Silver Nitrate-impregnated Silica Gel Research Articles

A facile route to semi-synthesis of acetyl glycerylether phosphoethanolamine and its choline analogue.

A facile route to the semi-synthesis of acetyl glycerylether phosphoethanolamine and, subsequently, its choline analogue (platelet-activating factor) has been developed. In essence, this technique takes advantage of the fact that the phosphatidylethanolamine fraction of bovine erythrocytes contains 75-80% of a 1-O-alkyl-2 fatty acyl derivative. Isolation of the latter by silicic acid chromatography followed by base-catalyzed methanolysis allowed good recovery (60-70%) of the 1-O-alkyl-(lyso)-sn-glyceryl-3-phosphoethanolamine, which contained a mixture of long chain alkyl ethers. This compound was treated with acetic anhydride in the presence of trace amounts of perchloric acid for 45 sec to give, in excellent yield, 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphoethanolamine (AGEPE). This procedure gave a 70% yield of purified AGEPE, based on the starting component, 1-O-alkyl-(lyso)-sn-glyceryl-3-phosphoethanolamine. Separation of AGEPE into fractions individually enriched in the 16:0, 18:0, and 18:1 alkylether substituents was accomplished by silica gel G combined with silver nitrate-impregnated silica gel H thin-layer chromatography. The AGEPE or its individual molecular species can be converted in high yields to the corresponding 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphocholine (AGEPC) analogues by reaction with methyl iodide in the presence of a crown ether. Characterization of the derivatives was achieved through thin-layer chromatography, infrared spectroscopy, gas-liquid chromatography, and combined gas-liquid chromatography-mass spectrometry. The ability of these analogues to induce irreversible aggregation and secretion of serotonin from washed rabbit platelets was evaluated.

Detection of palm oil in vanaspati by thin layer chromatography

AbstractPalm oil (raw or refined), as such, or the unsaponifiable matter of palm oil and vanaspati (mostly hydrogenated soybean oil containing 5% sesame oil), when separated on a silver nitrate impregnated Silica Gel G plate or a Silica Gel G plate using (a) hexane/ether/acetic acid (80:20:1.5) or (b) chloroform, respectively, for development showed distinct differences. On the basis of this, two systems have been suggested for the detection of palm oil in vanaspati. About 5% adulteration can be detected by the first method and 10% by the second.

Thin-layer and gas–liquid chromatographic identification of neutral steroids in human and rat feces

Natural steroids from rat and human feces were fractionated by sequential thin-layer chromatography (TLC) on Florisil, silica gel, and silver nitrate-impregnated silica gel and analyzed by gas--liquid chromatography (GLC). Cholesterol, coprostanol, and coprostanone accounted for more than 95% of the endogenous neutral steroid in human feces, the remainder being predominantly cholestanol. In addition, evidence was obtained for the presence in human feces of trace amounts of epicoprostanol and cholestanone. In rat feces, several cholesterol precursors that probably originated in the skin (and were ingested during fur=licking) were detected in relatively large amounts, accounting for as much as 27% of the total fecal neutral steroids, whereas these steroids were quantitatively trivial in human feces. As with cholesterol, the major dietary plant sterols (sitosterol, campesterol, and stigmasterol) were converted by intestinal bacteria to the corresponding coprostane and ketonic derivatives during intestinal transit in both human beings and rats. This combined use of TLC and GLC provided for the separation of steroids of endogenous and dietary origin that could not be resolved by either system alone. A majority of the fecal steroids could be tentatively identified by their chromatographic behavior in different TCL systems and on GLC, even when reference standards were unavailable.

Synthesis and purification of the allofarnesenes

The eight isomers of allofarnesene (3,7,11-trimethyl-2,4,6,10-dodecatetraene) were prepared using Wittig reactions. The four E-4 isomers could be separated using GC but the unstable Z-A isomers required HPLC on silver nitrate impregnated silica gel for analysis. Purified samples of each isomer were prepared for spectral studies. The configuration of the pseudoionone (6,10-dimethyl-3,5,9-undecatriene-2-one) starting materials was also studied, confirming previous results.

Liquid chromatographic separation of fatty acid methyl esters and phosphatidic acid dimethyl esters with silver nitrate-impregnated silica gel columns

Standard fatty acid methyl esters were separated by high-performance liquid chromatography with a silver nitrate-impregnated silica gel column with benzene as eluent and a differential refractometer as the detector. The separation, based on the number of double bonds, was greatly improved when the benzene was dried over calcium chloride for two days. Phosphatidic acid dimethyl esters derived from egg phosphatidylcholines were also resolved into three major fractions on the basis of the degree of unsaturation on a silver(I)-loaded resin column with diethyl ether as eluent and detected with a flame ionization monitor.

