What is mycotoxin?
Mycotoxin is secondary metabolite produced by microfungi that are capable of causing disease and death in humans or other animals.
All mycotoxins has low molecular weight, and they are natural products produced as secondary metabolites by filamentous fungi.

Mycotoxin caused a serious problem in 1962, during an incident near London which about 100000 turkeys died. This incident was found out to be due to the consumption of peanut meal which is contaminated with secondary metabolites from Aspergillus flavus. Since then, researchers have come to know that many other metabolites can also be dangerous to human beings.

Classification of mycotoxin
Usually arrange by the organ they affect. Mycotoxin are classified as followed:
Hepatotoxin, nephrotoxin, neurotoxin, immunotoxin, etc. Followed which would be the classification into generic groups such as teratogens, mutagens, carcinogens and allergens.

Examples of common mycotoxins
1.1 Aflatoxins
There are 4 major types of aflatoxins: B1, B2, G1 and G2 based on their fluorescence under UV light and relative chromatographic mobility. Aflatoxin B1 is the most dangerous natural carcinogen known and is the most common produced by toxicgenic strains.

1.2 Citrinin
It is being identified in many species of Penicillium and several species of Aspergillus. It is often associated with yellow rice disease in Japan. It is also one of the reason for porcine nephropathy. Wheat, oats, rye, corn, barley and rice are the sources of citrinin.

There are also many other mycotoxins, and the major one also includes ergot alkaloids, fumonisins, ochratoxin, patulin, trichothecenes and zearalenone.

Reference
1. J. W. Bennett and M. Klich. Mycotoxins. American Society for Microbiology, Clinicl Microbiology Reviews (July 2003) http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=164220; accessed on 1st June 2008