Natural aflatoxin inhibitors from medicinal plants

Abstract

Aflatoxins (AF) are real public health hazards due to their potential carcinogenic, teratogenic, and mutagenic activities toward humans and a wide range of animal species (Allameh and Razzaghi-Abyaneh 2001; Bennett and Klich 2003). They are a major group of polyketide mycotoxins produced mainly by specific members of Aspergillus section Flavi. AF-producing fungi, especially Aspergillus flavus and Aspergillus parasiticus, have worldwide distribution and they are able to contaminate a wide range of substrates including cereal grains, oilseeds, and tree nuts under favorable conditions of temperature and relative humidity (Bennett and Klich 2003). The importance of these toxins, especially aflatoxin B1 (AFB1), the most potent natural hepatocarcinogen, led to significant advances in the field of secondary metabolism, from biochemistry to genetics and control strategies. Genetic studies of AF biosynthesis in the major producers, A. flavus and A. parasiticus, led to the identification of at least 25 clustered genes within a 70 kb DNA region responsible for the enzymatic conversions in the AF biosynthetic pathway (Yu et al. 2005). The role of regulatory elements, nutritional and environmental factors and fungal development in AF formation has been studied with special focus on micro-array technology using expressed sequence tags of A. flavus and A. parasiticus (Yu et al. 2004). Despite these promising data, concerns over AF contamination concerns are still far from being solved, due to our low level of understanding about signal transduction pathways underlying toxin formation by producing fungi, and about the dynamics of toxigenic fungus-host plant interactions during the infection process. Since the discovery of AF in the early 1960s, a large number of chemicals have been screened with the aim of finding AF biosynthesis inhibitors (Zaika and Buchanan 1987; Razzaghi-Abyaneh et al. 2006a). © 2010 Springer-Verlag Berlin Heidelberg.