Evidence of ochratoxin A conjugates in urine samples from infants and adults
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Ochratoxin A (OTA), a mycotoxin with nephrotoxic and carcinogenic properties, is an important contaminant of food and feed. Analysis of OTA in human biological fluids (blood, urine, or breast milk) has documented frequent exposure to this mycotoxin, yet at quite variable levels in different population groups across the world. Urine is the preferred matrix in biomonitoring since sample collection is non-invasive and better accepted by study participants. As only a small fraction of the ingested OTA is excreted in urine, determination of urinary OTA requires sensitive analytical techniques, and phase-II-metabolites should be also considered as biomarkers of exposure. Yet, data published so far on the presence of OTA-glucuronide/sulfate in human urine have been contradictory. In this study, urines (n = 38) from two groups of breastfed infants (German and Turkish) and from German adults were now analysed for the presence of OTA glucuronides or sulfates by an indirect method, i.e. by comparing the levels of OTA (aglycone) in urines without and after enzymatic hydrolysis with ß-glucuronidase/arylsulfatase. Additionally, ochratoxin A-8-β-glucuronide and open lactone ochratoxin A-8-β-glucuronide were synthesized to serve as reference materials for metabolite analysis. Attempts for definitive confirmation of glucuronides of OTA via direct identification in LC–MS/MS analysis were hampered by the lower ionizability of the conjugates compared to the parent compound. Considerable increases in OTA levels were found after enzymatic hydrolysis in several (not all) urine samples and provide clear evidence for the excretion of OTA-conjugates. The latter observation is of importance, since OTA phase-II-metabolites may escape detection when direct methods are applied for urinary biomarker analysis. In conclusion, enzymatic hydrolysis of urine samples is highly advisable in order to avoid an underestimation of the OTA-exposure.
KeywordsOchratoxin A Ochratoxin A-glucuronide Biomonitoring Urine
The authors want to thank Iris Glaeser (IfADo) for their technical help and Dr. Meinolf Blaszkewicz for his comments on an earlier version of this manuscript. Finally, we want to thank DAAD and CONICYT for their support.
Conflict of interest
Source of funding
This study was funded by Leibniz Research Centre for Working Environment and Human Factors (IfADo).
- Ali N, Blaszkewicz M, Manirujjaman M, Degen GH (2016) Biomonitoring of concurrent exposure to ochratoxin A and citrinin in pregnant women in Bangladesh. Mycotoxin Res:1–10Google Scholar
- Castegnaro M, Maru V, Petkova-Bocharova T, Nikolov I, Bartsch H (1991) Concentrations of ochratoxin A in the urine of endemic nephropathy patients and controls in Bulgaria: lack of detection of 4-hydroxyochratoxin A. IARC Scie Publ (115):165–169Google Scholar
- Croom E (2012) Chapter three—metabolism of xenobiotics of human environments. In: Ernest H (ed) Progress in molecular biology and translational science, vol 112. Academic Press, p 31–88Google Scholar
- Degen GH (2015) Are we ready to estimate daily ochratoxin A intake based on urinary concentrations? Environ Int. in press. doi: 10.1016/j.envint.2015.10.010)
- EFSA (2006) Opinion of the scientific panel on contaminants in the food chain on a request from the commission related to ochratoxin A in food. The EFSA Journal 365:56Google Scholar
- Malir F, Ostry V, Dofkova M, Roubal T, Dvorak V, Dohnal V (2013) Ochratoxin A levels in blood serum of Czech women in the first trimester of pregnancy and its correspondence with dietary intake of the mycotoxin contaminant. Biomarkers 18(8):673–678. doi: 10.3109/1354750x.2013.845609 CrossRefPubMedGoogle Scholar
- Muñoz K (2012) Development of biomonitoring methods for the mycotoxin ochratoxin A and their application to assess infants’ exposure with human milk. Dissertation, Technische Universität DortmundGoogle Scholar
- Muñoz K, Blaszkewicz M, Degen GH (2010) Simultaneous analysis of ochratoxin A and its major metabolite ochratoxin alpha in plasma and urine for an advanced biomonitoring of the mycotoxin. J Chromatogr B Analyt Technol Biomed Life Sci 878(27):2623–2629. doi: 10.1016/j.jchromb.2009.11.044 CrossRefPubMedGoogle Scholar
- Pena A, Seifrtova M, Lino C, Silveira I, Solich P (2006) Estimation of ochratoxin A in Portuguese population: new data on the occurrence in human urine by high performance liquid chromatography with fluorescence detection. Food Chem Toxicol 44(9):1449–1454. doi: 10.1016/j.fct.2006.04.017 CrossRefPubMedGoogle Scholar
- Solfrizzo M, Gambacorta L, Lattanzio VT, Powers S, Visconti A (2011) Simultaneous LC–MS/MS determination of aflatoxin M1, ochratoxin A, deoxynivalenol, de-epoxydeoxynivalenol, α and β-zearalenols and fumonisin B1 in urine as a multi-biomarker method to assess exposure to mycotoxins. Anal Bioanal Chem 401(9):2831–2841. doi: 10.1007/s00216-011-5354-z CrossRefPubMedGoogle Scholar
- Stazi F, Palmisano G, Turconi M, Clini S, Santagostino M (2004) Accelerated Koenigs-Knorr glucuronidation of a deactivated nitrophenol: unveiling the role of polyamine additive 1,1,4,7,10,10-hexamethyltriethylenetetramine through design of experiments. J Org Chem 69(4):1097–1103. doi: 10.1021/jo035285n CrossRefPubMedGoogle Scholar
- Walker R (2002) Risk assessment of ochratoxin: current views of the European Scientific Committee on Food, the JECFA and the Codex Committee on Food Additives and Contaminants Mycotoxins and Food Safety. Springer, p:249–255Google Scholar