Showing papers on "Citral published in 1991"

The metabolism of 3,7-dimethyl-2,6-octadienal (citral) in rat hepatic mitochondrial and cytosolic fractions. Interactions with aldehyde and alcohol dehydrogenases.

Abstract: Citral (3,7-dimethyl-2,6-octadienal), a flavoring and fragrance agent, is associated with a variety of biochemical and toxicological effects. Reports of the in vivo metabolism of citral suggest that a primary route of metabolism is conversion to the corresponding acid species presumably by aldehyde dehydrogenases (ALDH). In the present study, hepatic mitochondrial and cytosolic fractions were prepared from male Sprague-Dawley rats to assess in vitro metabolism of citral. Evidence of ALDH-mediated citral oxidation was not seen in either subcellular fraction. On the contrary, citral was found to be a potent inhibitor of acetaldehyde oxidation by the low-KM mitochondrial form of ALDH. Measurement of the in vitro acetaldehyde oxidation rates of this isozyme in the presence of citral lead to the estimation of a Ki of 360 nM. Further studies of citral effects on low-KM mitochondrial ALDH indicate that inhibition is by a linear mixed-type mechanism and does not involve citral binding at the NAD+ binding site. In addition, it was observed that citral was readily reduced to the corresponding alcohol by alcohol dehydrogenase (ADH) in the cytosolic fraction. The reduction of citral in the presence of NADH proceeded at two distinct rates; an initial "fast" rate followed by a "slow" rate. Individual kinetic constants were calculated for the two rates. It is possible that the differential ADH-mediated reduction rates of citral are the result of varying affinities for the enzyme of the two citral isomers, geranial (trans) and neral (cis).(ABSTRACT TRUNCATED AT 250 WORDS)

Surface Organometallic Chemistry on Metals: Selective Hydrogenation of Citral into Geraniol and Nerol on Tin Modified Silica Supported Rhodium.

Abstract: A bi-metallic Rh-Sn(n-C 4 H 9 ) 2 /SiO 2 catalyst, obtained by the organometallic route, has been found to be extremely active and selective in the hydrogenation of citral (A: geranial and b: neral) to the corresponding unsaturated alcohols (geraniol and nerol). The synthesis of the “bimetallic catalyst” from the organometallic precursor as well as the kinetics of hydrogenation is described. A tentative explanation for the extremely high chemoselectivity (96% at 100% conversion) for the hydrogenation of the C=O double bond is given.

Acyloin condensation of acyclic unsaturated aldehydes byMucor species

Abstract: 2E,6Z-Nonadienal, 2E,4E-nonadienal, citral and geraniol as precursors of geranial from acyloins enzymatically by reaction with activated acetate during fermentation by Mucor circinelloides CBS 39 468. The acyloins were reduced immediately by the fungus to (2S,3R)-diols. Reduction of the aldehyde group, including hydrogenation of the conjugated C-C double bond, hydroxylation of these alcohols and of the formed diols and some cyclizations are found as side reactions.

Composition for mite control

Abstract: PURPOSE:To provide the subject composition excellent in the controlling effect on mite living indoors, also highly safe to human. CONSTITUTION:The objective composition containing, as active ingredient(s), at least one kind of compound selected from citronellal, methyl salicylate, butyl salicylate, benzyl propionate, isoeugenol, benzyl acetate, ethyl isovanillate, geranyl acetate, citral, isosulphol, and beta-phenethyl acetate.

α-hydroxy-acids, preparation process and the use thereof

Abstract: The present invention relates to novel α-hydroxyacids of the general formula (I), to the process of preparing them and to the use thereof as intermediates allowing access to homologous lower aldehydes (such as prenal or citral) by oxidative decarboxylation. ##STR1##

Special Methods for the Essential Oil of Ginger

Abstract: Ginger oil is produced by steam or hydrodistillation of ground rhizomes of Zingiber officinale Roscoe (Zingiberaceae). It is valued for its pleasant, aromatic, more or less lemony odor. Ginger oil finds much use in the food and drink industry, e.g., ginger ale, ginger beer, and various cookies and desserts. The oil is further used in small quantities in the cosmetic, pharmaceutical, and perfume industry. It has still not been clarified which compounds are responsible for the characteristic ginger aroma. The various investigations have all come to different conclusions and in some respects contradict each other. The citral (= geranial and neral combined) content is responsible for the lemony note.