6] Separation of partialy deuterated methyl palmitate from nondeuterated methyl palmitate by high-pressure liquid chromatography

This chapter describes separation of partially deuterated methyl palmitate from nondeuterated methyl palmitate by high-pressure liquid chromatography. High-pressure liquid chromatography columns of high efficiency have made possible separations of fatty acids that could be accomplished only by gas chromatography. Methyl esters of fatty acids were isolated from 1.75 g of rat liver that had been perfused with 70% D20. Gas chromatographic analysis of the total lipid extract showed that the methyl palmitate contained 13.7% deuterated palmitate. Methyl esters of the saturated fatty acids were then separated from methyl esters of all unsaturated fatty acids on a silver nitrate-impregnated silica gel column, 0.41 cm in diameter and 25 cm in length, packed with Adsorbosil-5-ADN 25% AgNO 3 . It is found that for separation of the deuterated and nondeuterated palmitates, the material was injected into the same column and elution with methanol was started. It is observed that after elution of one column volume, the recycle valve was closed and the methyl palmitate was allowed to recycle 13 times.

Glycosides of marine invertebrates—VI. Steroid glycosides from holothurian Stichopus japonicus

1. 1. Steroid glycosides from holothurian Stichopus japonicus Selenka were investigated. The β-monoside fraction has been isolated by chromatography on silica gel columns with subsequent preparative thin-layer chromatography on a fixed silica gel layer. 2. 2. Hydrolytic products of the isolated glycosides were examined by gas chromatography, paper chromatography, silver nitrate impregnated silica gel column chromatography, infrared absorption and nuclear magnetic resonance spectrometries. 3. 3. It was shown that aglycones of these glycosides are C 26, C 27, C 28 and C 29-sterols with saturated and monounsaturated nucleus. The double bond in the steroidal nucleus is located at C(7)-C(8). A side chain contains a double bond at C(22)-C(23) or C(24)-C(28). The monosaccharide proved to be d-xylose. 4. 4. Similar glycosides were identified in holothurians Isostichopus hadionotus, Synapta lappa and other species.

An efficient method for the synthesis and purification of trans-[ 14C]geranylgeranyl pyrophosphate

A simple procedure for the preparation and purification of trans-[ 14C]geranylgeranyl pyrophosphate from dl-[ 14C]mevalonate is described. This procedure involves biosynthesis of trans-[ 14C]geranylgeraniol from dl-[ 14C]mevalonate by cell-free extracts of the fungus Gibberella fujikuroi and chemical synthesis of trans-[ 14C]geranylgeranyl pyrophosphate from trans-[ 14C]geranylgeraniol. The purification of trans-[ 14C]geranylgeraniol is achieved by chromatography on a silver nitrate-impregnated silica gel column. The pyrophosphate ester is purified on a silica gel column.

Argentation Thin-Layer Chromatography of thep-Nitrobenzyl Esters of Gibberellins and Their Precursors

Abstract Thirteen p-nitrobenzyl esters of gibberellins and their precursors have been separated by thin-layer chromatography on silver nitrate-impregnated silica gel. The fluorescence produced by sulfuric acid was used for their detection.

硝酸銀含浸シリカゲルカラムクロマトグラフィーによる高度不飽和脂肪酸の分離

硝酸銀含浸シリカゲルカラムクロマトグラフィーによる高度不飽和脂肪酸の分離

The triglyceride composition of Corchorus olitorius seed oil.

AbstractCorchorus olitorius seed oil and its randomised product have been subjected to pancreatic hydrolysis. Glyceride compositions have been calculated from the original fatty acid composition and those of the monoglycerides produced by hydrolysis. The percent GS3 content of the seed oil and of its interesterified product have also been determined by the combined techniques of thin layer chromatography on silver nitrate impregnated silica gel and colorimetry.

A method for the rapid qualitative and quantitative analysis of 4,4-dimethyl sterols

A simple and relatively rapid technique has been developed for the separation of several 4,4-dimethyl steryl acetates, some of which contain sterically hindered nuclear double bonds. The method involves thin-layer chromatography on silver nitrate-impregnated silica gel and silver nitrate-impregnated alumina. The separated steryl acetates may then be analyzed quantitatively by gas-liquid chromatography.

"Dry-Column" Chromatography; IV. Use of Silver Nitrate-Impregnated Silica Gel

"Dry-Column" Chromatography; IV. Use of Silver Nitrate-Impregnated Silica Gel

The fractionation of phosphatidylinositol into molecular species by thin-layer chromatography on silver nitrate-impregnated silica gel

The fractionation of phosphatidylinositol into molecular species by thin-layer chromatography on silver nitrate-impregnated silica gel

The fractionation of phosphatidylinositol into molecular species by thin-layer chromatography on silver nitrate-impregnated silica gel.

