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1.4 Toxicity and clinical manifestations of aflatoxin
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1.2 Found aflatoxins
2.2.2 Chemical analysis method:
2.2.3 Instrument analysis method:
2.2.4 Immunoassay:
3.1 enzyme-linked immunosorbent assay (ELISA)
3.1.1 Principles and steps:
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Application of MD microplate reader in quantitative detection of aflatoxin
First, aflatoxin introduction
1.1 What is aflatoxin
Aflatoxin (AFT) is a class of compounds of similar chemical structure, all of which are derivatives of dihydrofuran coumarin. Aflatoxin is a secondary metabolite mainly produced by Aspergillus flaw, Aspergillus parasitwus and Aspergillus nomius. In China, the aflatoxin producing aflatoxin is mainly yellow. Aspergillus.
Aflatoxins are widely found in nature, and aflatoxins are most likely to occur in foods and feeds in hot and humid regions. They are found in soil, animals and plants, and various nuts. Especially, they are easy to pollute peanuts, corn, rice, soybeans, wheat and other grain and oil products. They are the most toxic and harmful to human health. According to the current toxicity classification, the animal's median lethal dose <10mg/kg body weight is highly toxic, while the median lethal dose of aflatoxin B1 is only 0.36mg/kg body weight, which is a highly toxic poison range.
On October 27, 2017, the World Health Organization's International Agency for Research on Cancer published a preliminary list of carcinogens, aflatoxins in a list of carcinogens.
1.2 Found aflatoxins
In 1960, the United Kingdom discovered that 100,000 turkeys died of a disease that had never been seen before. It was called "turkey X disease" and later the ducks were affected. Tracing back to the source, the biggest suspicion is feed. These turkeys and ducks eat peanut cakes. Peanut cake is the residue left after the peanut oil is extracted. It is rich in protein and is a good feed for poultry. These peanut cakes were contaminated with a toxic substance from fungi. After further research and confirmation, it was discovered that the toxic metabolite produced by Aspergillus. flavus, Aflatoxins, is a yellow Aspergillus and Metabolites of Aspergillus parasiticus.
1.3 Classification, chemical structure and physicochemical properties of aflatoxins
There are more than 300 mycotoxins, including aflatoxin, zearalenone/F2 toxin, ochratoxin, T2 toxin, vomiting mycotoxin/deoxynivalenol, fumagillin/fumagillin Wait. Among them, aflatoxins are the most toxic mycotoxins discovered so far, and nearly 20 kinds of B1, B2, M1, M2, G1, G2, P1, Q and H1 have been isolated and identified in this class. toxin. Their chemical structures are similar, and they are derivatives of dihydrofuran and coumarin. The difuran ring structure in the aflatoxin molecule is an important structure for producing toxicity. Different types of aflatoxin have different structures and their toxicity (from There are also differences (B1, M1, G1, B2). There are four main types of aflatoxins: B1, B2, G1, G2, of which B1 is considered to be the main toxic substance, and there are two metabolic products of these toxins.
M1 and M2. Among them, aflatoxin B1 is mainly found in agricultural products, animal feed, traditional Chinese medicine and other products; aflatoxin M1 is a product of hydroxylation metabolism in the body after ingestion of aflatoxin B1 in animals, part of which is excreted from urine and milk, and part of which is present in The edible parts of animals, such as milk, liver, eggs, kidneys, blood and muscle, of which milk is most common. The toxicity and carcinogenicity of aflatoxin M1 is substantially similar to that of aflatoxin B1. The molecular formula of aflatoxin B1 (CAS No. 1162-65-8):
C17H12O6, molecular weight: 312.27
In 1993, aflatoxin was classified as a Class 1 carcinogen by the World Health Organization (WHO) Cancer Research Institute. It is a highly toxic and highly toxic substance with severe carcinogenicity, teratogenicity and mutagenicity. Aflatoxin-tRNA adducts can inhibit the binding of tRNA to certain amino acids. Different inhibitory effects on essential amino acids in protein biosynthesis, such as lysine leucine, arginine and glycine, and tRNA binding. Thus, at the level of translation, protein biosynthesis affects cellular metabolism. Its toxicity is equivalent to 10 times that of potassium cyanide and 68 times that of arsenic. After the aflatoxin intake, the animals are most distributed in the liver, and the content can be 5-15 times that of other organ tissues. It can also be detected in the kidney, spleen and adrenal glands. There is a very small amount in the blood, which is generally not detected in the muscle. If the aflatoxin is not continuously ingested, it generally does not accumulate in the body. Because it has a destructive effect on human and animal liver tissue, it can cause liver cancer and even death in severe cases. Aflatoxin B1 is the most common in naturally contaminated foods, and its toxicity and carcinogenicity are also strongest. Aflatoxin content is low toxicity at 30~50μg/kg, poisoning at 50~100μg/kg, high toxicity at 100~1000μg/kg, and extremely toxic at 1000μg/kg. The symptoms of aflatoxin poisoning are usually symptoms of hepatic poisoning such as transient fever, vomiting, anorexia, jaundice, ascites, and lower extremity edema. In severe cases, fulminant hepatic failure and death occur. There are three clinical manifestations, namely acute poisoning, chronic poisoning and carcinogenicity; aflatoxin is pure colorless crystal, aflatoxin B1, B2 emits blue fluorescence under ultraviolet light, and aflatoxin G1, G2 emits green Fluorescence. The relative molecular weight of aflatoxin is 312-346. Hard to dissolve in water, soluble in oil, organic solvents such as methanol acetone and chloroform, but insoluble in petroleum ether hexane and ether. Generally stable in neutral solution, but slightly decomposed in strong acidic solution, rapidly decomposes in a strong alkaline solution of pH 9-10. The decomposition temperature of the high temperature aflatoxin B1 is 268 ° C. The ultraviolet light is destructive to the low concentration aflatoxin.
• Acute poisoning: Its toxic effects, whether for any animal or liver, are acute hepatitis, hemorrhagic necrosis, hepatic steatosis and bile duct hyperplasia. There are also mild lesions in the spleen and pancreas.
• Chronic poisoning: The main change is characterized by chronic liver damage such as hepatic parenchymal cell degeneration and cirrhosis. There are a series of symptoms such as slow growth, weight loss, infertility or low birth weight.
• Carcinogenicity: It can induce a variety of cancers. AFT mainly induces liver cancer, and can also induce tumors in gastric cancer, kidney cancer, lacrimal adenocarcinoma, rectal cancer, breast cancer, ovary and small intestine, and teratogenesis. table of Contents
First, aflatoxin introduction
1.1 What is aflatoxin
1.3 Classification, chemical structure and physicochemical properties of aflatoxins
1.4 Toxicity and clinical manifestations of aflatoxin
1.5 Aflatoxin harm
1.5.1 Aflatoxin and animal diseases
1.5.2 Aflatoxin and human health
1.6 Preventive measures and methods of resistance
Second, aflatoxin detection methods and standards
2.1 Development history and trend of testing methods
2.2 Classification of detection methods
2.2.1 Biological identification method:
2.3 Status and prospects of aflatoxin detection technology
2.4 Current aflatoxin detection process and final identification method
3. Brief introduction of aflatoxin detection instruments, reagents and methods
3.1.2 Recommended reagents:
3.1.3 Recommended instruments:
3.1.4 Example of competitive ELISA method for detection of aflatoxin B1