitro stability of commonly measured vitamins and carotenoids in whole blood.

BACKGROUND: The pre-analytical stabilities of vitamins A, E, K, B1, B2, B6, B12, C, carotenoids and folates in whole blood were studied. The aim of this work was to provide clear and workable pre-analytical procedures specifying optimal delay before freezing for laboratories which perform themselves such analyses or which receive and transfer such specimens to referral laboratories. METHODS: The stability of vitamins was studied in whole blood at room temperature after light exposure up to 24 h (vitamin C), 48 h (vitamins A, E, B1, B2, B6 and carotenoids) and 72 h (vitamins K, B12, red blood cell (RBC) and serum folates). Vitamin C stability after baseline acidification was analysed up to 48 h. Changes observed were compared to a clinical cut-off defined as total change limit based on a combination of analytical performance and within-subject variation. RESULTS: Clinically and statistically significant changes occurred only in vitamins C (-22.5%), B6 (+9.9%) and serum folates (-16.8%) concentrations after 6, 24 and 48 h, respectively. Vitamins A, E, K, B1, B2, B12, RBC folates and carotenoids showed good stability up to 48 or 72 h. Vitamin C in acidified serum conserved at room temperature appeared unstable. The optimal condition for acidified vitamin C conservation was at less than -20℃. CONCLUSION: The majority of vitamins remain stable for up to 48 h. Vitamin C quantification requires serum acidification followed by freezing as soon as possible. Freezing, respectively, within 12 h and 24 h for determination of plasma vitamin B6 and serum folates concentrations is recommended.

Folate degradation due to ultraviolet radiation: possible implications for human health and nutrition.

Folate is essential for human health in the prevention of megaloblastic anemia and neural tube birth defects and plays important roles in cardiovascular disease and cancer. Therefore, research into environmental factors that may impact folate status, such as solar ultraviolet (UV) radiation, is of great health significance. In vitro studies have shown that UV radiation can degrade folate and folic acid in human blood and this has been confirmed in several human studies. Despite these findings, there is a dearth of epidemiological research into investigating the relationship between folate status and the links to solar UV exposure.

Irradiation stability of folic Acid in powder and aqueous solution.

This study attempts to examine the folic acid stability after irradiation treatment, under different physical states, pH values, and atmosphere conditions. Aqueous folic acid samples, folic acid in powder, and wheat flour fortified with folic acid were irradiated by an electron beam (E-beam) between 0 (control) and 10.0 kGy. It was realized that the physical state of folic acid plays an important role on its stability toward E-beam processing, being largely unstable in solution, no matter the pH and atmosphere conditions assayed. Otherwise, folic acid in powder showed huge irradiation stability, even when mixed in a dry food matrix, such as fortified wheat flour samples.

Effect of narrowband ultraviolet B phototherapy on serum folic acid levels in patients with psoriasis.

Narrowband ultraviolet B phototherapy (NB-UVB) is a widely used modality in the treatment of psoriasis and is generally accepted as safe in pregnancy. Previous studies have described photodegradation of serum folate after exposure to UVA radiation but the effect of UVB is not known. We studied the effect of NB-UVB phototherapy on serum folic acid levels in patients with psoriasis and the relationship between changes in serum folate levels and the total cumulative dose of NB-UVB. Included in the study were 30 psoriatic patients between 13 and 55 years of age. Serum folate levels were measured at baseline, and after exposure to 18 and 36 sessions of NB-UVB irradiation. There were significant decreases in mean serum folate levels after NB-UVB exposure. After exposure to 18 and 36 sessions the decreases were 19% and 27%, respectively. After 18 sessions, the mean serum folate level had decreased in 18 patients (60%) from 8.64 ng/ml at baseline to 7.02 ng/ml (mean NB-UVB cumulative dose 40.02 J/cm(2); P = 0.019). After 36 sessions, the mean serum folate levels had decreased in 22 patients (73%) to 6.32 ng/ml (mean NB-UVB cumulative dose 118.16 J/cm(2); P = 0.002). The present study showed that high cumulative NB-UVB doses can induce folate photodegradation and decrease serum folate levels in patients with psoriasis and that this effect is directly related to the total cumulative dose of NB-UVB.

Mechanism of photooxidation of folic acid sensitized by unconjugated pterins.