Repellent for aquatic life

Abstract: PURPOSE:To obtain an extremely safe repellent for aquatic life, exhibiting repelling effect against aquatic adhesive life with an extremely small amount and effective for preventing the damage caused by the proliferation or adhesion of the aquatic life by using a monoterpene and/or sesquiterpene as active components CONSTITUTION:The objective agent contains 001-50wt% of monoterpene and/or sesquiterpene (eg limonene, terpineol, citral, citronellal, 1,8-cineole or bisabolene) as active components The active component is used in the form of an antifouling paint by substituting the conventional antifouling agent or in the form of an aqueous solution or emulsion by using a solubilizing agent or an emulsifier Essential oils containing monoterpene and sesquiterpene (eg orange oil, lemon oil and eucalyptus oil) can be used in the similar manner

Selective Hydrogenation of Citral in the Liquid Phase over Unsupported Nickel-Molybdenum Catalysts Nil-xMox.

Abstract: Summary The hydrogenation of citral has been investigated in cyclohexane and in 2-propanol, with un-supported Ni l-x Mo x catalysts, prepared by co-reduction of mixtures of iodides of appropriated composition with naphthalene-sodium as reducing agent. High yields in citronellol were observed in 2-propanol. The selectivity of the different steps in both solvents is discussed using as selectivity criteria the ratios k i b Ni /k J D N for each reaction step (competitive or consecutive). These ratios have been computed by fitting the measured product compositions to the functions obtained by analytical integration of the LANGMUIR-HINSELWOOD rate expressions.

Acyclic isoprenoid 1,3-dieneamines in the Diels-Alder reaction

Abstract: The dieneamines obtained from 3-methyl-2-butenal and citral (Ia) and (Ib, c) enter into [4 + 2]-cycloaddition with monoethyl citrylidenemalonate (II) and prenylidenemalonate (III), respectively, forming the esters of substituted 1,3-cyclohexadiene-1-carboxylic acids with side chains of the isoprenoid type. The same or analogous cyclohexadiene can be obtained from “citral dieneamine” (Ib, c) and typical dienophiles (methyl acrylate, diethyl fumarate, etc.) in a two-stage path, including the initial production of derivatives of 2-amino-3-cyclohexene-1-carboxylic acid in the Diels-Alder reaction and then elimination of the amino group from the cyclic adducts. The isomeric composition of the mixture of cyclic adducts formed in the reaction of (Ib + Ic) with diethyl fumarate under strictly aprotic conditions correlates with the ratio of the structural isomers with a δ3 and δ3(9) bond (Ib, c) in the “citral dieneamine.” In the reaction of the dieneamine with the less reactive methyl acrylate the obtained mixture of cyclic adducts contains a significantly larger fraction of the isomer corresponding to the minor δ3(9) isomer of the dieneamine.

Process for the purification of citral

Abstract: A method is disclosed for separating citral from a mixture. The method comprises the steps of: adjusting the pH of the mixture to greater than about 3 and less than 7; fractionally distilling the resulting mixture to provide a substantially pure citral containing fraction; and recovering the citral containing fraction. The adjustment of the pH substantially inhibits isomerization of the citral to isocitral during fractional distillation.

Method for the preparation of Citral

Abstract: Method for the preparation of citral by vapour phase cracking of the diprenyl acetal of prenal in the presence of an acidic heterogeneous type catalyst.

Cyclodimerization of a citral dienamine

Abstract: The dienamine (a mixture of isomers) obtained from citral and diethylamine is converted to a mixture of citral anhydro cyclodimers by the action of weak proton-donor agents. The principal reaction product corresponds to [4 + 2]-cycloaddition of 1-diethylamino-7-methyl-3-methylene-1,6-octadiene (the minor component in the starting dienamine) to the enimmonium form of the protonated dienamine.

Process for the preparation of citral

Abstract: A process for the preparation of citral by the cracking of prenal diprenyl acetal in a vapor phase in the presence of a heterogeneous type of acid catalyst.