Conselho Nacional de Desenvolvimento Científico e Tecnológico / The objective of this dissertation was to evaluate the impacts of aflatoxin in a concentration of 2,8mg/kg, and sodic montmorillonite on performance, enzyme activity and liver function in broilers from 1 to 21 days, as well as compare to other products already on the market. Were utilize 540 chickens housed in cages. Experimental design was completely randomized, with 9 treatments and 6 replications. The treatments were: Control (basal diet), Ads0,50 (basal diet + 0,50% Test adsorbent), Afla (basal diet + 2,8mg/kg of Aflatoxin), Ads0,25 + Afla (basal diet + 0,25% Test adsorbent + 2,8mg/kg of Aflatoxin), Ads0,50 + Afla (basal diet + 0,50% Test adsorbent + 2,8mg/kg of Aflatoxin), AdsA + Afla (basal diet + 0,50% A adsorbent + 2,8mg/kg of Aflatoxin), AdsB + Afla(basal diet + 0,50% B adsorbent + 2,8mg/kg of Aflatoxin), AdsC + Afla (basal diet + 0,50% C adsorbent + 2,8mg/kg of Aflatoxin), AdsD + Afla (basal diet + 0,50% D adsorbent + 2,8mg/kg of Aflatoxin). The adsorbents A, B, C, D are based sodic montmorillonite, but come from different companies. The data collected were subjected to analysis of variance and comparison of means by Tukey test (P ≤ 0.05). It is concluded that the test adsorbent in a concentration of 0,50% was effectively promoted and a reduction of toxic effects of aflatoxin on performance of broilers at 21 days of age but did not avoided changes in liver function and liver enzymes. And gave results similar to the products C and D, and higher than product B. / O objetivo desta dissertação foi avaliar os impactos da aflatoxina, na concentração de 2,8mg/kg, e da montmorilonita sódica sobre o desempenho, atividade enzimática e função do fígado em frangos de corte de 1 aos 21 dias, bem como comparar o produto à outros já existentes no mercado. Foram utilizados 540 frangos, alojados em baterias metálicas. O delineamento experimental foi inteiramente casualizado, composto por 9 tratamentos e 6 repetições. Os tratamentos utilizados foram: Controle (dieta basal), Ads0,50 (dieta basal + 0,50% adsorvente Teste), Afla (dieta basal + 2,8mg/kg de aflatoxina), Ads0,25+Afla (dieta basal + 0,25% adsorvente Teste + 2,8mg/kg de aflatoxina), Ads0,50+Afla (dieta basal + 0,50% adsorvente Teste + 2,8mg/kg de aflatoxina), AdsA+Afla (dieta basal + 0,50% adsorvente A + 2,8mg/kg de aflatoxina), AdsB+Afla (dieta basal + 0,50% adsorvente B + 2,8mg/kg de aflatoxina), AdsC+Afla (dieta basal + 0,50% adsorvente C + 2,8mg/kg de aflatoxina), AdsD + Afla (dieta basal + 0,50% adsorvente D + 2,8mg/kg de aflatoxina). Os adsorventes A, B, C, D são à base de montmorilonita sódica, porém oriundos de diferentes empresas. Os dados coletados foram submetidos à análise de variância, e a comparação entre médias pelo teste de Tukey (P≤0,05). Conclui-se que o adsorvente Teste na concentração de 0,50% foi eficaz e promoveu uma redução dos efeitos tóxicos da aflatoxina sobre o desempenho zootécnico de frangos de corte aos 21 dias de idade, porém não evitou alterações nas enzimas e função hepática. E ainda, apresentou resultados semelhantes aos produtos C e D, e superior ao produto B.

Ochratoxin A (OTA) is a potent mycotoxin found in a wide range of agricultural products that has been linked to mitochondrial damage and renal disease. The standard methods for OTA analysis currently rely on the use of high-performance liquid chromatography (HPLC) coupled to fluorescence detection or mass spectrometry. Toward a highthroughput analysis of OTA, a single-stranded DNA aptamer, modified with a fluorophore, coupled to a complementary sequence, modified with a FRET-based quencher that dissociates in the presence of the target toxin, is proposed. In order to integrate “target trapping,” aptamer immobilization methods were explored to mediate interference issues. Assays were evaluated using wine and blood serum matrices. A solution-based assay in a 96-well plate format provided a limit-of-detection of 2.7 ng/mL which would be suitable for many of the proposed applications. Immobilized aptamer formats, however, were not reliable, and a range of limitations to applications of the assay were identified.

