Chemical Transformation Products Research Articles

Silvestrol and episilvestrol, potential anticancer rocaglate derivatives from Aglaia silvestris.

Two cytotoxic rocaglate derivatives possessing an unusual dioxanyloxy unit, silvestrol (1) and episilvestrol (2), were isolated from the fruits and twigs of Aglaia silvestris by bioassay-guided fractionation monitored with a human oral epidermoid carcinoma (KB) cell line. Additionally, two new baccharane-type triterpenoids, 17,24-epoxy-25-hydroxybaccharan-3-one (3) and 17,24-epoxy-25-hydroxy-3-oxobaccharan-21-oic acid (4), as well as eleven known compounds, 1beta,6alpha-dihydroxy-4(15)-eudesmene (5), ferulic acid (6), grasshopper ketone (7), apigenin, cabraleone, chrysoeriol, 1beta,4beta-dihydroxy-6alpha,15alpha-epoxyeudesmane, 4-hydroxy-3-methoxyacetophenone, 4-hydroxyphenethyl alcohol, ocotillone, and beta-sitosterol 3-O-beta-D-glucopyranoside, were also isolated and characterized. The structures of compounds 1-4 were elucidated by spectroscopic studies and by chemical transformation. The absolute stereochemistry of silvestrol (1) was established by a X-ray diffraction study of its di-p-bromobenzoate derivative, and the structure of 3 was also confirmed by single-crystal X-ray diffraction. The isolates and chemical transformation products were evaluated for cytotoxicity against several human cancer cell lines, and silvestrol (1) and episilvestrol (2) exhibited potent in vitro cytotoxic activity. Silvestrol (1) was further evaluated in vivo in the hollow fiber test and in the murine P-388 leukemia model.

Isolation and Absolute Stereochemistry of Coussaric Acid, a New Bioactive Triterpenoid from the Stems of Coussarea brevicaulis.

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Isolation and absolute stereochemistry of coussaric acid, a new bioactive triterpenoid from the stems of Coussarea brevicaulis

Coussaric acid (1), a triterpenoid based on an ursane skeleton, and an oleanane-type triterpene acid, 3-epi-spathodic acid (2), as well as four known compounds, barbinervic acid, scutellaric acid, stigmasterol and stigmasterol glucoside, have been isolated from an EtOAc-soluble extract of the stems of Coussarea brevicaulis. The structures of compounds 1 and 2 were elucidated on the basis of spectroscopic investigation, and single-crystal X-ray crystallography was used to confirm the structure of 1. The absolute stereochemistry of 1 was established by chemical transformations and by the Mosher ester procedure. The potential of the isolates and chemical transformation products to induce quinone reductase was evaluated in mouse Hepa lclc7 hepatoma cells.

Persistence of Parent Compounds and Transformation Products in a Level IV Multimedia Model

An approach to extend the concept of persistence to transformation products of environmental chemicals is presented. First, the residence time in a steady-state scenario and the lifetime in a pulse scenario as two commonly used persistence measures are compared with respect to their mathematical formulation, and concentration functions as time-dependent solutions of a dynamic multimedia model are calculated. Second, it is shown how the model system needs to be modified in order to calculate concentration functions for any number of transformation products. On the basis of these concentration functions, two new persistence measures describing the additional exposure of the environment that is caused by the presence of transformation products are introduced. These two measures, called Joint Persistence and Secondary Persistence, are explicitly calculated for two pairs of parent compounds and transformation products, namely, methyl tert-butyl ether (MTBE) and atrazine and their transformation products tert-b...

Investigation of molecular structure of LDPE modified by itaconic acid grafting

Using thermomechanical spectroscopy, the molecular-weight distribution and relaxation transitions have been investigated in commercial LDPE and grafted by itaconic acid (LDPE-g-IA). This grafting in the molten LDPE was done by reactive extrusion with varied content of reactants in the blend under alternating of a shearing rate applied onto the melt. The dependence of structural relaxation changes in LDPE is shown upon the depth of the mechanochemical transformations and the competing reactions at IA grafting, and also on the chemical crosslinking of the macromolecules. The reason for MWD bimodality for LDPE-g-IA obtained in dynamic mixing is the raised homogenization degree of the reactive blend and the higher grafted product yield compared with static mixers. The mixer type substantially affects the structure of the LDPE-g-IA amorphous phase. The data obtained reflect chemical transformations of LDPE molecules in IA's presence without an initiator of radical reactions (DCP). Most probable is the IA initiation of molecular crosslinking reactions. There could also occur IA thermodegradation and oligomerization. LDPE and IA or products of acid chemical transformations do not agree thermodynamically (the calculated solubility parameters are 16.1 (MJ/m3)0.5 for polyethylene and 26.4 (MJ/m3)0.5 for IA). From the above procedure it can be supposed that nongrafted IA (or its oligomers) exerts an antiplastifying effect on LDPE and LDPE-g-IA. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1771–1779, 1999

