The work presented here represents research done on mycotoxins and plant toxins by the author and his postgraduate students over a period from 1964 to date. The first phase, which ends at 1980, mainly addresses the biosynthesis of the aflatoxins. The involvement of anthraquinone derivatives in this process was investigated and the role of versicolorin A and its derivatives was partially elucidated. Novel active enzymes systems were derived from protoplasts and used in these studies. The period lasting from 1980 to 1992 concentrates on the occurrence of mycotoxins in agricultural commodities and effects on animals and their systems. Over 7000 samples were analysed using a multimycotoxin analytical method and a fungal screen. The most common mycotoxin found was aflatoxin B₁ and prevalent fungus was Fusarium moniliforme. Later work is indicating that fumonisin B₁ is the most commonly occurring mycotoxin. As this was only discovered in 1988, its presence was only looked from 1995 onwards. It was also found that rumen fluid could metabolise trichothecenes. During this period (1980-1992) further work on aflatoxin metabolism was done and a novel dehydrogenase involved in aflatoxin B₁ was isolated and characterised. An Elisa assay was developed for atractyloside, a toxin found in a plant (Callilepis laureola) used in tradition medicine. The site of atractyloside storage was found to be in the plant vacuole. The final period covers 1992 to the present, where the occurrence and effects of mycotoxins in human disease were studied. The major and most important finding is that fumonisin B₁ is present in the blood and tissues of many of the Black population examined in Kwazulu Natal. This includes, oesophageal cancer patients, eclamptic patients, school children and members of the rural population. A similar circumstance also appertains for the presence of aflatoxin B₁. It seems likely from these results that chronic mycotoxicoses are a common occurrence, particularly in the Black rural population and are not the sporadic rare event that is found in the first world countries. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1999.

This thesis presents the development of chlorophyll, cholic acid, aflatoxin B1 molecularly imprinted polymer (MIP) particles and cholic acid MIP nanofibers for application as selective solid phase extraction (SPE) sorbents. The particles were prepared by bulk polymerization and the nanofibers by a novel approach combining molecular imprinting and electrospinning technology. The AFB1 MIP particles were compared with an aflatoxin specific immunoextraction sorbent in cleaning-up and pre-concentrating aflatoxins from nut extracts. They both recorded high extraction efficiencies (EEs) of > 97 % in selectively extracting the aflatoxins (AFB1, AFB2, AFG1 and AFG2). High reproducibility marked by the low %RSDs of < 1% and low LODs of ≤ 0.02 ng/g were calculated in all cases. The LODs were within the monitoring requirements of the European Commission. The results were validated with a peanut butter certified reference material. The chlorophyll MIP on the other hand selectively removed chlorophyll that would otherwise interfere during pesticide residue analysis (PRA) from > 0.6 to <0.09 Au in green plants extracts. The extracted chlorophyll was removed to far below the level of ≥ 0.399 Au that is usually associated with interference during PRA. Furthermore, the MIP demonstrated better selectivity by removing only chlorophyll (> 99%) in the presence of planar pesticides than the currently employed graphitized carbon black (GCB) that removed both the chlorophyll (> 88%) and planar pesticides (> 89%). For the interfering cholic acid during drug residue analysis, cholic acid MIP electrospun nanofibers demonstrated to be more sensitive and possessing higher loading capacity than the MIP particles. 100% cholic acid was removed by the nanofibers from standard solutions relative to 80% by the particles. This showed that the nanofibers have better performance than the micro particles and as such have potential to replace the particle based SPE sorbents that are currently in use. All the templates were optimally removed from the prepared MIPs by employing a novel pressurized hot water extraction template removal method that was used for the first time in this thesis. The method employed only water, an environmentally friendly solvent to remove templates to ≥ 99.6% with template residual bleeding of ≤ 0.02%.