Mirabiquinone,a new unsymmetrical binaphthoquinone from the sea urchin Scaphechinus mirabilis

Mirabiquinone [7,5′-anhydroethylidene-6,6′-bis(2,3,7-trihydroxynaphthazarin)], a new unsymmetrical binaphthoquinone, was isolated from the sea urchin Scaphechinus mirabilis along with the known symmetrical binaphthoquinones ethylidene-6,6′-bis(2,3,7-trihydroxynaphthazarin) and 7,7′-anhydroethylidene-6,6′-bis(2,3,7-trihydroxynaphthazarin). The structure of mirabiquinone was established using ¹H NMR, ¹³C NMR, HSQC and HMBC data, along with a spectroscopic analysis of its pentamethoxy derivative. Mirabiquinone and the symmetrical binaphthoquinones demonstrated excellent scavenging of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical.     

A new binaphthoquinone fromStrongylocentrotus intermedius

Summary From a mixture of the pigments of the sea urchinStrongylocentrotus intermedius, in addition to the known spinochrome D, we have isolated a new binaphthoquinone having the structure of 6,6-ethylidenebis(2,3,7-trihydroxynaphthazarin).Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center of the Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 439–441, July–August, 1976.     

Quinoid pigments of echinodermata V. Pigments of the sea urchinStrongy locentrotus dr?ebachiensis

Summary From a mixture of the pigments of the sea urchinStrongy locentrotus dröebachiensis, in additionto the known spinochromes A, C, D, and E, we have isolated a binaphthoquinone and its anhydro derivative. On the basis of¹³C NMR spectra the position of the ethylidene bridge symmetrically binding the two naphthazarin fragments of the binaphthoquinone has been definnitely established, and the structure of this compound has been determined as ethylidene-6,6-bis(2,3,7-trihydroxynaphthazarin).Pacific-Ocean Institute of Bioorganic Chemistry, Far-Eastern Scientific Center of the Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 438–441, July–August, 1978.     

Quinoid pigments of echinodermata III. Minor pigments of the sea urchin Strongylocentrotus nudus

Summary 1. 3-Acetyl-2,7-dihydroxy-6-methylnaphthazarin, not previously described, has been isolated from the test and needles of the sea urchinStronglyocentrotus nudus.2. The pigments of this sea urchin have been shown to include 2,7-dihydroxynaphthazarin and spinochrome E.3. A number of minor pigments forming naphthazarin derivatives has been isolated. One of them is connected with spinochrome C by mutual transformations.The subject matter of the present paper was given in part at the All-Union Conference on Biological Resources of the Seas of the Far East (Vladivostok, 1975).Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center of the Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 202–207, March–April, 1977.     

Evaluation of Free Radical-Scavenging Activity of Sea Urchin Pigments Using HPTLC with Post-Chromatographic Derivatization

Chromatographic separation, analysis of in situ radical-scavenging activity, and quantitative analysis of green sea urchin shell pigments were carried out by online HPTLC-DAD and HPTLC-DPPH methods. Methanol:chloroform:acetic acid:water (11:50:5:2, v/v) was selected as the best mobile phase on silica gel plates for the separation of the pigments. Two pigment spots, S1 and S2, were observed on the TLC plates, while echinochrome A was not detected in the pigment extract of green sea urchin shells. Based on the estimated ID₅₀ values, the antiradical activity was S2 (0.043 μg) > S1 (0.058 μg) > echinochrome A (0.134 μg).     

Use of combined chromatographic methods including thin-layer chromatography for analysis of complex polymer systems. Determination of the polydispersity of block copolymers of styrene and methyl methacrylate by gel permeation, thin-layer and pyrolysis gas chromatography.

