RESUMEN
A new polyene pigment, melanocrocin, has been isolated either from fruit bodies or mycelial cultures of the subterranean fungus Melanogaster broomeianus. The structure of the pigment was determined by spectroscopic methods and chemical transformations. Melanocrocin is the N-acyl derivative of L-phenylalanine methyl ester with a polyolefinic carboxylic acid.
Asunto(s)
Basidiomycota/química , Fenilalanina/química , Polienos/química , Cromatografía en Capa Delgada , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Conformación Molecular , Estructura Molecular , Fenilalanina/análogos & derivados , Fenilalanina/aislamiento & purificación , Polienos/aislamiento & purificación , Espectrometría de Masa por Ionización de Electrospray/métodosRESUMEN
Feeding experiments with 13C- and fluorine-labelled precursors were performed to reveal the biosynthesis of 2-aminobenzaldehyde in flowers of Robinia pseudoacacia and Philadelphus coronarius. The results are in agreement with the transformation of anthranilic acid to indole followed by oxidative ring opening and hydrolysis of the resulting N-formyl-2-aminobenzaldehyde. This route differs from that observed in Hebeloma sacchariolens (Basidiomycetes) in which anthranilic acid is directly reduced to 2-aminobenzaldehyde.
Asunto(s)
Asteraceae/metabolismo , Benzaldehídos/metabolismo , Rosales/metabolismo , Biotransformación , Isótopos de Carbono , Flúor , Oxidación-Reducción , Tallos de la Planta/metabolismo , ortoaminobenzoatos/metabolismoRESUMEN
The ring expansion of 3-hydroxyindolin-2-one to 2-hydroxy-1,4-benzoxazin-3-one (HBOA) was investigated by labelling experiments. Action of the cytochrome P450 enzyme BX4 from maize on 3-hydroxyindolin-2-one under an 18O2 atmosphere induced production of 2-hydroxy-1,4-benzoxazin-3-one in which the ring oxygen--but not the 2-hydroxy group of HBOA--is labelled. A mechanism for this transformation is proposed.
Asunto(s)
Sistema Enzimático del Citocromo P-450/metabolismo , Indoles/metabolismo , Oxazinas/metabolismo , Zea mays/metabolismo , Benzoxazinas , Biotransformación , Espectrometría de Masas , Conformación Molecular , Estructura Molecular , Isótopos de OxígenoRESUMEN
Lipid peroxidation (LPO) processes observed in diseases connected with inflammation involve mainly linoleic acid. Its primary LPO products, 9-hydroperoxy-10,12-octadecadienoic acid (9-HPODE) and 13-hydroperoxy-9,11-octadecadienoic acid (13-HPODE), decompose in multistep degradation reactions. These reactions were investigated in model studies: decomposition of either 9-HPODE or 13-HPODE by Fe(2+) catalyzed air oxidation generates (with the exception of corresponding hydroxy and oxo derivatives) identical products in often nearly equal amounts, pointing to a common intermediate. Pairs of carbonyl compounds were recognized by reacting the oxidation mixtures with pentafluorobenzylhydroxylamine. Even if a pure lipid hydroperoxide is subjected to decomposition a great variety of products is generated, since primary products suffer further transformations. Therefore pure primarily decomposition products of HPODEs were exposed to stirring in air with or without addition of iron ions. Thus we observed that primary products containing the structural element R-CH=CH-CH=CH-CH=O add water and then they are cleaved by retroaldol reactions. 2,4-Decadienal is degraded in the absence of iron ions to 2-butenal, hexanal and 5-oxodecanal. Small amounts of buten-1,4-dial were also detected. Addition of m-chloroperbenzoic acid transforms 2,4-decadienal to 4-hydroxy-2-nonenal. 4,5-Epoxy-2-decenal, synthetically available by treatment of 2,4-decadienal with dimethyldioxirane, is hydrolyzed to 4,5-dihydroxy-2-decenal.
Asunto(s)
Aldehídos/análisis , Compuestos Epoxi/análisis , Ácido Linoleico/química , Aire , Aldehídos/síntesis química , Arteriosclerosis/metabolismo , Cationes Bivalentes , Cromatografía Líquida de Alta Presión , Compuestos Epoxi/síntesis química , Cromatografía de Gases y Espectrometría de Masas , Humanos , Hidroxilaminas , Hierro , Ácido Linoleico/metabolismo , Ácidos Linoleicos/química , Peroxidación de Lípido , Peróxidos Lipídicos/química , Lipooxigenasa/química , Espectroscopía de Resonancia Magnética , Modelos Químicos , Estructura Molecular , Oxidación-ReducciónRESUMEN
Auxin biosynthesis was analyzed in a maize (Zea mays) kernel culture system in which the seeds develop under physiological conditions similar to the in vivo situation. This system was modified for precursor feeding experiments. Tryptophan (Trp) is efficiently incorporated into indole-3-acetic acid (IAA) with retention of the 3, 3' bond. Conversion of Trp to IAA is not competed by indole. Labeling with the general precursors [U-(13)C(6)]glucose and [1, 2-(13)C(2)]acetate followed by retrobiosynthetic analysis strongly suggest that Trp-dependent IAA synthesis is the predominant route for auxin biosynthesis in the maize kernel. The synthesis of IAA from indole glycerol phosphate and IAA formation via condensation of indole with an acetyl-coenzyme A or phosphoenolpyruvate derived metabolite can be excluded.
Asunto(s)
Ácidos Indolacéticos/biosíntesis , Ácidos Indolacéticos/metabolismo , Reguladores del Crecimiento de las Plantas/metabolismo , Semillas/metabolismo , Zea mays/metabolismo , Aminoácidos/análisis , Cromatografía de Gases y Espectrometría de Masas , Espectroscopía de Resonancia Magnética , Reguladores del Crecimiento de las Plantas/biosíntesis , Triptófano/metabolismoRESUMEN
Catalytic amounts of Fe2+ or Fe3+ ions are widely applied to induce simulated biological lipid peroxidation reactions. Independently, whether Fe2+ or Fe3+ were used, similar products were obtained. We show in this paper that the product spectrum is indeed very different, whether one ion species, either Fe2+ or Fe3+, is present in excess; thus, decomposition of (13S,9Z,11E) 13-hydroxyperoxy-9, 11-octadecadienoic acid (13S-HPODE) generates in the presence of equimolar amounts of Fe2+ ions mainly the corresponding alcohol (13S, 9Z,11E) 13-hydroxy-9,11-octadecadienoic acid besides 12,13-epoxy-11-hydroxy-9-octadecenoic acid (12,13-epHOD) and 13-oxo-9,11-octa-decadienoic acid (13-KODE), while decomposition of 13S-HPODE with equimolar amounts of Fe3+ produces mainly 12,13-epHOD, hydrolysis products thereof and other oxidized products, e.g., hydroxyoxo acids. In addition, unusually large amounts of aldehydes are formed, e.g., the amount of 4-hydroxy-nonenal was found to exceed that obtained by Fe2+ induced air oxidation for a factor of about 100. Since these further oxidation products are suspected to cause cell damage, liberated Fe3+ ions seem to be responsible for generation of toxic products in inflammatory diseases, e.g., atherosclerosis.