Orientador: Delia B. Rodriguez-Amaya / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-03T02:37:31Z (GMT). No. of bitstreams: 1 Navas_SandraAparecida_M.pdf: 2479689 bytes, checksum: 059ad37b33bafb968f424afd2d492264 (MD5) Previous issue date: 2003 / Resumo: Tendo em vista o fato das crianças serem mais sensíveis aos efeitos adversos de aflatoxina M1 (AFM1) e ocratoxina A (OTA) comparativamente aos adultos, este trabalho teve como objetivo padronizar metodologia para determinação de AFM1 e OTA em leite matemo, avaliar a incidência das citadas toxinas em Banco de Leite Humano do Hospital Regional Sul, da cidade de São Paulo, e correlacionar os resultados obtidos com a alimentação consumida pelas mães. Os métodos estabelecidos para a determinação de AFM1 e OT A envolveram extração da AFM1 com metanol e OT A com bicarbonato de sódio 1 % e metanol, seguido da limpeza por colunas de imunoafinidade com anticorpos especificos para cada micotoxina e separação por cromatografia líquida de alta eficiência e quantificação com detector de fluorescência. A confirmação de AFM1 foi realizada através da reação de derivatização com ácido trifluoroacético (TFA) e para OTA por meio da reação de derivatização com ácido clorídrico concentrado (HCI). O método estabelecido para AFM1 apresentou porcentagem de recuperação e coeficiente de variação de 93,6% e 17,S%, respectivamente para a contaminação de 0,01 ng/mL. Para o método de OTA, os valores correspondentes são 83,9% e 14,1% no mesmo nível de contaminação (0,01 ng/mL). O limite de quantificação para ambos os métodos foi de 0,01 ng/mL. Do total de SO amostras analisadas, apenas uma continha a AFM1 (2% do total), em nível de 0,024 ng/mL e duas com OTA (4% do total), em nível de 0,011 e 0,024 ng/mL. Portanto, houve baixa incidência de AFM1 e OTA em leite materno proveniente do Banco de Leite do Hospital Regional Sul da cidade de São Paulo / Abstract: Since infants are more susceptible than adults to the adverse effects of aflatoxin M1 (AFM1) and ochratoxin A (OTA) , this work was carried out to establish and evaluate methods for the determination of AFM1 and OT A in human milk collected by the Human Milk Bank of the Southern Regional Hospital, city of São Paulo, and correlate the incidence of these mycotoxins to the mothers' diets, information obtained through a questionnaire. The methods established for the determination of AFM1 and OT A involved the extraction of AFM1 with methanol and OT A with 1 % sodium bicarbonate and methanol, followed by clean-up with immunoaffinity columns with antibodies specific for each mycotoxin and quantification by high performance liquid chromatography with a fluorescent detector. Confirmation of the identity of AFM1 was carried out by derivatization with trifluoroacetic acid (TFA) and of OT A by derivatization with concentrated hydrochloric acid (HCI). The method established for AFM1 had mean recovery percentage and coefficient of variation of 93.6% and 17.5%, respectively, at the contamination levei of 0.01 ng/mL. For the OTA method, the corresponding values were 83.9% and 14.1% at the same levei of contamination. The limit of quantification for both methods was 0.01 ng/mL. Of a total of 50 samples analyzed, only one was contaminated with AFM1 (2%), at 0.024 ng/mL and two with OTA at 0.011 and 0.024 ng/ml. There was low incidence of AFM1 and OT A, therefore, in human milk from the Milk Bank of the Southern Regional Hospital, city of São Paulo / Mestrado / Mestre em Ciência de Alimentos

This master thesis deals with monitoring of a content of deoxynivalenol, its metabolite deoxynivalenol-3-b-D-glucopyranoside and ochratoxin A in beer samples collected from retail market in the Czech Republic, Poland and Slovakia. The theoretical part describes general characteristics of mycotoxins, its transfer from field barely through malt to beer and its occurrence in beers. Malting process and brewing technology were also mentioned. Subsequently possibilities for a determination of the mycotoxins by the chromatografic and immunochemical method were presented. The experimental section describes analysis of 30 samples of beer. The analyses were conducted using ultra high-performance liquid chromatography with fluorimetric detection (UPLC/FLR) for ochratoxin A and high-performance liquid chromatography coupled with mass spectrometer (HPLC/MS) for deoxynivalenol and its metabolite. Ochratoxin A was detected in 25 of the 30 samples in concentration range of 0,6 - 82,5 ng·l-1. Deoxynivalenol was found in 24 of the 30 samples with concentration range of 2,29 - 12,57 ug·l-1 and deoxynivalenol-3-b-D-glucopyranoside was occure in 19 of the 30 samples in concentration range of 2,45 - 12,47 ug·l-1. It was also assessed the relationship between beer gushing and presence of mycotoxins in beer. No connection between the parameters has been found. Consequently it is not possible to predict beer gushing from the presence of mycotoxins.