A combination of gel permeation chromatography (GPC), thin-layer chromatography (TLC) and pyrolysis gas chromatography (PGC) has been used for investigations of a polymethyl methacrylate-polystyrene-polymethyl methacrylate block copolymer. Continuous distribution of the polymer (40-mg sample) was attained according to the content of the styrene and methyl methacrylate units and of the block copolymer and according to the composition of the copolymer as functions of the hydrodynamic radius of the macromolecules. The polymer was subjected to a preliminary fractionation with an analytical gel chromatograph. The fractions were investigated by TLC, which permitted the separation of the block copolymer and the homopolymers. The composition of the fractions obtained by GPC and TLC was determined by PGC. As a result, it was possible to establish the composition of the block copolymer and its ratio to polymethyl methacrylate in each fraction. This investigation was based on a combination of highly effective fractionation by chromatographic methods with precise quantitative ratios obtained from Benoit's universal calibration graph and from determinations of the composition of the polymer fractions by PGC. The mechanism of the TLC of polymers, including the appearance of artefacts that distort the results of analysis, is also discussed.     

Separation and tentative identification of the main pigment fraction of raisins by thin-layer chromatography-Fourier transform infrared and high-performance liquid chromatography-ultraviolet detection

The soluble color pigments of raisin are separated by reversed-phase thin-layer chromatography (TLC), and the capacity of TLC-Fourier transform infrared (FTIR) with both on-line and off-line coupling is assessed for the identification of the main fraction. TLC has also been used as a pilot technique for the development of a gradient elution method for the separation of pigments by high-performance liquid chromatography (HPLC). On-line TLC-FTIR cannot be used for identification because of the strong adsorbance of the stationary phase. Off-line TLC-FTIR combined with the retention behavior of the main pigment fraction indicates that it is a polymer, caramel-like compound composed of erythrose and fructose monomers. Baseline separation of pigments is achieved by HPLC using TLC as a pilot method.     

Direct amination of naphthopurpurin and mompain,sea urchin pigments,and their O-methyl ethers by the reaction with ammonia

Russian Chemical Bulletin - The regiochemistry of direct amination of 2-hydroxynaphthazarin (naphthopurpurin) and 2,7-dihydroxynaphthazarin (mompain), sea urchin pigments, and their O-methyl ethers...     

Harnessing anionic rearrangements on the benzenoid ring of quinoline for the synthesis of 6,6'-disubstituted 7,7'-dihydroxy-8,8'-biquinolyls

7,7'-Bis(((dimethylamino)carbonyl)oxy)-8,8'-biquinolyl (5) was prepared in 71% yield by regioselective directed ortho metalation (DoM) of N,N-dimethyl O-quinol-7-yl carbamate (2) with LDA followed by oxidation with anhydrous ferric chloride. DoM of 5 with excess LDA induced double anionic ortho-Fries rearrangement and gave 6,6'-bis((dimethylamino)carbonyl)-7,7'-dihydroxy-8,8'-biquinolyl (8). Treatment of N,N-diethyl O-(8-iodoquinol-7-yl) carbamate (16) with LDA in THF solvent at -78 degrees C, followed by addition of anhydrous ferric chloride, resulted in an efficient tandem halogen-dance dimerization process which afforded 7,7'-bis(((diethylamino)carbonyl)oxy)-6,6'-diiodo-8,8'-biquinolyl (17) directly in 54% yield.     

Preparative isolation and purification of alkannin/shikonin derivatives from natural products by high-speed counter-current chromatography

Alkannin and shikonin (A/S) and their derivatives have been found in the roots of several Boraginaceous species and are also produced through plant tissue cultures. The chiral compounds A/S are potent pharmaceutical substances with a wide spectrum of biological and pharmacological activities like wound healing, antimicrobial, anti-inflammatory, anticancer and antioxidant activity. High-speed counter-current chromatography (HSCCC) was applied for the first time to the separation, preparative isolation and purification of A/S and their esters from extracts of Alkanna tinctoria roots, as well as commercial samples. The constituents of HSCCC fractions and their purity were determined by high-performance liquid chromatography-diode array detection-mass spectrometry (HPLC-DAD-MS), since DAD cannot detect oligomeric A/S derivatives that are present in most of the samples containing the respective monomeric derivatives. The purity of HSCCC fractions was compared with the one of fractions isolated by column chromatography (CC) using as stationary phases silica gel and Sephadex LH-20. As shown, the purity of monomeric alkannin/shikonin was greater by HSCCC than CC separation of commercial A/S samples.     

