Aflatoxin (B1, B2, G1 and G2)
- By Aspergillus flavus and A. parasiticus
- Toxic to liver
- Found in cereal and dry legumes
- B1 is the most toxic and often found
Aflatoxin is probably the most important mycotoxin in food; mycotoxin has now become a generic term and is defined as any toxin of fungal origin. Aflatoxin refers to toxins produced by Asperigillus flavus. When grains stored at high moisture levels, the mold is prevalent in nuts, cottonseeds, corn, and figs. Most animals, including humans, and poultry are particularly susceptible to aflatoxicosis. In developing countries, there is a direct relationship between dietary aflatoxin and liver cancer, and human males are more susceptible. Incidences have been high in India and Africa, where populations have been forced to survive by eating moldy grains. Acute toxicity can occur within 3 weeks of ingestion. Epidemiological data indicate that exposure to aflatoxin B1 (AFB1) and hepatitis is required for populations to have a significant risk of cancer.
Aflatoxins are heat stable and easily transformed to toxic products. Treatment with ammonia reduces and inactivates aflatoxins. Lactic fermentation at pH < 4.0 results in the conversion of AFB1 to AFB2a, which is less toxic. Other environmental conditions, such as the presence of organic acid, also irreversibly convert AFB1 to aflatoxicol B, which is 18 times less toxic than AFB1. The LD 50 of aflatoxin is 0.5 mg/kg of the body weight, and death occurs within 72 h. Death is due to liver damage and hemorrhaging in the intestinal tract and peritoneal cavity. Consumption of aflatoxin at sublethal concentration for several days to several weeks results in moderate to severe liver damage. The prevalence of hepatitis B virus is also correlated with liver cancer in many of the areas around the world; thus, aflatoxin contamination may be an important etiological factor resulting in synergistic effects with hepatitis B virus exposure.