Ochratoxins structures

Fig. 16 Structures of chlorophenols and metabolites of ochratoxin A (OTA) with an OH group [ochratoxin hydroquinone (OTHQ)] and a hydrogen atom [nonchlorinated OTA (OTB)].

Some natural products, or their degradation products, represent a hazard for mammals not because of general toxicity but for subtle, adverse properties, such as carcinogenicity and tumor promotion. They are best known fi om marine dinoflagellates (okadaic acid and structural analogues), filamentous fungi (trichothecenes and ochratoxins), and plants (pyrrolizidine alkaloids). 

Figure 11 Structures of ochratoxin A and C8-ochratoxin A-deoxyguanosine adduct (a) and biosynthesis of ochratoxin A (b).

Fig. 2. Structure of the ochratoxins. These metaholites form different classes depending on the nature of the amide group (a-c), and the presence or absence of a chlorine moiety at in the phenyl. 

Fig. 11.1 Chemical structure of ochratoxins (reprinted from Ringot et al. 2006, permission to be obtained)...

Representative Compounds Aflatoxins Citrinin Ergot alkaloids Fumonisins Ochratoxin A Patulin Trichothecenes Zearalenone Stachybotrys toxin Chemical Formula C17H12O6 (Aflatoxin Bi) Chemical Structure Aflatoxin Bi... 

Ochratoxin A 57 is a highly toxic metabolite isolated from Aspergillus ochraceus Wilh The structure assigned to it on the basis of spectral data, was confirmed by an anambiguous synthesis, which is shown below >. 

Ochratoxin A (OTA) is dangerous to human health, and its legal limits in grape and wine are fixed. The molecule consists of an isocoumarin derivative linked to phenylalanine through a carboxyl group (structure reported in Fig. 8.1). 

ORGANIC ANION TRANSPORT Structurally diverse organic anions are secreted in the proximal tubule. The primary function of organic anion secretion appears to be the removal from the body of xenobiotics, including many weakly acidic drugs (e.g., pravastatin, captopril, p-amino-hippurate [PAH], and penicillins) and toxins (e.g., ochratoxin). 

Other experiments have also aimed to identify the chemical structure of potential ochratoxin A adducts. In in vitro studies, incubation of ochratoxin A with DNA or dG in the presence of various activation systems did not reveal any adducts, neither by P-postlabelling nor by liquid chromatography/tandem mass spectrometry (LC-MS/MS). Subsequently, DNA was isolated from the livers and kidneys of male Fischer rats treated with a single dose of P C]ochratoxin A (0.5 mg/kg bw) and analysed by C-accelerated mass spectrometry. No significant difference between control group and treated group could be observed in C activity in isolated DNA from treated animals, and no specific ochratoxin A-DNA adducts were detected with C-accelerated mass spectrometry (Mally et al., 2004). The EFSA opinion pointed out that a concern in the interpretation of these results is that DNA adducts may have been repaired, as DNA was isolated 72 h after a single treatment with a relatively low dose, which is in contrast to other studies, in which DNA was isolated within 24 h after exposure to ochratoxin A (European Food Safety Authority, 2006),... 

As made evident in Table 2, immunoassays are also in routine use for analysis of mycotoxins, a group including the most dangerous and analytically elusive food-related toxins. In spite of the small structural differences within specific groups of mycotoxins (aflatoxins, ochratoxins, trichothecenes), assay specificity toward the other mycotoxin groups is always total. Determination of AEBi, toxin T-2, and ochratoxin A in a single extract from barley grains has been reported. Mycotoxins may be determined in crude extracts of various foodstuffs at concentration over 20 ng per kg. This detection limit can... 

CNTs were used successfully to enhance the binding capacity of a molecularly imprinted polypyrrole modified stainless steel frit for determination of ochratoxin A in red wines (Yu J.C.C. Lai, 2007 Wei et al., 2007). In a different work (li Y. et al., 2010), a molecularly imprinted polymer-graphene oxide hybrid material was synthesized by reversible addition and fragmentation chain transfer (RAFT) pwlymerization for the selective detection of 2,4-dichlorophenol in aqueous solution with an ajipredable selectivity over structurally related compounds. 

Citrinin is a quinone similar in structure to unsubstituted ochratoxin. 

FIGURE 6.4 Chemical structure of most common grain mycotoxins. (a) Zeralenone. (b) Ochratoxin A or OTA. (c) Fumonisin. (d) Trichothecenes or T-2. (e) Deoxynivalenol or DON. (f) Ergotamine. 

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