Natural toxic substances (1. LF UK, NT)

Natural anti-nutritional and toxic substances

Natural anti-nutritional and toxic substances include:

• antinutritional substances – interference (nutrients),
• toxic substances - poisons (toxics),
  • natural toxic substances - toxins,
  • products of anthropogenic activity – xenobiotics.

The toxic effects of these substances can be acute or late (e.g. chronic).

Amount of risk:

• contaminants,
• toxins,
• additive substances,
• antinutritional substances.

Their content in food is subject to legislative measures.

Feeding trials → NOAEL → ADI = NOAEL / 100, (mg/kg), safety factor (100)

• MLR = ADI * 60, (NPM, PM, SM), food basket, taking into account the amount of consumption

Antinutritional substances

Antinutritional substances are substances of plant origin that cause potential risks. Is part of them:

1. enzyme inhibitors, antienzymes,
2. compounds interfering with vitamin metabolism, antivitamins, vitamin antagonists,
3. compounds interfering with the metabolism of mineral substances,
4. phenolic compounds (tannins) reacting with proteins,
5. some oligosaccharides causing flatulence.

raffinose

1. Inhibitors of serine proteases (trypsin, chymotrypsin, elastase):

• lead to a slowdown in the growth of farm animals,
• heat inactivation occurs (they are proteins).

2. Antivitamins:

• structural analogues (oxythiamine, linatin),
• enzymes (ascorbase, thiaminase, lipoxygenase),
• forming unusable complexes (avidin).

tannin

3. Compounds binding mineral substances:

• phytic acid and phytin – Fe, Zn,
• oxalic acid – Ca,
• glucosinolates and their breakdown products – I.

4. Tannins:

• slowing down the growth of farm animals,
• reduction of digestibility of proteins and absorption of mineral substances.

oxalic acid

5. α-galactosides:

• raffinose, higher homologues,
• cause gastrointestinal problems.

Toxic substances

Toxic substances present real risks:

• causing food intolerance ( intolerance ), toxic for certain individuals,
• causing intoxication , toxic for all individuals. Substances causing food intolerance:
• allergies (immunological reactions), allergens (immunogens), (do not) induce IgE formation,
  • celiac disease, gluten-free diets (<100 mg/kg gliadin dry weight),
• intolerance (non-immunological manifestations), metabolic disorders, hypersensitivity (anaphylaxis), aversion (idiosyncrasy),
  • lactose intolerance, foods with a low content (<10 g/kg), lactose-free (100 mg/kg),
  • phenylketonuria, hydrolysates without Phe,
  • favism, broad bean ( Vicia faba ).
    

Toxins and other substances causing intoxication

Classification:

• by structure,
• physical properties,
• by origin (plant, animal),
• by effects,
• main groups of toxins,
• alkaloids,
• saponins,
• cyanogens,
• glucosinolates,
• lectins,
• estrogenic substances,
• phototoxic substances,
• amino acids,
• biogenic amines.

Antinutritional and toxic substances of legumes:

• protease and amylase inhibitors,
• α-galactosides,
• substances causing favism,
• lectins,
• cyanogenic glycosides,
• estrogens,
• saponins,
• lathyrogens.

Toxic substances of higher mushrooms:

• proteins,
• peptides,
• amino acids,
• amines,
• hydrazines,
• alkaloids,
• terpenoids.

Alkaloids

Classification:

• true alkaloids (N-heterocycles, derived from amino acids),
  • pyridine (nicotine) and tobacco,
  • piperidine and pepper,
  • pyrrolizidines and senecias (necines),
  • quinolizidine and. lupins,
  • quinoline and cinchona bark,
• pseudoalkaloids (N-heterocycles, derived from other precursors),
  • purine a. coffee, tea, cocoa,
  • terpenoid (glycoalkaloids) a. potatoes, tomatoes,
• protoalkaloids (not N-heterocycles, derived from amino acids),
  • capsaicinoids and peppers.

Pyridine alkaloids

Nicotine and minor alkaloids (~20 compounds):

• tobacco (obligation to indicate content in tobacco products, warnings)
  

Piperidine alkaloids

Piperine, homologs, geometric isomers, related substances, pepper (hot substances)

Pyrrolizidine alkaloids

Many related esters (mono-, di-, macrocyclic), hepatotoxic substances

Quinolizidine alkaloids

A number of related compounds, lupine

Quinoline alkaloids

Contents in pod.

Legislation: additive, alcoholic beverages 300 mg/l, non-alcoholic (tonics) 75 mg/l (teratogenicity)

Purine alkaloids

a number of related compounds, coffee, tea, cocoa (chocolate), mate, guarana.

• caffeine R 1 = R 2 = R 3 = CH 3
• theobromine R 1 = H, R 2 = R 3 = CH 3
• theophylline R 1 = R 2 = CH 3 , R 3 = H

Steroidal glycoalkaloids

• a number of related compounds, potatoes, tomatoes, eggplant,
• heteroglycosides, aglycone, sugar.

