Ingen diastitel

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MICROBIAL DEGRADATION
OF TOXIC AND ANTINUTRITIONAL GLYCOSIDES
Comparison between cyanogenic glycosides and
other classes of glycosides
Technology and biotechnology for the removal of
plant toxins
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A chemical compound may be Toxic (poisonous)
Compounds that destroy life or impair health by
their own action or by the action of their
metabolites formed (in the body) after uptake.
Antinutritional Compounds that impair health
by destroying nutrients/vitamins or by reducing
the uptake of such essential compounds
(different mechanisms). Palatability reducing
Compounds that make products, in which they
occur, less pleasant to the taste (e.g. strongly
bitter compounds).
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• Well-known food crops that contain toxic,
• antinutritional or palatability reducing
• (e.g. bitter) constituents (examples)
• Soybean proteinase inhibitors, phytic acid
• oligosaccarides
• Cotton seeds gossypol
• Yam tubers alkaloids
• A large number of glycoside containing crops

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• Toxic glycosides in food and feed
• plants
• Cucurbitacins
• Cyanogenic glycosides
• Glucosinolates
• Glycoalkaloids
• Glycosides of vitamin D3
• Glycosides of organic nitriles
• Glycosides of aliphatic nitrocompounds
• Methylazoxymethanol (MAM) glycosides
• Naringin
• Carboxyatractyloside (CAT)
• Platyphylloside
• Polyphenoles (e.g. 2-hydroxyarctiin)
• Anthraquinone, anthrone dianthrone glycosides
• Ptaquiloside
• Ranunculin
• Saponins

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• Toxic glycosides in food and feed
• plants
• Cucurbitacins
• Cyanogenic glycosides
• Glucosinolates
• Glycoalkaloids
• Glycosides of vitamin D3
• Glycosides of organic nitriles
• Glycosides of aliphatic nitrocompounds
• Methylazoxymethanol (MAM) glycosides
• Naringin
• Carboxyatractyloside (CAT)
• Platyphylloside
• Polyphenoles (e.g. 2-hydroxyarctiin)
• Anthraquinone, anthrone dianthrone glycosides
• Ptaquiloside
• Ranunculin
• Saponins

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Cucurbitacins In cucumbers, marrows and
squashes. Most compounds very bitter, cucurbitacin
B thus can be detected in concen- trations down
to 1 ppb (?g/L). Some toxic with LD10 (oral mice)
5 mg/kg b.w.
Carnosiflosid III
Cucurbitacin L
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Glucosinolates In plants from the order
Cappa- rales among others. For example in species
of Brassica, including rape. The
compounds release different toxic
degradation-products upon processing of the
plant organs.
R
Basic structure
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Glycoalkaloids In subsection Potatoe of
the family Solanacea, among others in Solanum
tuberosum (the common potato). This may contain
up to 390 mg/kg f.w. Abdominal pain, vomiting
and different neurological symptoms.
1
1 ?-solanine 2 ?-chaconine
2
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Methylazoxymethanol (MAM) glycosides In species
of Macrozamia and Cycas. The seeds of a number of
Cycas species are traditionally eaten by native
Australians. Upon hydrolysis by a ?-glycosidase
the aglycone is released. This is highly
mutagenic and carcinogenic (causes canser).
Cycasin
Macrozamin
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Naringin In citrus fruits, notably in C.
Paradisi (grapefruit), C. Grandis (pommelo) and
sour oranges (C. aurantium). The flavonoid is
non-toxic but very bitter. The juice industry
regularly face problems with bitterness of
pressed juices due to a high content of naringin.
Naringin
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Vicine convicine In Vicia faba (faba
bean). The compounds are hydrolysed (split) in
the intestine, and the genins are absorbed.
These cause haemolytic anaemia (favism)
in glucose-6-phosphate dehydrogenase
deficient individuals.
Vicine
Convicine
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• How has mankind delt with the problems of
• unwanted (sometimes deadly poisonous)
• constituents in plants otherwise valuable as
• food or feed?
• By selection cultivars with a low
• concentration
• By scientific breeding for a low content
• By developing methods of processing that
• reduce the content of unwanted compounds
• By selection of well producing, good tasting
• highly toxic cultivars to process!

