Bile acids bound to polymers

Summary Bile acids are steroids containing one — lithocholic acid, two — desoxycholic acid, and three — cholic acid hydroxyl groups, respectively. The hydroxyl group in position 3 of the steroid skeleton after esterification of the carboxyl group at C-24 under suitable conditions selectively reacts with methacryloyl chloride to give the corresponding methacrylic ester derivatives which undergo radically initiated uni- and copolymerizations to yield high molecular weight polymers.This paper is dedicated to Professor Georg Manecke on the occasion of his 70th birthday     

Antioxidant efficacy of amino acids in methyl linoleate at different relative humidities

Antioxidant efficacy of the amino acids methionine, tryptophan, aspartic acid, serine, alanine and arginine in methyl linoleate were compared to a methyl linoleate control at 2,50 or 79% relative humidity (RH) at 37°C. Antioxidant efficacy varied with RH and the individual amino acids. Arginine had the highest antioxidant efficacy at all RH values compared to the control. The efficacy of alanine was equal to that of arginine at RHs of 50 and 79% but was lower at 2% RH. The presence of aliphatic, alkaline amino, hydroxyl or thiol groups in the side chain of the amino acids increased the antioxidant efficacy at high RHs.     

The antioxidant activity of amino acids in two vegetable oils

Of 27 amino acids studied, most had some antioxidant activity when added in aqueous solution to either safflower oil or a mixture of sunflower and cottonseed oil (active oxygen and storage methods). Cysteine-HCl, glutamic acid-HCl (in the mixture), and glutamic acid-HCl (in safflower oil) behaved as prooxidants. When added as a solid, most amino acids were ineffective. The protection factors of these amino acids were less than 1.3 in safflower oil with methionine, proline, lysine and cysteine providing the highest activ-ity. In the oil mixture (which had a higher metal content) lysine, arginine, glutamic acid, methionine, and hydroxyproline were anti-oxidant with protection factors of up to 1.85. Chelation of metals by amino acids was presumably responsible for the antioxidant activity. The increase in cysteine concentration up to 1% has more than doubled the protection factor in Bint oil (compared with the 0.01% level), whereas with some other amino acids the increase was either small or slight.     

Antioxidant activity of amino acid sodium and potassium salts in vegetable oils at frying temperatures

Previous studies reported that several amino acids had strong antioxidant activity in vegetable oils under frying conditions. In this study, amino acids were converted to their sodium or potassium salts, and a heating study was conducted with 5.5 mM amino acid salts in soybean oil (SBO) at 180°C. Sodium salts of amino acids including alanine, phenylalanine, and proline and disodium glutamate had significantly stronger antioxidant activity than the corresponding amino acids, and potassium salts had stronger antioxidant activity than sodium salts. Potassium salts of alanine and phenylalanine more effectively retained tocopherols in SBO than the corresponding amino acids during heating. Phenylalanine potassium salt had stronger antioxidant activity than phenylalanine in other vegetable oils including olive, high oleic soybean, canola, avocado, and corn oils. Phenylalanine potassium salt at 5.5 mM more effectively prevented oil oxidation than tert-butyl hydroquinone, a synthetic antioxidant, at its legal concentration limit (0.02%) indicating its feasibility as a new antioxidant for frying.     

Reaction of gossypol with amino acids and other amino compounds

The reactions of gossypol with certain amino acids and other amino compounds have been studied spectroscopically with respect to the effect of time and pH in the range from 5.7 to 7.5 at 37 C. The rate of reaction of gossypol with amino acids increases with increase in pH and has been shown to be related to the distance of the amino group from the carboxyl group within the molecule. Reaction products of gossypol with amino acids and other amino compounds were subjected to various purification procedures and analysis to determine combination ratios. In addition to the expected gossypol-to-amino compound ratio of 1:2, dictated by the formation of Schiff base-type bonds with the two aldehyde groups of gossypol, compounds with ratios of 1:3 and 1:4 were isolated. These results indicate that each of the two aldehyde groups of gossypol can react with two amino groups under the conditions studied. Deceased March 9, 1969.     

Formation of dityrosine and other fluorescent amino acids by reaction of amino acids with lipid hydroperoxides

Formation of fluorescence by the reaction of various amino acids with lipid hydroperoxides,i.e., linoleic acid 13-monohydroperoxide, methyl linoleate 13-monohydroperoxide and phosphatidylcholine hydroperoxide, in the presence of methemoglobin was investigated. Two types of fluorescence were produced: fluorescent dityrosine (3,3′-dityrosine) from tyrosine, and unidentified fluorophores with α- and ε-amino groups of various amino acids. While the former was stable after treatment with borohydride, the latter fluorophores were readily destroyed. The rate of dityrosine formation was rapid, and the yield of dityrosine was dependent on the concentrations of tyrosine and the lipid hydroperoxides. Butylated hydroxytoluene and tocopherol inhibited the formation of dityrosine, but did not affect the formation of fluorophores on the amino groups. Dityrosine appears to be formed by radical reaction of the lipid hydroperoxides, while the other fluorophores seem to be created by nonradical mechanisms.     