A comparison of linear optical properties and redox properties in chalcogenopyrylium dyes bearing ortho-substituted aryl substituents and tert-butyl substituents

A series of thiapyrylium pentamethine dyes (4 and 12-15) bearing 2,2'-di-tert-butyl-6,6'-diphenyl, 2,2'-di-tert-butyl-6,6'-bis(2,6-dimethylphenyl), 2,2'-di-tert-butyl-6,6'-bis(2-methylphenyl), 2,2',6,6'-tetrakis(2,6-dimethylphenyl), and 2,2',6,6'-tetrakis(2-methylphenyl) substituents, respectively, were prepared and their linear optical properties and electrochemical redox properties were measured and compared to thiapyrylium pentamethine dyes 3 and 5. The tert-butyl and 2,6-dimethylphenyl substituents give nearly identical chromophores with respect to values of lambda(max), molar extinction coefficients (epsilon), bandwidths at half-height (nu(1/2)), and lack of absorption in the visible spectrum. The 2-methylphenyl substituent imparts linear optical properties that are intermediate between those of the tert-butyl and phenyl substituents. The 2,6-dimethylphenyl and 2-methylphenyl substituents impart greater oxidative stability based on anodic shifts in oxidation potential.     

Isolation of flavanol-anthocyanin adducts by countercurrent chromatography

Pigments of the flavanol-anthocyanin (F-A+) type detected earlier in wine are synthesized using a protocol adapted from the synthesis of procyanidin dimers. The F-A+ adduct thus obtained is purified by countercurrent liquid-liquid partition, currently referred to as countercurrent chromatography (CCC). The solvent system consists of tert-butyl methyl ether-n-butanol-acetonitrile-water (2:2:1:5, acidified with 0.1% trifluoroacetyl) with the light organic phase acting as a stationary phase and the aqueous phase as the mobile phase. Four fractions are recovered and analyzed by high-performance liquid chromatography coupled to a diode-array detector and electrospray ionization mass spectrometer. The multilayer CCC method allowed the separation of pigments in three different groups. The first group consists of hydrosoluble pigments present in fraction 1; the second group consists of the F-A+ adducts [catechin-malvidin 3 glucoside (Mv3glc), along with some (catechin)2-Mv3glc]; and the third group is their anthocyanin precursor, Mv3glc.     

Identification of spontaneous conversion products of unstable 2,4,6-trinitrotoluene metabolites, hydroxylamino-dinitrotoluenes, by combination of thin-layer chromatography and laser time-of-flight mass spectrometry

Two kinds of hydroxylamino-dinitrotoluenes, 2-hydroxylamino-4, 6-dinitrotoluene (2HADNT) and 4-hydroxylamino-2, 6-dinitrotoluene (4HADNT), are known to be major metabolites produced from 2,4,6-trinitrotoluene (TNT) by bacteria. The amounts of 2HADNT and 4HADNT in distilled water are found to spontaneously decrease with time, albeit abiotic conditions, and many white precipitates are educed in the processes of this phenomenon; however, how these compounds are converted is unclear. We evinced the mystery of this phenomenon by using thin-layer chromatography (TLC) and laser time-of-flight mass spectrometry (TOFMS). TLC analyses in the spontaneous conversion processes of 2HADNT, 4HADNT, and 2HADNT plus 4HADNT demonstrats that three novel spots emerge on the TLC plate, respectively. These products are individually extracted into acetonitrile by collecting each spot. The purity of these extracts, which have retention times of 14.0, 17.7, and 15.4 min, is approximately 98%, judging from the results of high-performance liquid chromatographic analyses. The spontaneous conversion products of 2HADNT, 4HADNT, and 2HADNT plus 4HADNT are identified as 4,4',6,6'-tetranitro-2,2'-azoxytoluene (2,2'AZT), 2,2',6,6'-tetranitro-4,4'-azoxytoluene (4,4'AZT), and 4,2',6, 6'-tetranitro-2,4'-azoxytoluene (2,4'AZT) by obtaining their mass spectra with laser TOFMS. It is confirmed that most of the spontaneous conversion products are 2,2'AZT, 4,4'AZT, or 2,4'AZT, judging from the results of mass balance in the spontaneous conversion processes of 2HADNT, 4HADNT, and 2HADNT plus 4HADNT.     

