Monday, June 15, 2020

Properties of aflatoxin

Aflatoxins were first identified in 1961 in United Kingdom in animal feed responsible for the deaths of 100 000 turkeys. The typical mold that produces this aflatoxin is Aspergillus flavus which is related to Aspergillus oryzae. This producer widely distributed in the tropical and subtropical areas, such as Southeast Asia, the US, and Brazil among others, and grows in feed, especially in peanut and cottonseed, causing aflatoxin contamination.

Aflatoxins occur in the crops before harvesting and regarded as the mycotoxins originating from the field compared to the other mycotoxins, which are noticed in the post harvesting of field crops.

Aflatoxins are colourless to pale yellow crystals, exhibiting fluorescence under UV light. They are slightly soluble in water (10-20µg/ml) and freely soluble in moderately polar solvents such as chloroform, menthol and dimethyl sulfoxide.

In acute toxicosis, hepatic presentations such as jaundice and cirrhosis are characteristic in aflatoxins. Hepatic disorders manifest also in secondary signs such as loss of appetite, reduced growth rate, etc. Many also reported of hemorrhagic diarrhea. In lactating cows, reduced lactation is also observed. In pathologic histology studies, fibrosis around the portal vein, proliferation of bile ductless is characteristic signs.

Aflatoxin consists of a group of 20 fungal metabolites. Out of them only B1, B2, G1, G2, M1 and M2 are usually found in foods, where “B” and “G” referring to the blue and green fluorescent colors produced on thin layer chromatography plates under UV light, while the subscript numbers 1 and 2 indicate major and minor compounds, respectively. M1, M2 is the metabolites of B1, B2 found in human and animal milk.

Among these toxins, Aflatoxin B1 (AFB1) is considered the most recurrent and also the most harmful. Its carcinogenicity and immunosuppression capacity have been extensively reported in all kind of animals, including poultry, trout, cattle and rats with different incidence across species, gender and age. The toxicity in humans has been assessed in association with different outbreaks of acute intoxication, especially in developing countries [10]. Many epidemiological studies focused on the connection between aflatoxins assumption through contaminated food and health problems.

Another toxin causing great concern is Aflatoxin M1 (AFM1), the principal hydroxylated metabolite of AFB1, found in milk (hence the designation M) of mammals fed upon contaminated feedstuff. Carry-over of AFB1 as AFM1 in the milk of dairy cows has been established to range from 0.3% to 6.2%.
Properties of aflatoxin
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