Vitamin B1 B2 B12

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physiological role and significance of vitamin B1, B2, B12


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Definition of vitamin:

Definition of vitamin Any of a group of organic compounds which are essential for normal growth and nutrition and are required in small quantities in the diet because they cannot be synthesized by the body.

Chemistry & physiological significance of vitamins:

Chemistry & physiological significance of vitamins

Vitamin B1 (Thiamin):

Vitamin B1 (Thiamin) Vitam in B 1 , thiamin, or thiamine enables the body to use carbohydrates as energy. It is essential for glucose metabolism, and it plays a key role in nerve, muscle, and heart function. Vitamin B 1 is a water- soluble vitamin, as are all vitami ns of the B complex.


DIETARY SOURCES Cereals Pulses Oil seeds Nuts Yeast Also present in Pork Liver Heart Milk kidney


DEFICENCY SYMPTOMS Beri- beri Loss of appetite (anorexia) Weakness Constipation Nausea Mental depression Peripheral neuropathy

Chemistry of vitamin B1:

Chemistry of vitamin B1


Thiamine or vitamin B1 named as the "thio-vitamine" ("sulfur-containing vitamin") is a water-soluble of the B complex. It is water soluble vitamin. It is anti beri - beri vitamin. It has specific coenzyme Thiamine pyrophosphate (TPP) which is mostly associated with carbohydrates metabolism. In 1936 williams and his associates determines the structure of Thiamine. Thiamine contain pyrimidine ring Thiazole ring held by methylene bridge. Thiamine is only natural compound which having thiazole ring. Alcohol group of thiamine esterified with phosphate


The conversion of thiamine to its coenzyme form is carried out by the enzyme thiamine diphosphokinase , with adenosine triphosphate (ATP) as the pyrophosphate (PP) donor.

Physiological significance of vitamin B1:

Physiological significance of vitamin B1 The active from of vitamin B1 in the body is thiamin pyrophosphate (TPP) which along with lipoic acid acts as a prosthetic group for carboxylases. Thiamine pyrophosphate is formed by the esterification of alcoholic group of thiamine with phosphate. TPP transferase catalyzes the transfer of pyrophosphate group from ATP to thiamine.




The coenzyme, thiamine pyrophosphate or cocarboxylase is intimately connected with the energy releasing reactions in the carbohydrate metabolism The enzyme pyruvate dehydrogenase catalyses (oxidative decarboxylation) the irreversible conversion of pyruvate to acetyl CoA. This reaction is dependent on TPP. D-Ketoglutarate dehydrogenase is an enzyme of the citric acid cycle. This enzyme is comparable with pyruvate dehydrogenase and requires TPP. Transketolase is dependent on TPP. This is an enzyme of the hexose monophosphate shunt (HMP shunt). The branched chain D-keto acid dehydrogenase (decarboxylase) catalyses the oxidative decarboxylation of branched chain amino acids (valine, leucine and isoleucine) to the respective keto acids. This enzyme also requires TPP. TPP plays an important role in the transmission of nerve impulse. It is believed that TPP is required for acetylcholine synthesis and the ion translocation of neural tissue


Reaction dependent on thiamine pyrophosphate

Vitamin B2 (Riboflavin):

Vitamin B2 (Riboflavin) Riboflavin is a B vitamin . Riboflavin is necessary for growth and for the production of red blood cells. Riboflavin also plays an important role in how our bodies gets energy from carbohydrates, fats, and proteins.


DIETARY SOURCES Milk and milk products Meat Eggs Liver Kidney Comparatively less obtained Cereals Fruits Vegetables fish


DEFICIENCY SYMPTOMS Cheilosis (fissures at the corners of mouth) Glossitis (tongue smooth and purplish) Dermatitis. It is mostly seen with other vitamin deficiencies. Chronic alcoholics are susceptible to B2 deficiency

Chemistry of vitamin B2:

Chemistry of vitamin B2


It is water soluble vitamin. It aids in the metabolism your fats, carbohydrates, protein and ketone bodies. It is also important for your energy metabolism


Riboflavin contains 6,7-dimethyl isoalloxazine (a heterocyclic 3 ring structure) attached to D- ribitol by a nitrogen atom ( 9 th position) sugar alcohol called ribitoyal group is attached. Ribitol is an open chain form of sugar ribose with the aldehyde group (CHO) reduced to alcohol (CH2OH). Riboflavin is stable to heat but sensitive to light. When exposed to ultra-violet rays of sunlight, it is converted to lumiflavin which exhibits yellow fluorescence. The substances namely lactoflavin (from milk), hepatoflavin (from liver) and ovoflavin (from eggs) which were originally thought to be different are structurally identical to riboflavin.

