Mycotoxin Fact Sheets (sound familiar)

[Guest guest]

Even though they are speaking about the effects of these mycotoxins

through ingestion, I think many of you that have been exposed

through inhalation/ingestion to these toxins are suffering and

experiencing the exact same symptoms that they mention in this

report. And yet they want to continue to deny the true effects of

these toxins through inhalation and just continue coming up with the

same olde crap that the science is just not there. Who are they

truly fooling or lying to? Are they trying to convince us or

themselves. Like the old saying goes, " if it walks like a duck,

QUACKS like a duck, then it must be a duck, " but they keep telling

us its a frog, (or dimwits.)

KC

Fact sheet 8

http://www.mycotoxins.org/

Trichothecenes

Type A-trichothecenes:

T-2:

(R1 = OAc) HT-2 (R1 = OH)

Photos

Type B-trichothecenes:

DON (R1 = OH, R2 = H, R3 = OH, R4 = OH)

NIV (R1 = OH, R2 = OH, R3 = OH, R4 = OH)

Natural occurrence

The trichothecenes are a large group of chemicals characterised by a

double bond between C9 and C10 and an epoxy ring at the C12- C13

position in the chemical structure. The `12,13-epoxytrichothecenes'

are a group of related and biologically active mycotoxins often

wrongly referred to as the Fusarium toxins as several other fungal

genera including Trichoderma, Stachybotrys, Verticimonosporium,

Cephalosporium and Myrothecium can also produce them. Although the

number of compounds of this type runs into the hundreds, only a few

have been shown to be agriculturally important. However the fusaria

are by far the most important mycotoxin-producing species occurring

widely in field crops with more than 20 species of Fusarium,

including F. poae, F. sporotrichioides, F. moniliforme, F. culmorum,

and F. graminearum among the most important trichothecene producers.

They are often classified as Group A and Group B compounds depending

on whether they have a side chain on the C7 atom. The most commonly

reported Group A trichothecenes include, T-2 toxin, HT-2 toxin,

neosolaniol, monoacetoxy scirpenol and diacetoxyscirpenol. Common

group B trichothecenes are deoxynivalenol, nivalenol, 3- and 15-

acetoxynivalenol and fusarenon X (a separate fact sheet is devoted

to deoxynivalenol). In addition to producing mycotoxins these fungi

include important plant pathogens that cause a number of serious

diseases in growing crops.

Another group of trichothecenes which are generally more acutely

toxic than T-2 toxin are known as the macrocyclic trichothecenes

produced by mould species such as Stachybotrys atra. These include

the satratoxins, verrucarins and roridins.

Chemical and Physical Properties

All trichothecenes containing an ester group are hydrolysed to their

respective parent alcohols when treated with alkali. A dilute

solution of potassium carbonate, sodium hydroxide or ammonium

hydroxide hydrolyses T-2 toxin and neosolaniol to T-2 tetraol and

diacetoxy- and monoacetoxy- scirpenol to scirpentriol. Many of the

alcohols are unaffected, even by hot dilute alkali. Trichothecenes

are thus chemically stable and can persist for long periods once

formed. Prolonged boiling in water or under highly acidic conditions

causes a skeletal rearrangement due to opening of the epoxide ring.

Owing to the hindered nature of the epoxide and stability of the

ring system, reactions of the trichothecenes usually proceed in a

manner predictable from sound chemical principles, e.g. primary and

secondary hydroxyl groups are easily oxidised to the aldehyde and

ketone derivatives by reagents such as CrO3-H2SO4 in acetone, CrO3-

pyridine and CrO3-acetic acid.

Group A trichothecenes, T-2 toxin, HT-2 toxin, neosolaniol,

monoacetoxy scirpenol and diacetoxyscirpenol are highly soluble in

ethyl acetate, acetone, chloroform, methylene chloride and diethyl

ether. The Group B trichothecenes, deoxynivalenol (commonly

called `DON' or `vomitoxin'), nivalenol, 3-acetyldeoxynivalenol, 15-

acetyldeoxynivalenol, fusarenone-X, scirpentriol and T-2 tetraol are

highly hydroxylated and relatively polar being soluble in methanol,

acetonitrile and ethanol.

Toxicity and Importance

When given orally or by intraperitoneal injection, the

trichothecenes are acutely toxic at low concentrations although the

acute toxicity varies considerably as shown. T-2 toxin and the

macrocyclic mycotoxins are far more toxic than deoxynivalenol, but

occur less commonly in agricultural products. Acute trichothecene

toxicity is characterised by gastrointestinal disturbances, such as

vomiting, diarrhoea and inflammation, dermal irritation, feed

refusal, abortion, anaemia and leukopenia. This group of toxins are

acutely cytotoxic and strongly immunosuppresive.

LD50 values for mice (intraperitoneal route) for some trichothecenes

trichothecene

LD50 (mg/kg bw)

deoxynivalenol

70

diacetoxyscirpenol

23

neosolaniol

14.5

HT-2 toxin

9.0

T-2 toxin

5.2

nivalenol

4.1

verrucarin A

0.5

Dosed animals become listless or inactive and develop diarrhoea and

rectal haemorrhaging. Necrotic lesions may develop in the mouth

parts. The mucosal epithelium of the stomach and small intestine

erodes, accompanied by haemorrhage, which may develop, into severe

gastroenteritis, followed by death. In larger animals, massive

haemorrhages develop in the small intestine. The cells of the bone

marrow, lymph nodes and intestines undergo a pathological

degeneration. The trichothecenes have not been shown to be mutagenic

or carcinogenic, but do inhibit DNA and protein synthesis.

