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Vitamin b2 (riboflavin)
1.
2. Ribose alcohol: D-Ribitol
Tricyclic Heterocyclic structure
Isoalloxazine
Ribityl is alcohol derived from pentose
sugar D-ribose
A= Pyrimidine ring
B= Azine ring
C=Benzene ring
3. FAD & FMN both are biological active form
FMN: phosphoric acid ribityl alcoholic
group at C5 flavin-ribityl-po4
FAD: linked to adenine nucleotide through
pyrophosphate linkage
Flavoprotein = FMN/FAD + Protein
Metallo-flavinprotein
4. Higher plants form Riboflavin protein
Occurs in ‘free form’ & ‘nucleotide’
Human and animal can’t synthesize
Metabolism
Absorb in small intestine
Blood/plasma level: 2.5 - 4.0µgm% . Conc
in R.B cells 15 - 30µg/100gm,leucocyte
and platelets 250µg/100gm
5. 50% as nucleotide in urine, Daily urinary
excretion 0.1 – 0.4mg
Milk: 40 – 80% free form
Faeces: 500 – 750µg daily from
unabsorbed bacteria
FMN/FAD act as coenzyme in H-transfer
reaction
6. Antagonist
Dichlororiboflavin: Replace two –CH3 groups
In riboflavin with Cl atoms
Iso-riboflavin:-CH3 group shifted to another
position
No definite disease entity
In human lesions of mouth, tongue, skin with
weakness report
7. Adults: 1.5 – 1.8mg
Women in later hall of pregnancy: 2.0mg
Children : 0.6mg
Adolescence: 2.0 – 2.5mg