Release Of Folic Acid Research Articles

ABC triblock copolymers with pH-responsive LCST for controlled drug delivery

The thermo- and amphiphilic ABC triblock copolymers, single-methoxypoly(ethylene glycol)-b-poly(N-isopropylacrylamide-co-acrylic acid)-b-poly(methyl methacrylate), were synthesized by reversible addition fragmentation chain transfer radical polymerization. The triblock copolymers were characterized by Fourier transform infrared spectroscopy, 1H-NMR, and gel permeation chromatography. The copolymers self-assemble into thermo-responsive nano-sized micelles in aqueous media. Transmission electron microscopy and dynamic light scattering showed that the micelles were regularly spherical in shape with an average diameter ~120 nm. Fluorescence analysis indicated that the triblock copolymer had a low critical micelle concentration of 2.5 mg/L in aqueous media at pH 7.4 and room temperature. The lower critical solution temperature (LCST) of the micelles could be altered by simply changing the pH. The LCST of the triblock copolymer at pH 5.5 was altered to 37.5 ° C (close to physiological temperature) by copolymerizing N-isopropylacrylamide with acrylic acid. When the pH was increased to 7.4, the LCST increased to 55°C and it decreased to 33°C when the pH was 2.0. The micelles exhibited good biocompatibility with human embryonic kidney cells, when the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay was performed. The controlled release of folic acid (FA) from FA-loaded micelles under different conditions was evaluated. The rate and amount of the drug released were greater above the LCST than below it.

Nutritional effects of folic acid controlled release from mesoporous materials

Folic acid deficiency causes serious disorders in humans and supplementation has numerous health benefits. However, there is initial evidence that suggest a negative impact of an increased exposure to folic with respect to certain developmental and degenerative disorders. In this line, controlled release of folic acid by using mesoporous silica materials, MCM-41, has been studied as an alternative to direct supplementation. For this purpose, various mesoporous solids MCM-41 loaded with folic acid (S1) and functionalized with 3-[2-(2- aminoethylamino)ethylamino]propyl-trimethoxysilane (S2) acting as “gate” have been tested. The results show that at pH 2 a strongly hindered vitamin release is observed, whereas at pH 7.5 a controlled delivery is found. Based on the obtained results of this study, folic acid controlled release could be feasible during a period of 5h using a sensitive to pH gate, and this might reduce traditional fortification negative effects, while nutritional benefits are maintained.

A sustained folic acid release system based on ternary magnesium/zinc/aluminum layered double hydroxides

This study first synthesized and characterized the ternary magnesium/zinc/aluminum layered double hydroxides (Mg/Zn/Al-LDHs) intercalated with folic acid. We prepared the ternary (Mg, Zn, Al) LDH carrier by the introduction of zinc, because magnesium and zinc are both vital minerals of human body. The nanohybrids were prepared by the method of coprecipitation and were characterized by powdered sample X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), UV–vis spectra, and MTT assay. The loading amount of intercalated folic acid was increased to 45.2%, and showed a profile of sustained release with 75% in 250 min. In addition, the folic acid-LDH nanohybrids showed an enhanced thermal stability and a profound buffering property, which demonstrated that the hybrids could protect folic acid against heat degradation and prompt its available diffusion. The cell viability of HEK293T was over 80% after treated with nanohybrids for 72 h. Our results suggested that the ternary folic acid-LDH nanohybrids may function as a useful nutritional tablet to promote the bioavailability of folic acid delivery.

Release of Folic Acid in Mesoporous NFM-1 Silica

Mesoporous NFM-1 silica with folic acid as template was prepared taking advantage of the supramolecular self-assembly of pterin groups and their abilities to form hexagonal liquid crystal phases. NFM-1 materials with the varied morphologies such as fiber, chiral twisting long-rod, gyroid, and amorphous particles were prepared by varying the amount of the co-structure directing agent, stirring speed and changing pH value of the synthesis. The release kinetics of NFM-1 samples with different morphologies were studied in phosphate buffer with pH = 7.4 in 37 degrees C under stirring. All the release kinetic curves are fitted by the power law and Higuchi equations. The fitting of the power law equation was separately done as for the released amount up to 60% or 100%. The materials show slow, long-term and sustained release of folic acid from mesoporous NFM-1 silica, which establishes a new foundation for the potential application in drug delivery and bioimaging.

