**2.3. Deoxynivalenol**

Trichothecene of type B (deoxynivalenol) is produced by *Fusarium graminearum* and *Fusarium culmorum*; these mycotoxin-producing species are found in wheat, rye, barley and oats [18]. These are a group of toxins with a keto group at carbon 8 of the parent epoxytrichothecene nucleus [19]. Deoxynivalenol is divided into five types (deoxynivalenol, 15-acetyldeoxynivalenol, 3-acetyldeoxynivalenol, fusarenon-X and nivalenol). "ribotoxic stress response" is produced by deoxynivalenol added the ribosome in eukaryotic cells [20]. The impact of deoxynivalenol on the immune system ranges from immunosuppression to immunostimulation, according to its concentration, duration and time of exposure [19].

rots are *F. graminearum* followed by *F. verticillioides*, *F. proliferatum* and *F. culmorum* [21]. These *Fusarium* species are also capable of producing mycotoxins, which contribute to pre-harvest contamination of human food and animal feed impacting health [7]. Among *Fusarium* spp., *F. graminearum* is the most common agent causing *Fusarium* head blight [26]. The major mycotoxin type of *F. graminearum*, *F. sporotrichioides* and *Fusarium avenaceum* is the trichothecene type-B mycotoxin class of fungi capable of producing deoxynivalenol and its derivatives (3Ac-deoxynivalenol, 15Ac-deoxynivalenol) or nivalenol. The nivalenol-producing isolates of *F. graminearum* have been found to be more aggressive in maize than the deoxynivalenolproducing isolates [15]. On the other hand, maize production is mainly affected by diseases caused by the species *Fusarium proliferatum*, *F. verticillioides* and *F. subglutinans* and mycotoxin generators including fusaric acid, fusarins and fumonisins. Among fumonisins, fumonisin B1 (FB1), FB2 and FB3 are most frequently encountered in maize kernels [1, 27]. *Fusarium spo-*

*Fusarium* Mycotoxins and Metabolites that Modulate Their Production

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*rotrichioides* is a common soil-borne plant pathogen causing dry rot of potato [28].

A component of the plant resistance to *Fusarium* and their toxins is related to the capacity of plant tissues to reduce the fungal infestation and mycotoxin accumulation (e.g. zearalenone, type B trichothecenes, fumonisins) throughout the presence of secondary metabolites. Secondary metabolites are compounds produced by plants for which no role has yet been found in growth, photosynthesis, reproduction or other "primary" functions; however, it has been found that they are implicated in plant defense. The presence of secondary metabolites along with temperature, water activity, pH and nutrients have been identified as key features

Plant endogenous compounds can be both constitutively synthesized and induced in response to pathogen infection. Recent metabolomic studies have pointed an important amount of cereal metabolites produced by cereals such as fatty acids, amino acids and their derivatives, carbohydrates, amines and polyamines, terpenoids, benzoxazinoid derivatives and phenylpropanoids that contribute to the resistance of *Fusarium* and low mycotoxin accumulation (**Figure 2**). These metabolites are derived from primary and secondary metabolism [30]. Based on their biosynthetic origins, plant secondary metabolites can be divided into three major groups: phenylpropanoids, terpenoids and nitrogen-containing alkaloids. The secondary metabolites that play a

role in the plant resistance to *Fusarium* and mycotoxin accumulation are listed below.

Phenolic compounds are secondary metabolites that are produced by descend from the phenylpropanoid pathway and are synthesized by plants from the amino acid phenylalanine. Plant biosynthesis produces various phenols that can be grouped commonly as flavonoids and phenolics. Flavones, flavonols, flavanones, flavan-3-ols, anthocyanidins, isoflavones, coumarins, stilbenes and lignans are the main flavonoids. These are structurally distinct because of their specific hydroxylation, methylation and conjugation patterns, with various monosaccharides and disaccharides. Phenolic acids found in cereals exist in both soluble (free) and insoluble

**4. Cereal secondary metabolites with antifungal activity**

regulating *Fusarium* and their mycotoxins [29].

**4.1. Phenylpropanoids**
