19165-63-0Relevant articles and documents
Pigments of fungi. LXIX.* Total synthesis of (R)-ochratoxin α and the formal total synthesis of ochratoxin A
Donner, Christopher D.,Gill, Melvyn
, p. 213 - 217 (2002)
(R)-Ochratoxin α, the monochiral carboxylic acid component of the biologically active dipeptide ochratoxin A, is synthesized for the first time over nine steps from (R)-propylene oxide. The method constitutes a versatile and general route to functionalized dihydroisocoumarins.
Identification and in vitro cytotoxicity of ochratoxin A degradation products formed during coffee roasting
Cramer, Benedikt,Koenigs, Maika,Humpf, Hans-Ulrich
, p. 5673 - 5681 (2008)
The mycotoxin ochratoxin A is degraded by up to 90% during coffee roasting. In order to investigate this degradation, model heating experiments with ochratoxin A were carried out, and the reaction products were analyzed by HPLC-DAD and HPLC-MS/MS. Two ochratoxin A degradation products were identified, and their structure and absolute configuration were determined. As degradation reactions, the isomerization to 14-(R)-ochratoxin A and the decarboxylation to 14-decarboxy-ochratoxin A were identified. Subsequently, an analytical method for the determination of these compounds in roasted coffee was developed. Quantification was carried out by HPLC-MS/MS and the use of stable isotope dilution analysis. By using this method for the analysis of 15 coffee samples from the German market, it could be shown that, during coffee roasting, the ochratoxin A diastereomer 14-(R)-ochratoxin A was formed in amounts of up to 25.6% relative to ochratoxin A. The decarboxylation product was formed only in traces. For toxicity evaluations, first preliminary cell culture assays were performed with the two new substances. Both degradation products exhibited higher IC50 values and caused apoptotic effects with higher concentrations than ochratoxin A in cultured human kidney epithelial cells. Thus, these cell culture data suggest that the degradation products are less cytotoxic than ochratoxin A.
A kinetic study into the hydrolysis of the ochratoxins and analogues by carboxypeptidase A
Stander,Steyn,Van der Westhuizen,Payne
, p. 302 - 304 (2001)
The hydrolyses of the ochratoxins and analogues by carboxypeptidase A were assessed. This was done by measuring the amount of phenylalanine formed with liquid chromatography coupled to tandem electrospray mass spectrometry. The kinetic data of ochratoxin A, ochratoxin B, and the synthetic bromo-ochratoxin B were compared to the values of a number of synthesized structure analogues, namely, ochratoxin A methyl ester, ochratoxin B methyl ester, N-(2-hydroxybenzoyl)phenylalanine, N-(5-chloro-2-hydroxybenzoyl)phenylalanine, N-(5-bromo-2-hydroxybenzoyl)phenylalanine, and N-(5-fluoro-2-hydroxybenzoyl)phenylalanine. The halogen-containing analogues had lower turnovers than their des-halo analogues. There are no substantial differences in the kinetic data between the different halogen-containing analogues.
Structural and functional characterization of ochratoxinase, a novel mycotoxin-Degrading enzyme
Dobritzsch, Doreen,Wang, Huaming,Schneider, Gunter,Yu, Shukun
, p. 441 - 452 (2014)
Ochratoxin, with ochratoxin A as the dominant form, is one of the five major mycotoxins most harmful to humans and animals. It is produced by Aspergillus and Penicillium species and occurs in a wide range of agricultural products. Detoxification of contaminated food is a challenging health issue. In the present paper we report the identification, characterization and crystal structure (at 2.2 A) of a novel microbial ochratoxinase from Aspergillus niger. A putative amidase gene encoding a 480 amino acid polypeptide was cloned and homologously expressed in A. niger. The recombinant protein is N-terminally truncated, thermostable, has optimal activity at pH ~6 and 66°C, and is more efficient in ochratoxin A hydrolysis than carboxypeptidase A and Y, the two previously known enzymes capable of degrading this mycotoxin. The subunit of the homo-octameric enzyme folds into a two-domain structure characteristic of a metal dependent amidohydrolase, with a twisted TIM (triosephosphateisomerase)- barrel and a smaller β-sandwich domain. The active site contains an aspartate residue for acid-base catalysis, and a carboxylated lysine and four histidine residues for binding of a binuclear metal centre.
Efficient synthesis of (R)-ochratoxin alpha, the key precursor to the mycotoxin ochratoxin A
Lenz, Cesar Antonio,Rychlik, Michael
, p. 883 - 886 (2013/02/25)
Two new routes for the synthesis of enantiomerically pure ochratoxin alpha ((3R)-OTα) are presented, which is the key intermediate for the synthesis of ochratoxin A (OTA) by coupling reaction with the amino acid l-phenylalanine. The key step of both routes is the one pot directed ortho-metalation/alkylation/ lactonization of unprotected and suitably functionalized aromatic carboxylic acids, using lithium tetramethylpiperidide (LTMP) and (R)-propylene oxide.