Im Gegensatz zu den renalen Transportmechanismen von OTA ist die gastrointestinale Absorption dieses Mykotoxins weitaus weniger untersucht worden. Die bisherigen Untersuchungen deuten darauf hin, dass OTA aus der Nahrung über einfache passive Diffusion der nicht-dissoziiert vorliegenden Form aufgenommen wird. Weitere Informationen zur Absorption von OTA aus dem Verdauungstrakt in vivo, insbesondere zur Beteiligung von Transportsystemen, wie sie in der Niere beobachtet wurden, liegen nicht vor. In der vorliegenden Arbeit sollte daher mittels einer in situ-Perfusionsmethode an Ratten die Aufnahme von OTA aus dem Darmlumen ins Blut untersucht werden. Zunächst konnte, wie es auch schon in früheren Arbeiten beobachtet worden war, gezeigt werden, dass im proximalen Jejunum im Vergleich zum mittleren und distalen Abschnitt des Jejunums eine höhere Aufnahme von OTA stattfand. Des Weiteren trat eine deutliche Abhängigkeit vom luminalen pH-Wert in der OTA-Absorption auf, wobei signifikant mehr OTA aufgenommen wurde, je niedriger der luminale pH-Wert war. Ein saturabler Transportmechanismus konnte in dem untersuchten Konzentrationsbereich nicht beobachtet werden. Weiterhin traten keine signikanten Unterschiede bei einem Zusatz von Glucose im Vergleich zur Kontrollgruppe auf, was den parazellulären Weg für die Absorption von OTA als unwahrscheinlich erscheinen lässt. Auch Substrate verschiedener Transportsysteme (Glycylsarcosin, Aspartam, Phenyalalanin, Leucin und Taurocholat) zeigten keinen statistisch signifikanten Einfluss auf die OTA-Absorption. Die Bindung von OTA an Proteine verhinderte die intestinale OTA-Absorption deutlich. Aufgrund der eigenen Befunde und der Daten aus der Literatur scheint die intestinale OTA-Absorption hauptsächlich transzellulär über einfache Diffusion der nicht-dissoziierten Form zu erfolgen. Es bestehen somit deutlich Unterschiede zur renalen Absorption von OTA.