The fungus Macrophomina phaseolina (Tassi) Goidanich (Mp) is the causal agent of charcoal rot in soybean and infects over 500 plant species worldwide. Mp produces various mycotoxins and is suspected of utilizing a toxin-mediated process to penetrate host tissue. Identification and evaluation of secondary metabolites produced by Mp will further elucidate the pathogenesis mechanisms used by the fungus. Mp cultures isolated from soybean were evaluated for phytotoxicity in a hydroponic soybean bioassay and chemically analyzed by LC-MS/MS. All Mp cultures at two dilutions induced phytotoxicity symptoms including chlorosis, necrosis, wilting, stunting, and death. Analysis identified 13 unreported secondary metabolites including mellein, a compound with various biological activities. The phytotoxicity of mellein was evaluated against soybean seedlings in hydroponic culture, and symptoms of wilting and stunting were observed at levels above 40 MUg/L. Observations suggest that mellein does not directly contribute to the phytotoxic effects of Mp cultures.

No description available.

Le Deoxynivalenol (DON) est une mycotoxine majeure retrouvée dans l’alimentation animale et celle-ci est connue pour réduire la fertilité des truies en inhibant la sécrétion de progestérone par les cellules de granulosa. Chez le bétail, DON est métabolisée en de-epoxy DON (DOM-1) dans le rumen, et DOM-1 peut atteindre des concentrations élevées dans le sang et les liquides folliculaires. Une des voies majeures de signalisation activée par DON est le ribotoxic stress response (RSR), lequel induit une auto-phosphorylation de la protéine kinase R (PKR) et réduit l’activation des MAP kinases incluant la MAPK3/1. Il n’a pas encore été démontré que ces mycotoxines affectent la reproduction chez les bovins. Les objectifs de cette thèse sont (1) de déterminer comment et à quelles doses DON affecte la fonction des cellules de granulosa et d’élucider les mécanismes d’action entrant en jeu; et (2) déterminer comment et à quelles doses la mycotoxine majeure DON et son métabolite DOM-1, affectent la fonction des cellules de la thèque chez le bétail. Les résultats sont présentés dans trois articles distincts. Dans le premier article, nous explorons les effets de DON sur les cellules de granulosa bovines; les traitements avec DON résultant en une inhibition significative de la sécrétion d’oestradiol et de progestérone (P4), et en une augmentation de la proportion de cellules apoptotiques après 4 jours de traitement. Les expériences de Western-Blot démontrent une stimulation significative de la phosphorylation de ERK1/2 et de MAPK14 entre 15 et 30 minutes après le début du traitement des cellules par DON. Par la suite, nous avons déterminé les effets de DON sur les gènes cibles de ERK1/2. En effet, les niveaux d’ARNm de EGR1 et FOS sont transitoirement augmentés avec des niveaux maximum à 1h de traitement par DON, tandis que les niveaux d’ARNm de iv COX2 et GADD45B sont augmentés mais plus de 24h après le début du traitement par DON. Dans le second article, les effets de DON et DOM-1 sur les cellules de thèque ont été étudiés. Le traitement des cellules par DOM-1 résulte en une inhibition dosedépendante de la sécrétion de P4 et de testostérone, et en une augmentation de la proportion de cellules apoptotiques, tandis que DON inhibe la sécrétion de P4 sans altérer celle de la testostérone ou bien le pourcentage de cellules mortes. Les deux mycotoxines sont effectives de manière maximale à des concentrations de 1 ng/ml (en revanche, DON affecte les cellules de granulosa à 100 ng/ml). Les résultats de Western-Blot démontrent la phosphorylation rapide de MAPK3/1, PKR et de JUN kinase après un traitement par DON ou DOM-1. En présence d’un inhibiteur spécifique de PKR, DON et DOM-1 sont incapables d’induire la phosphorylation de MAPK3/1, et l’effet inhibiteur de DON sur la phosphorylation de MAPK14 est en partie abrogé. Néanmoins, l’inhibiteur de PKR augmente davantage la phosphorylation de MAPK14 induite par DOM-1. Ensemble, ces résultats suggèrent que DON active le RSR dans les cellules de thèque et les cellules de granulosa bovines, et que les cellules de la thèque sont plus sensibles que les cellules de granulosa aux effets de DON. Ces données démontrent pour la première fois l’habilité de DOM-1 à affecter les fonctions et la survie cellulaires. / Deoxynivalenol (DON) is a major mycotoxin found in animal feed and is known to reduce fertility