Vitamin B6 – Chemistry, Sources, Requirement, Biochemical Functions, Deficiency Symptoms

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VitaminB6 usually represents three compounds namely pyridoxine, pyridoxal, and pyridoxamine. These are also known as vitaminers of vitamin B6.

Chemistry:

Vitamin B6 compounds are pyridine derivatives. They differ from each other in the structure of functional group attached to the fourth carbon atom in the pyridine ring. Pyridoxine is a primary alcohol, pyridoxal is an aldehyde and pyridoxamine is an amine form. Pyridoxamine is mostly found in plants but pyridoxal and pyridoxine are found in animal foods. Pyridoxine can be converted in to pyridoxal and pyridoxamine but not vice versa.

The active form of vitamin B6 is its coenzyme pyridoxal phosphate PLP. It can be synthesized from all the three vitaminers of vitamin B6.

Biochemical functions:

·Pyridoxal phosphate is closely associated with the metabolism of amino acid.

·The synthesis of serotonin and histamine from amino acid is dependant on pyridoxine.

·Pyridoxal phosphate participates in the reactions such as transamination, transsulphuration, decarboxylation, deamination and condensation

·PLP is needed for the absorption of amino acids from the intestine.

·It prevents hyperoxaluria.

·It also helps in avoiding urinary stone formation

Recommended dietary allowance:

The dietary requirement of pyridoxine for an adult is 2 – 2.2 mg/day.

During pregnancy, lactation and old age an intake of 2.5 mg daily is recommended

Dietary sources:

Animal sources such as egg yolk, fish, milk and meat are rich in vitamin B6. Wheat, corn, cabbage, roots and tubers are good sources.

Deficiency symptoms:

Pyridoxine deficiency is associated with neurological symptoms such as depression, irritability, nervousness and mental confusion. Convulsions and peripheral neuropathy are observed in severe deficiency. These symptoms are related to the decreased synthesis of biogenic amine s such as histamine, serotonin etc. And in children convulsions are produced due to decrease in GABA production.

Hypo chromic microcytic anaemia due to reduced haeme production is seen in found in vitamin B6 deficiency.

Dietary deficiency of pyridoxine is rather rare and is mostly observed in women taking oral contraceptive pills and also found in alcoholics.

Drug induced B6 deficiency:

Isoniacid a tuberculosis drug can induce B6 deficiency and also pencillamine. So while treating with these drugs it is essential to give vitamin B6 supplement.

Pyridoxine antagonists:

Isoniacid, deoxypyridoxine, methoxy pyridoxine are antagonists of vitamin B6.

In toxic amounts Vitamin B6 may cause neurological damage.

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