La détection rapide et sensible des agents pathogènes est d’une très grande importance pour la biosécurité. Les biopuces sont bien adaptées à cet effet, car elles permettent la détection multiplexe des cibles. Une limitation cruciale des biopuces est leur manque de fiabilité et de sensibilité. L’objectif de cette thèse est de développer une architecture reproductible de biopuces à base de couche mince de silicium amorphe carboné (a-SiC:H) déposée sur un réflecteur en aluminium pour une détection fiable et sensible des pathogènes. Nous avons choisi comme système modèle l’interaction de la toxine alimentaire ochratoxine A (OTA) avec son aptamère AntiOTA de longueur 36mer. Les aptamères (simples brins d’ADN) sont de plus en plus utilisés comme sondes en raison de leur grande spécificité et affinité vis-à-vis d’une large gamme de cibles (i.e. protéines, bactéries…). La stratégie de fabrication consiste en un greffage de monocouches organiques d’acides carboxyliques via des liaisons Si-C robustes, suivi de l’accrochage covalent des aptamères par un couplage peptidique. Les processus de greffage ont été mis au point sur silicium cristallin permettant la quantification des couches greffées par spectroscopie infrarouge en mode ATR (Attenuated total reflexion). La quantification IR des interactions OTA – AntiOTA a été montrée pour la première fois sur des surfaces par IR-ATR. La spécificité de l’aptamère a été démontrée en utilisant une molécule chimiquement similaire (warfarin), pour laquelle l’AntiOTA ne montre aucune affinité. Ces protocoles bien contrôlés ont été transférés sur l’architecture de la biopuce a-SiC:H. Les aptamères immobilisés sont hybridés avec des brins complémentaires marqués avec des fluorophores. En présence de l’OTA une déshybridation des brins complémentaires est attendue, conduisant à une diminution du signal fluorescent. Différentes longueurs de brins complémentaires ont été comparées, montrant jusqu’à 13% de diminution due à l’interaction de l’OTA. / Rapid and sensitive detection of pathogenic targets play a crucial role in biosecurity. Biochips are ideal for this, as they allow easy and multiplex detection of targets. A crucial limitation in biochips is that they often suffer from low reliability and sensitivity. The goal of this thesis is to develop a stable and reproducible architecture for biochips based on an amorphous silicon carbon alloy (a-SiC:H) deposited on an aluminium back-reflector for reliable and sensitive detection of pathogens. On these biochips we introduced the interaction of the food and feed toxin ochratoxin A (OTA) with its 36mer aptamer AntiOTA as a model system. Aptamers (single strands of DNA) are ideal as probes for biochips as they display high specificity and affinity towards a wide range of targets (i.e. proteins, bacteria…). The well-controlled multi-step fabrication process consists of the reliable photochemical grafting of acid-terminated organic monolayers on silicon surfaces by robust Si C bonds, which in turn were functionalized with aptamers by stable peptide coupling. Carrying out this process on crystalline silicon allowed monitoring and quantification of every step by infrared spectroscopy (IR-ATR). The interaction OTA – AntiOTA was shown for the first time on surfaces by IR, and an IR in situ calibration allowed the quantification of OTA which was bound by the aptamers on the surface. The specificity of AntiOTA towards OTA was demonstrated by using a chemically similar molecule (warfarin), for which AntiOTA shows no affinity. The well-controlled protocols were transferred to the a-SiC:H biochip. The immobilized aptamers were hybridized with complementary and fluorescent-labeled DNA-strands. In presence of OTA, dehybridization of the complementary strands is expected, resulting in a decrease of fluorescent signal. Different lengths of complementary strands were compared, exhibiting up to 13% signal decrease due to OTA.

