**3. Ochratoxin A**

Mycotoxin ochratoxin A (OTA) was discovered in 1965 in South Africa (Van der Merwe et al., 1965): it was isolated as a toxic metabolite of *Aspergillus ochraceus* from corn meal artificially inoculated with the fungus. In 1969, naturally occurring OTA was isolated from a commercial corn sample in the United States (Shotwell et al., 1969). Later, it was recognized as a secondary metabolite of several *Aspergillus* and *Penicillium* spp. which are characterized by widespread occurrence and different behavior which depends on the ecological niches, the products affected and the environment (Duarte et al., 2010).

OTA is one of the most relevant mycotoxins, with great public health and agroeconomic significance, due to the confirmed nephrotoxic, genotoxic, neurotoxic, imunotoxic, embriotoxic and teratogenic effects and its suspected carcinogenicity (JECFA, 2008). OTA has been documented as a global contaminant of a wide variety of commodities and staple food. Humans are directly and indirectly exposed to OTA: it can enter the food chain, through contamination of the ingredients or foodstuffs consumed by humans, or the feed chain, through contamination of the feeds for animals destined for human consumption (Cark & Snedeker, 2006).

The chemical name of OTA is N-[(3R)-(5-Chloro-8-hydroxy-3-methyl-1-oxo-7 isochromanyl)carbonyl]-L-phenylalanine; OTA belongs to a group of metabolites with a similar chemical structure, as shown in Figure 2 and Table 2.

Fig. 2. General structure of OTA and its metabolites (El Khoury & Atoui, 2010).

The biosynthetic pathway for OTA has not yet been completely established; however, the isocoumarin group is a pentaketide skeleton formed from acetate and malonate via a polyketide synthesis pathway with the L-phenylalanine being derived from the shikimic acid pathway (O'Callaghan et al., 2003).

OTA is a weak organic acid (the pKa is 7.1 and the molar mass is 403.8 g mol-1). In acidic conditions, OTA is soluble in polar organic solvents, slightly soluble in water and insoluble in petroleum ethers and saturated hydrocarbons. In alkaline conditions, OTA is soluble in aqueous sodium bicarbonate solutions and in all alkaline ones. It has a melting point of about 90 °C, when crystallized from benzene as a solvate (El Khoury & Atoui, 2010; Keeper-Goodman & Scott, 1989). Due to its resistance to acidic conditions and high temperatures, OTA is characterized by high stability. Thus, it is very difficult to eliminate the molecule: OTA is only partially degraded at normal cooking conditions and after three hours of high pressure steam sterilization at 121 °C, or even at 250 °C, its destruction is not complete (Boudra et al., 1995).

metabolic detoxications. The toxic and carcinogenic effects of aflatoxin B1 are intimately linked to both the rate of activation and the rate of detoxification at the primary and secondary levels

Mycotoxin ochratoxin A (OTA) was discovered in 1965 in South Africa (Van der Merwe et al., 1965): it was isolated as a toxic metabolite of *Aspergillus ochraceus* from corn meal artificially inoculated with the fungus. In 1969, naturally occurring OTA was isolated from a commercial corn sample in the United States (Shotwell et al., 1969). Later, it was recognized as a secondary metabolite of several *Aspergillus* and *Penicillium* spp. which are characterized by widespread occurrence and different behavior which depends on the ecological niches,

OTA is one of the most relevant mycotoxins, with great public health and agroeconomic significance, due to the confirmed nephrotoxic, genotoxic, neurotoxic, imunotoxic, embriotoxic and teratogenic effects and its suspected carcinogenicity (JECFA, 2008). OTA has been documented as a global contaminant of a wide variety of commodities and staple food. Humans are directly and indirectly exposed to OTA: it can enter the food chain, through contamination of the ingredients or foodstuffs consumed by humans, or the feed chain, through contamination of the feeds for animals destined for human consumption

The chemical name of OTA is N-[(3R)-(5-Chloro-8-hydroxy-3-methyl-1-oxo-7 isochromanyl)carbonyl]-L-phenylalanine; OTA belongs to a group of metabolites with a

The biosynthetic pathway for OTA has not yet been completely established; however, the isocoumarin group is a pentaketide skeleton formed from acetate and malonate via a polyketide synthesis pathway with the L-phenylalanine being derived from the shikimic

R3

H R4

CH2R5

OTA is a weak organic acid (the pKa is 7.1 and the molar mass is 403.8 g mol-1). In acidic conditions, OTA is soluble in polar organic solvents, slightly soluble in water and insoluble in petroleum ethers and saturated hydrocarbons. In alkaline conditions, OTA is soluble in aqueous sodium bicarbonate solutions and in all alkaline ones. It has a melting point of about 90 °C, when crystallized from benzene as a solvate (El Khoury & Atoui, 2010; Keeper-Goodman & Scott, 1989). Due to its resistance to acidic conditions and high temperatures, OTA is characterized by high stability. Thus, it is very difficult to eliminate the molecule: OTA is only partially degraded at normal cooking conditions and after three hours of high pressure steam sterilization at 121 °C, or even at 250 °C, its destruction is not complete

Fig. 2. General structure of OTA and its metabolites (El Khoury & Atoui, 2010).

R1 O

R2

O OH O

of metabolism, in a similar way to chlorinated hydrocarbon (Olaniran et al., 2006).

the products affected and the environment (Duarte et al., 2010).

similar chemical structure, as shown in Figure 2 and Table 2.

**3. Ochratoxin A** 

(Cark & Snedeker, 2006).

acid pathway (O'Callaghan et al., 2003).

(Boudra et al., 1995).


Table 2. Radicals in OTA metabolites \*(Phenylalanine; Tyrosine; Serine; Hydroxyproline; Lysine) (El Khoury & Atoui, 2010).
