Agriculture Reference
In-Depth Information
analysed for the presence of total nitrofuran metabolites, then the standard acid
hydrolysis and o-nitrobenzaldehyde derivatisation procedure will convert the
furazolidone to AOZ. This means that it may be possible to detect nitrofurans
in eggs as their parent drugs using simpler procedures [56].
6.
M
UTAGENICITY AND
T
OXICITY
Carcinogenicity and mutagenicity of compounds in food products are
among the toxicological issues that pose, nowadays, the highest health related
concern. Toxicology is assigned the parallel tasks of performing safety
evaluations for the uses of new chemicals before human exposure is permitted,
and assessing the potential hazards posed by exposure to chemicals that lack
safety evaluations [57]. The mutagenic potential of chemicals can be assessed
with relatively simple test methods, but the standard bioassay in rodents used
to assess the carcinogenic potential of chemicals is extremely long and costly
and requires the sacrifice of large numbers of animals.
Other toxicological effects have been reported in what pertains to
nitrofurans, including central nervous system degeneration, gastrointestinal
disturbances, methemoglobinemia, poor weight gain and reduced
spermatogenesis. Various hypersensitivity reactions have also been described.
When excessive doses of furazolidone are administered to small calves, such
as Jersey calves, neurotoxicity is common. In humans, polyneuropathy is
associated with nitrofurantoin use. On the other hand, nitrofurantoin has been
linked to yellow discoloration of the teeth in young animals [34].
As mentioned previously, the nitro-group, coupled to the furan ring is the
key structural element in the mechanism of nitrofuran antimicrobial action. To
be active and to interact with macromolecules, these compounds need to be
metabolized by microbial nitroreductases [58]. The final metabolite is also
inactive, but the metabolic intermediates attack a variety of cellular
constituents including proteins and nucleic acids. Enzymatic nitroreduction of
nitrofurans has also been described in animal tissues [34], implying that toxic
and mutagenic effects could also occur in mammalian cells and tissues
exposed to these chemicals [58].
Mutagenicity and toxicity of nitrofurans are discussed not only in relation
to their abuse in livestock production, but special attention has also been
devoted to the toxicology of semicarbazide which has been found in food
produced from raw materials not subjected to nitrofurazone administration
[15].
