1304. Mycotoxins. Part II. The constitution of ochratoxins A, B, and C, metabolites of Aspergillus ochraceus wilh

Merwe, K. J. van der; Steyn, Pieter S.; Fourie, L.J.

doi:10.1039/jr9650007083

Cited by 251 publications

(109 citation statements)

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“…d-OA, OE-OA, OM-OA, and OP-OA were synthesized according to Xiao et al (1995Xiao et al ( , 1996; OC was synthesized according to van der Merwe et al (1965avan der Merwe et al ( , 1965b. The molecular weight of OA is 403.…”

Section: Methodsmentioning

confidence: 99%

Free Radical Generation as Induced by Ochratoxin A and Its Analogs in Bacteria (Bacillus brevis)

Hoehler¹,

Marquardt

McIntosh

et al. 1996

Journal of Biological Chemistry

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Lipid peroxidation is considered as one of the manifestations of cellular damage in the toxicity of ochratoxin A (OA). OA; its three natural analogs, OB, OC, and O␣; and four synthetic analogs, d-OA, the ethylamide of OA (OE-OA), O-methylated OA (OM-OA), and the lactoneopened OA (OP-OA) were used to study free radical generation in bacteria with Bacillus brevis as a model system. The uptake of the different ochratoxins by B. brevis varied substantially depending on the molecular structures. Electron paramagnetic resonance spectroscopy using ␣-(4-pyridyl-1-oxide)-N-tert-butyl nitrone as a spin trapping agent showed an enhanced free radical generation due to the addition of OA and most of the analogs. The EPR signals could be further enhanced by the addition of Ca 2؉ , a calcium ionophore and an ATPase uncoupler, whereas they were eliminated by incubating the growing cells with vitamin E. The spin adduct hyperfine splitting constants indicate the presence of ␣-hydroxyethyl radicals resulting from generated hydroxyl radicals, which are trapped by ␣-(4-pyridyl-1-oxide)-N-tertbutyl nitrone. The results further suggest that OA induces free radical production in this model system by enhancing the permeability of the cellular membrane to Ca 2؉ .

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Section: Methodsmentioning

confidence: 99%

Free Radical Generation as Induced by Ochratoxin A and Its Analogs in Bacteria (Bacillus brevis)

Hoehler¹,

Marquardt

McIntosh

et al. 1996

Journal of Biological Chemistry

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“…M erwe e t a 1. (2 ) and Steyn a nd Holzapfel ( 3, 4 ) . I ts ch e mi ca l stru c t u r e co n s i s ts of a s -c mcrc -e-nycrcxy-a , 4 …”

Section: Fluoromet Ri C a Nd S Pectrophotometr Ic S T Ud I E S D E Momentioning

confidence: 99%

Mechanism of ochratoxin a stimulated lipid peroxidation

Omar

Hasinoff

Mejilla

et al. 1990

Biochemical Pharmacology

126

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“…It shows antibiotic and antifungal activity and is one of a small group of metabolites used as taxonomic markers in various Penicillium species. Zeeck and co-workers [4] synthesised (3R,3'R)-xanthomegnin (8) from the corresponding 'monomer', (R)-semixanthomegnin (9), a cometabolite of 8 in T. megnini, however, neither xanthomegnin (8) nor semixanthomegnin (9) had been the subjects of total synthesis prior to our work.…”

Section: Resultsmentioning

confidence: 99%

“…Our synthesis of (R)-semixanthomegnin (9), is shown in Scheme 2. In the knowledge that the stereochemistry of the natural product is (R), our approach began from (R)-propylene oxide (10).…”

Section: Resultsmentioning

confidence: 99%

“…The enantiomeric melleins 12 and 13 are the structural parents of the family and occur themselves in both stereochemical modifications [7,8]. (R)-Ochratoxin A (14), first isolated by Steyn and co-workers [9], is arguably the most dangerous member of the group and has, consequently, been the subject of numerous publications [10]. It occurs in several Penicillium and Aspergillus species and is a powerful nephrotoxin, immunosuppressant, teratogen and carcinogen.…”

Section: Resultsmentioning

confidence: 99%

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