Thin-layer chromatography of pitch and a petroleum vacuum residue. Relation between mobility and molecular size shown by size-exclusion chromatography

A coal tar pitch and a petroleum vacuum residue have been separated by TLC using pyridine, acetonitrile, toluene and pentane to develop the chromatograms. The bands of material detected were recovered in 1-methyl-2-pyrrolidinone (NMP) solvent and examined by size-exclusion chromatography (SEC) in NMP eluent. The relation between elution time in SEC and mobility on the TLC plate indicated that molecular size increased steadily with increasing immobility on the plate. This relation was reinforced by UV fluorescence spectroscopy in that the fluorescence moved to longer wavelengths with increasing immobility. The molecular size of the material excluded from the porosity of the SEC column remains undefined; some excluded material was found in all of the fractions from both samples. The valley of zero intensity separating the retained material from the excluded material may suggest a change of structure from near-planar in the retained region to three-dimensional in the excluded region.     

Hindered rotation in an "exploded" biphenyl

The first cases of hindered rotation around the triple bond in simple diphenylacetylenes were observed, including that in chiral 2,2'-bis(trimethylsilyl)-6,6'-bis(dimethylthexylsilyl)diphenylacetylene.     

Utilization of flash chromatography for the fractionation of coal derived liquids

Summary The suitability of flash chromatography for the fractionation of coal liquids in compound classes has been studied. TLC data obtained from standards were used for establishing the sequence, composition and volume of eluents in order to collect the main components of coal liquids in six fractions of increasing polarity. The method was tested by the fractionation of a SCG coal extract and separations were evaluated by TLC, SEC, and IR and NMR spectroscopy.     

Cone thin-layer chromatography

A new variant of chromatography, cone chromatography, is suggested. In this variant, a thin-layer chromatography (TLC) plate on a flexible support (for example, foil) is cone-shaped. This variant is compared with the classic linear and circular variants using chromatographic characteristics (retardation factor R _f and efficiency H, μm) and the time of chromatographing with ethanol as a mobile phase. Cone chromatography is intermediate in the series linear-cone-circular TLC variants.     

A review of advances in two-dimensional thin-layer chromatography

Although there are many simple thin-layer chromatography (TLC) separations, many more are complex and involve more than a few components, that means having to use special high-performance TLC (HPTLC) plates or microspotting or banding devices to increase its resolving power if developing in only one direction. However, adding a second development to perform two-dimensional TLC (2D TLC) allows even better resolution of complex samples. This is because different modes of chromatography are being invoked by the use of one stationary phase with two mobile phases, bilayer plates, graft TLC, or multidimensional TLC. This paper is a review of recent applications that have benefitted from using 2D TLC in its various forms. They were chosen for their variety of sample types as well as the unique choices of plates and/or mobile phases made by the researchers to yield improved separations.     

Effect of reduced glutathione on the stability of pigments in paprika powders studied by multiwavelength spectrometry and high-performance liquid chromatography

Multiwavelength spectrometry and reversed-phase high-performance liquid chromatography have been employed for the study of the effect of reduced glutathione and storage time on the pigments of paprika powders. The evaluation of the data by principal component analysis and cluster analysis proved that the storage time exerts the highest effect of the decomposition rate of pigments. The stability of some pigment fractions was modified in the presence of reduced glutathione. However, the effect was of secondary importance. Multiwavelength spectrometry combined with HPLC can be successfully used for the study of the stability of pigments of paprika powder.     

Simplified and rapid method for extraction of ergosterol from natural samples and detection with quantitative and semi-quantitative methods using thin-layer chromatography

A new and simplified method for extraction of ergosterol (ergosta-5,7,22-trien-3beta-ol) from fungi in soil and litter was developed using pre-soaking extraction and paraffin oil for recovery. Recoveries of ergosterol were in the range of 94-100% depending on the solvent to oil ratio. Extraction efficiencies equal to heat-assisted extraction treatments were obtained with pre-soaking extraction. Ergosterol was detected with thin-layer chromatography (TLC) using fluorodensitometry with a quantification limit of 8 ng. Using visual evaluation of images of TLC plates photographed in UV-light the quantification limit was 16 ng.