Mykotoxine sind giftige Naturstoffe, die im Rahmen des Sekundärstoffwechsels von Schimmelpilzen beim Wachstum auf pflanzlichen Substraten gebildet werden. Zu den bekanntesten Mykotoxinen zählt das Ochratoxin A (OTA), welches überwiegend in Getreide und davon abgeleiteten Erzeugnissen, aber auch in Wein und Kaffee sowie Gewürzen und Bier nachgewiesen wurde. OTA ist unter anderem immunotoxisch, nephrotoxisch und besitzt teratogene sowie kanzerogene Eigenschaften. Darüber hinaus wird OTA eine hormonelle Wirkung zugesprochen. Aufgrund der Toxizität und des relativ häufigen Vorkommens in Lebensmitteln wurden für OTA Grenzwerte festgelegt. Diese liegen für Wein, Röstkaffee und diätetische Produkte zwischen 0,5 mikrogramm /kg und 10 mikrogramm /kg. Grenzwerte für Gewürze und Bier sind geplant. Im Rahmen der Methodenentwicklung zur Bestimmung von OTA in Lebensmitteln wurden verschiedene clean-up-Techniken miteinander verglichen. Dabei wurde vor allem den kombinierten Ionentauscher/reversed phase-Säulen und der LC-MS/MS wesentliche Bedeutung beigemessen. Innerhalb der Methodenvalidierung wurden die Ergebnisse mit dem entsprechenden Standardverfahren verglichen. Es konnte gezeigt werden, dass mit oben genanntem Material in Kombination mit der LC-MS/MS sehr gute Ergebnisse erzielt werden können. Diese wurden im Rahmen der Validierung durch statistische Auswertung bestätigt. Ferner wurden im Rahmen der Methodenentwicklung, speziell bei der Bestimmung von OTA in Kaffee, Extraktionstechniken miteinander verglichen. Dabei wurde die bislang kaum beachtete ASE (Accelerated Solvent Extraction, Dionex) sowie Ultraschallextraktion mit der Schüttelextraktion aus der gültigen Norm verglichen und ihre Anwendbarkeit auf weitere Lebensmittel geprüft. In diesem Zusammenhang waren die ASE und Ultraschallextraktion der konventionellen Schüttelextraktion überlegen. Darüber hinaus wurde die Ultraschallextraktion in Kombination mit dem Ionentauscher/reversed phase clean-up erfolgreich auf Weizen und Chili angewandt. Parallel zur Methodenentwicklung wurde die Stabilität und Homogenität von OTA in Wein und Röstkaffee untersucht. Sowohl die Homogenität als auch die Stabilität des Analyten sind wichtige Faktoren bei der Entwicklung neuer Verfahren, da zusammen mit Ergebnissen der Validierung, die Messunsicherheit innerhalb neuer Verfahren eingegrenzt werden. / Mycotoxins are naturally occurring toxic substances and produced as secondary metabolites by fungi which are growing on plants predominantly. One of the most interesting mycotoxins is ochratoxin A (OTA), which was found in several foods and feed stuff like wheat and its related products, wine, coffee, spices and beer. Among other things OTA is immunotoxic, nephrotoxic and has teratogenic and cancerogenic properties. Further more OTA shows hormonal effects. Because of its toxicity and common appearance in food and feed the OTA content had to be regulated in European and or national directives. The maximum values are determined between 0.5 micrograms/kg and 10 micrograms/kg for wine, roasted coffee and dietetic products. Other maximum levels for beer and spices are intended. During the investigation of analytical methods for the determination of OTA in food stuff different clean-up techniques were compared. Thereby the mixed anion exchange/reversed phase clean-up in combination with LC-MS/MS was researched intensively. Within method validation the results were compared with the corresponding standard methods. This work shows that the mixed mode clean-up in combination with LC-MS/MS gives excellent results. These results were statistically confirmed during method validation. Further more different extraction techniques were compared during the development of analytical methods, especially for the determination of OTA in coffee. Thereby the ASE (accelerated solvent extraction, Dionex) and the ultrasonic extraction were compared with the shaking technique from current standard methods. The adaptability for other food and feed products was researched as well. In this context the new extraction techniques were superior to conventional shaking techniques. In addition the ultrasonic extraction with mixed mode clean-up and LC-MS/MS detection was applied to chilli and wheat effectively. Besides the investigation of analytical methods the stability and homogeneity of OTA in wine and roasted coffee was researched. The homogeneity and stability of OTA in matrix are very important factors during the investigation of analytical methods. In combination with the relevant results of the method validation these results can be used to determine the uncertainty of the new analytical methods.