Synthesis and characterization of polyion complex micelles and their controlled release of folic acid

Stable and narrow distribution polyion complex micelles (PICMs) were prepared in an aqueous milieu through electrostatic interaction between a pair of oppositely charged block copolymers poly( N-vinylpyrrolidone)-block-poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PVP-b-PAMPS) and monomethoxy poly(ethylene glycol)-block-poly(4-vinyl pyridine) (PEG-b-P4VP). The critical aggregate concentration (CAC), hydrodynamic size, and surface morphology of the prepared PICMs were characterized by fluorescence spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM), respectively. The resulting CAC and the average diameter of the PICMs were about 43 mg/L and 121 nm, indicating high structural stability of micelles and a size favorable for delivery of drug. In addition, the PICMs exhibited good biocompatibility using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay with human embryonic kidney (HEK293) cells. All of these features are quite feasible for utilizing the PICMs as a novel intelligent drug delivery system. In order to assess its application in the biomedical area, the model drug folic acid (FA) was loaded into the micelles and the in vitro drug release behavior was investigated. We found that by manipulating the pH value and salt concentration of the release solution, it was possible to control the release rate of FA.

Ethyl Cellulose Microcapsules for Protecting and Controlled Release of Folic Acid

Ethyl cellulose microcapsules were developed for use as a drug-delivery device for protecting folic acid from release and degradation in the undesirable environmental conditions of the stomach, whilst allowing its release in the intestinal tract to make it available for absorption. The controlled release folic acid-loaded ethyl cellulose microcapsules were prepared by oil-in-oil emulsion solvent evaporation using a mixed solvent system, consisting of a 9:1 (v/v) ratio of acetone:methanol and light liquid paraffin as the dispersed and continuous phase. Span 80 was used as the surfactant to stabilize the emulsion. Scanning electron microscopy revealed that the microcapsules had a spherical shape. However, the particulate properties and in vitro release profile depended on the concentrations of the ethyl cellulose, Span 80 emulsifier, sucrose (pore inducer), and folic acid. The average diameter of the microcapsules increased from 300 to 448 microm, whilst the folic acid release rate decreased from 52% to 40%, as the ethyl cellulose concentration was increased from 2.5% to 7.5% (w/v). Increasing the Span 80 concentration from 1% to 4% (v/v) decreased the average diameter of microcapsules from 300 to 141 microm and increased the folic acid release rate from 52% to 79%. The addition of 2.5-7.5% (w/v) of sucrose improved the folic acid release from the microcapsules. The entrapment efficiency was improved from 64% to 88% when the initial folic acid concentration was increased from 1 to 3 mg/ml.

Bilayer Tablets Based on Poly (ε‐Caprolactone) and Polymethylmethacrilates as Controlled‐Release Systems for Ruminants

Rumen‐stable devices ensure a protection of active ingredients against chemical degradation and bacterial fermentation processes that occur in the rumen. These systems should also provide postruminal bioavailability and controlled release of the active ingredient. The objective of this study was the preparation of bilayer tablets as rumen‐stable delivery systems, designed for the oral administration of active ingredients (folic acid) to ruminants. The tablets are composed of two layers: layer A (“high‐density layer”) constituted by poly (ε‐caprolactone) mixed with iron powder and characterized by sufficient density to avoid rumination; layer B (“release layer”), containing folic acid (25 mg), poly (ε‐caprolactone) or polymethylmethacrylates (Eudragit RS and RL) designed to be rumen‐stable and to target a controlled release of folic acid in the intestinal tract. In vitro rumen‐protection tests were performed in buffer systems at pH 5.5 and pH 2.0, simulating a ruminal and abomasal environment, to verify the stability of bilayer tablets at these conditions. In vitro release tests were carried out in phosphate buffer at pH 7.4, to study the release behavior of the dosage forms in the intestinal environment. A preliminary in vivo test was carried out with radiographic images made after administration of the tablets to sheep, to evaluate their capacity to be retained in the reticulum–rumen. The amount of iron powder used provides a density of about 2.3 g/cm3 to the whole tablet. The tablets having layer B constituted by poly (ε‐caprolactone) or Eudragit RS do not disintegrate in buffer media at pH 5.5 and pH 2.0, and they are characterized by a sustained release at pH 7.4. Radiological preliminary tests show that these prepared bilayer tablets are able to be retained in the reticulum–rumen tract of the sheep.