Physiological significance of vitamin B2:

Physiological significance of vitamin B2 Riboflavin is the component of two flavin enzymes The flavin mononucleotide (FMN) The flavin adenine dinucleotide Both these flavin enzymes take part in various oxidation-reduction reactions. The oxidized flavines are yellow in colour while upon reduction ( one hydrogen atom at 1 and other at 10 positions acquisition occurs ) and they become colourless.

The reaction can also proceed in the reverse direction.:

The reaction can also proceed in the reverse direction. Hydrogen addition occurs in 2 steps -


Structure and biosynthesis of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)


Both the coenzymes function with a group of proteins known as the flavoproteins. These flavoproteins due to their diverse nature can act as oxidases, dehydrogenases, hydroxylases ,oxidative decorboxylases. Riboflavin or vitamin B2 is an essential nutrient in human nutrition and plays a key role in the production of energy. Vitamin B2 is needed to process amino acids and fats, activate and folic acid, and help convert carbohydrates into the fuel the body runs on.


V itamin B2 can act as an antioxidant. Vitamin B2 is an intermediary the transfer of electrons in the cellular oxidation-reduction reactions which generate energy from protein, carbohydrate and fat.

Vitamin B12:

Vitamin B12 Vitamin B12 does a lot of things for your body. It helps make your DNA and your red blood cells . B 12 is the most chemically complex of all the vitamins


DIETARY SOURCES Food and animal are the only origin sources for vitamin B 12 Liver Kidney Milk Curd Eggs Fish Pork Chicken Curd is better source than milk, due to the synthesis of B12 by LACTOBACILLUS Vitamin B12 is synthesised only by microorganisms (anaerobic Bacteria) plants cannot synthesize B12 is never found in plant foods Animals obtain B12 either by eating foods, derived from other animals or from the intestinal bacterial synthesis


DEFICENCY SYMPTOMS The most important disease associated with vitamin B 12 deficiency is pernicious anemia . It is characterized by low hemoglobin levels, decreased number of erythrocytes and neurological manifestations B 12 deficiency is also associated with neuronal degeneration and demyelination of nervous system .

Chemistry of vitamin B12:

Chemistry of vitamin B12


Vitamin B 12 is the only naturally occurring organic compound which contains cobalt (35%). It is water soluble, deep red, tasteless, crystalline compound with a molecular weight of 1355 and is hence stable at neutral pH but not at alkaline pH.


The salient features of the structure of Vitamin B 12 are given below: There are many closely related compounds having B 12 activity. All are cobalamins and contain in their molecules a portion called corrin ring which to a large extent resembles the tetrapyrrole ring structure of porphyrins. A single cobalt atom having one positive charge is present in the center of this ring. The Co atom is attached to all the four N atoms of corrin ring in the same way as Fe++ is attached to 5,6, dimethylbenzimidazole ribose which is attached to the side chain on ring IV through Phosphate and aminopropanol. The positive charge on Co atom is balanced by one of the several groups which give rise to more than one type of vitamin B 12 . These different types of vitamin B 12 are given below along with their characteristic groups attached to the Co atom 28


B12: Cyanocobalamin: It has CN. It is the commonly used form of the vitamin B12 B12-a : hydroxocobalamin: It has OH. It is claimed to be retained in the body B12-b : aquocobalamin: It has H 2 O B12-c: nitrocobalamin: It has NO 2


Role of vitamin B12 in isomerization of methyl malonyl CoA to succinyl CoA

Physiological significance of vitamin B12:

Physiological significance of vitamin B12 1. Supports Energy Vitamin B12 plays a key role in how your body creates energy . It keeps your cells fed, happy, and healthy. Wi thout it, your cells get hungry and you feel weak, tired, and like you’re dragging all the time. The nutrient releases energy into the cell and provides you with the appropriate balance you need for thinking and moving throughout your day. 2. Protects the Heart Your heart and entire cardiovascular system needs B12. One of its jobs is to remove a dangerous protein called homocysteine from the blood. If homocysteine is allowed to roam through blood, it damages your arteries leading to inflammation and heart disease. Get enough B12 and you’ll keep homocysteine levels down and your heart happy.


3. Your Bones Need It Studies have found patients with osteoporosis have higher levels of homocysteine and low levels of B12 than people with strong, healthy bones.Could B12 be a viable adjunct to future osteoporosis approache. If you suffer from osteoporosis or similar bone issues, speak to your doctor about getting your vitamin B12 levels tested. 4. Prevents Nerve Damage Your nerves have a protective covering to keep them safe from toxins and free radicals in your blood. Without these coverings, called myelin sheaths, exposed nerves get damaged and may even die. These dead nerves disrupt signals to and from the brain and may play a role in nerve-related conditions. Vitamin B12 supports the way your body . 31


5. Protects Brain Health Researchers have noted Alzheimer’s patients have much lower levels of B 12 than those of a similar age who have sharp, clear memory. In the same way B 12 helps protect nerve cells, it helps protect the myelin sheaths of brain cells that are often lacking in Alzheimer’s patients. Some research suggests that cobalamin deficiency may cause a type of dementia in elderly patients that is in fact reversible with the right nutritional intervention. 6. Keeps You Looking and Feeling Young Aging happens when your cells begin to wear and tear, and they age faster when your DNA doesn’t replicate correctly. Many factors can affect DNA replication, like free radicals , toxins in the blood, high blood sugar, and high levels of omega-6 fats in your diet. B12 supports DNA health, thereby keeping your cells younger. And when your cells are young, you look and feel young too. 32


About ten enzymes requiring vitamin B12 have been identified. Most of them are found in bacteria (glutamate mutase, ribonucleotide reductase etc.). There are only two reactions in mammals that are dependent on vitamin B12. Synthesis of methionine from homocysteine : Vitamin B12, as methylcobalamin is used in this reaction. This is an important reaction involving N5-methyl tetrahydrofolate from which tetrahydrofolate is liberated (enzyme-homocysteine methyltransferase or methionine synthase). This metabolic step signifies the interrelation between vitamin B12 and folic acid Isomerization of methymalonyl CoA to succinyl CoA : The degradation of odd chain fatty acids, certain amino acids (valine, isoleucine etc.) and pyrimidines (thymine and uracil) produce directly or through the mediation of propionyl CoA, an important compound methylmalonyl CoA. This is converted by the enzyme methylmalonyl CoA mutase to succinyl CoA in the presence of B12 coenzyme, deoxyadenosyl cobalamin. This reaction involves hydrogen transfer and intramolecular rearrangement. In B12 deficiency, methylmalonyl CoA accumulates and is excreted in urine as methylmalonic acid.


References B2,chemistry Of Vitamin B2,physiological Importance,synthesis Of Riboflavin,reactions, Vitamin B2 Deficiency Symptoms,functions,uses Of Riboflavin. 5. 4. B y D r . E d ward Group Dc, N p , Dac b n , Dcbc n , Dab f m Published On March 19, 2015, Last Updated On April 24, 2017 Michael B. Davies, John Austin, David A. Partridge: Vitamin C- Its Chemistry And Biochemistry 6. Dr. P. Ravisankar M. Pharm., Ph.D 1. Feeding And Nutrition Of Companion And Hobby Animals, János , Tossenberger (2011) , Kaposvar University 2. Vitamin B1 [Thiamine] Medicinal Chemistry By P. Ravisankar [ Source] 3. Vitaminb2[ riboflavin] Medicinal Chemistry, by P . Ravisankar [Sources Of Vitamin

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