Ochratoxin A formation

Ramakrishna N, Lacey J and Smith J E (1996a), Colonization of barley grain by Penicillium verrucosum and ochratoxin A formation in the presence of competing fungi . J. Food Protect., 59, 1311-1317. 

Ochratoxin A formation in apricot jam has been investigated by Ruhland et al. (1998). Apricot jam prepared conventionally was inoculated with ochratoxin A-producing A. ochraceus and P. verrucosum. Fungal growth was detected after two weeks and mycotoxin production after five weeks. Ochratoxin A contents reached up to 86.3 pg/kg for A. ochraceus and 94.6 pg/kg for P. verrMcosum-inoculated jams. Seven of twelve naturally contaminated jam samples contained 0.09-14.33 pg/kg ochratoxin A. In a market survey, Engel (2000) could not detect ochratoxin A at a concentration higher than 0.1 pg/kg in 42 commercial jam samples. 

Scudamore K A (1999), A Study to Determine Whether On-floor Ambient Drying Systems are Conducive to the Formation of Ochratoxin A in Grain, Home Grown Cereals Authority Project Report 196, UK. 

Coffee has been the focus of many studies regarding formation of ochratoxin A, its destruction during roasting, and its presence in brews. Mechanical color sorting leads to minor reductions in ochratoxin A levels, however steaming produces approximately 25% reduction. The effect of heat on stability is considerable, 80% of ochratoxin is destroyed during bean... 

This NRL sensor was used for fhe rapid detection of Campylobacter jejuni and small toxins, including several mycotoxins [ochratoxin A, fumonisin B, aflafoxin Bi, and deoxynivalenol (DON)] from food pro-ducfs (Ngundi et ah, 2005, 2006 Sapsford et ah, 2006). They used a sandwich immunoassay formaf fo detect C. jejuni in milk and yogurt and a competitive immunoassay format to detect the mycotoxins. 

Three methods are usually adopted for confirmation of ochratoxin A (a) methylation (methods A and B), (b) ammonia derivative formation, and (c) LC-MS confirmation. 

Ammonia derivative formation The derivatization is carried out using a 10% ammonia solution mixed with the column effluent (64). The main advantages are an increase in sensitivity (1.7 times the signal of the underivatized ochratoxin A), and the availability of a confirmation test for ochratoxin A, as a consequence of this change of sensitivity. A second HPLC pump, similar to that described in Fig. 2 for aflatoxins, and a reaction coil of 10 cm are necessary. Conditions are as follows 0.5 ml/min as flow rate, room temperature, excitation wavelength of 370 nm, and emission wavelength... 

In a comparison experiment, the possibility that vitamin C and P-carotene could affect PhIP-DNA adduct formation has been examined. Previous reports have already demonstrated the protective role of vitamin C in certain types of cancer and low intake of foods rich in vitamin C is associated with an increased risk of gastric cancer [100]. Vitamin C prevents DNA adduct formation in mice treated with the mycotoxins ochratoxin A and zearalenone [101]. Wu et al. [102] reported that vitamin C inhibited aiylamine N-acetyltransferase (NAT) activity in human bladder tumor cells. This is one possible mechanism by which vitamin C can attenuate the formation of DNA adducts. It... 

Grosse Y, Chekir-Ghedira L, Hue A, Obrecht-Pflumio S, Dirheimer G, Bacha H, Pfohl-Leszkowicz A. Retinol, ascorbic acid and alpha-tocopherol prevent DNA adduct formation in mice treated with the mycotoxins ochratoxin A and zearalenone. Cancer Lett 1997 114 225-229. 

The metabolism of ochratoxin A was studied in cultured rat and human primary hepatocytes incubated with non-cytotoxic concentrations of PH]ochratoxin A ranging from 10 to 10 mol/l for 8 h. In rat hepatocytes, ochratoxin A was metabolized to small amounts of three products. In addition to 4-hydroxy-ochratoxin A, which is a known product of ochratoxin A biotransformation, two novel metabolites were detected and tentatively identified as hexose and pentose conjugates of ochratoxin A. In vitro induction with 3-methylcholanthrene increased the formation of 4-hydroxy-ochratoxin A but did not alter the formation of the conjugated metabolites (Gross-Steinmeyer et al., 2002). 

Intraperitoneal administration of 120 pg ochratoxin A/kg bw per day to Wistar rats, for 10, 30 or 60 days, produced oxidative stress and doseAime-related apoptosis in both proximal and distal epithelial kidney cells. Ochratoxin A concentrations in the kidneys were proportional to the time of exposure and amounted to 547, 753 and 930 ng/g kidney tissue after 10, 30 and 60 days, respectively. Oxidative stress was evident from increased malondialdehyde formation in the kidney cells (Petrik et al., 2003). 

Several hypotheses on the mode of action of ochratoxin A as a carcinogen have been proposed, and evidence has been generated in support of each of them. Some of these would completely account fortumourformation, whereas others have been considered as possible contributors to tumour formation. They can be summarized as follows ... 

Faucet-Marquis, V., Pont, F., Stormer, F.C., Rizk, T., Castegnaro, M. Rohl-Leszkowicz, A. (2006) Evidence of a new dechlorinated ochratoxin A derivative formed in opossum kidney cell cultures after pretreatment by modulators of glutathione pathways correlation with DNA adduct formation. Mol. Nutr. Food Res. 50, 530-542. 

Grosse, Y., Baudrimont, I., Castegnaro, M., Betbeder, A.M., Creppy, E.E., DIrhelmer, G. Pfohl-Leszkowicz, A. (1995) Formation of ochratoxin A metabolites and DNA-adducts in monkey kidney cells. Chem.-Blol. Interact. 95, 175-187. 

Mally, A. Dekant, W. (2005) DNA adduct formation by ochratoxin A review of the available evidence. Food Addit. Contam. 22(1), 65-74. 

Obrecht-Pflumio, S. Dirheimer, G. (2000) In vitro DNA and dGMP adducts formation caused by ochratoxin A. Chem.-Biol. Interact. 127, 29-44. 

Pfohl-Leszkowicz, A. Manderville, R.A. (2007) Ochratoxin A an overview on toxicity and carcinogenicity in animals and humans. Mol. Nutr. Food Res. 51,61-99. Pfohl-Leszkowicz, A., Chakor, K., Creppy, E. Dirheimer, G. (1991) DMA adduct formation in mice treated with ochratoxin A. In Castegnaro, M., Plestina, R., Dirheimer, G., Chernozemsky, I.N. Bartsch, H., eds. Mycotoxins, endemic nephropathy and urinary tract tumours. Lyon, France, International Agency for Research on Cancer, pp. 245-253 (IARC Scientific Publications No. 115). 

Zepnik, H., Pahler, A., Schauer, U. Dekant, W. (2001) Ochratoxin A-induced tumor formation is there a role of reactive ochratoxin A metabolites Toxicol. Scl. 59, 59-67. 

Magan, N., Aldred, D. (2005). Conditions of formation of ochratoxin A in drying, transport and in different commodities. Food Additives and Contaminants (Supplement 1), 10-16. 

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