Failure of prescription prenatal vitamin products to meet USP standards for folic acid dissolution.

To determine whether prescription prenatal vitamins meet United States Pharmacopeial Convention (USP) standards for folic acid dissolution. Dissolution was measured using USP Apparatus II and test conditions specified in the 23rd revision of the United States Pharmacopeia (USP 23). Folic acid was assayed by a chromatographic method modified from that specified in the official monographs, for oil- and water-soluble vitamins with minerals tablets, in USP 23. Only three out of nine multivitamin products met USP specifications for folic acid release. Most missed by a wide margin; folic acid dissolution from two products was less than 25%. Because a wide variety of brand-name and generic prescription prenatal multivitamin products were tested, these results are likely to be representative of the multivitamin products on the market. Given the significance of folic acid to public health, the authors believe that this subject should be studied further and that prompt action should be taken to ensure that folic-acid-containing products are of the highest quality possible.

On the mechanism of folate transport in isolated intestinal epithelial cells.

The mechanism of folic acid (FA) uptake was studied in isolated intestinal epithelial cells prepared from 2- to 6-wk-old chicks. The cells accumulated FA, reaching a level of three- to fivefold that at equilibrium. In the presence of the metabolic inhibitors, NaN3 or KCN, FA was taken up only until equilibration while accumulation of FA was inhibited. Addition of these inhibitors at a steady state of FA accumulation caused a release of intracellular FA. The kinetics of FA uptake were found to be saturable (Km = 3.5 x 10(-5) M), indicating a carrier-mediated mechanism. The steady-state level of FA accumulation was higher as the concentration of NA+ in the medium increased from 0 to 120 mM. This stimulation of FA uptake by Na+ was not due to the stimulation of glucose uptake, because in experiments carried out in the presence of phlorizin, a glucose-transport inhibitor, FA accumulation was not diminished. It is suggested that FA is taken up by a Na+-coupled transport system.

Isolation of Pteroyl-γ-oligoglutamyl Endopeptidase from Chicken Intestine with the Aid of Affinity Chromatography

Abstract An enzyme which performs the first step in the catalytic release of folic acid from pteroyl-γ-oligoglutamates was isolated from chicken intestine by the use of affinity chromatography. The enzyme-interacting ligand system consisted of synthetic γ-oligoglutamyl peptides attached covalently to Sepharose 4B by cyanogen bromide activation. The retained enzyme was eluted from the affinity column with 1 m NaCl. DEAE-cellulose chromatography and gel filtration with Sephadex G-200 were required for a final purification of 1,200-fold with a 20 % recovery of the initial enzyme. The purified enzyme appeared as a single band on disc gel electrophoresis. The estimated molecular weight determined by gel filtration was 80,000, and the isoelectric point was 4.8. The isolated enzyme was characterized as specific endopeptidase which cleaves pteroyl-γ-oligoglutamates between pteroyl glutamyl-γ-glutamate (pteroyl diglutamate) and the remaining γ-glutamyl peptide. With pteroyl-γ-heptaglutamate as substrate, the Km(app) was determined as 6.3 x 10-5 m. The Vmax was 1.8 x 10-3 µmole per min.

