Chapter 2 Mycotoxin Flashcards
What are mycotoxins?
Secondary metabolites of fungi which can be toxic to humans/amimals when ingested/inhaled.
What are the features of mycotoxin?
- Low molecular weight; non protein, non-carbohydrate
- Structural diverse
- Potent biological effector
- Wide range of specific toxic effect
Are mycotoxins natural occuring?
Yes
Are mycotoxins natural occuring?
Yes
Does secondary metabolites directly function in the process of growth and development?
No, they are produced to influence a competitive outcome
Where can we find mycotoxins?
Maize, wheat, nuts, coffee, cereals…
25% of global argriculture producs
How many mycotoxins are identified? How many of them are toxigenic?
- 10,000 identified
- 500 toxigenic
Where can the contamination be?
- during growth of the cereal plant on the field
- during storage of the grain
Give example for
1. Field fungi
2. Storage fungi
- Fusarium sp.
- Asperigillus sp.
- Penicillium sp.
Mycotoxins can be eliminated by cooking, T/F?
False
Rice usually less contain mycotoxins, T/F?
True
What are the 2 reasons for mycotoxin production?
- genetic resistance of the plant cultivar to fungal infection; natural plant-derived detoxification-systems (enzymes)
- environmental conditions and stress during growth and at the time of crop harvest
What are the factors for mycotoxin production in storage?
- moisture level of the produce
- storage conditions (temperature, humidity!) and duration
- insect damage and infestation
- The presence of substrate for fungi growth
Name some chemical, environmental and biological factors affecting mycotoxin occurence
Biological: Suceptible crops, compatible toxogenic fungus
Chemcial: CO2 O2, composition of substrate, pesticides and fungicides
Environmental: Temp, humidity, injury
What are the 3 types of mycotoxin focused in this chapter?
- Aflatoxin
- Deoxynivalenole (DON)
- zearalenone (ZEN)
Give some general characteristics of mycotoxins
- low molecular weight
- varying water solubility
- chemically stable
- Heat resistant (stabilization through binding to proteins orother compounds)
What is the main way of exposure?
oral ingestion of contaminated
food/feed
A kind of direct exposure
Is indirect exposure to mycotoxin also possible?
Yes
Some animal derived food has residues. Inhalation and skin contact also
What primarily produces Aflatoxin?
Also give some general features
A. flavus & A. parasiticus
Important agent of disease (acute death/ chronic tumour)
Give some examples of Aflatoxin incidents
- “turkey X disease”
- Acute poisoning due to presence in rice, Taiwan
- Kenya: maize high level of aflatoxin
What food is the primary contamination of aflatoxin?
High energy content foods
grain, nut and soy products
What is the secondary contamination of aflatoxin?
Dairy products
What is the main cause of toxicity in the metabolic transformation of aflatoxin B1?
Aflatoxin-exo 8,9-epoxide
unlikely to be asked
What are the 5 toxicities of aflatoxin?
- Carcinogenicity
- Immunotoxicity:Immunosuppressive
- Malnutrition
- Retarted physical and mental maturity
- Reproduction and nervous system disease
Why aflatoxin has a high carcinogenicity?
- Aflatoxin B1 is highly mutagenic
1. epoxidation resulting in covalent binding to DNA
2. specific mutation at tumor-suppressor gene p53
Why intake estimates are not accurate?
- Recall what they eat
- Over/underestimate the actual amount
- biased/ non-reliable results
What is the relationship between chronic hepatitis B and aflatoxins?
Increase the risk of liver cancer
Synergy
Breast milk cannot transmit aflatoxin to infants, T/F?
False, the kids have retarded growth
Breast milk cannot transmit aflatoxin to infants, T/F?
False, the kids have retarded growth
What family does Deoxynivalenol (DON) belong to?
Trichothecenes
Trichothecenesbelongs to Type B
What are the common contaminants of DON?
- cereal crops
- processed grains
What is the alternative name of DON?
Vomitoxin
What are the toxicities of DON?
- digestive disorders
- oral and dermal lesions, haemorrhages, necroses
- reduced productivity and performance
- immunosuppression
- Reduced growth
What is the problem of immunosuppression?
Severe adverse health effects could be found in chronic low level exposure.
What are the consequences of immunesuppression?
- increased risk of infections
- more severe disease processes
- more difficult therapies
- impaired vaccination response
- activation of tumor formation
- impaired health status - decreased productivity
Why is immunosupression/DON exposure difficult to detect?
overlaying secondary diseases or infections
Why is immunosupression/DON exposure difficult to detect?
overlaying secondary diseases or infections
DON and ZEA has synergism, T/F
True
Can be produced by same fungal species F. graminearum
ZEA is heat stable and resistant to standard decontamination process, T/F?
True
Suggest the direct and indirect contamination of ZEA
- Direct contamination: food or feed infected by fungi
- Indirect contamination: Processed food, e.g. Beer, flour, soybean, bread, milk, cheese, meat
Why can ZEA cause the “estrogen-like syndrom”?
It acts as an endocrine disrupter cuz has** high sturcture similarity w/ estrogen**
What is the toxicokinetics of ZEA for animals?
affecting primarily the reproductive system (infertility, abortions, various hyperstrogenism-effects)
leading to reduced performance and reproduction in farm animals
What is the toxicokinetics of ZEA for humans?
- Pre-mature pubertal changes
- Scabby grain toxicosis
ZEA is classified as a carcinogen, T/F?
False, the carcinogenic properties of ZEA are not yet well defined
What are the 3 ways to counteract mycotoxins?
- Prevention (food production)
- Decontamination (physical/chem treatments, during food processing)
- Deactivation ( During food digestion)
