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.

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).

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.

5. α-galactosides:


 * raffinose, higher homologues,
 * cause gastrointestinal problems.

Vnitřní odkazy

 * Přírodní toxické látky (1. LF UK, NT)

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 ).Toxiny-vicin.jpg

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
 * 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.

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

Vnitřní odkazy

 * Přírodní toxické látky (1. LF UK, NT)

Internal links

 * Toxické látky
 * Antinutriční látky