Homeostasis of folic acid in patients undergoing maintenance hemodialysis.

Folic acid balance, studied in patients on chronic dialysis to define the mechanisms rendering them susceptible to folic acid deficiency, showed adequate folic acid available to sustain hematopoiesis and to provide mature erythrocytes with a normal complement of folic acid. Losses through dialysis were replaced from diets of estimated normal folic acid content. Slow release of folic acid from stores constituted the primary mechanism offsetting folic acid loss through dialysis. This occurred at physiologic vitamin levels and was unaffected by rapid lowering of extracellular folic acid concentration. An incidental finding was the limited contribution of biliary excretion to net folic acid loss in man.

SYMPOSIUM ON PREPARATION OF SAMPLES FOR MICROBIOLOGICAL ASSAY

The precision and reliability of most of the In samples heated to destroy the natural encommonly used microbiological assay techniques zymes, 5 mg of chicken pancreas enzyme effected have been fairly well established. Many of the maximum release of folic acid from 1 gm of problems encountered in obtaining satisfactory spinach. Samples could be autoclaved over a pH analyses are due, not to the assay procedure per range of 5 to 13 without any loss of folic acid se, but to difficulties in preparation of the sample activity. for assay. With the growing popularity of microIn the extraction of pantothenic acid from biological methods, there has been an increase foods, a double enzyme system of alkaline intesin the complexity of the materials that are subtinal phosphatase and pigeon liver enzyme was jected to analysis, and consequent emphasis on superior to mylase-P. Maximum release was obthe need for good extraction procedures. This served when samples were incubated in the pressymposium was organized to focus attention on ence of both enzymes. A hog kidney enzyme some of the problems encountered, and to discuss preparation was found to be as effective as a few of the specific methods which have been pigeon liver enzyme in the double enzyme system. extensively studied. Care must be exercised in the preparation and Toepfer and Reynolds, whose paper was preuse of either of these enzymes to prevent loss of sented by their colleague, Dr. O'Barr, discussed conjugase activity and consequent low pantothe preparation of samples for vitamin assay, thenic acid values. Evidence of the efficiency of with particular reference to folic acid, pantothe double enzyme system in releasing pantothenic acid, vitamin B6 and vitamin B12. Working thenic acid from conjugates in several foods primarily with various foods, they found that, was provided by the results of parallel microbiowith the exception of vitamin B12, enzymatic logical and bioassays. digestion of food samples generally was necessary In assaying selected food for vitamin B6 acto assure complete liberation of these vitamins in tivity with Saccharomyces carlsbergensis, autoforms available to the assay organisms used. claving samples for 15 min with 0.055 N HCl, Of several enzyme preparations tested for the followed by overnight incubation with clarase or release of folic acid from a variety of foods, intestinal phosphatase was as effective as autochicken pancreas enzyme was found to be suclaving for 5 hr in 0.055 N HCl in releasing this perior to papain, takadiastase or hog kidney vitamin. These enzymes also were effective in enzyme. Using dried spinach as a substrate, they releasing pyridoxal from pyridoxal phosphate. found naturally occurring enzymes in unheated Current evidence indicates that enzymatic disuspensions which were about as effective as gestion generally is not required in the preparachicken pancreas enzyme in releasing folic acid. tion of samples for microbiological assay of vita-