A characteristic of a number of the trichothecenes is to cause

vomiting and this may limit the amount of food ingested by

livestock. For example, pigs are very sensitive to the presence of

deoxynivalenol and will reject contaminated feed effectively

limiting any further toxic effects. However, many compounds of this

group are immunosuppresive in low concentrations and this may be

more important than their acute toxicities. Because of the number of

closely related metabolites likely to occur in combination in foods

or animal feeds, the toxicology is complex with both synergistic and

antagonistic effects observed.

Alimentary toxic aleukia (ATA) is the most well recognised human

trichothecene mycotoxicosis. T-2 toxin is thought to have

contributed to the epidemiology of alimentary toxic aleukia in

Russia last century, which was responsible for widespread disease

and many deaths. Continuous exposure to trichothecenes results in

skin rashes, which may proceed to necrotic lesions. Many outbreaks

of acute human diseases involving nausea, vomiting, gastrointestinal

upset, dizziness, diarrhoea and headache have occurred particularly

in Asia and these outbreaks have been attributed to the consumption

of Fusarium-contaminated grain. High concentrations of

deoxynivalenol have been detected in some samples from such

outbreaks.

Products affected and Natural Occurrence

Surveys have shown that trichothecenes occur in cereal grains such

as wheat, barley, maize, oats, rice, soya beans and in derived

products such as breakfast cereals and beer. There are also reports

of occurrences in other food commodities including sorghum,

potatoes, bananas, mustard seed, groundnuts, mangoes, sunflower

seeds and cassava. Past surveillance of cereals commonly targeted

deoxynivalenol only although other trichothecenes are highly likely

to be present and the recent trend is to screen for the range of

related compounds that may be expected to occur.

Satratoxins, verrucarins and roridins and may be produced in hay and

straw stored under unsatisfactory conditions and may cause symptoms

including decreased performance in race horses, haemorrhaging and

death, particularly in equines. However, there is little evidence

that these compounds occur in human food although the presence of

macrocyclic trichothecenes in air-borne fungal spores may contribute

to some forms of `sick building' syndrome.

Sampling and Analysis

Since the trichothecenes are a group of closely related compounds,

physicochemical analytical methods are usually intended to determine

more than one single trichothecene. Analytical procedures differ in

extraction, clean up and determination steps, depending on which

group of trichothecenes is to be analysed. Detailed information on

analysis including the extraction solvents, cleanup methods and

detection systems used is provided in the analytical series of fact

sheets.

Most trichothecenes with the exception of some of the macrocyclics

such as roridin A and verrucarin, possess little absorption in the

UV, other than end absorption. Thus the original methods developed

based on TLC were insensitive and non-specific requiring a range of

derivatisation reagents such as concentrated H2SO4 and p-

anisaldehyde to give characteristic colours for their detection.

Because of this, together with the complexity of the mixtures that

are now known to occur naturally, the analytical method of choice

for quantitative results today is often GC either with electron

capture or mass spectrometric detection (MS). Recently, LC-MS, has

been employed for the determination and identification of

trichothecenes at trace levels. In addition, reliable and quite

sensitive HPLC methods have been developed for some of the Group B

compounds.

Immunoassays are available as screening tests for DON, T-2- and HT-2

in cereals or for rapid screening of trichothecenes. Accurate

quantification by immunological assays is often prevented or limited

due to cross reactivity. Future development of more specific

antibodies may improve quantification and sensitivity.

Stability and Persistence

The trichothecene structure is quite stable so that most compounds

are relatively unchanged during processing although the number of

studies reported is limited. Recent studies have shown that when

flour containing deoxynivalenol was used to produce bread using

fermentation temperatures between 30º and 50ºC the maximum reduction

in concentration was about 50%. The effects of moisture, pH and heat

on the stability of nivalenol and deoxynivalenol in naturally

contaminated ground maize were shown to be relatively small over a

pH range of 1-10. Conditions of pH 12, high salt concentration and

80ºC for a prolonged time were required to give substantial

breakdown.

Legislation and Control

Legislation for selected trichothecenes has existed in only a few

countries. Recently, high levels of deoxynivalenol were found in

infant/foods in the Netherlands and this mycotoxin and related

trichothecenes have since come under close scrutiny within the EC.

One difficulty in considering possible legislation is how to deal

with mixtures of toxins of different toxicity that can occur

together but often in widely varying proportions. However in 2000

the EC proposed action levels for deoxynivalenol of 500ppb for

cereal products as consumed, and for other cereal products at the

retail stage, 750 ppb for flour used as raw material in food

products and 750 ppb as a monitoring level for raw cereals. At the

time, The Commission indicated that these levels were unlikely to be

published but asked Member States to consider the practicalities of

advising on and using the levels. Trichothecenes were evaluated by

JECFA in February 2001 and among the recommendations was the need to

obtain much more information on many aspects related to the toxicity

and occurrence of these mycotoxins.