Phytoinhibition of Growth and Aflatoxin Biosynthesis in Toxigenic Fungi

Abstract

Aflatoxins are primarily produced by the fungi Aspergillus flavus and Aspergillus parasiticus, which contaminate a wide variety of food and feed commodities including maize, oilseeds, spices, groundnuts, tree nuts, milk and dried fruits [Strosnider et al., 2006]. Presence of aflatoxins in food chain is associated with decrease in quality and quantity of food and feed materials. In addition, consumption of aflatoxin-contaminated products can pose a risk of development of various diseases in human and animals. Aflatoxins are produced in toxigenic fungi after undergoing biosynthesis pathway involving several enzymes and reactions. Upon consumption of aflatoxin contaminated products by human and animals, the toxin undergoes metabolism via cytochrome P450 enzymes in the liver. Aflatoxin metabolism in mammalian organs is a committed process and different metabolites are produced which can exert adverse effects of toxic metabolites. Aflatoxin epoxide (8,9-epoxide) is the major toxic metabolite which can bind to DNA and induce hepatocellular carcinoms. The extent of aflatoxin toxicity and carcinogenicity in human and animals depends on several factors including the metabolic capacity of the organism. Aflatoxin contamination of food products is associated with health and socioeconomic costs which is difficult to valuate in the developing countries. Moreover, the current regulations do little to help reduce aflatoxin and related health effects. Therefore the focus should be on promoting the adaptation of strategies that can control aflatoxin and its associated health risks. According to Wu and Khlangwiset (2010), interventions to reduce aflatoxin-induced illness can be grouped into three categories; agricultural, dietary and clinical. Agricultural interventions are methods that can be applied either in the field (preharvest) or in drying, storage and transportation (postharvest) to reduce aflatoxin levels in food. The dietary and clinical interventioans are considered as secondary interventions by which the aflatoxinrelated illness can be reduced. These two types interventions are associated with advantages and disadvantages. Due to concern for the potential effects of aflatoxins on human health, most countries have legislation that restricts marketing of aflatoxin-contaminated grains [Van Egmond, 1989]. The United States Food and Drug Administration has set an aflatoxin limit of 20 μg/kg for