in pigs by inhibiting progesterone secretion from granulosa cells. In cattle, it is metabolized to de-epoxy DON (DOM-1) in the rumen, and DOM-1 can reach high concentrations in blood and follicular fluid. One of the major pathways activated by DON is the ribotoxic stress response (RSR), which involves autophosphorylation of protein kinase R (PKR) and downstream activation of MAP kinases including MAPK3/1. It is not known if these mycotoxins affect bovine reproduction. The objectives of present thesis were (1) to determine how and at what doses DON affects ovarian granulosa cell function and to elucidate its mechanism of action; and (2) to determine how and at what doses major mycotoxin DON and its metabolite DOM-1 affect theca cell function in cattle. The results are separated into three articles. In the first article the effects of DON on granulosa cells were explored; treatment with DON resulted in a significant inhibition of estradiol and progesterone (P4) secretion, and an increase in the proportion of apoptotic cells after 4 days of treatment. Western blot demonstrated significant upregulation of ERK1/2 and MAPK14 phosphorylation within 15-30 minutes of adding DON. We then determined the effect of DON on ERK1/2 target genes; EGR1 and FOS mRNA levels were transiently stimulated with maximum levels at 1 h of adding DON, whereas COX2 and GADD45B mRNA levels were upregulated but not until 24 h after DON treatment. In the second article, the effects of DON and DOM-1 on theca cells were assessed. Treatment with DOM-1 resulted in a dose-dependent inhibition of P4 and testosterone secretion, and an increase in the proportion of apoptotic cells, while DON inhibited P4 but did not alter testosterone secretion or the percentage of dead cells. Both ii DON and its metabolite were maximally effective at concentrations of 1 ng/ml (in contrast, the effects of DON on occur at 100ng/ml). Western blot demonstrated rapid phosphorylation of MAPK3/1, PKR and of JUN kinase after addition of DOM-1 or DON. Interestingly, phosphorylation of MAPK14 was significantly increased by DOM-1 but decreased by DON. The addition of a PKR inhibitor abrogated the ability of DON and DOM-1 to increase phosphorylation of MAPK3/1, and partly abrogated the inhibitory effect of DON on MAPK14 phosphorylation, however, the PKR inhibitor further increased the phosphorylation of MAPK14 caused by DOM-1. Together, these results suggest that DON activates the RSR in bovine granulosa and theca cells, and that theca cells are more sensitive than granulosa cells to the effects of DON. The data also demonstrate for the first time in any cell type the ability of DOM-1 to affect cell function and health.

O aumento da demanda, a falta de fiscalização sanitária efetiva e de especificações adequadas para verificar a qualidade de drogas vegetais são fatores que contribuem para o acesso a produtos sem garantia da qualidade e segurança. Embora sejam consideradas seguras por sua origem natural, as drogas vegetais apresentam elevadas cargas microbianas e podem oferecer riscos potenciais aos usuários, tanto pela presença de microrganismos potencialmente patogênicos, quanto pela contaminação com toxinas. O objetivo deste estudo foi avaliar a contaminação microbiana presente em 91 amostras de drogas vegetais, o potencial toxigênico de fungos isolados e a presença de aflatoxinas, ocratoxina A e citrinina nestas amostras. Os resultados obtidos demonstraram que 73,6% das amostras apresentaram populações microbianas superiores a 2X103 UFC de bactérias aeróbias/g e 2X102 UFC de bolores e leveduras/g e que 81,3% apresentaram ao menos um dos microrganismos considerados indicadores de risco. Com relação à contaminação fúngica, observou-se o predomínio dos gêneros Aspergillus e Penicillium, sendo que a análise micotoxicológica revelou que 21,49% apresentaram capacidade para produção de aflatoxinas, ocratoxina A e citrinina. Apesar de fungos toxigênicos terem sido detectados em 35 amostras de drogas vegetais, a análise micotoxicológica, realizada conforme Farmacopéia Americana, não revelou a presença de aflatoxinas, ocratoxina A e citrinina em nenhuma das amostras de drogas vegetais, indicando que os microrganismos podem não terem sido submetidos a condições favoráveis à expressão de sua capacidade toxigênica. / The increase in the demand, the lack of effective sanitary fiscalization and adjusted specifications to verify the quality of crude herbal drugs