scholarly journals Isolation of oligomers of 5,6-dihydroxyindole-2-carboxylic acid from the eye of the catfish

1974 ◽  
Vol 143 (1) ◽  
pp. 207-217 ◽  
Author(s):  
Shosuke Ito ◽  
J. A. Colin Nicol
Keyword(s):  
Carboxylic Acid ◽  
Methyl Ester ◽  
Methyl Esters ◽  
Tricarboxylic Acid ◽  
Oxidation Products ◽  
Molecular Weight Determination ◽  
Mushroom Tyrosinase ◽  
Natural Pigment ◽  
Elemental Analyses ◽  
Tapetum Lucidum

The reflecting material of the tapetum lucidum of the sea catfish (Arius felis) was chromatographed on Sephadex LH-20 in methanol–dimethyl sulphoxide–formic acid. Two components were present: one, showing an absorption maximum at 330nm, was tapetal pigment; the other, at 257nm, was an associated nucleoside. The tapetal pigment was extracted in methanol–HCl and isolated by adsorption chromatography on Sephadex LH-20. It yielded a methoxy methyl ester on treatment with diazomethane, and permanganate oxidation gave pyrrole-2,3,5-tricarboxylic acid. From the information provided by u.v. and i.r. spectra of the pigment and its methoxy methyl ester, from elemental analyses and from the oxidation products, we suggest that the tapetal pigment is derived from oxidative coupling of 5,6-dihydroxyindole-2-carboxylic acid. A molecular-weight determination and chromatography of the methoxy methyl ester indicate that the pigment is a mixture of oligomers, among which the tetramers probably predominate. We consider that the monomers are joined mainly by C-C linkages at positions 4 and 7. A synthetic pigment having spectral properties nearly identical with those of the natural pigment was prepared by enzymic oxidation of 5,6-dihydroxyindole-2-carboxylic acid with mushroom tyrosinase. The identity of the tapetal pigment with the synthetic pigment was further confirmed by comparing u.v. and i.r. spectra of their methoxy methyl esters. Formation of the tapetal pigment from tyrosine and relationships of the tapetal pigment to melanin are discussed.

Juvenile Hormone Analogs in Conifers. II. Isolation, Identification, and Biological Activity of cis-4-[1′(R)-5′-Dimethyl-3′-oxohexyl]-cyclohexane-1-carboxylic Acid and (+)-4(R)-[1′(R)-5′-Dimethyl-3′-oxohexyl]-1-cyclohexene-1-carboxylic Acid from Douglas-fir Wood

1974 ◽  
Vol 52 (7) ◽  
pp. 1192-1199 ◽  
Author(s):  
I. H. Rogers ◽  
J. F. Manville ◽  
T. Sahota
Keyword(s):  
Carboxylic Acid ◽  
Methyl Ester ◽  
Juvenile Hormone ◽  
Methyl Esters ◽  
Petroleum Ether Extract ◽  
Douglas Fir ◽  
Ether Extract ◽  
Biological Assays ◽  
Hormone Analogs ◽  
Derivatives Of

The petroleum ether extract from the whole-wood meal of a number of British Columbia Interior-Intermediate variety Douglas-fir trees have yielded two carboxylic acids (+)-todomatuic acid (3b) and cis-dihydrotodomatuic acid (4b) which as their methyl esters are potentially useful juvenile hormone analogs. These compounds possess the R,R and R stereoconfigurations, respectively. The configuration at C-1′ is opposite to that reported by others for "(+)-juvabione" isolated from Abiesbalsamea grown in Czechoslovakia. Whereas (+)-juvabione naturally occurs as and is the methyl ester of (+)-todomatuic acid (4b), in this variety of Douglas-fir these compounds appear as the free acids. Results of biological assays on certain insects indicate that the methyl ester derivatives of these acids are effective ovicides and juvenilizing hormones.

scholarly journals Influence of Oryzanols Concentrate on the Oxidation of Methyl Ester Linoleic Acid and Study of Their Oxidation Products

2019 ◽  
Vol 8 (4) ◽  
pp. 37
Author(s):  
Bruno Irigaray ◽  
Iván Jachmanián ◽  
María A. Grompone
Keyword(s):  
Linoleic Acid ◽  
Methyl Ester ◽  
Sunflower Oil ◽  
Rice Bran Oil ◽  
Methyl Esters ◽  
Acid Methyl Ester ◽  
Oxidation Products ◽  
Antioxidant Power ◽  
Linoleic Acid Methyl Ester ◽  
Acid Methyl

Oryzanols are frequently found in rice bran oil but almost completely removed in the neutralization step when the oil is chemically refined. In this way, oryzanols can be recovered from the soapstocks to generate a concentrate. Thereby, they could be used as antioxidants in lipids for specific purposes. In the present work the antioxidant power of oryzanols concentrate (33% purity) was studied together with pure oryzanols and butylhydroxytoulene (BHT). Methyl esters were prepared from regular sunflower oil without antioxidants to which the antioxidants before mentioned were added in an effective concentration of 3x10-3 M. The samples were oxidized in a heating block with oxygen flow and the hydroperoxides of linoleic acid methyl ester were analyzed. It was observed that all antioxidants were able to protect the sunflower oil methyl esters from oxidation with respect to methyl esters without antioxidants. Oryzanols presented a notoriously lower protection ability compared to BHT. However, the formation of the linoleic acid methyl ester hydroperoxides and their proportion, for the same oxidation stage, did not show differences between the antioxidants used. Therefore, the oxidation kinetics were similar between the different antioxidants studied.

