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Toxins 2018, 10(7), 256; https://doi.org/10.3390/toxins10070256

Interaction of Ochratoxin A and Its Thermal Degradation Product 2′R-Ochratoxin A with Human Serum Albumin

1
Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstr. 45, 48149 Münster, Germany
2
Department of Pharmacology, Faculty of Pharmacy, University of Pécs, Szigeti út 12, H-7624 Pécs, Hungary
3
János Szentágothai Research Center, Ifjúság Útja 20, H-7624 Pécs, Hungary
4
Institute of Pharmaceutical and Medicinal Chemistry, Department of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany
5
John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC) & Institute for Complex Systems-Structural Biochemistry (ICS 6), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Str., 52425 Jülich, Germany
6
Department of General and Physical Chemistry, University of Pécs, Ifjúság útja 6, H-7624 Pécs, Hungary
7
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Pécs, Rókus utca 2, H-7624 Pécs, Hungary
*
Author to whom correspondence should be addressed.
Received: 8 June 2018 / Revised: 14 June 2018 / Accepted: 20 June 2018 / Published: 22 June 2018
(This article belongs to the Collection Ochratoxins-Collection)
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Abstract

Ochratoxin A (OTA) is a toxic secondary metabolite produced by several fungal species of the genus Penicillium and Aspergillus. 2′R-Ochratoxin A (2′R-OTA) is a thermal isomerization product of OTA formed during food processing at high temperatures. Both compounds are detectable in human blood in concentrations between 0.02 and 0.41 µg/L with 2′R-OTA being only detectable in the blood of coffee drinkers. Humans have approximately a fifty-fold higher exposure through food consumption to OTA than to 2′R-OTA. In human blood, however, the differences between the concentrations of the two compounds is, on average, only a factor of two. To understand these unexpectedly high 2′R-OTA concentrations found in human blood, the affinity of this compound to the most abundant protein in human blood the human serum albumin (HSA) was studied and compared to that of OTA, which has a well-known high binding affinity. Using fluorescence spectroscopy, equilibrium dialysis, circular dichroism (CD), high performance affinity chromatography (HPAC), and molecular modelling experiments, the affinities of OTA and 2′R-OTA to HSA were determined and compared with each other. For the affinity of HSA towards OTA, a logK of 7.0–7.6 was calculated, while for its thermally produced isomer 2′R-OTA, a lower, but still high, logK of 6.2–6.4 was determined. The data of all experiments showed consistently that OTA has a higher affinity to HSA than 2′R-OTA. Thus, differences in the affinity to HSA cannot explain the relatively high levels of 2′R-OTA found in human blood samples. View Full-Text
Keywords: ochratoxin A; 2′R-ochratoxin A; mycotoxin; human serum albumin; dialysis; fluorescence spectroscopy; circular dichroism; high performance affinity chromatography; molecular modelling ochratoxin A; 2′R-ochratoxin A; mycotoxin; human serum albumin; dialysis; fluorescence spectroscopy; circular dichroism; high performance affinity chromatography; molecular modelling
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Sueck, F.; Poór, M.; Faisal, Z.; Gertzen, C.G.W.; Cramer, B.; Lemli, B.; Kunsági-Máté, S.; Gohlke, H.; Humpf, H.-U. Interaction of Ochratoxin A and Its Thermal Degradation Product 2′R-Ochratoxin A with Human Serum Albumin. Toxins 2018, 10, 256.

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