are factors that contribute for accessing products without guarantee of the quality and safety. Although they are considered safe by their natural origin, herbal drugs present high microbial loads and can offer potential risks to the users, as much for the presence of potencially pathogenic microorganisms, how much for the contamination with toxins. The goal of this study was evaluated the microbial contamination present in 91 samples of crude herbal drugs, the toxigenic potencial of fungal isolates and the presence of aflatoxins, ochratoxin A and citrinin in these samples. The obtained results demonstrated 73.6% of the samples presented microbial populations higher than 2X103 CFU of aerobic bacteria/g and 2X102 CFU of yeast and molds/g and 81.3% presented at least one of the microorganisms considered as risk indicators. With regard to the fungal contamination, the Aspergillus and Penicillium genera were predominant and the mycotoxicological analysis revealed that 21.49% of these isolates presented ability for aflatoxins, ochratoxin A and citrinin production. Although toxigenic fungi have been detected in 35 samples of herbal drugs, the mycotoxicological analysis, carried through as The United States Pharmacopeia, showed no detection of aflatoxins, ochratoxin A or citrinin in any samples of herbal drugs, indicating that these fungi can not have been submitted a favorable conditions to the expression of their toxigenic ability.

Bostrychia tenella, proveniente dos costões rochosos da Praia Dura, no Estado de São Paulo. Para atingir este objetivo, foram realizados culturas isoladas dos microrganismos e a co-cultura entre o fungo T68 e a cianobactéria CENA139; técnicas de extração por partição volume/volume; métodos cromatográficos como cromatografia em camada delgada (CCD) e cromatografia líquida de alta eficiência (CLAE), bem como técnicas espectroscópicas e espectrométricas de RMN 1-D e 2-D, CL-EM, CG-EM, além de desreplicação (utilizando o banco de dados MarinLit® e o Dicionário de Produtos Naturais. Foram isoladas três substâncias do fungo estudado: Esterigmatocistina, T68ARf60_a e T68ARf60_b. A micotoxina esterigmatocistina foi isolada também a partir da co-cultura entre o fungo e a cianobactéria. Este trabalho mostrou que houve interações ecológicas competitivas na cultura mista entre Cyanobium sp. CENA139 e o fungo T68, resultando na prevalência da cultura fúngica. Para finalizar, este trabalho avaliou a atividade biológica dos extratos brutos das culturas isoladas e co-cultura, não apresentando atividade antimicrobiana. Entretanto, o extrato bruto T68 mostrou-se fototóxico nos ensaios de fototoxicidade e a substância isolada esterigmatocistina foi citotóxica e fotoxóxica no mesmo ensaio, além de exercer citotoxicidade frente à linhagem tumoral HepG2 no ensaio de citotoxicidade MTT. / This study had as main objective the evaluation of the chemical and biological profiles of two strains of microorganisms, the cyanobacteria Cyanobium sp. CENA139, from Ilha do Cardoso mangroves, São Paulo State, and the endophytic fungus T68, Xylariaceae family, isolated from the red algae Bostrychia tenella, from the rocky shores at Praia Dura, São Paulo State. To accomplish this objective, we performed isolated cultures of the microorganisms and the co-culture between the fungus T68 and the cyanobacteria CENA139; partition extraction techniques; chromatographic methods such as thin layer chromatography and high performance liquid chromatography. Also, we performed spectroscopic and spectrometric techniques of NMR 1-D and 2-D, LC-MS, GC-MS, besides dereplication using data sources as MarinLit® and the Dictionary of Natural Products. Three compounds were isolated from the endophytic fungus culture: Sterigmatocystin, T68ARf60_a and T68ARf60_b. The mycotoxin sterigmatocystin was also isolated from the co-culture. This study showed that there was competitive ecological interactions between Cyanobium sp. CENA139 and the fungus T68 in the co-culture, resulting in the prevalence of the fungal culture. Finally, this study evaluated the biological potential of the crude extract from both isolated cultures and the co-culture, not exerting antimicrobial activity. Nevertheless, the T68 crude extract was shown to be phototoxic on the phototoxicity assays and the isolated sterigmatocystin was both cytotoxic and phototoxic in the same assay, besides exerting cytotoxicity on the tumor cell line HepG2 in the MTT assay.