SYMPOSIUM ON PREPARATION OF SAMPLES FOR MICROBIOLOGICAL ASSAY1

The precision and reliability of most of the In samples heated to destroy the natural encommonly used microbiological assay techniques zymes, 5 mg of chicken pancreas enzyme effected have been fairly well established. Many of the maximum release of folic acid from 1 gm of problems encountered in obtaining satisfactory spinach. Samples could be autoclaved over a pH analyses are due, not to the assay procedure per range of 5 to 13 without any loss of folic acid se, but to difficulties in preparation of the sample activity. for assay. With the growing popularity of microIn the extraction of pantothenic acid from biological methods, there has been an increase foods, a double enzyme system of alkaline intesin the complexity of the materials that are subtinal phosphatase and pigeon liver enzyme was jected to analysis, and consequent emphasis on superior to mylase-P. Maximum release was obthe need for good extraction procedures. This served when samples were incubated in the pressymposium was organized to focus attention on ence of both enzymes. A hog kidney enzyme some of the problems encountered, and to discuss preparation was found to be as effective as a few of the specific methods which have been pigeon liver enzyme in the double enzyme system. extensively studied. Care must be exercised in the preparation and Toepfer and Reynolds, whose paper was preuse of either of these enzymes to prevent loss of sented by their colleague, Dr. O'Barr, discussed conjugase activity and consequent low pantothe preparation of samples for vitamin assay, thenic acid values. Evidence of the efficiency of with particular reference to folic acid, pantothe double enzyme system in releasing pantothenic acid, vitamin B6 and vitamin B12. Working thenic acid from conjugates in several foods primarily with various foods, they found that, was provided by the results of parallel microbiowith the exception of vitamin B12, enzymatic logical and bioassays. digestion of food samples generally was necessary In assaying selected food for vitamin B6 acto assure complete liberation of these vitamins in tivity with Saccharomyces carlsbergensis, autoforms available to the assay organisms used. claving samples for 15 min with 0.055 N HCl, Of several enzyme preparations tested for the followed by overnight incubation with clarase or release of folic acid from a variety of foods, intestinal phosphatase was as effective as autochicken pancreas enzyme was found to be suclaving for 5 hr in 0.055 N HCl in releasing this perior to papain, takadiastase or hog kidney vitamin. These enzymes also were effective in enzyme. Using dried spinach as a substrate, they releasing pyridoxal from pyridoxal phosphate. found naturally occurring enzymes in unheated Current evidence indicates that enzymatic disuspensions which were about as effective as gestion generally is not required in the preparachicken pancreas enzyme in releasing folic acid. tion of samples for microbiological assay of vita-

Studies on the measurement of the folic acid and citrovorum factor potencies of certain natural products

The pteroylglutamic (folic) acid and citrovorum factor potencies of yeast extract and animal tissues have been estimated by differential microbiological analysis with Lactobacillus casei and Leuconostoc citrovorum 8081 as test organisms. The total folic acid activity of beef liver was markedly increased by the addition of cysteine during enzymatic or heat treatment, but little or no increases attributable to cysteine addition were demonstrated with other animal tissues or with yeast extract. The effect of cysteine was more evident when L. casei was used as compared to Streptococcus faecalis R as the test organism. The vitamin potency of crystalline pteroylglutamic acid, synthetic citrovorum factor (leucovorin), and of animal tissues after autoclaving samples at pH 4 or 7, or with acid and alkali, was studied. From these studies and control studies with thymidine, it was concluded that thymidine present in the samples did not contribute significantly to the total folic acid or citrovorum factor potencies of the samples. The most effective method for the release of folic acid or citrovorum factor from bound forms (short-term autoclaving at pH 7, enzymatic treatment or autoclaving at pH 4) varied with different samples. With short-term autoclaving the total folic acid potency attributable to the citrovorum factor approximated 10% for beef liver and kidney, 35% for yeast extract, 50% for ribeye muscle, and 70% for beef spleen and heart.

The Production of Folic Acid by Rat Liver in Vitro

The occurrence in urine and in acid-autoclaved grass and liver extracts of a substance which appears to participate in the synthesis of folic acid by rat liver in vitro is described. A similar effect is produced by synthetic xanthopterin. The effect of these materials might be accomplished by (1) catalysis of the enzymatic synthesis of folic acid; (2) the release of folic acid not liberated by takadiastase from tissue complexes; or (3) their serving as substrate material for the enzymatic synthesis of folic acid. The data presented favor the last hypothesis and suggest that xanthopterin, or a substance derived from it, may constitute a portion of the folic acid molecule. The probable involvement of compounds related to ranthopterin in the formation of hemocytopoietic substances in several animal species is discussed.