Toxic substances mycotoxins

Also see POISONS, Table P-2, Some Potentially Poisonous [Toxic] Substances—Mycotoxins and SPOILAGE OF FOOD.)... 

Flannigan, B. (1991). Mycotoxins In D MeUo J.P.F, Duffus, C.M., and Duffus, J.H. (Eds.) Toxic Substances in Crop Plants. London Royal Society of Chemistry, 226-250. 

Assessment of whether a chemical has the potential to cause adverse effects in humans arises usually from direct observation of an effect in animals or humans, such as the acute poisoning episodes that have occurred when potatoes contain high levels of glycoalkaloids. Epidemiological studies have also been used to infer a possible relationship between intake of a particular type of food, or constituent of that food, and the potential to cause an adverse effect. Such observations led to the characterisation of the aflatoxins as human carcinogens. However, natural toxic substances that occur in plant foods have often been identified through observations in animals, particularly farm animals. It was observations of adverse effects in farm animals that led to the further characterisation of the phytoestrogens and the mycotoxins. In other instances, the concern arises from the chemical similarity to other known toxins. 

Mycotoxins are toxic substances produced by molds and fiingi, such as mushrooms. These toxic substances, known as secondary metabolites, are by-products of metabolism that are inessential to fungal growth. Although some mycotoxins can be used for medicinal purposes, most are poisonous if eaten in sufficient quantity. 

However, many moulds are far from beneficial to man. They may damage stored food, clothing, leather, wood and other materials of economic importance. They may also cause extensive crop losses in the form of blights and rusts. Finally, they may pose health hazards by producing toxic substances called mycotoxins (from the Greek mukes mashroom, toxikon-toxic). The enormous public health and economic implications of mycotoxin contamination are illustrated by the fact that the Food and Agricultural Organisation of the United Nations estimates that up to 25% of the worlds food crops are affected by mycotoxins. 

Toxins Toxic substance of natural origin produced by an animal, planf or microbe. They differ from chemical substances in that they are not manmade. Toxins may include botulism, ricin, and mycotoxins. 

Mycotoxins should be handled as toxic substances and special care should be taken when handling pure toxins in a dry form, or samples (including TLC plates), which may be a source of dust. Accidental spillages of material containing toxin can generally be treated with 1% sodium hypochlorite bleach, left for 10 min, and swabbed down with 5% aqueous acetone initially and subsequently with plenty of water. 

The analysis of mycotoxins, toxic substances produced by some fungi, is essential to guaranteeing the safety of foods such as cereals, nuts, oilseeds, and spices since the discovery of their significance to human health. The main mycotoxins, like aflatoxins and ochratoxin A, are determined using HPLC with octyl-or octadecyl-bonded phases and polar solvents such as methanol, acetonitrile, and water. For detection with the required sensitivity and selectivity, spectrofluori-metric detection is the most common method, with increasing use of mass spectrometric interfaces. 

Due to adsorptive property, clays can adsorb a variety of toxic substances, such as strychnine, mycotoxins, aflatoxin and toxins. Clay can provide active protection against disturbances dming gastrointestinal transit. However, if the toxin is incubated with smectite for 24 h beforehand, no increase in the rate of gastric emptying and small intestinal transit occurs. Smectite can also adsorb the enterotoxin of Clostridium difficile. In rats, this toxin causes intestinal permeability to increase through hyperseeretion of colonic water. 

This document deals only with estimating exposure to direct additives and chemical contaminants. The procedures used to estimate exposure to chemical contaminants in food (including naturally occurring toxicants, such as mycotoxins) are essentially the same as those used for direct additives. Thus, contaminants will be considered in the discussion of direct additive exposure estimation. The procedures discussed herein are equally applicable to color additives, GRAS substances, prior-sanctioned ingredients, and pesticide residues. 

Air, water, soil, and food are all unavoidable components of the human environment. Each of those elements influences the quality of human life, and each of them may be contaminated. Food is not only the elementary source of nutrients, but may also contain natural chemical substances with toxic properties, e.g., cyanogenic glycosides (many plants), solanine (green parts of potatoes, sprouted potatoes, and potatoes stored in light), industrial pollutants (heavy metals), biogenic amines (fish), or mycotoxins (moldy foodstuffs). 

Naturally occurring substances include many phytotoxins, mycotoxins, and minerals, all occurring in the environment. The recently expanded and now extensive use of herbal remedies and dietary supplements has become a cause of concern for toxicologists and regulators. Not only is their efficacy frequently dubious, but their potential toxicity is largely unknown. 

Variations in the use pattern of industrial and agricultural chemicals throughout the world preclude standardization by international organizations such as OECD. Despite this fact, common dietary constituents, which are known to influence toxicity are antioxidants, unsaturated fatty acids, and selenium. These must be present in interfering concentrations. The potential impact of several common dietary contaminants on chronic toxicity assessment therefore, necessitates that special attention be given to their presence. In this respect, substances of concern include pesticide residues, chlorinated and polycyclic aromatic hydrocarbons, estrogens, heavy metals, nitrosamines, and mycotoxins. 

Mycotoxins are chemicals manufactured by fungi, some of which are extremely toxic to humans and animals [49]. When moulds make them, they also make synergisers, substances that can enhance the potency of other toxins in the environment. Some of these compounds may not be toxic in themselves but become toxic when combined with other substances. 

Substances with xenobiotic bonds are not necessarily more toxic than those without them. The aflatoxins (mycotoxins that are produced by Aspergillusflavus) are the most carcinogenic substances known but lack xenobiotic bonds, whereas the synthetic Freons are almost biologically inert but are also very stable. (They escape the lower atmosphere, reaching the stratosphere, where they are split into free radicals that react and destroy ozone, which helps to shield the Earth from too much ultraviolet light. These ozone-depleting reactions have dramatic environmental effects, but the direct toxicity of the Freons is modest.)... 

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