Preparation and evaluation of a chitosan-coated antioxidant liposome containing vitamin C and folic acid

Vitamin C (VC) and folic acid (FA) are the important nutrient and antioxidant in human body. In order to improve their stability, their co-loaded liposomes (VCFA-Lip) and chitosan-coated liposomes (CS-VCFA-Lip) are prepared and characterised. The mean particle size of VCFA-Lip and CS-VCFA-Lip is 138?nm and 249?nm, respectively. The encapsulation efficiencies of both drugs for CS-VCFA-Lip are much higher than those for VCFA-Lip. Furthermore, the experimental results show that the antioxidant activity of CS-VCFA-Lip is higher than that of VCFA-Lip. Moreover, the storage stability study reveals that the chitosan coating can efficiently improve the physical stability of VCFA-Lip. These results indicate that stability of VC and FA can be greatly improved after being wrapped by liposomes. In addition, the performance of CS-VCFA-Lip is better than VCFA-Lip, indicating CS-VCFA-Lip can be applied as a promising delivery system for the antioxidant defence system to the food industry and cosmetic industry.     

Preparation and in vitro evaluation of celecoxib-amino acid conjugates as a colon specific prodrug

To develop a colon specific prodrug of celecoxib with improved therapeutic potency and cardiovascular toxicity for chemoprevention of colorectal adenomas, we prepared glycyl celecoxib (GC), aspart-1-ylcelecoxib (A1C) and glutam-1-ylcelecoxib (G1C) and examined colon specific properties in vitro. The amino acid conjugation lowered the apparent partition coefficient of celecoxib (4.6) to 1.2 (GC), 0.6 (A1C) and 0.8 (G1C). The celecoxib-amino acid conjugates were stable in pH 1.2 and 6.8 buffer solutions. On incubation with the contents of small intestine, while GC was stable up to 10?h, A1C and G1C were degraded and liberated celecoxib up to 19?C32?% of the dose at 10?h. In the cecal contents, the three conjugates were cleaved to release celecoxib and amounts of celecoxib released from GC, A1C and G1C were 20, 64 and 55?% at 10?h and 30, 75 and 60?% of the dose at 24?h, respectively. Taken together, while GC may deliver celecoxib to the large intestine without premature degradation in the upper intestine, A1C and G1C may have advantages over GC in that they are less absorbable in the upper intestine due to lower partition coefficient and are converted to celecoxib more efficiently at the target site.     

Detection and measurement of antagonism to folic acid

Methods of testing competitive antagonism in bacterial systems are considered and evaluated with particular reference to antifolic acids. Four antifolic acids—pteridine O/129, methotrexate, CB2295 and CB2335—were examined for competitiveness and potency in three test systems—Leuc. citrovorum and folinic acid, Str. faecalis and folinic acid, and Str. faecalis and pteroylglutamic acid. For comparison, phenol and formaldehyde were studied in the Leuc. citrovorum and folinic acid system. Interpretation of results was based on families of log. concentration/growth curves obtained in each system in the presence and absence of each antagonist. These curves were usually simple sigmoids. From these families of curves, pA values were derived and reciprocal growth/reciprocal concentration curves were drawn. Pteridine O/129 was fully competitive in all systems, while methotrexate was fully competitive in the Str. faecalis and folinic acid system, but did not give simple sigmoids in the other two systems. CB2295 showed some competitive features in all and CB2335 in the two systems in which it was active. It is concluded that the methods adopted, based on those used in vertebrate pharmacology, provide a stringent test of competitiveness in bacterial systems.     

In vitro evaluation of the viscoelastic properties of chitosan-thioglycolic acid conjugates.

The aim of this study was to evaluate the viscoelastic properties of chitosan-thioglycolic acid conjugates with different amounts of thiol groups immobilized on the polymer. The modification of chitosan was achieved via the covalent attachment of thioglycolic acid mediated by a carbodiimide. Chitosan-thioglycolic acid conjugates displaying 120, 209 and 439 microM thiol groups per gram of polymer were synthesized. The rheological properties of the three different conjugates were investigated. The elastic properties of the gels were found to increase significantly at pH 5.5. After 6 h the elastic modulus G' of chitosan-TGA 120, chitosan-TGA 209 and chitosan-TGA 439 gels increased 7-, 32- and 168-fold, respectively. In parallel the formation of disulfide bonds was observed. Accordingly, proof of principle that chitosan modified by the introduction of thiol groups has in situ gelling properties due to the formation of inter- and intramolecular disulfide bonds at physiological pH values is provided. Based on their in situ gelling properties, chitosan-thioglycolic acid conjugates seem to be very promising new excipients for liquid or semisolid formulations which should stabilize themselves once applied on the site of drug delivery.     