Intracellular uptake and inhibitory activity of aromatic fluorinated amino acids in human breast cancer cells

Nonproteinogenic amino acids that either occur naturally or are synthesized chemically are becoming important tools in modern drug discovery. In this context, fluorinated amino acids have great potential in the development of novel pharmaceuticals and drugs. To assess whether different fluorinated aromatic amino acid analogues of phenylalanine, tyrosine, and tryptophan are potentially interesting as therapeutic drugs, we examined their cytostatic and cytotoxic effects on the growth of the human breast cancer cell line MCF-7. Of all the tested analogues L-4-fluorotryptophan, L-6-fluorotryptophan and L-p-fluorophenylalanine effectively and irreversibly inhibited cell growth with IC(50) values in the low micromolar range (3-15 microM). Additionally, using L-4-[14C]fluorotryptophan, and L-6-[14C]fluorotryptophan, we discovered that the cellular uptake of these fluorinated amino acids occurs through active transport with a 70-fold excess of intracellular over extracellular concentrations. We identified system L as the responsible amino acid transporter. Our findings fully support the idea that fluorinated aromatic amino acid analogues are promising chemotherapeutics with the potential for use in combination with classical cancer therapy, and as new cytotoxic drugs for certain tumor types such as melanoma.     

帽蕊木抗氧化活性研究

用二苯代苦味肼基自由基(DPPH)、铁离子还原/抗氧化力测定法(FRAP)和2,2′-连氨-(3-乙基苯并噻唑啉-6-磺酸)二氨盐(ABTS)3种体外抗氧化活性分析方法,与阳性对照没食子酸丙酯(PG)、丁基羟基茴香醚(BHA)和二丁基羟基甲苯(BHT)比较,对帽蕊木进行了抗氧化活性评价。在帽蕊木叶和皮的6个提取物中,叶乙酸乙酯提取物清除DPPH和ABTS自由基的能力最强(IC50=2.24 mg/L和IC50=1.165 mg/L),强于阳性对照BHA(IC50=3.43 mg/L和IC50=1.675 mg/L)和BHT(IC50=18.79 mg/L和IC50=4.555 mg/L),弱于阳性对照PG(IC50=0.94 mg/L和IC50=0.885 mg/L);叶正丁醇提取物还原Fe3+能力最强(FRAP值=1 395.94μmol TE/g),皮正丁醇提取物次之(FRAP值=1 275.43μmol TE/g),都强于阳性对照BHT(FRAP值=238.11μmol TE/g),弱于阳性对照PG(5 159.97μmol TE/g)、BHA(2 573.96μmol TE/g)。结果表明,帽蕊木叶和皮的乙酸乙酯和正丁醇提取物都有很好的抗氧化活性,并且帽蕊木叶的活性强于茎皮。该文报道工作的新颖性已为河南大学图书馆2008年8月25日出具的第CX 2008007号《科技查新报告》所证实。     

Antioxidant properties of α-tocopherol derivatives and relationship of antioxidant activity to biological activity

A series of α-tocopherol analogs substituted at the 5-methyl group were evaluated for their ability to protect β-carotene dissolved in hydrogenated, tocopherol-stripped corn oil from air oxidation. These results were compared with the ability of these compounds to prevent the development of dietary necrotic liver degeneration in rats and vitamin E deficiency-induced muscular dystrophy in rabbits. Although a good correlation was seen between the antioxidant activities of some of the compounds and their biological activities, in the case of other compounds the correlation was poor. The importance of the phytyl side chain of the tocopherols and their derivatives for their antioxidant activities was evident from these studies.     

Antioxidant properties of hymatomelanic acids from brown coal

The antioxidant activity of a low-temperature fraction of hymatomelanic acids from brown coal in a model process of the radical chain oxidation of cumene was determined using a gas-volumetric method. Their antiradical activity was evaluated by spectrophotometry using a reaction with 2,2-diphenyl-1-picrylhydrazyl (DPPH). The pronounced ability of hymatomelanic acids to cause antioxidant and antiradical effects in model systems was demonstrated. It was found that the antioxidant and antiradical activities increased with the concentration of hymatomelanic acids. The determined properties of hymatomelanic acids from brown coal can be useful for technical and biomedical applications.