Il tema principale di questa tesi di dottorato verte sul metabolismo secondario di F. verticillioides, con particolare interesse alla via biosintetica, produzione e mascheramento delle fumonisine B (FB), fumonisine A (FA), fumonisine C (FC) e bikaverina, studiati in relazione all’ecologia fungina. E’ stato osservato che l’acqua libera (aw) esercita un effetto significativo maggiore rispetto alla temperatura sul metabolismo secondario di F. verticillioides. Alti valori di aw favoriscono l’espressione dei geni FUM ed una maggiore sintesi delle FB, FA e FC. Inoltre la produzione di bikaverina e l’espressione di BIK1 sono influenzate dall’ aw nello stesso modo che la produzione di FB e l’espressione dei geni FUM. Anche il tempo di incubazione è un fattore critico per la produzione di FB in F. verticillioides, così come per F. proliferatum: la produzione di FB, FA e FC aumenta nel tempo fino a 30 giorni, periodo dopo il quale si notano differenze tra le due specie fungine. Riguardo le fumonisine nascoste, queste sono state ritrovate in colture sia di F. verticillioides che di F. proliferatum. Non è stata registrata sintesi alcuna in colture cresciute su substrato di crescita sintetico, ma al contrario solo su colture cresciute su substrato a base di mais. / The main topic of this PhD thesis is F. verticillioides secondary metabolism, with regard to fumonisin B (FB), fumonisin A (FA), fumonisin C (FC) and bikaverin biosynthetic pathways and production and masking, studied in relation to fungal ecology. What we found is that water activity (aw) has a more significant effect than temperature on F. verticillioides secondary metabolism. Moreover bikaverin production and BIK1 expression are influenced by aw in the same way as FB production and FUM gene expression respectively. High aw levels favour FUM gene expression and allow the highest synthesis of FB, FA and FC. Incubation time is also critical for FB production both for F. verticillioides and F. proliferatum: the general trend is that FB, FA and FC production increases with time, up to 30 days, period after which differences can be noticed between F. verticillioides and F. proliferatum. As regard masked fumonisins, they are recovered in F. verticillioides and also F. proliferatum cultures, furthermore no synthesis is observed on cultures grown on synthetic medium, but only in those grown on maize-based substrates.

Το πρόβλημα με τις μυκοτοξίνες είναι σημαντικό και δικαιολογημένα προκαλεί ανησυχίες. Αναφέρεται ως παγκόσμιος κίνδυνος και θεωρείται ως μία από τις πλέον σοβαρές προκλήσεις για την ασφάλεια των τροφίμων, την υγεία των ανθρώπων, των ζώων, και για τη σύγχρονη τοξικολογία. Με τον «όρο» μυκοτοξίνες εννοούμε τοξίνες οι οποίες παράγονται από μύκητες. Συγκεκριμένα πρόκειται για προϊόντα δευτερογενούς μεταβολισμού των μυκήτων (Aspergillus spp Fusarium spp, Penicillium spp, κ.α). Υπάρχει μία πληθώρα από διάφορες μυκοτοξίνες οι οποίες απαντώνται σε πολλές τροφές, όπως στο γάλα, στα δημητριακά, στους ξηρούς καρπούς, στα αποξηραμένα φρούτα, στο αλεύρι κ.α. που καταναλώνουν καθημερινά οι άνθρωποι, αλλά και σε ζωικές τροφές. ωστόσο μόνο για κάποιες από αυτές υπάρχουν τεκμηριωμένες μελέτες ενώ ακόμα λιγότερες είναι αυτές, για τις οποίες έχουν προσδιοριστεί τα νόμιμα επιτρεπτά όρια συγκέντρωσης στις τροφές, που καταναλώνονται καθημερινά. Οι μυκοτοξίνες θεωρούνται γενικά επικίνδυνες ενώσεις που παράγονται από ορισμένα είδη μυκήτων, οι οποίοι αναπτύσσονται σε προϊόντα αγροτικών καλλιεργειών είτε πριν τη συγκομιδή, είτε κατά την αποθήκευσή τους σε γεωργικές εγκαταστάσεις και παραμένουν δραστικές