Investigation of molecular structure of LDPE modified by itaconic acid grafting

Using thermomechanical spectroscopy, the molecular-weight distribution and relaxation transitions have been investigated in commercial LDPE and grafted by itaconic acid (LDPE-g-IA). This grafting in the molten LDPE was done by reactive extrusion with varied content of reactants in the blend under alternating of a shearing rate applied onto the melt. The dependence of structural relaxation changes in LDPE is shown upon the depth of the mechanochemical transformations and the competing reactions at IA grafting, and also on the chemical crosslinking of the macromolecules. The reason for MWD bimodality for LDPE-g-IA obtained in dynamic mixing is the raised homogenization degree of the reactive blend and the higher grafted product yield compared with static mixers. The mixer type substantially affects the structure of the LDPE-g-IA amorphous phase. The data obtained reflect chemical transformations of LDPE molecules in IA's presence without an initiator of radical reactions (DCP). Most probable is the IA initiation of molecular crosslinking reactions. There could also occur IA thermodegradation and oligomerization. LDPE and IA or products of acid chemical transformations do not agree thermodynamically (the calculated solubility parameters are 16.1 (MJ/m3)0.5 for polyethylene and 26.4 (MJ/m3)0.5 for IA). From the above procedure it can be supposed that nongrafted IA (or its oligomers) exerts an antiplastifying effect on LDPE and LDPE-g-IA. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1771–1779, 1999

Catechins and proanthocyanidins ofAlhagi sparsifolia. I

Ten individual compounds have been isolated from the epigeal part ofAlhagi sparsifolia Shap. in various stages of vegetative growth. Their structures have been established by a study of PMR spectra, physicochemical properties, and the products of chemical transformations: (−)-epicatechin, (−)-epigallocatechin, (−)-epigallocatechin gallate, (+)-catechin, (+)-gallocatechin, proanthocyanidin B-2, (−)-epigallocatechin-(4β−8)-(−)-epicatechin, epigallocatechin gallate-(4β−8)-(−)-epicatechin, proanthocyanidin B-1, and (−)-epicatechin-(4β−8)-gallocatechin.

Proanthocyanidins ofZiziphus jujuba

The catechin and proanthocyanidin compositions of the leaves and bark ofZiziphus jujuba have been studied over the vegetation periods. This has led to the isolation of 16 compounds, including 8 monomeric catechins — (−)-epiafzelechin, (−)-epicatechin, (−)-epigallocatechin, (−)-epicatechin gallate, (−)-epigal-locatechin gallate, (+)-catechin, (+)-catechin gallate, and (+)-gallocatechin; 4 dimeric proanthocyanidins — (−)-epiafzelechin-(4β-8)-(−)-epicatechin, proanthocyanidin B-2, (−)-epicatechin-(4β-8)-(−)-epigallocatechin, and (−)-epiafzelechin-(4β-8)-(−)-epigallocatechin; and 4 oligomeric proanthocyanidins consisting of epiafzelechin, epigallocatechin, catechin, and epicatechin with different degrees of polymerization. Their structures have been established by a study of PMR and13C NMR spectra and the products of chemical transformation.

Polycyclic aromatic hydrocarbons: Products of chemical and biochemical transformation of Alicyclic precursors

Abstract The range of polycyclic aromatic hydrocarbons produced by biogenic reactions from steroids and terpenoids is summarized, and plausible chemical and biochemical transformation reactions for their formation proposed. The problem of microbiological synthesis of PAHs is briefly noted together with procedures for the structural determination of biogenic PAHs and comments on their possible environmental significance.

A Review Of Recent Studies On The Sources Of Hazardous Compounds Emitted From Solid Waste Landfills: A U.S. Experience

Municipal solid waste landfills operating in the United States receive a large variety of materials generated by an industrialized, "throwaway" society. As a result, liquid and gas emissions (produced during the normal decomposition processes occurring within the landfill) are often contaminated with hazardous compounds. The presence of hazardous pollutants in liquid and gaseous emissions is well documented, however, the source of these pollutants is not always apparent. Potential sources of these hazardous contaminants in municipal solid waste landfills may include small quantity generators of hazardous wastes, household hazardous wastes, wastes disposed prior to the 1980 enactment of U.S. hazardous waste disposal legislation, and biological and chemical transformation products of buried refuse. Source identification will facilitate characterization and quantification of emissions necessary for the design and operation of leachate gas collection and treatment facilities.

A Review of Recent Studies On the Sources of Hazardous Compounds Emitted From Solid Waste Landfills: a U.S. Experience

Municipal solid waste landfills operating in the United States receive a large variety of materials generated by an industrialized, "throwaway" society. As a result, liquid and gas emissions (produced during the normal decomposition processes occurring within the landfill) are often contaminated with hazardous compounds. The presence of hazardous pollutants in liquid and gaseous emissions is well documented, however, the source of these pollutants is not always apparent. Potential sources of these hazardous contaminants in municipal solid waste landfills may include small quantity generators of hazardous wastes, household hazardous wastes, wastes disposed prior to the 1980 enactment of U.S. hazardous waste disposal legislation, and biological and chemical transformation products of buried refuse. Source identification will facilitate characterization and quantification of emissions necessary for the design and operation of leachate gas collection and treatment facilities.