Philosophiae Doctor - PhD / Polyaniline nanocomposites doped with poly(vinylsulphonate) (PV-SO3) and nanostructured polystyrene (PSNP) latex beads functionalized with amine (PSNP-NH2) and sulphate ((PSNP-OSO3) were prepared and characterised for use as nitrite electro-catalytic chemosensors and ochratoxin A immunosensors. The resultant polyaniline electrocatalytic chemosensors (PANI, PANI|PSNP-NH2 or PANI|PSNP-OSO3 −) were characterized by cyclic voltammetry (CV), ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM). Brown-Anson analysis of the multi-scan rate CV responses of the various PANI films gave surface concentrations in the order of 10−8 mol/cm. UV-vis spectra of the PANI films dissolved in dimethyl sulphoxide showed typical strong absorbance maxima at 480 and 740 nm associated with benzenoid p-p* transition and quinoid excitons of polyaniline, respectively. The SEM images of the PANI nanocomposite films showed cauliflower-like structures that were <100 nm in diameter. When applied as electrochemical nitrite sensors, sensitivity values of 60, 40 and 30 μA/mM with corresponding limits of detection of 7.4, 9.2 and 38.2 μM NO2 −, were obtained for electrodes, PANI|PSNP-NH2, PANI and PANI|PSNP-SO3 −; respectively. Immobilisation of ochratoxin A antibody onto PANI|PSNP-NH2, PANI and PANI|PSNPSO3 - resulted in the fabrication of immunosensors. / South Africa

<p>Polyaniline nanocomposites doped with poly(vinylsulphonate) (PV-SO3 &minus / ) and nanostructured polystyrene (PSNP) latex beads functionalized with amine (PSNP-NH2) and sulphate (PSNP-OSO3 &minus / ) were prepared and characterised for use as nitrite electro-catalytic chemosensors and ochratoxin A immunosensors. The resultant polyaniline electrocatalytic chemosensors (PANI, PANI|PSNP-NH2 or PANI|PSNP-OSO3 &minus / ) were characterized by cyclic voltammetry (CV), ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM). Brown-Anson analysis of the multi-scan rate CV responses of the various PANI films gave surface concentrations in the order of 10&minus / 8 mol/cm. UV-vis spectra of the PANI films dissolved in dimethyl sulphoxide showed typical strong absorbance maxima at 480 and 740 nm associated with benzenoid p-p* transition and quinoid excitons of polyaniline, respectively. The SEM images of the PANI nanocomposite films showed cauliflower-like structures that were &lt / 100 nm in diameter. When applied as electrochemical nitrite sensors, sensitivity values of 60, 40 and 30 &mu / A/mM with corresponding limits of detection of 7.4, 9.2 and 38.2 &mu / M NO2 &minus / , were obtained for electrodes, PANI|PSNP-NH2, PANI and PANI|PSNP-SO3 &minus / , respectively. Immobilisation of ochratoxin A antibody onto PANI|PSNP-NH2, PANI and PANI|PSNPSO3 - resulted in the fabrication of immunosensors.</p>

<p>Polyaniline nanocomposites doped with poly(vinylsulphonate) (PV-SO3 &minus / ) and nanostructured polystyrene (PSNP) latex beads functionalized with amine (PSNP-NH2) and sulphate (PSNP-OSO3 &minus / ) were prepared and characterised for use as nitrite electro-catalytic chemosensors and ochratoxin A immunosensors. The resultant polyaniline electrocatalytic chemosensors (PANI, PANI|PSNP-NH2 or PANI|PSNP-OSO3 &minus / ) were characterized by cyclic voltammetry (CV), ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM). Brown-Anson analysis of the multi-scan rate CV responses of the various PANI films gave surface concentrations in the order of 10&minus / 8 mol/cm. UV-vis spectra of the PANI films dissolved in dimethyl sulphoxide showed typical strong absorbance maxima at 480 and 740 nm associated with benzenoid p-p* transition and quinoid excitons of polyaniline, respectively. The SEM images of the PANI nanocomposite films showed cauliflower-like structures that were &lt / 100 nm in diameter. When applied as electrochemical nitrite sensors, sensitivity values of 60, 40 and 30 &mu / A/mM with corresponding limits of detection of 7.4, 9.2 and 38.2 &mu / M NO2 &minus / , were obtained for electrodes, PANI|PSNP-NH2, PANI and PANI|PSNP-SO3 &minus / , respectively. Immobilisation of ochratoxin A antibody onto PANI|PSNP-NH2, PANI and PANI|PSNPSO3 - resulted in the fabrication of immunosensors.</p>