για μεγάλο χρονικό διάστημα και μετά την καταστροφή των μυκήτων από τους οποίους προήλθαν. Η εμφάνισή τους στα τρόφιμα και στα ποτά έχει αναγνωριστεί ως απειλή για την υγεία τόσο του ανθρώπου όσο και των ζώων, είτε αυτή προέρχεται από την άμεση μόλυνση των φυτικών ιστών, είτε από προϊόντα που έχουν παραχθεί από αυτά, είτε από την μεταφορά των μυκοτοξινών και των μεταβολιτών τους στους ζωικούς ιστούς, και κατά συνέπεια στο γάλα, στα αυγά και αλλού. Μερικές από αυτές τις μυκοτοξίνες, όπως για παράδειγμα οι αφλατοξίνες, παρουσιάζουν εξαιρετικά υψηλή τοξικότητα, γεγονός που τις καθιστά ενώσεις που χρήζουν ιδιαίτερη προσοχή. ως εκ τούτου κρίνεται απαραίτητο όλα τα αγροτικά προϊόντα που προορίζονται για τον άνθρωπο ή για ζωοτροφές να υποβάλλονται σε συνεχή και σχολαστικό έλεγχο. Αντικείμενο μελέτης της παρούσας εργασίας είναι να μελετήσει τις παραμέτρους (θερμοκρασία και υγρασία) οι οποίοι επηρεάζουν την ανάπτυξη της μυκοτοξίνης ζεαραλενόνης χρησιμοποιώντας ως υπόστρωμα αλεύρι από αποθηκευμένο αραβόσιτο. Στόχος ήταν ο έλεγχος των συνθηκών καλλιέργειας, αποθήκευσης και συντήρησης των πρωτογενών γεωργικών προϊόντων έτσι ώστε να ελαττώνεται η ανάπτυξη μυκοτοξινών στα γεωργικά προϊόντα και στα τρόφιμα. Η δραστηριότητα βοήθησε στη διερεύνηση του μηχανισμού δράσης των συνθηκών που οδηγούν στην ανάπτυξη μυκοτοξινών τόσο κατά την αποθήκευση της πρώτης ύλης, όσο και κατά τα στάδια επεξεργασίας, παραγωγής και τυποποίησης του τελικού προϊόντος. / The problem with mycotoxins is a significant and legitimate concern. Referred to as global risk and is considered one of the most serious challenges to food security, human health, animals, and modern toxicology. With the "average" mean toxins mycotoxins produced by fungi. It is a secondary metabolic products of fungi (Aspergillus spp Fusarium spp, Penicillium spp, etc.). There is a plethora of different mycotoxins found in many foods such as milk, cereals, nuts, dried fruits, flour, etc. consumed daily by people, but also in animal feeds. But only some of them are documented studies and even fewer are those, which have been identified, legally permissible concentration limits in foods consumed daily. The mycotoxins are generally considered harmful compounds produced by certain species of fungi which grow on agricultural products or crops before harvest or during storage in agricultural systems and remain active for a long time after the destruction of fungi of which came. Their occurrence in foods and beverages has been recognized as a health threat to both human and animal, whether it comes from direct infection of plant tissues or products derived there from, or the transfer of mycotoxins and their metabolites in animal tissues, and hence in milk, eggs and elsewhere. Some of these mycotoxins such as aflatoxins, are extremely high toxicity, which makes compounds that deserve particular attention. Therefore it is essential that all agricultural products intended for human or animal feed can be subjected to constant and meticulous. The subject of this paper is to study the parameters (temperature and humidity) that influence the development of the mycotoxin zearalenone using as substrate flour stored maize. The aim was to check the growing conditions, storage and maintenance of primary agricultural products and thus reduce the development of mycotoxins in agricultural products and foodstuffs. The activity helped to investigate the mechanism of action of the conditions that lead to the development of both mycotoxins during storage of raw materials and in processing, production and packaging of finished product.