Insulin compatibility with polymer materials used in external pump infusion systems.

In a study designed to mimic actual user conditions for external insulin pump infusion, the insulin quality after passage through the infusion set was assessed by various analytical methods, including high performance liquid chromatography. The two infusion sets tested consisted of, firstly, a polyvinylchloride/rubber syringe and a polyvinylchloride catheter sterilized by gamma irradiation and, secondly, a polyethylene/polypropylene syringe connected to a polyethylene catheter and sterilized by ethylene oxide. The insulin solution delivered through the PVC infusion set showed a reduction of preservative to less than 30% of the initial content and increased formation of chemical transformation products of insulin varying from twice the reference level during the first day to more than three times on the third day. By contrast, the polyethylene/polypropylene infusion system showed only a minor decrease in preservative content and no increase in chemical transformation. These effects were observed irrespective of the brand of insulin and were not affected by increase of the zinc content of the insulin solution. Investigation of the influence of the sterilization methods performed on polyvinylchloride and polyethylene catheters revealed that gamma irradiated polyvinylchloride catheters were markedly harmful to the insulin solution, whereas ethylene oxide sterilization did not influence the chemical stability of insulin.

Further seco-labdanes from Hebeclinium macrophyllum

A reinvestigation of the aerial parts of Hebeclinium macrophyllum afforded in addition to known compounds several further seco-labdane derivatives; all being epimeric pairs at C-5. The structures were elucidated by high field NMR techniques. The stereochemistry was assigned by NOE difference spectroscopy and the absolute configurations were deduced from the Cotton-effects of the natural compounds and of chemical transformation products.

Alkaloids ofFumaria indica: Further Studies on Narceimine and Narlumidine

The structures of the FUMARIA INDICA alkaloids narceimine and narlumidine, earlier proposed by us, have been substantiated by further chemical reactions and characterisation of chemical transformation products. Isolation and characterisation of two naturally occurring alkaloid salts, protopine nitrate and tetrahydrocoptisine hydrochloride, along with (+)-adlumidine, norsanguinarine and an uncharacterised alkaloid, C (20)H (17)NO (6) (M (+) 367), mp 250-251 degrees C, from the same plant are also reported.

Regularities of initiation of deep polymerization of methyl methacrylate using benzoyl peroxide

A study was made of deep polymerization of methyl methacrylate in benzene and acetonitrile. The rate constant of decomposition of benzoyl peroxide is practically independent of the presence of polymer in the reaction medium and the degree of monomer conversion. With the same viscosity values of the reaction mixture the efficiency of initiation in benzene decreases with a reduction of monomer concentration. The breakdown of benzoyl peroxide during the process is accelerated in acetonitrile, which is due to the effect of products of chemical transformations of the solvent.

The structure of nocamycin, a new antitumor antibiotic.

The structure of nocamycin, a new antitumor antibiotic, has been elucidated with the aid of mass- and PMR-spectroscopic investigation of the antibiotic and its various chemical transformation products. Nocamycin is structurally related to tirandamycins.

Antitumor activity of some microbial and chemical transformation products of anguidine (4,15-diacetoxyscirpene-3-ol)

The in vivo antitumor activities, as measured by inhibition of transplanted P-388 and L-1210 leukemia in mice, have been determined for a series of analogs of anguidine including triacetoxyscirpenol, the three diacetoxyscirpenols, the three monoacetoxyscirpenols, and scirpenetriol. An acetoxy function at position 15 appears to be required for good activity.

Fexeridin and fexerinin — New esters fromFerula xeromorpha

The new esters fexeridin and fexerinin have been isolated from the roots ofFerula xeromorpha Eug. Kor. On the basis of the products of chemical transformations and spectral characteristics, it has been established that fexerinin is an ester of juniferol with vanillic acid at C2, and fexeridin is an ester of vanillic acid and 1,1,4,8-tetramethylcycloundec-3-ene-2,5,8-triol.

The structures of juniferin and juniferinin

Two new esters of the new sesquiterpene alcohol juniferol — juniferin and juniferinin — have been isolated from the roots ofFerula juniperina. On the basis of the products of chemical transformations and spectral characteristics the structure of 2,5-dihydroxy-1,1,4,8-tetramethylcycloundeca-3,7-diene has been proposed for juniferol.

Structures of angrendiol, ferolin, and chimganidin

On the basis of the results of a study of the products of chemical transformations and spectra, the structure of angrendiol has been established as 4,8-dihydroxygermacra-1(10), 5(6)-diene. It has been shown that ferolin and chimganidin are monoesters of angrendiol with parahydroxybenzoic and vanillic acids, respectively, at the secondary hydroxy group.