Potatoes

• α-solanine = solanidine + β-solatriose,
• α-chaconine = solanidine + β-chacotriose,
  

• distribution,
• legislation: 200 mg/kg.

Tomatoes

• tomatine = tomatidine + β-lycotetraose

• legislation: 200 mg/kg, teratogenicity

Capsaicinoids

capsaicin, homologues, paprika (hot substances):

• the effect of technological processing,
• 
  capsaicin, (E)-8-methyl-N-vanillylnon-6-enamide .

Saponins

a number of related compounds, foods of plant origin:

• heteroglycosides, aglycone, sugar,
• aglycon = sapogenin (sapogenol),
  • triterpene alcohols,
  • sterols (4-demethylsterols).

Biological effects:

• hemolysis of erythrocytes, other cells, damage to the intestinal mucosa.

Properties

• toxicity to cold-blooded animals,
• bitter taste,
• detergent effects, emulsion (o/w),
• fungicidal, antioxidant, anticarcinogenic, anticholesterolemic effects.

Use

• foaming agents (cosmetics),
• emulsifiers (cosmetics),
• sweeteners (glycyrrhizin, licorice: 0.2−5.6% saponins).
• 

Cyanogenic glycosides

• a number of related compounds, foods of plant origin,
• HCN content in cyanogens,
• heteroglycosides, aglycone, sugar,
• aglycone = 2-hydroxynitrile (cyanohydrin),
• 
  2-hydroxy acid nitrile.

Substituents - Chirality:

• aliphatic – acetone, methyl (ethyl) ketone,
• aromatic – benzaldehyde.

Sugar

• usually Glu,
• genciobiosis disaccharides etc.

Properties

• decomposition (β-glucosidase) → HCN, toxicity (inhibition of cytochrome oxidase in the respiratory chain),
• acute intoxication, chronic intoxication (cassava, cassava).

Glucosinolates

• thioglucosides (glucosides of mustard oils), a number of related compounds, foods of plant origin (cruciferous plants),
• names and structure,
• dominant glucosinolates in vegetables,
  • heteroglycosides, aglycone, sugar, aglycone = thiohydroxamate-O-sulfonate, counterion K+

Substituents

• aliphatic,
• aromatic,
• heterocyclic.

Sugar

• exclusively Glc.

Properties

• decomposition (myrosinase) → isothiocyanates, nitriles, etc.,
• toxicity, isothiocyanates and goitrin strumogenic, nitriles hepatotoxic.
  • 

Plant phenols

Estrogenic substances

phytoestrogens - foods of plant origin,

• • isoflavones,
  • content in soybeans.
    

daidzin, R = H aglycon daidzein

genistin, R = OH aglycon genistein

soybeans (0.13−0.42%)

• • pterocarps,
  • lignans.

content in food

coumestrol − sprouting − soybeans

secoisolariciresinol − flax seeds

• mycoestrogens,
• xenoestrogens.

Properties

• simultaneously useful and harmful.

Phototoxic substances

• coumarins,
• furanocoumarins,
• foods of plant origin.
• 

Properties

• phototoxicity (sensitivity of non-pigmented skin, association with skin cancer, acute dermatitis),
• phytoalexins (phytonicides, plant antibiotics, pesticides), blastocolins (inhibits seed germination),
• antimicrobial and other effects.

Phototoxic pigments

• hypericin (St. John's wort), fagopyrin (buckwheat).

Lectins (phytohemagglutinins)

foods of plant origin (seeds and other parts)

Proteins with a non-catalytic center:

• merolectins (1 center, catalytic no),
• hololectins (2 centers, no catalytic),
• chimerolectins (1−2 centers, catalytic yes).

Soy lectin

• metalloprotein, 120 kDa, hololectin, N-acetyl-D-galactosamine binding.

Properties

• precipitation of erythrocytes, interaction with sugars in glycoproteins and glycolipids of membranes (plant protection mechanism against predators, parasites),
• toxic intravenously, some orally, some not at all, some probiotics (garlic).

Amino acids

Lathyrogens:

• foods of plant origin (seeds of vetiver and peas),
• 
  amino acids (peptides, nitriles) -3-(N-oxalyl)-2,3-diaminopropanoic acid

Properties

• structural form with proteinogenic amino acids, metabolic disorders,
• deformation of the lower limbs (osteolathyrism), damage to blood vessels (angiolatyrism), disorders of the nervous system (neurolathyrism), humans, mainly farm animals.

Biogenic amines:

• precursors,
• aliphatic, aromatic, heterocyclic bases with biological activity, fermented and microbially degraded foods of plant and animal origin

Emergence

• from amino acids by microorganisms
  • 
    
    histamine (His) , cadaverine (Lys)

Properties

• tissue hormones (allergic reactions, anaphylactic shock)
• psychoactive and vasoactive substances

Content

• changes in salami

Links

Internal links

• Toxic substances
• Antinutritional substances

Source

• DAVÍDEK, Jiří. 12. PŘÍRODNÍ ANTINUTRIČNÍ A TOXICKÉ LÁTKY [online]. [cit. 2012-03-13]. <https://el.lf1.cuni.cz/p30693038/>.