New Cyclodimerization Reaction of (3,5-Di-tert-butyl-4-oxocyclohexa-2,5-dienylidene)acetic Acid

2001 ◽  
Vol 66 (8) ◽  
pp. 1250-1256 ◽  
Author(s):  
Peter Nesvadba ◽  
Piotr Rzadek ◽  
Günther Rist
Keyword(s):  
Acetic Acid ◽  
Sulfuric Acid ◽  
Carboxylic Acid ◽  
Methyl Ester ◽  
Structure Elucidation ◽  
Methyl Esters ◽  
Tert Butyl ◽  
Isomeric Methyl

(3,5-Di-tert-butyl-4-oxocyclohexa-2,5-dienylidene)acetic acid 1a underwent on heating a new cyclodimerization reaction affording a 1 : 1 mixture of the racemic cis- and trans-isomeric lactone-acids 2. The decisive structure elucidation of 2 was carried out after its mild esterification with diazomethane and separation of the racemic isomeric methyl esters 3a and 3b. The attempted esterification of 2 with methanol and sulfuric acid gave only the methyl diarylacetate 4. In contrast to 1a, which contains the carboxylic acid functionality no cyclodimerization was observed with the corresponding methyl ester 1b or nitrile 1c.

Activity of Plasmin and Streptokinase-Activator on Substituted Arginine and Lysine Esters

1966 ◽  
Vol 16 (01/02) ◽  
pp. 018-031 ◽  
Author(s):  
S Sherry ◽  
Norma Alkjaersig ◽  
A. P Fletcher
Keyword(s):  
Molecular Structure ◽  
Methyl Ester ◽  
Comparative Studies ◽  
Esterase Activity ◽  
Methyl Esters ◽  
Hydrolytic Activity ◽  
The Other ◽  
Other Hand

SummaryComparative studies have been made of the esterase activity of plasmin and the streptokinase-activator of plasminogen on a variety of substituted arginine and lysine esters. Human plasmin preparations derived by different methods of activation (spontaneous in glycerol, trypsin, streptokinase (SK) and urokinase) are similar in their esterase activity; this suggests that the molecular structure required for such esterase activity is similar for all of these human plasmins. Bovine plasmin, on the other hand, differs from human plasmin in its activity on several of the substrates studied (e.g., the methyl esters of benzoyl arginine and tosyl, acetyl and carbobenzoxy lysine), a finding which supports the view that molecular differences exist between the two animal plasmins. The streptokinase-activator hydrolyzes both arginine and lysine esters but the ratios of hydrolytic activity are distinct from those of plasmin and of other activators of plasminogen. The use of benzoyl arginine methyl ester as a substrate for the measurement of the esterase activity of the streptokinase-activator is described.

scholarly journals Propylphosphonic acid anhydride–mediated amidation of Morita–Baylis–Hillman–derived indolizine-2-carboxylic acids

2021 ◽  
pp. 174751982098715
Author(s):  
Khethobole C Sekgota ◽  
Michelle Isaacs ◽  
Heinrich C Hoppe ◽  
Ronnett Seldon ◽  
Digby F Warner ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Carboxylic Acids ◽  
Coupling Agent ◽  
Methyl Esters ◽  
Acid Anhydride

Propylphosphonic acid anhydride has been successfully used as a coupling agent in the synthesis of a series of indolizine-2-carboxamido derivatives from indolizine-2-carboxylic acid and its 3-acetylated analogue. The acid substrates were obtained by saponification of the corresponding methyl esters produced, in turn, selectively and efficiently, by time-controlled cyclisation of a single Morita–Baylis–Hillman adduct. Various amino and hydrazino compounds with medicinal potential have been used to prepare indolizine-2-carboxamido and hydrazido derivatives.

scholarly journals Evaluation of 3-Methylbutanoic Acid Methyl Ester as a Factor Influencing Flavor Cleanness in Arabica Specialty Coffee

2021 ◽  
Vol 11 (12) ◽  
pp. 5413
Author(s):  
Keiko Iwasa ◽  
Harumichi Seta ◽  
Yoshihide Matsuo ◽  
Koichi Nakahara
Keyword(s):  
Methyl Ester ◽  
Methyl Esters ◽  
Acid Methyl Ester ◽  
Chemical Compounds ◽  
Gas Chromatography Mass Spectrometry ◽  
Arabica Coffee ◽  
Acid Methyl ◽  
Coffee Brew ◽  
Coffee Beans ◽  
Specialty Coffee

This paper reports on the chemical compounds in arabica coffee beans with a high Specialty Coffee Association (SCA) cupping score, especially those in specialty coffee beans. We investigated the relationship between the chemical compounds and cupping scores by considering 16 types of Coffea arabica (arabica coffee) beans from Guatemala (SCA cupping score of 76.5–89.0 points). Non-targeted gas chromatography-mass spectrometry-based chemometric profiling indicated that specialty beans with a high cupping score contained considerable amounts of methyl-esterified compounds (MECs), including 3-methylbutanoic acid methyl ester (3-MBM), and other fatty acid methyl esters. The effect of MECs on flavor quality was verified by spiking the coffee brew with 3-MBM, which was the top-ranked component, as obtained through a regression model associated with cupping scores. Notably, 3-MBM was responsible for the fresh-fruity aroma and cleanness of the coffee brew. Although cleanness is a significant factor for specialty beans, the identification of compounds that contribute to cleanness has not been reported in previous research. The chemometric profiling approach coupled with spiking test validation will improve the identification and characterization of 3-MBM commonly found in arabica specialty beans. Therefore, 3-MBM, either alone or together with MECs, can be used as a marker in coffee production.

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