The ochratoxins, metabolites of certain Aspergillus and Penicillium species are the first group of mycotoxins discovered subsequent to the epoch-making discovery of the aflatoxins. Ochratoxin A (OTA) is a very important mycotoxin owing to its frequent occurrence in nature, its established role in Danish porcine nephropathy and in poultry mycotoxicoses and its implicated role in Balkan endemic nephropathy and urinary system tumors among population groups in North Africa. Chapters 2 and 3 highlight the importance of OTA and the research currently being done on mycotoxins. These efforts are focused on the molecular genetics of toxinogenic fungi; the mechanism of their action; species differences in metabolism and pharmacokinetics; quantification of mycotoxins; risk assessments on the exposure of man and animals to mycotoxins and regulations for the control of mycotoxin contamination. Methods developed to analyse OTA in different matrices by using reversed phase high performance-liquid chromatography with fluorescence detection and tandem liquid chromatography-mass spectrometry techniques are described in Chapter 10. Amino propyl solid phase extraction columns were used for the first time in cleanup steps of ochratoxin analysis. These techniques and methods were applied to the first survey on the levels of OTA in coffee on the South African retail market (Chapter 5). The results suggest that the levels of OT A in the coffee on the South African market are somewhat higher than the levels of OTA in coffees on the European market. The possibility to biologically produce different halogen-ochratoxins by supplementing the growth medium of Aspergillus ochraceus with halogen salts was investigated. Bromoochratoxin A was produced for the first time in this way. Supplementation of inoculated wheat with potassium iodide and -fluoride resulted in the poisoning of the yeast and no iodoor fluoro-ochratoxin B was produced. It was found that Aspergillus ochraceus produced OTA in higher yields at elevated levels of potassium chloride. This finding has important commercial applications in the production ofOTA (Chapter 4). The ochratoxins are hydrolyzed in vivo by carboxypeptidase A. The hydrolysis of the ochratoxins and analogues by carboxypeptidase A was measured in vitro in a structurefunction relation study by employing mass spectrometric techniques. The kinetic data of the ochratoxins were compared to the values of a number of synthesized structural analogues. It was found that the halogen containing analogues had lower turnovers than their des-halo analogues. There were no substantial differences in the kinetic data between the different halogen containing analogues (Chapter 8). The toxicokinetics of OTA in vervet monkeys were determined for the first time. The clearance of OTA from the plasma suggested a two-compartment model and the elimination half-life was determined to be 19-21 days. The half-life of OTA in humans was determined by allometric calculations to be 46 days. We came to the conclusion that the long term consumption of OT A contaminated foods will lead to potentially hazardous levels of the toxin in the body (Chapter 9). This hypothesis can be substantiated by the incidence of OTA in the blood of various population groups. Possible ways to decontaminate OT A contaminated foods by degrading the compound biologically with yeast; moulds or lipases to non-toxic compounds were investigated. Eight moulds, 323 yeasts and 23 lipases were screened for ochratoxin degradation. A lipase from Aspergillus niger is the first lipase that was proven to degrade OTA (Chapter 7). Four yeasts were found to degrade OT A of which one, Trichosporon mucoides degraded OTA substantially within 48 hours in a growing culture (Chapter 6). In addition to this first report of yeasts which have the ability to degrade OTA, the fungi Cochliobolus sativus, Penicillium islandicum and Metarhizium anispoliae also proved to degrade OT A. OT A was degraded in all instances to the non-toxic ochratoxin a and the amino acid phenylalanine. / Thesis (PhD (Chemistry))--Potchefstroom University for Christian Higher Education, 2000

