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Produced by : Aspergillus ochraceus, Penicillium viridictum
Introduction and structure
Ochratoxins are produced by several species of the fungal genera Aspergillus and Pencillium. These fungi are ubiquitous and the potential for contamination of foodstuffs and animal feed is widespread. Ochratoxin A, the major compound, has been found in more than 10 countries in Europe and the USA. Ochratoxin formation by Aspergillus species appears to be limited to conditions of high humidity and temperature, whereas at least some Pencillium species may produce ochratoxin at temperatures as low as 5°C.
Structure of ochratoxins
Ochratoxin A has been found in maize, barley, wheat, and oats, as well as in many other food products, but the occurrence of ochratoxin B is rare. Residues of ochratoxin A have been identified in the tissues of pigs in slaughterhouses, and it has been shown, under experimental conditions, that residues can still be detected in pig tissues one month after the termination of exposure.
Effects on human health
The toxic effects of ochratoxin A have been studied extensively in a variety of experimental animals. All the animals studied so far have been susceptible to orally administered ochratoxin A, but to various degrees. At high levels of ochratoxin A, changes were found in the kidneys and also in other organs and tissues. However, only renal lesions were observed at exposure levels identical to those occurring environmentally.
Feed levels as low as 200 µg/kg produced renal changes in the course of 3 months in rats and pigs. Field cases of ochratoxin A-induced nephropathy are regularly encountered in pigs and poultry. Ochratoxin A is teratogenic in the mouse, rat, and hamster.
Ochratoxin B, rarely found as a natural contaminant, is much less toxic; the other ochratoxins have never been encountered in natural products.
The nephrotoxic potential of ochratoxin A is well documented from all experimental studies, with a feed level of 200 µg/kg causing nephropathy in pigs and rats. Lower levels have not been tested. Field eases of ochratoxin A-induced nephropathy in farm animals have long been recognized. The toxin has been found in a variety of foodstuffs, with levels in commodities used as feed ranging up to 27 mg/kg, and with levels in foodstuffs used for human consumption in the range of trace to about 100 µg/kg. In one area where endemic nephropathy was prevalent in the human population, home produced foodstuffs were more frequently contaminated with ochratoxin A than those from control areas. However, the total intake of ochratoxin A by man has not been assessed so far, and there is, at present, no proof that ochratoxin A is causally involved in human diseases.
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