Aflatoxins and Related Compounds

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Food Infections/Poisoning Bacterial Food Intoxications Bacterial Food Borne Diseases Serotypes of Clostridium Botulinum Bacterial Food Infections Food Borne Fungal Intoxications - Mycotoxins Food Borne Bacterial Infections

Aflatoxins and Related Compounds

	Aflatoxins and Related Compounds - Moldy feed toxicosis was recognized as a serious livestock problem in the 1950's but it was only in 1960 during the investigations in the United Kingdom of moldy feed toxicosis which was called "Turkey X disease", that A. flavus and A. parasiticus were identified as the organisms responsible for the elaboration of the toxin in the feed. The earliest symptoms of the disease are lithargy and muscular weakness followed by death. The term aflatoxin now refers to group of bisfuranocoumarin metabolites isolated from strains of A. flavus group of fungi.
These aflatoxins flurosece strongly in ultra violet light. The major members are designated as B1, B2, GI and G2. B1 and B2 fluoresce blue, while Gl and G2 fluoresce green. In some animal species such as in dairy cattle, aflatoxin B1 and B2 are partially metabolized to the hydroxylated derivates namely M I and M2, respectively. Aflatoxin PI is a urinary l11etabolite of Bl in monkeys. The structure of the four aflatoxins and lists the details of these toxins All aflatoxins absorb UV light in the range of 362-363 nm, a characteristic used in preliminary identification. The growth of toxigenic molds and elaboration of the toxin Occurs if moisture conditions are ideal following harvest and storage.
Although initially aflatoxin was detected in the peanut meal it is now known that a variety of cereals, and other plant products are susceptible to fungal invasion and mycotoxin production. Because of the wide spread nature of fungi producing aflatoxins in food materials, it has become almost impossible to lay down standards. As a result, international agencies have now permitted the presence of 20 ppb of aflatoxin in food materials as the maximum permissible level. A large number of fungi are today known to produce different toxins and some of these are Patulin, Ochratoxin, Sterigmatocystin, Penicillic acid etc. Patulin was first isolated in 1942 and described as an antibiotic but later classified as a mycotoxin.
Today, several molds including aspergilli and penicilli. have been reported to produce this toxin which is effective against bacteria such as E. coli and stapbylococci. It is also fungistatic and is toxic to seed and seedlings of higher plants. Oral and intravenous injection of patulin are fatal (0.3-2.4 mg/g of body weight) to mice and rats. Pathological changes include brain edema, lung haemorrhage and capillary damage in the liver and kidneys. This toxin has also been found to be a potenital carcinogen. Patulin has been detected in apple juice and cider, prepared from apples infected with patulin producing strains of Penicillium expansum. Ochratoxin is another fungal metabolite first isolated from the culture filtrates of Aspergillus ochraceus. Several types are known which differ in the type of fluorescence. These are toxic to ducklings, chicks and rats and are heat resistant.
	Citrinin was first isolated in 1937 from Penicillium citrinum as an antibiotic but later found to be a toxin. Many species of Penicillium, Aspergillus terreus and Aspergillus niveus are now known to produce this mycotoxin. Several fungi are known to produce toxins which cause sustained tremors, convulsion and death and these are collectively called as tremorogenic mycotoxins. None of these have been found as naturally occurring contaminants in feed material. However, toxigenic isolates have been obtained from conventional cattle feed, peanuts, etc.

Species of Fusarium are widespread in nature. Mostly saprophytes although some cause plant diseases. In recent years, these organisms have also been implicated in mycotoxicosis. Barley infected with F. saubinette has been found to be toxic to swine. Several species of Fusarium are known to produce more than one type of toxin when colonizing plants or cereal grains. These toxins include Zearalenone, a variety of Trichothecenes group of toxins. These cause a hyperestrogenic syndrome, haemorrhage and in some cases even abortion in swine.

The list of mycotoxins is far from complete and the number of fungi producing toxins is steadily increasing. Some of these metabolites may also be carcinogenic. The wide range of effects of different toxic metabolite has made the establishment of a safe level in human foods difficult.

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Aflatoxin and Related Compounds Chemical and Physical Properties of Aflatoxins and Derivatives Viruses in Food Microbiology of Drinking Water Microbiological Quality

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