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• Toxic glycosides in food and feed
• plants
• Cucurbitacins
• Cyanogenic glycosides
• Glucosinolates
• Glycoalkaloids
• Glycosides of vitamin D3
• Glycosides of organic nitriles
• Glycosides of aliphatic nitrocompounds
• Methylazoxymethanol (MAM) glycosides
• Naringin
• Carboxyatractyloside (CAT)
• Platyphylloside
• Polyphenoles (e.g. 2-hydroxyarctiin)
• Anthraquinone, anthrone dianthrone glycosides
• Ptaquiloside
• Ranunculin
• Saponins

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• Cyanogenic compounds release the toxic agent
• hydrogencyanide (HCN) upon simple, often
• enzymatically catalyzed, degradation. The known
• naturally occurring constituents belong to one of
• the subgroups
• Cyanogenic glycosides
• Cyanogenic lipids
• Cyanogenic epoxides
• Cyanohydrins
• In addition, some naturally occurring
  nitriles of a different
• stucture are supposed to be able to form HCN
  as a result
• of metabolisation in the animal body.

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Reactions to form cyanide cyanogenic compounds
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Lima beans (Phaseolus lunatus).
Baudoin et al. 1991 Bull. Rech. Agron. Gembloux
26, 367-88.
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Glycosides of organic nitriles Studies have been
done to develop economic ways of detoxifying
jojoba meal. Including both chemical, enzymatic
and fermentative methods, none of these had been
employed commercially by 1991, being either too
expensive or, as for a Lactobacillus based
method, non-reproducible (Abbott et al., 1991).
Hence, Abbott et al. (1990) screened
micro-organisms for their ability to degrade the
nitriles. Two strains, Pseudalescheria boydii
NRRL 13766 and Fusarium moniliforme NRRL 13767
proved effective. Having demonstrated that also
water extraction, and 20 days of ensiling also
can produce meals, that support growth of mice at
a 20 level of diet substitution, the authors
still concluded, that Fusarium fermentation is
inevitable.It does not produce a heavily polluted
water stream, and do allow the necessary
post-extraction hexane recovery by heating
(Abbott et al., 1991).
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Naringin The citrus industry face problems with
bitterness of juices due to both limonoids and
naringin. Problems are due to bitterness of early
season fruits, of special cultivars, and enhanced
release of bitter compounds as a result of higher
pressure to maximise the yield of juice (Shaw,
1990). Several commercial preparations of
different microbiological origin are available
under the designation "naringinase", i.e.
preparations from e.g. Aspergillus and
Penicillium spp. (Lea, 1991). These can
hydrolyse the bitter principle of several citrus
juices, naringin (4',5,7-trihydroxyflavanone-7-O-(
rhamno-pyranosyl)-D-glucopyranoside (Lea, 1991
Esaki et al., 1993). According to Lea (1991)
preparations from Penicillium spp. seem superior
in industrial scale. Commercial enzyme from
Penicillium decumbens have been shown to
hydrolyse naringin to rhamnose and prunin, the
latter being degraded to glucose and naringenin
(Romero et al., 1985).
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Vicine and convicine (favism agents) Reduction
in the content of the favism factors (vicine and
convicine) in faba beans is not obtained by
germination, as for certain other antinutritional
constituents, and the reduction obtained by
cooking is also limited (Hegazy and Marquardt,
1983). The authors therefore developed a method
for the enzymatic hydrolysis, using glucosidase
from almond (addition of 10 w/w finely ground
almond to a bean paste). PH was regulated adding
lemon juice. A method giving a palatable product
was obtained, the cost of the enzyme (almonds)
being considerable, however (Arbid and Marquardt,
1985). The results were later confirmed by Meijer
and Muuse (1989). Faba beans has been
investigated as a source of isolated proteins,
prepared directly from germinated beans to reduce
the content of antinutritional factors such as
phytic acid and proteolytic enzyme inhibitors
(Bednarski et al., 1985), no observations were
made concerning vicine and convicine, however.
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Thanks for now and have a good congress with a
lot of dancing
Leon Brimer, Royal Vet.- Agric.
University, Frederiksberg (Copenhagen),
Denmark. Fax [phone] - e-mail LBR_at_KVL.DK
L. BRIMER