1. Two methods for the fractionation of phosphatidylinositol into molecular species were developed. In addition to preserving the fatty acid moiety of the molecule, the first method preserves the phosphorus, and the second preserves both the phosphorus and inositol ring. 2. In the first method, phosphatidylinositol was oxidized with periodate and the products reacted with diazomethane. I.r. examination showed that the main product was identical with dimethylphosphatidic acid. Fractionation to molecular species was carried out on thin layers impregnated with silver nitrate. The fatty acid composition of the species was determined by gas-liquid chromatography, and their distribution in lamb liver phosphatidylinositol was studied by a method using [(3)H]methanol. 3. In the second method, phosphatidylinositol was acetylated under mild reaction conditions. The major product was the triacetylated derivative of this phospholipid. This was reacted with diazomethane and the methylated-triacetylated phosphatidylinositol was fractionated into molecular species on silver nitrate-impregnated thin layers. Solvent mixtures containing acetone and distilled chloroform were found most suitable for this purpose. The fatty acid composition of the molecular species was determined by g.l.c., and their distribution in lamb liver phosphatidylinositol was studied by a method using [1-(14)C]acetic anhydride during the acetylation reaction. 4. Results from both methods agree fairly well. The most predominant species of lamb liver phosphatidylinositol is the monoenoic (60%) followed by the tetraenoic (17%). The di- and tri-enoic species existed as minor components.

Triglyceride Composition of Milk Fat: II. Separation of Triglycerides by Argentation-TLC and GLC

Fractions of milk fat separated by column chromatography on silicic acid were further analyzed by thin-layer chromatography on silver nitrate impregnated silica gel and gas chromatography of triglycerides and their component fatty acids. The triglyceride types in 8 bands on the thin-layer chromatograms were characterized and their composition determined.

The triglyceride composition ofMoringa concanensis seed fat

AbstractMoringa concanensis seed fat and its randomized product have been subjected to pancreatic hydrolysis. Glyceride compositions have been calculated from the original fatty acid composition and those of the monoglycerides produced by hydrolysis. The per cent GS3 content of the interesterified product has also been determined by the combined techniques of thin layer chromatography on silver nitrate impregnated silica gel and colorimetry.

Presence of polyunsaturated acids in bacteria: isolation of hexatriacontapentaene-4,8,12,16,20-oic acid and acid analogs from Mycobacterium phlei lipids

So far, bacteria were considered as devoid of polyunsaturated fatty acids. In spite of this assumption, the lipids of Mycobacterium phlei have a relatively high content (about 5% of the total free lipids) of acids with the general formula CH3–(CH2)n (CH=CH–CH2–CH2)m–CO2H (I), where n = 14 or 12 and m = 5, 6 or 4. The main component of this mixture is hexatriaconta 4,8,12,16,20-pentanoic acid. These acids can be isolated by saponification of the crude lipids, and detected by gas chromatography and thin layer chromatography on silver nitrate-impregnated silicagel. Their structure was established by means of spectrographic methods (infrared and ultraviolet spectrography, nuclear magnetic resonance and mass spectrometry), by study of the products obtained after oxidative degradation, and by comparison of the hydrocarbons prepared from these acids with synthetic hydrocarbons. The polyunsaturated acids are present in several complex lipids, including only a minor fraction of phospholipids. Because of their structure, the acids I belong to a new type of natural polyunsaturated fatty acids and might require a peculiar mode of biosynthesis, involving a repetition process.

Dünnschicht-Chromatographische trennung von tomatidenol, solasodin und soladulcidin bzw. yamogenin, diosgenin und tigogenin

A description is given of the separation of tomatidenol, solasodine and soladulcidine and yamogenin, diosgenin and tigogenin by thin-layer chromatography. Use was made of silver nitrate impregnated Silica Gel G.

Thin Layer Densitometric Determination of Rotenone and Deguelin

Abstract Rutenone and deguelin are separated by chromatography on silver nitrate-impregnated silica gel G with chloroform acetone: acetic acid (196:3:1) solvent system. Glass plates, 20 × 20 cm, are coated with a special spreader producing a 0.25 mm layer and a 1.00 mm band at the upper end. Since additional solvent is required to saturate the thicker band, such plates give resolutions comparable to plates twice as long. Developed plates are treated with nitric acid vapor, then ammonia vapor, to produce dark spots for the rotenoids. Plates are scanned with a commercial densitometer, and the quantity of rotenoids is calculated from peak area in the resultant curve. Kecoveries of rotenone and deguelin added to extracts of Tephrosia vogelii, Lonchocarpus nicou, and Derris elliptica averaged 104.1 and 99.4%, respectively. The standard deviation of the method applied to plant extracts was 7.9% for rotenone and 8.3% for deguelin. The amounts of rotenone in the L. nicou samples were comparable to those determined by the AOAC crystallization and infrared methods.