Un des dangers chimiques les plus importants relevés par l'OMS concerne la contamination des céréales par les mycotoxines et notamment les aflatoxines et les fumonisines. La réglementation recommande des contaminations maximales d'aflatoxines dans les céréales inférieures à 20 mg/kg ; cependant on relève couramment des taux supérieurs à 200 mg/kg dans le maïs au Mexique. Bien qu'il ait été évalué que le processus de nixtamalisation détruit plus de 90 % des fumonisines et de 80 à 95 % des aflatoxines, le taux résiduel peut encore être élevé : certaines publications rapportent des concentrations jusqu'à 100 mg/kg dans les tortillas, ce qui représente un risque avéré vue la grande consommation de tortillas au Mexique (325g/j). Le JECFA (2001) a établi une dose maximale acceptable de 2μg/kg pc/j pour la fumonisine et recommande de réduire l'exposition aux aflatoxines au plus faible niveau possible en considérant que le seuil de 1 ng/kg pc/j ne devrait pas être atteint. Au cours de cette thèse 3 enquêtes aléatoires et représentatives ont été menées dans 40 tortillerias de la ville de Veracruz. La consommation de maïs de la population a été évaluée à partir d'un questionnaire de consommation. L'analyse des mycotoxines a été réalisée par HPLC-FD par utilisation de colonnes à immunoaffinité selon la réglementation européenne (CIRAD-Montpellier). L'analyse des données obtenues a été effectuée selon une méthode probabiliste permettant de construire une fonction de distribution de probabilités à partir de la méthode de Monte Carlo (UBO). La représentativité de la population a été validée à partir d'évaluation de quotas de population après échantillonnage aléatoire initial. La contamination des tortillas a été mesurée à 0.54-1.96 mg/kg pour les aflatoxines et à 65-136 mg/kg pour les fumonisines. La consommation moyenne de tortillas a été mesurée à 148 g de maïs par jour. L'exposition de la population aux aflatoxines apparaît alors comprise entre 0,94 et 3,14 ng/kg pc/j et celle aux fumonisines entre 146 et 315 ng/kg pc/j. Les échantillons les plus contaminés proviennent des tortillerias réalisant elles-mêmes leur procédure de nixtamalisation. L'analyse des résultats montre que 60 % de la population de Veracruz serait à risque selon les préconisations du JECFA. L'exposition aux fumonisines atteint 5 % de la dose maximale acceptable, du fait d'une relativement faible contamination du maïs à cette mycotoxine. Les résultats montrent donc un risque sanitaire pour la population de la ville de Veracruz. Une extension de ce travail à la totalité de l’Etat de Veracruz, incluant la population rurale, devrait être menée du fait du risque probablement accru de cette dernière catégorie de population en lien avec sa plus forte consommation de maïs. / One of the chemical hazards that WHO has reported more frequently is cereals contamination with mycotoxins, mainly aflatoxins and fumonisins. NOM-188-SSA1-2002 establishes that aflatoxin concentration in grain should not exceed 20 mg kg-1 ; however, there are reported concentrations > 200 mg kg-1 in maize. Although it has been documented that nixtamalizacion removes more than 90% of fumonisins and between 80 and 95% of aflatoxins, the residual amount could be important, finding reports concentrations higher than 100 mg kg-1 of aflatoxin in tortilla, representing a risk due to the high consumption of tortillas in Mexico (325 g d-1). The JECFA (2001) establishes a maximum intake of 2 mg kg-1 pc d-1 for fumonisin and aflatoxin recommends reducing “as low as reasonably achievable” levels. 3 random and representative sampling in Veracruz city, each in 40 tortillerias, were made. Corn intake and weight of the population were estimated using a consumption questionnaire. Mycotoxins analysis were performed by HPLC-FD using immunoaffinity columns according to European standard UNE-EN ISO 14123 : 2008 for aflatoxins and UNE-EN 13585 : 2002 for fumonisin in the CIRAD (Montpellier, France). Statistical analysis were performed under a probabilistic approach in collaboration with the University of Bretagne Occidentale (Brest, France), building probability density function (PDF) and using the Monte Carlo method. PDF parameters of the weight of the population was 74.15kg for men (which coincides with reported by CANAIVE) and 65.83kg for women ; the pollution aflatoxin tortilla was 0.54 – 1.96mg kg-1 and fumonisin from 65.46 – 136.00mg kg-1 ; the tortilla consumption was 148.3g of corn per person per day ; the daily intake of aflatoxins was 0.94 – 3.14ng kg-1 bw d-1 and fumonisin of 146.24 – 314.99ng kg-1 bw d-1. Samples with higher aflatoxin contamination came from tortillerias that make the nixtamalization in situ. In assessing exposure it was found that up to 60% of the population could be consuming more than the recommended by JECFA (2001) for aflatoxin dose (1ng kg-1 bw d-1). Exposure to fumonisins intake was < 5% due to low contamination by these mycotoxins. The results suggest that the population of the city of Veracruz could be in food risk by eating contaminated corn tortillas AFT. It is advisable to extend this study in rural communities, where risk factors could increase.