Folic acid, or pteroyl-l-glutamic acid (PteGlu), is a precursor of coenzymes involved in the metabolism of nucleotides and amino acids. PteGlu is composed of three moieties: a 6-methylpterin (Mep) residue, a p-aminobenzoic acid (PABA) residue, and a glutamic acid (Glu) residue. Accumulated evidence indicates that photolysis of PteGlu leads to increased risk of several pathologies. Thus, a study of PteGlu photodegradation can have significant ramifications. When an air-equilibrated aqueous solution of PteGlu is exposed to UV-A radiation, the rate of the degradation increases with irradiation time. The mechanism involved in this "auto-photo-catalytic" effect was investigated in aqueous solutions using a variety of tools. Whereas PteGlu is photostable under anaerobic conditions, it is converted into 6-formylpterin (Fop) and p-aminobenzoyl-l-glutamic acid (PABA-Glu) in the presence of oxygen. As the reaction proceeds and enough Fop accumulates in the solution, a photosensitized electron-transfer process starts, where Fop photoinduces the oxidation of PteGlu to Fop, and H(2)O(2) is formed. This process also takes place with other pterins as photosensitizers. The results are discussed with the context of previous mechanisms for processes photosensitized by pterins, and their biological implications are evaluated.

Photoinduced fluorimetric determination of folic acid and 5-methyltetrahydrofolic acid in serum using the kinetic evolution of the emission spectra accomplished with multivariate second-order calibration methods.

Second-order multivariate calibration methods in combination with a continuous flow system, which allows for the continuous on-line irradiation of the analytes, have been employed for the determination of folic acid and its main metabolite 5-methyltetrahydrofolic acid in serum samples. An experimental central composite design, together with response surface methodology, has been used to find the optimum instrumental variables to perform the photochemical reaction. The time evolution of the emission spectra of the generated photoproducts, in the range 330-540 nm, after irradiation at 275 nm for 20 min, provided the three-way data set employed. On the basis of the differences on the kinetic rates of the photoreaction of both analytes, direct determination of the compounds in human plasma has been accomplished. The second-order methods assayed were parallel factor analysis (PARAFAC), self-weighted alternating trilinear decomposition (SWATLD), and unfolded partial least-squares (U-PLS), multidimensional partial least-squares (N-PLS), and bilinear least-squares (BLLS), all three in combination with the residual bilinearization procedure (RBL).

Determination of dissociation constants of folic acid, methotrexate, and other photolabile pteridines by pressure-assisted capillary electrophoresis.

Pressure-assisted CE (PACE) was applied to determine the previously inaccessible complete set of pK values for folic acid and eight related multiprotic compounds. PACE allowed the determination of all acidity macroconstants at low (

Photodegradation of 5-methyltetrahydrofolate: biophysical aspects.

5-methyltetrahydrofolate (5MTHF) absorbs UV radiation and has an absorption coefficient of 24250+/-1170 M(-1) cm(-1) at 290 nm. It has a weak fluorescence emission in the wavelength region around 360 nm. Our data demonstrated induction of 5-methyldihydrofolate by exposure to UVB and, after continues irradiation, p-aminobenzoyl-L-glutamic acid was found. The photodegradation of 5MTHF follows a first order kinetic with a degradation rate constant of 9.2 x 10(-3) min(-1) under our conditions (fluence rate of 2.15 mW cm(-2), exposure wavelengths from 280 to 350 nm). Our results indicate that a direct degradation of 5MTHF by UV exposure in humans in vivo is rather unlikely. 5MTHF mainly absorbs, and is degraded by, UVB and UVC, radiation that does not penetrate the earth's atmosphere and the human skin well.

Influence of human serum albumin on photodegradation of folic acid in solution.

It has been proposed that photodegradation of folates may be the reason for the pigmentation of races living under high fluence rates of ultraviolet radiation. The photodegradation of folic acid (FA) induced by ultraviolet-A (UV-A) radiation, in solution and in the presence of human serum albumin (HSA), was studied with absorption and fluorescence spectroscopy. FA photodegradation, with formation of p-aminobenzoyl-l-glutamic acid, 6-formylpterin and pterin-6-carboxylic acid, was found to follow an exponential trend. A scheme of FA photodegradation, which involves photosensitization of FA degradation by its photoproducts, was proposed. The rate of FA photodegradation decreased drastically in the presence of HSA, whereas the spectral characteristics of the photoproducts remained constant. The reduction of the FA photodegradation rate by HSA was accompanied by degradation of tryptophan in HSA. Tryptophan, when added to solutions of FA, had a similar effect as HSA. In solutions of FA and HSA the FA photoproducts cause photodamage mainly to HSA rather than to FA itself. The oxygen dependence of FA photodegradation and the inhibition of this process by sodium azide indicate that singlet oxygen may participate in the photosensitizing activity of FA photoproducts.

Ultraviolet photodegradation of folic acid.

