Antivitamins

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Antivitamins or vitamin antagonists are the antagonists of vitamin effects . Excessive consumption of antivitamins can lead to vitamin deficiency symptoms . In practice, however, this danger only exists in the case of massive malnutrition or extremely one-sided nutrition. Most of the examples below are used to artificially create vitamin deficiencies in vitamin research. The mechanism of action of vitamin antagonists is different and can be explained as follows:

  • Inhibition of vitamin synthesis. Examples:
    • Acidomycin is an antibiotic that is active against mycobacteria (tubercle bacilli) by blocking their biotin synthesis.
    • Dicoumarol (produced in spoiled sweet clover ) intervenes in the vitamin K metabolism by inhibiting vitamin K epoxide reductase and vitamin K reductase and thus the biosynthesis of coagulation factors 2, 7, 9 and 10.
    • Lapachol (part of the bark of the South American Lapacho tree and the seeds of some other tropical plants) is a powerful inhibitor of vitamin K reductase.
  • Inhibition of vitamin absorption in the intestine. Examples:
    • Alcohol abuse leads to impaired vitamin B1 absorption in the intestine and decreased storage in the liver.
    • Alcohol-induced zinc deficiencies inactivate the alkaline phosphatase in the jejunum and thereby inhibit the absorption of vitamin B6 ( pyridoxal phosphate absorption ).
    • Avidin (contained in egg white, is inactivated by heat) forms a stable complex with biotin that is not absorbed in the intestine.
  • Competitive inhibition of the vitamin effect in the vitamin metabolism. Examples:
    • Hydrazine derivatives (for example Linatin, in small quantities contained in flaxseed;. Phenylhydrazine in morel ; agaritine, in small amounts in Zuchtchampignon included) connect the body with vitamin B6 to Pyridoxalhydrazonen that the Pyridoxalphosphatkinase inhibit and thus the phosphorylation of vitamin B6 to active form.
    • Canalin (easily arises from canavanine in legumes) can, as a substituted hydroxylamine, form oximes with pyridoxal or pyridoxal phosphate. Oximes can block pyridoxal phosphate kinase and thus the activation of vitamin B6.
    • Cycloserine , an antibiotic used in tuberculosis therapy, can form oximes with pyridoxal phosphate .
    • Mimosine, which is found in the leaves of the legumes Mimosa and Leucaena, forms a complex with pyridoxal phosphate and blocks some vitamin B6-dependent enzymes.
    • The alcohol breakdown product in the liver acetaldehyde blocks the vitamin B1-dependent pyruvate dehydrogenase and thus the oxidative decarboxylation of 2-oxo acids.
    • Norbiotin, dehydrobiotin, biotin sulfone, desthiobiotin and homobiotin are complete biotin antagonists.
    • Roseoflavin (an antibiotic obtained from Streptomyces davawensis ) is a vitamin B2 antagonist and has an antibiotic effect on Staphylococcus aureus .
    • Methotrexate is a folic acid antagonist. It is used in the treatment of cancers such as leukemia , rheumatoid arthritis, and psoriasis .
  • Inhibition of coenzymes in vitamin metabolism. Example:
    • Penicillamine complexes copper, which could explain the effect on collagenosis . Vitamin B6 and copper are cofactors in lysine oxidase, the rate-limiting step in collagen biosynthesis.
    • Phytates (inositol hexaphosphates, contained in high concentrations in breads that have been baked with whole grain flours containing bran and short dough, in black tea, in cereal bran and numerous legumes) can bind zinc and inhibit absorption. Zinc is an important coenzyme in the folic acid, vitamin B6 and vitamin A metabolism.
  • Breakdown of vitamins. Examples:
    • Thiaminases (in black tea, in ferns, in haddock) break down vitamin B1 into thiazole and pyrimidine derivatives.

Numerous foods, medicines and environmental pollutants are antivitamins - but often only after a certain dose. The following table is incomplete and is therefore only a rough guide.

vitamin Vitamin antagonists Exemplary foods
Vitamin B1 Coffee , beans , shrimp , alcohol , tea , betel nuts and blueberries
Vitamin B6 Hydrazine , linatin , alcohol
Biotin Avidin , niacin Egg white , corn , millet
Vitamin K Dicumarol , vitamin A , vitamin E.

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