Chemistry and antitumor evaluation of selected classical 2,4-diaminoquinazoline analogues of folic acid

A series of six 2,4-diaminoquinazoline analogues of folic acid which bear close structural resemblance to methotrexate, 1a, were synthesized by unequivocal routes. Three of these have not been described previously, while complete structural characterization of the remaining compounds is presented for the first time. Each of the compounds was a potent inhibitor of dihydrofolate reductase (DHFR) from rat liver or L1210 leukemia cells having I50 values in a range similar to that of 1a. However, a wide divergence in inhibitory activity toward the growth of human gastrointestinal adenocarcinoma or L1210 leukemia cells in vitro was observed. Compounds having a normal folate configuration at positions 9 and 10 were more inhibitory than their isomeric reversed-bridge counterparts. The N-formyl modifications were the least active of the compounds studied. Unsubstituted or N-methyl modifications competed effectively with tritiated 1a for uptake into L1210 leukemia cells, while N-formyl modifications did not. Against an L1210 cell line resistant to 1a by virtue of altered transport and overproduction of DHFR, partial but not complete cross-resistance was observed for certain analogues. Of the three compounds selected for in vivo evaluation against L1210 leukemia in mice, two had a similar level of antitumor activity to that of 1a. The compound 5,8-dideazamethopterin, 2b, however, was slightly more active than 1a but at substantially reduced dose levels.     

Tumor cell targeting of liposome-entrapped drugs with phospholipid-anchored folic acid-PEG conjugates

Targeting of liposomes with phospholipid-anchored folate conjugates is an attractive approach to deliver chemotherapeutic agents to folate receptor (FR) expressing tumors. The use of polyethylene glycol (PEG)-coated liposomes with folate attached to the outer end of a small fraction of phospholipid-anchored PEG molecules appears to be the most appropriate way to combine long-circulating properties critical for liposome deposition in tumors and binding of liposomes to FR on tumor cells. Although a number of important formulation parameters remain to be optimized, there are indications, at least in one ascitic tumor model, that folate targeting shifts intra-tumor distribution of liposomes to the cellular compartment. In vitro, folate targeting enhances the cytotoxicity of liposomal drugs against FR-expressing tumor cells. In vivo, the therapeutic data are still fragmentary and appear to be formulation- and tumor model-dependent. Further studies are required to determine whether folate targeting can confer a clear advantage in efficacy and/or toxicity to liposomal drugs.     

High-pressure liquid chromatographic assay of folic acid: a collaborative study.

A collaborative study of the USP high-pressure liquid chromatographic assay for folic acid was performed. Two samples were analyzed in duplicate by 14 participating laboratories. Relative standard deviations for a single determination (RSDS) ranged from +/-0.40 to +/-2.39%. Based on an analysis of variance, it was concluded that the method of peak measurement was a major determinant of reproducibility and that graphical measurement was associated with a high standard deviation. Adequate resolution was obtained using a variety of columns and operating conditions. The interlaboratory RSDS was +/-1.8%.     

共递送柔红霉素与高三尖杉酯碱的叶酸修饰脂质体的制备与质量评价

目的 评估柔红霉素(DNR)与高三尖杉酯碱(HHT)联合用药对HL60细胞增殖的抑制作用;制备叶酸修饰的共递送DNR+HHT的复合脂质体。方法 采用MTT法检测细胞增殖,CompuSyn软件计算DNR与HHT的联合用药指数。以薄膜水化法制备脂质体,在单因素试验基础上,采用Box-Behnken响应面法优化共递送脂质体的处方;通过正交试验设计优化制备工艺。结果 DNR+HHT的联合用药指数为0.69,两者具有协同作用。优选处方为：磷脂10.7μmol·mL^-1,磷脂-胆固醇的摩尔比为4:1,磷脂-DNR的用量比为15:1。优选制备工艺为：水合时间2 h,水合温度40℃,油水比例为2:1。结论 Box-Behnken响应面法结合正交试验设计可有效优化共递送脂质体的处方与制备工艺,所得脂质体的包封率高、粒度均匀。     

Use of folic acid and delivery outcome: a prospective registry study

Periconceptional use of folic acid is thought to reduce the risk for both neural tube defects and other congenital malformations. Most published data were obtained retrospectively. We used the Swedish Medical Birth Registry to study congenital malformations in infants born of women who reported the use of folic acid in early pregnancy (of which 70% probably used it also preconceptionally) and compared them with population rates. We divided the material according to two major confounders: subfertility problems and use of antiepileptic drugs. We found no protective effect of folic acid tablet use on the rate of congenital malformations but data on neural tube defects were scarce. Our results support the scepticism recently expressed in the literature on the beneficial effect of folic acid in preventing congenital malformations, especially of a non-neural tube defect type.     