The vitamin folate is vital for all living creatures. Scientists have suggested that ultraviolet degradation of folate in vivo played a role in the evolution of mankind. In order to better understand the photodegradation of folate, we have provided a spectroscopic study of the ultraviolet photodegradation of aqueous folic acid under aerobic conditions. We found strong indications that the folic acid molecule is cleaved into p-aminobenzoyl-L-glutamic acid and 6-formyl pterin when exposed to ultraviolet radiation. When the irradiation continues, 6-formyl pterin is degraded to pterin-6-carboxylic acid. The photodegradation of folic acid is divided into three phases. In the first phase, the formation of photoproducts follows a zero order rate law. In the second phase the presence of photoproducts sensitizes the degradation of folic acid and the degradation process is accelerated. In the third phase the degradation of 6-formyl pterin to pterin-6-carboxylic acid is the dominating process. This reaction follows a first order rate law. We show that both 6-formyl pterin and pterin-6-carboxylic acid sensitize the photodegradation of folic acid. However, experiments performed in heavy water indicate that generation of singlet oxygen is probably not the explanation for the photosensitizing of folic acid.

Use of a sample translation technique to minimize adverse effects of laser irradiation in surface-enhanced Raman spectrometry.

Surface-enhanced Raman spectroscopy (SERS) has proven to be a very powerful tool in the analysis of a wide range of compounds. However, continuous irradiation of the laser beam over the SERS substrate can promote the gross decomposition of the sample analytes and significantly broaden and diminish the intensities of observed spectral bands. In addition, the incident radiation can promote thermal or photolytic fragmentation of analytes, thereby altering the observable bands and possibly leading to a misinterpretation of analytical data. Finally, chemical or morphological changes in the SERS substrate are possible. This work presents the use of a sample translation technique (STT) as a means to minimize these adverse effects. By spinning the sample rapidly, the effective residence time of analytes and substrate within the irradiated zone is dramatically decreased without reduction of spectral acquisition time or the density of analyte in the zone. The technique is studied by acquiring SERS spectra of Naproxen USP, riboflavin, folic acid, Rhodamine 6G, and 4-aminothiophenol using silver islands on glass and silver-poly(dimethylsiloxane) composite substrates under various spinning and stationary conditions. In all cases, spectra show improvements upon spinning at laser powers as low as 4.2 (+/- 0.1) mW. Specific differences in the appearance of the spectra and the potential use of STT for improved SERS qualitative and quantitative determinations are presented.

Chemiluminescence inhibition assay for folic acid using flow injection analysis.

A new flow injection method for the determination of folic acid is described. A fast oxidation reaction occurred when folic acid was mixed with potassium ferricyanide generating ferrocyanide which then inhibited the chemiluminescent reaction of ferricyanide and luminol in alkaline medium. The decrease of chemiluminescence intensity was correlated with the folic acid concentration in the range 0.1-21 microg/mL; the detection limit for the assay was 0.03 microg/mL (3sigma). A complete analysis of folic acid, including sampling and washing, could be performed within 2 min with a relative standard deviation of less than 4.0%. The proposed method has been applied successfully to the determination of folic acid in pharmaceutical preparations.

Light-dependent generation of reactive oxygen species in cell culture media.

Cell culture media (RPMI 1640, Dulbecco's Minimal Essential Medium and yeast extract-peptone-glucose medium) were found to oxidize dichlorodihydrofluorescein diacetate and dihydrorhodamine 123, and to generate spin adduct of 5,5'-dimethyl-1-pyrroline N-oxide, which indicates formation of reactive oxygen species (ROS). The production of ROS was light dependent. The main component of the media responsible for the generation of ROS was riboflavin, but tryptophan, tyrosine, pyridoxine, and folic acid enhanced the effect of riboflavin. These observations point to exposure of cells to ROS under in vitro culture conditions.

Photodegradation of folic acid in aqueous solution.

A study of the photodegradation of folic acid by ultraviolet radiation in aqueous solution has been made. Folic acid is photolysed by an apparent first-order kinetics and the log k-pH profile shows a gradual decrease in rate in the pH range 2.0-10.0. The profile indicates the appearance of three steps which reflect the participation of different ionic species of folic acid (pKa(1) 2.3, pKa(2) 8.3) in the photolysis reaction. The rate of photodegradation varies from 0.1550 x 10(-3) min(-1) (pH 10.0) to 5.04 x 10(-3) min(-1) (pH 2.5) in the pH range studied. The photolysis of folic acid shows that it is degraded to pterine-6-carboxylic acid and p-amino-benzoyl-L-glutamic acid. A maximum yield of these products is obtained at 3-8 h, depending upon the pH. An HPLC method has been used for the assay of folic acid and its degradation products.