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BIOL3207 Toxicology > Chapter 2 Mycotoxin > Flashcards

Chapter 2 Mycotoxin Flashcards

1
Q

What are mycotoxins?

A

Secondary metabolites of fungi which can be toxic to humans/amimals when ingested/inhaled.

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2
Q

What are the features of mycotoxin?

A
  • Low molecular weight; non protein, non-carbohydrate
  • Structural diverse
  • Potent biological effector
  • Wide range of specific toxic effect
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3
Q

Are mycotoxins natural occuring?

A

Yes

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4
Q

Are mycotoxins natural occuring?

A

Yes

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5
Q

Does secondary metabolites directly function in the process of growth and development?

A

No, they are produced to influence a competitive outcome

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6
Q

Where can we find mycotoxins?

A

Maize, wheat, nuts, coffee, cereals…
25% of global argriculture producs

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7
Q

How many mycotoxins are identified? How many of them are toxigenic?

A
  • 10,000 identified
  • 500 toxigenic
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8
Q

Where can the contamination be?

A
  1. during growth of the cereal plant on the field
  2. during storage of the grain
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9
Q

Give example for
1. Field fungi
2. Storage fungi

A
  1. Fusarium sp.
  2. Asperigillus sp.
  3. Penicillium sp.
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10
Q

Mycotoxins can be eliminated by cooking, T/F?

A

False

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11
Q

Rice usually less contain mycotoxins, T/F?

A

True

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12
Q

What are the 2 reasons for mycotoxin production?

A
  1. genetic resistance of the plant cultivar to fungal infection; natural plant-derived detoxification-systems (enzymes)
  2. environmental conditions and stress during growth and at the time of crop harvest
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13
Q

What are the factors for mycotoxin production in storage?

A
  • moisture level of the produce
  • storage conditions (temperature, humidity!) and duration
  • insect damage and infestation
  • The presence of substrate for fungi growth
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14
Q

Name some chemical, environmental and biological factors affecting mycotoxin occurence

A

Biological: Suceptible crops, compatible toxogenic fungus
Chemcial: CO2 O2, composition of substrate, pesticides and fungicides
Environmental: Temp, humidity, injury

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15
Q

What are the 3 types of mycotoxin focused in this chapter?

A
  1. Aflatoxin
  2. Deoxynivalenole (DON)
  3. zearalenone (ZEN)
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16
Q

Give some general characteristics of mycotoxins

A
  1. low molecular weight
  2. varying water solubility
  3. chemically stable
  4. Heat resistant (stabilization through binding to proteins orother compounds)
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17
Q

What is the main way of exposure?

A

oral ingestion of contaminated
food/feed

A kind of direct exposure

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18
Q

Is indirect exposure to mycotoxin also possible?

A

Yes

Some animal derived food has residues. Inhalation and skin contact also

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19
Q

What primarily produces Aflatoxin?

Also give some general features

A

A. flavus & A. parasiticus

Important agent of disease (acute death/ chronic tumour)

20
Q

Give some examples of Aflatoxin incidents

A
  1. “turkey X disease”
  2. Acute poisoning due to presence in rice, Taiwan
  3. Kenya: maize high level of aflatoxin
21
Q

What food is the primary contamination of aflatoxin?

A

High energy content foods

grain, nut and soy products

22
Q

What is the secondary contamination of aflatoxin?

A

Dairy products

23
Q

What is the main cause of toxicity in the metabolic transformation of aflatoxin B1?

A

Aflatoxin-exo 8,9-epoxide

unlikely to be asked

24
Q

What are the 5 toxicities of aflatoxin?

A
  1. Carcinogenicity
  2. Immunotoxicity:Immunosuppressive
  3. Malnutrition
  4. Retarted physical and mental maturity
  5. Reproduction and nervous system disease
25
Q

Why aflatoxin has a high carcinogenicity?

A
  • Aflatoxin B1 is highly mutagenic
    1. epoxidation resulting in covalent binding to DNA
    2. specific mutation at tumor-suppressor gene p53
26
Q

Why intake estimates are not accurate?

A
  • Recall what they eat
  • Over/underestimate the actual amount
  • biased/ non-reliable results
27
Q

What is the relationship between chronic hepatitis B and aflatoxins?

A

Increase the risk of liver cancer

Synergy

28
Q

Breast milk cannot transmit aflatoxin to infants, T/F?

A

False, the kids have retarded growth

29
Q

Breast milk cannot transmit aflatoxin to infants, T/F?

A

False, the kids have retarded growth

30
Q

What family does Deoxynivalenol (DON) belong to?

A

Trichothecenes

Trichothecenesbelongs to Type B

31
Q

What are the common contaminants of DON?

A
  • cereal crops
  • processed grains
32
Q

What is the alternative name of DON?

A

Vomitoxin

33
Q

What are the toxicities of DON?

A
  1. digestive disorders
  2. oral and dermal lesions, haemorrhages, necroses
  3. reduced productivity and performance
  4. immunosuppression
  5. Reduced growth
34
Q

What is the problem of immunosuppression?

A

Severe adverse health effects could be found in chronic low level exposure.

35
Q

What are the consequences of immunesuppression?

A
  1. increased risk of infections
  2. more severe disease processes
  3. more difficult therapies
  4. impaired vaccination response
  5. activation of tumor formation
  6. impaired health status - decreased productivity
36
Q

Why is immunosupression/DON exposure difficult to detect?

A

overlaying secondary diseases or infections

36
Q

Why is immunosupression/DON exposure difficult to detect?

A

overlaying secondary diseases or infections

37
Q

DON and ZEA has synergism, T/F

A

True

Can be produced by same fungal species F. graminearum

38
Q

ZEA is heat stable and resistant to standard decontamination process, T/F?

A

True

39
Q

Suggest the direct and indirect contamination of ZEA

A
  • Direct contamination: food or feed infected by fungi
  • Indirect contamination: Processed food, e.g. Beer, flour, soybean, bread, milk, cheese, meat
40
Q

Why can ZEA cause the “estrogen-like syndrom”?

A

It acts as an endocrine disrupter cuz has** high sturcture similarity w/ estrogen**

41
Q

What is the toxicokinetics of ZEA for animals?

A

affecting primarily the reproductive system (infertility, abortions, various hyperstrogenism-effects)
leading to reduced performance and reproduction in farm animals

42
Q

What is the toxicokinetics of ZEA for humans?

A
  • Pre-mature pubertal changes
  • Scabby grain toxicosis
43
Q

ZEA is classified as a carcinogen, T/F?

A

False, the carcinogenic properties of ZEA are not yet well defined

44
Q

What are the 3 ways to counteract mycotoxins?

A
  1. Prevention (food production)
  2. Decontamination (physical/chem treatments, during food processing)
  3. Deactivation ( During food digestion)

BIOL3207 Toxicology (7 decks)

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