Mycotoxins general account, types & importance

Mycotoxins general account types &importance

1. Mycotoxins -General account, types & importance Vaishali S.Patil Professor, Department of Botany Shri Shivaji College of Arts, Commerce & Science Akola

2. Introduction A  mycotoxin  (from the  Greek   mykes , "fungus" and   toxini , "toxin ") is a  toxic  secondary metabolite produced by organisms of the  fungus  kingdom  and is capable of causing disease and death in both humans and other animals .   The term ' mycotoxin ' is usually reserved for the toxic chemical products produced by fungi that readily colonize crops . One mold species may produce many different mycotoxins , and several species may produce the same mycotoxin . M ycotoxins are not necessary for the growth or the development of the fungi. Mycotoxins weaken the receiving host, they may improve the environment for further fungal proliferation.

3. Examples of mycotoxins causing human and animal illness include  aflatoxin ,  citrinin ,  fumonisins ,  ochratoxin A,  patulin ,  trichothecenes ,  zearalenone , and ergot alkaloids such as ergotamine . Production- Most fungi are aerobic (use oxygen) and are found almost everywhere in extremely small quantities due to the diminute size of their spores. They consume  organic matter  wherever humidity and temperature are sufficient . Where conditions are right, fungi proliferate into colonies and mycotoxin levels become high.  The production of toxins depends on the surrounding intrinsic and extrinsic environments and these substances vary greatly in their toxicity, depending on the organism infected and its susceptibility, metabolism, and defence mechanisms .

4. Types 1.Aflatoxins  - It is produced by  Aspergillus   species of fungi, such as  A. flavus  and  A. parasiticus .   Types- B 1 , B 2 , G 1 , and G 2 . Aflatoxin B 1 , the most toxic , is a potent carcinogen  and has been directly correlated to adverse health effects, such as liver cancer, in many animal species. Aflatoxin are largely associated with commodities produced in tropic and subtropics such as cotton, peanuts, spices, pistachios and maize. They are regularly found in improperly stored staple commodities  such as cassava,  chili peppers, cottonseed, millet, peanuts, rice, sesame seeds, sorghum, sunflower seeds,  sweetcorn , tree nuts, wheat, and a variety of spices. 

5. Children are particularly affected by aflatoxin exposure, which is associated with stunted growth, delayed development, liver damage, and liver cancer.  Aflatoxin transformation products are sometimes found in eggs, milk products, and meat when animals are fed contaminated grains. High-level aflatoxin exposure produces an acute hepatic necrosis (acute aflatoxicosis ), resulting later in cirrhosis or carcinoma of the liver. Acute liver failure is made manifest by bleeding,  edema , alteration in digestion , changes to the absorption and/or metabolism of nutrients, and mental changes and/or coma . A regular diet including apiaceous vegetables, such as carrots, parsnips, celery, and parsley may reduce the carcinogenic effects of aflatoxin .

6. Aflatoxin

7. 2.Ochratoxin- It is produced by  Penicillium  and  Aspergillus  species Types- A, B, and C . The three forms differ in that Ochratoxin B (OTB) is a nonchlorinated form of Ochratoxin A (OTA) and that Ochratoxin C (OTC) is an ethyl ester form Ochratoxin A .   Aspergillus ochraceus  is found as a contaminant of a wide range of commodities including  beverages such as beer and wine . Ochratoxin A is known to occur in commodities such as cereals, coffee, dried fruit, and red wine.     Aspergillus carbonarius  is the main species found on vine fruit, which releases its toxin during the juice making process .  OTA has been labeled as a carcinogen and a nephrotoxin , and has been linked to tumors in the human urinary tract. Meat and meat products can be contaminated with this toxin. Exposure to ochratoxins through diet can cause acute toxicity in mammalian kidneys .

8. Ochratoxin

9. Ochratoxin A Ochratoxin B Ochratoxin C Ochratoxin TA

10. 3.Citrinin- Discovered by H. Raistrick and A.C. Hetherington in the 1930s It is produce by   species of  Penicillium  and Aspergillus . It is associated with yellowed rice disease in Japan and acts as a  nephrotoxin  in all animal species tested .   I t is associated with many human foods (wheat, rice, corn, barley, oats, rye, and food colored with  Monascus  pigment ). It can also act synergistically with Ochratoxin A to depress RNA synthesis in murine kidneys. Health hazards caused by inhaled citrinin or through dermal exposure of citrinin is largely unclear. Researchers found that citrinin is also used in indoor materials. Citrinin are acute toxicity, nephrotoxicity ,  genotoxicity  and

11. its carcinogenicity. Citrinin toxicity reduced cytokine production, inhibition of RNA and DNA synthesis, induction of oxidative stress, inhibition of nitride oxide gene expression, increase in ROS production and activation of apoptotic cell death via signal transduction pathways and the caspase -cascade system.

