Sources of major toxin groups and their toxicity

Mycotoxins are secondary metabolites produced by filamentous microfungi. Fungi are major plant and insect pathogens. Disease caused by fungi growth on animal hosts called mycoses. Whereas disease caused by exposures to toxic fungal metabolites known as mycotoxicoses which is what we concern mainly in package 2 currently.

In contrast to mycoses, mycotoxicoses are examples of “poisoning by natural means”. The symptoms of a mycotoxicosis depend on the type of mycotoxin; amount and duration of exposure; age, health, and individual gender. The majority of mycotoxicoses result from eating contaminated foods. Skin contact with mould-infested substrates and inhalation of spore-borne toxins are also important sources of exposure.

While all mycotoxins are of fungal origin, not all toxic compounds produced by fungi are called mycotoxins. Acute mycotoxicoses generally has a rapid onset and an obvious toxic response, while chronic mycotoxicoses is characterized by low-dose exposure over a long time period, resulting in cancers and other generally irreversible effects.

Generally, mycotoxin exposure is more likely to occur by poor methods of food handling and storage. Controlling mycotoxins can be prevented by applying good agricultural practice and sufficient drying of crops after harvest.

Below are summary of toxin groups, sources of origination, toxicity, and legal limit:

Aflatoxin
Aspergillus flavus and Aspergillus parasiticus; Aspergillus bombycis, Aspergillus ochraceoroseus, Aspergillus nomius, and Aspergillus pseudotamari

Possess toxicity and carcinogenicity. Disease called aflatoxicoses can cause death in acute case, chronic aflatoxicosis results in cancer & immune suppression. Liver is primary targeted organ.

Citrinin
First isolated from Penicillium citrinum.Also from species of Aspergillus, strains of Penicillium camemberti (used to produce cheese) and Aspergillus oryzae. Monascus ruber and Monascus purpureus ( industrial species used to produce red pigments).

Significance for human health is unknown.

Ergot Alkaloids
Sclerotia of Claviceps species(common pathogens of grass species)

The principal animals at risk are cattle, sheep, pigs, and chickens. Clinical symptoms of ergotism in animals include gangrene, abortion, convulsions, suppression of lactation, hypersensitivity, and ataxia.

Fumonisins
Fusarium verticillioides (formerly Fusarium moniliforme = Gibberella fujikuroi), Fusarium proliferatum, Fusarium nygamai, and Alternaria alternata f. sp. lycopersici

Probable link with esophageal cancer in human. Acute exposure to fumonisin B1 may cause abdominal pain, borborygmus, and diarrhea. neural tube defects in experimental animals

Ochratoxin
Aspergillus ochraceus, Aspergillus alliaceus, Aspergillus auricomus, Aspergillus carbonarius, Aspergillus glaucus, Aspergillus melleus, and Aspergillus niger, Penicillium verrucosum(common contaminant of barley)

Kidney is primary target organ. Ochratoxin A is a liver toxin, an immune suppressant, a potent teratogen, and a carcinogen. It inhibits the enzyme in synthesis of phenylalanine-tRNA complex and also inhibits mitochondrial ATP production and stimulates lipid peroxidation. European Union Scientific Committee recommended that ochratoxin A levels be reduced to below 5 ng/kg of body weight per day.

Patulin
Mold species. Penicillium patulum (later called Penicillium urticae, now Penicillium griseofulvum), Penicillium expansum

Toxic at high concentration in laboratory settings, but evidence for natural poisoning is indirect and inconclusive. Joint Food and Agriculture Organization-World Health Organization Expert Committee on Food Additives: maximum tolerable daily intake for patulin of 0.4 mg/kg of body weight per day

Trichothecenes
fungal genera, including Fusarium, Myrothecium, Phomopsis, Stachybotrys, Trichoderma, Trichothecium

Consumption result in alimentary haemorrhage and vomiting; direct contact causes dermatitis. It’s extremely potent inhibitors of eukaryotic protein synthesis.

Zearalenone

Fusarium graminearum

recommended safe human intake: 0.05 μg/kg of body weight per day

Reference: http://www.nzfsa.govt.nz/science/data-sheets/index.htm