The ochratoxins, metabolites of certain Aspergillus and Penicillium species are the first group of mycotoxins discovered subsequent to the epoch-making discovery of the aflatoxins. Ochratoxin A (OTA) is a very important mycotoxin owing to its frequent occurrence in nature, its established role in Danish porcine nephropathy and in poultry mycotoxicoses and its implicated role in Balkan endemic nephropathy and urinary system tumors among population groups in North Africa. Chapters 2 and 3 highlight the importance of OTA and the research currently being done on mycotoxins. These efforts are focused on the molecular genetics of toxinogenic fungi; the mechanism of their action; species differences in metabolism and pharmacokinetics; quantification of mycotoxins; risk assessments on the exposure of man and animals to mycotoxins and regulations for the control of mycotoxin contamination. Methods developed to analyse OTA in different matrices by using reversed phase high performance-liquid chromatography with fluorescence detection and tandem liquid chromatography-mass spectrometry techniques are described in Chapter 10. Amino propyl solid phase extraction columns were used for the first time in cleanup steps of ochratoxin analysis. These techniques and methods were applied to the first survey on the levels of OTA in coffee on the South African retail market (Chapter 5). The results suggest that the levels of OT A in the coffee on the South African market are somewhat higher than the levels of OTA in coffees on the European market. The possibility to biologically produce different halogen-ochratoxins by supplementing the growth medium of Aspergillus ochraceus with halogen salts was investigated. Bromoochratoxin A was produced for the first time in this way. Supplementation of inoculated wheat with potassium iodide and -fluoride resulted in the poisoning of the yeast and no iodoor fluoro-ochratoxin B was produced. It was found that Aspergillus ochraceus produced OTA in higher yields at elevated levels of potassium chloride. This finding has important commercial applications in the production ofOTA (Chapter 4). The ochratoxins are hydrolyzed in vivo by carboxypeptidase A. The hydrolysis of the ochratoxins and analogues by carboxypeptidase A was measured in vitro in a structurefunction relation study by employing mass spectrometric techniques. The kinetic data of the ochratoxins were compared to the values of a number of synthesized structural analogues. It was found that the halogen containing analogues had lower turnovers than their des-halo analogues. There were no substantial differences in the kinetic data between the different halogen containing analogues (Chapter 8). The toxicokinetics of OTA in vervet monkeys were determined for the first time. The clearance of OTA from the plasma suggested a two-compartment model and the elimination half-life was determined to be 19-21 days. The half-life of OTA in humans was determined by allometric calculations to be 46 days. We came to the conclusion that the long term consumption of OT A contaminated foods will lead to potentially hazardous levels of the toxin in the body (Chapter 9). This hypothesis can be substantiated by the incidence of OTA in the blood of various population groups. Possible ways to decontaminate OT A contaminated foods by degrading the compound biologically with yeast; moulds or lipases to non-toxic compounds were investigated. Eight moulds, 323 yeasts and 23 lipases were screened for ochratoxin degradation. A lipase from Aspergillus niger is the first lipase that was proven to degrade OTA (Chapter 7). Four yeasts were found to degrade OT A of which one, Trichosporon mucoides degraded OTA substantially within 48 hours in a growing culture (Chapter 6). In addition to this first report of yeasts which have the ability to degrade OTA, the fungi Cochliobolus sativus, Penicillium islandicum and Metarhizium anispoliae also proved to degrade OT A. OT A was degraded in all instances to the non-toxic ochratoxin a and the amino acid phenylalanine. / Thesis (PhD (Chemistry))--Potchefstroom University for Christian Higher Education, 2000