Aflatoxins (Af) are the secondary fungal metabolites that are produced by toxigenic fungi belonging to various Aspergillus species.
Author: Dr.Maria Jamil1, Dr.Kashif Saleemi1., Dr.Ali Raza2, Dr.Muhammad Tahir Aleem3
- Department of Pathology, Faculty of veterinary science, University of Agriculture, Faisalabad
- Department of Microbiology, Faculty of veterinary science, University of Agriculture, Faisalabad
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 210095 Nanjing, P.R.China
Aflatoxins in peanuts | Aflatoxins in Corn | Aflatoxins in Corn molds | Pale and hemorrhagic liver |
Aflatoxins
Aflatoxins (Af) are the secondary fungal metabolites that are produced by toxigenic fungi belonging to various Aspergillus species. These are usually produced by A. flavus and A. parasiticus. The occurrence of aflatoxins mainly in tropical and subtropical areas where environmental conditions like temperature and humidity are favorable for the production of toxins. The name aflatoxins have been resultant from a combination of “a” mean Aspergillus genus and “fla” mean flavus specie, and toxin means poison. Up till now, almost 18 various types of aflatoxins have been recognized and mainly involved AfB1, AfB2, AfG1, AfG2, and AfM1. Aflatoxins that are produced in a minor amount from A. flavus and A. parasiticus are Aflatoxin M1, M2, B2A, and G2A.
Temperature range for fungal growth | ||
Species | Minimum | Maximum |
A. flavus | 12-42°C | 28-35°C |
A. Parasiticus | 6-8°C | 44-66°C |
Aflatoxin level for human consumption | |
Range | 0-3000ng/kg/day |
Average | 10-200ng/kg/day |
European Committee Regulation (ECR) | 4ppb set total Af level (B1, B2, G1, and G2) |
2ppb for AfB1 alone | |
Aflatoxins Mode of Action:
AfB1 is highly carcinogenic and mutagenic among all the mycotoxins. It can penetrate the cell membrane and lead to irreversible mutation by attaching to its DNA. AfB1 is a highly lipophilic compound that is absorbed from the respiratory and intestinal tract to the bloodstream from where it can spread throughout the body. After ingestion of the mutagenic mycotoxins from the pollutant feedstuff, this can lead to entering the cells, and then they are metabolized by P450 cytochrome to aflatoxin 8, 9-epoxide. It is unstable and highly reactive that needs the DNA for binding to become stabilized. When Af 8,9-epoxide binds to DNA, it can lead to forming Af-N7 guanine, which causes the transversion mutation of guanine to thymine that will firmly affect the cell cycle by inhibiting the P53 gene that in the tumor suppressor protein for prevention of tumor and cancer.
Aflatoxin in Milk:
The contamination of milk and milk byproducts by Aflatoxinand now a day a serious problem for both humans as well as animals. Infants are usually more sensitive than adults. AfM1 was classified as a cause of human carcinogen by IARC in 1993. The European Union has been set 50ng/kg the maximum consumption of AfM1 in milk. However, as compare to AfB1, AfM1 is less harmful and carcinogenic.
Aflatoxins in Raw Drugs:
However, in modern medicine, significant advances have been attained, as there has been a renewed concern to the utilization of plant-based products for a different variation of beneficial derivatization.
Aflatoxins in Eggs:
An egg is known as a rich source of protein. Rare reports have been available for the pollutant of the egg by Af. Rather then, since in 1974, the European Union has been set the 20µg maximum limit of AfB1 in layer ration.
Effects of Aflatoxin to Human Health:
Aflatoxicosis is the poisoning of Af after intake of an excessive level of Af causes the acute aflatoxicosis. However, regular intake of Af even at the very low level in ppb may lead to loss of weight and stunting in children, and some reports have also been available for the growth of hepatocellular cancer. Hepatitis-B virus restricts the capability of hepatocytes to digest the Af, and AfM1-DNA conjugate occurs for a longer time in the liver. This can lead to enhancing the capability to inhibit the tumor suppressor genes. This synergistic effect can lead to greater damage then Af alone.
The FDA recommends tolerance level of Aflatoxin | Range |
Human food | 20µg/kg |
Livestock feed | 100µg/kg |
Breeding Cattle | 20µg/kg |
Poultry feed | 300µg/kg |
The FAO/WHO expert communities recommend tolerance limit of Af | Range |
Food products | 5µg/kg |
Milk products | 0.05µg/kg |
Raw peanuts | 15µg/kg |
Liver Cancer:
The intl. Agency for Research on Cancer (IARC) has been categorized the AfB1, AfB2, AfG1 AfG2 as Group 1 carcinogens.
Conclusion:
The role AfB1 to cause the mutation in the human genome was broadly studied. Various other mycotoxins are still to be inspected to recognize their mode of action when they are in contact with the human genome. This is mainly essential because various mycotoxins have been a closely related chemical composition and similar functions inside the human body.