Treatment of depression: time to consider folic acid and vitamin B12

We review the findings in major depression of a low plasma and particularly red cell folate, but also of low vitamin B12 status. Both low folate and low vitamin B12 status have been found in studies of depressive patients, and an association between depression and low levels of the two vitamins is found in studies of the general population. Low plasma or serum folate has also been found in patients with recurrent mood disorders treated by lithium. A link between depression and low folate has similarly been found in patients with alcoholism. It is interesting to note that Hong Kong and Taiwan populations with traditional Chinese diets (rich in folate), including patients with major depression, have high serum folate concentrations. However, these countries have very low life time rates of major depression. Low folate levels are furthermore linked to a poor response to antidepressants, and treatment with folic acid is shown to improve response to antidepressants. A recent study also suggests that high vitamin B12 status may be associated with better treatment outcome. Folate and vitamin B12 are major determinants of one-carbon metabolism, in which S-adenosylmethionine (SAM) is formed. SAM donates methyl groups that are crucial for neurological function. Increased plasma homocysteine is a functional marker of both folate and vitamin B12 deficiency. Increased homocysteine levels are found in depressive patients. In a large population study from Norway increased plasma homocysteine was associated with increased risk of depression but not anxiety. There is now substantial evidence of a common decrease in serum/red blood cell folate, serum vitamin B12 and an increase in plasma homocysteine in depression. Furthermore, the MTHFR C677T polymorphism that impairs the homocysteine metabolism is shown to be overrepresented among depressive patients, which strengthens the association. On the basis of current data, we suggest that oral doses of both folic acid (800 microg daily) and vitamin B12 (1 mg daily) should be tried to improve treatment outcome in depression.     

Cation substitution in cationic phosphonolipids: a new concept to improve transfection activity and decrease cellular toxicity

Cationic lipids have been shown to be an interesting alternative to viral vector-mediated gene delivery into in vitro and in vivo model applications. Prior studies have demonstrated that even minor structural modifications of the lipid hydrophobic domain or of the lipid polar domain result in significant changes in gene delivery efficiency. Previously, we developed a novel class of cationic lipids called cationic phosphonolipids and described the ability of these vectors to transfer DNA into different cell lines and in vivo. Up until now, in all new cationic lipids, nitrogen atoms have always carried the cationic or polycationic charge. Recently we have developed a new series of cationic phosphonolipids characterized by a cationic charge carried by a phosphorus or arsenic atom. In a second step, we have also examined the effects of the linker length between the cation and the hydrophobic domain as regards transfection activity. Transfection activities of this library of new cationic phosphonolipids were studied in vitro in different cell lines (HeLa, CFT1, K562) and in vivo using a luciferase reporter gene. A luminescent assay was carried out to assess luciferase expression. We demonstrated that cation substitution on the polar domain of cationic phosphonolipids (N --> P or As) results in significant increase in transfection activity for both in vitro and in vivo assays and decrease of cellular toxicity.     

Influence of green and black tea on folic acid pharmacokinetics in healthy volunteers: potential risk of diminished folic acid bioavailability

Previous in vitro studies using Caco-2 cell monolayers suggested a possible interaction between green and black tea and folic acid at the level of intestinal absorption. The main purpose of the present study was to investigate a possible pharmacokinetic interaction between tea and folic acid in healthy volunteers. In an open-labeled randomized cross-over study, the pharmacokinetic interaction between tea and folic acid (0.4 mg and 5 mg) was investigated in healthy volunteers. Water was used as the reference drink. Subjects ingested 0.4 mg folic acid tablets with water, green or black tea (0.3 g extract/250 ml) or 5 mg folic acid tablets with water or green tea (0.3 g extract/250 ml). Blood samples were collected over a period of 8 h. Serum folate analysis was carried out by a competitive immunoassay which uses direct chemiluminescent technology. At the 0.4 mg folic acid dose, green and black tea reduced the mean C(max) of serum folate by 39.2% and 38.6%, and the mean AUC(0 --> infinity) by 26.6% and 17.9%, respectively. At the 5 mg folic acid dose, the mean C(max) of serum folate was reduced by 27.4% and the mean AUC(0 --> infinity) was decreased significantly by 39.9% by the co-application of green tea. The present results suggest an in vivo interaction between tea and folic acid with even low concentrations of green and black tea extracts yielding decreased bioavailabilities of folic acid. Copyright (c) 2008 John Wiley & Sons, Ltd.