12. 4. Ergot Alkaloids-   They are compounds produced as a toxic mixture of alkaloids in the  sclerotia  of species of  Claviceps , which are common pathogens of various grass species. The ingestion of ergot sclerotia from infected cereals, commonly in the form of bread produced from contaminated flour, causes  ergotism , the human disease historically known as St. Anthony's Fire. There are two forms of ergotism : gangrenous, affecting blood supply to extremities, and convulsive, affecting the central nervous system . The severe burning sensations in the limbs which was one of the symptoms,muscle spasms, fever and hallucinations and the victims may appear dazed, be unable to speak, become manic, or have other forms of paralysis or tremors, and suffer from hallucinations and other distorted perceptions. This is caused by serotonergic stimulation of the central nervous system by some of the alkaloids. The second type of ergotism is marked by violent burning, absent peripheral pulses and shooting pain of the poorly vascularized distal organs, such as the fingers and toes,and are caused by effects of ergot

13.   alkaloids on the vascular system due to vasoconstriction, sometimes leading to gangrene and loss of limbs due to severely restricted blood circulation Ergot alkaloids have been used pharmaceutically. Types- G1 — land grasses of open meadows and fields; G2 — grasses from moist, forest, and mountain habitats; G3 ( C. purpurea  var.  spartinae ) — salt marsh grasses ( Spartina ,  Distichlis ). Ergot alkaloids have a wide range of biological activities including effects on circulation and neurotransmission. The neurotropic activities of the ergot alkaloids may also cause hallucinations and attendant irrational behaviour, convulsions, and even death. Other symptoms include strong uterine contractions, nausea, seizures, high fever, vomiting, loss of muscle strength and unconsciousness. Since the Middle Ages, controlled doses of ergot were used to induce abortions and to stop maternal bleeding after childbirth.

14. Ergot Alkaloids

15. 4.Patulin-  It is a toxin produced by the  P. expansum ,  Aspergillus ,  Penicillium , and  Paecilomyces fungal species.   P. expansum  is especially associated with a range of moldy  fruits and vegetables, in particular rotting apples and figs.  It is destroyed by the fermentation process and so is not found in apple beverages, such as cider. Although patulin has not been shown to be carcinogenic, it has been reported to damage the immune system in animals. Patulin was originally used as an antibiotic against Gram-positive and Gram-negative bacteria, It was specifically trialed to be used against the common cold. Patulin is used as a potassium-uptake inhibitor in laboratory applications. Patulin stimulates suicidal erythrocyte death under physiological concentrations. Patulin has shown antimicrobial properties against some microorganisms.

16. Patulin

17. 5.Fusarium- These toxins are produced by over 50 species of  Fusarium  and have a history of infecting the grain of developing cereals such as wheat and maize.  They include a range of mycotoxins , such as: the  fumonisins , which affect the nervous systems of horses and may cause cancer in rodents; the  trichothecenes , which are most strongly associated with chronic and fatal toxic effects in animals and humans; and  zearalenone , which is not correlated to any fatal toxic effects in animals or humans. Some of the other major types of  Fusarium  toxins include: beauvercin and enniatins ,  butenolide , equisetin , and  fusarins . Some species may cause a range of opportunistic infections in humans.

18. In humans whose immune systems are weakened in a particular way, ( neutropenia , i.e., very low  neutrophils  count), aggressive fusarial infections penetrating the entire body and blood stream (disseminated infections) may be caused by members of the  Fusarium solani complex,  Fusarium oxysporum ,  Fusarium verticillioides ,  Fusarium proliferatum  and, rarely, other fusarial species. In humans with normal immune systems, fusarial infections may occur in the nails ( onychomycosis ) and in the cornea ( keratomycosis  or mycotic keratitis ). 

19. Fusarium

20. 6.Wild mushrooms-   Ingestion of misidentified mushrooms containing mycotoxins may result in hallucinations. The cyclopeptide -producing  Amanita phalloides  is well known for its toxic potential and is responsible for approximately 90% of all mushroom fatalities. The other primary mycotoxin groups found in mushrooms include: orellanine , monomethylhydrazine , disulfiram -like, hallucinogenic indoles , muscarinic , isoxazole , and gastrointestinal (GI)-specific irritants cause vomiting and  diarrhea  (sometimes requiring hospitalization) Serious symptoms do not always occur immediately after eating, often not until the toxin attacks the kidney or liver, sometimes days or weeks later.

21. Poisonous mushrooms   Amanita pantherina Chlorophyllum molybdites Entoloma   Inocybe Clitocybe Tricholoma pardinum Hypholoma fasciculare , Paxillus involutus Rubroboletus satanas

22. Turbinellus floccosus Hebeloma crustuliniforme Russula emetica Agaricus hondensis Lactifluus piperatus Lactarius vinaceorufescens Ramaria gelatinosa Amanita muscaria Tricholoma equestre

23. In indoor environments- Buildings are another source of mycotoxins . Some of the mycotoxins in the indoor environment are produced by  Alternaria ,   Aspergillus  (multiple forms),  Penicillium , and  Stachybotrys .   Stachybotrys chartarum  contains a higher number of mycotoxins than other molds grown in the indoor environment and has been associated with allergies and respiratory inflammation. S. chartarum   can evoke allergic sensitization, inflammation, and cytotoxicity in the upper and lower respiratory tracts.  In food- Mycotoxins can appear in the food chain as a result of fungal infection of crops, either by being eaten directly by humans or by being used as livestock feed. Spices are susceptible substrate for growth of mycotoxigenic fungi and mycotoxin production.Red chilli, black pepper, and dry ginger were found to be the most contaminated spices. In animal food- Dimorphic fungi, which include  Blastomyces dermatitidis  and  Paracoccidioides brasiliensis , are known causative agents of endemic systemic mycoses.

24. Paracoccidioides brasiliensis Penicillium , Alternaria ,   Paecilomyces Stachybotrys   Blastomyces dermatitidis