Riboflavin: Vitamin B2
Also known as riboflavin it is present in plants, bacteria. However, it is absent in vertebrates. It is a colored micronutrient that is easily absorbed to maintain proper functioning of tissues and organs. The word riboflavin is derived from “Ribose” meaning sugar whose reduced form is ribitol and “flavin’ which is a ring moiety that is responsible for the yellow color of the oxidized molecule of vitamin B2.
Its structure is made up of a heterocyclic isoalloxazine ring and a sugar alcohol known as ribitol. Although sensitive to light and alkali it is stable against heat and acidic medium. The active forms of riboflavin are flavin mononucleotide (FMN) and flavin adenine mononucleotide (FAD).These forms the prosthetic groups of various enzymes known as flavoenzymes. The flavoenzymes play a key role in catalyzing oxidation-reduction reactions by acting as carriers of hydrogen atoms. On the other hand, the isoalloxazine rings participates in the oxidation reduction of substrates .The isoalloxazine ring is reduced to FMNH2 and FADH2.
Just like other B vitamins riboflavin is crucial for the normal physiologic processes. It is necessary for normal development, growth, reproduction, lactation, physical performance and general well-being. Vitamin B 2 being a precursor of essential coenzymes FAD and FMN takes part in a range of essential biochemical redox reactions, especially in those that yield high energy. It is involved in various metabolic reactions and takes part in the mitochondrial electron transport chain to produce energy.
Riboflavin is also required for the synthesis and repair of nucleic acids, namely RNA and DNA. As such, it promotes growth and fertility since it supports reproduction of the various body cells including sex cells. It also promotes good vision in combination with vitamin A. In addition, it is important for the maintenance of a healthy skin, nails and hair.
Riboflavin also plays a crucial role in neutralizing free radicals as it is involved in the regeneration of glutathione, the body’s main defense system against free radical damage. It is these free radicals that damage DNA and cells. Riboflavin is also necessary for folic acid activation. It also activates pyridoxine. Additionally, it plays a role in the conversion of tryptophan to niacin in the liver.
Riboflavin is also involved in the metabolism of fats, ketone bodies carbohydrates and proteins to produce energy. Therefore, riboflavin is important for stimulating growth by providing nutrients from the metabolized macromolecules. Being the central component of various co-factors such as flavin adenine mononucleotide and flavin mononucleotide it plays a key role in catalyzing redox reactions in the body to produce energy. As such, it is commonly known as one of the energy vitamins.
Riboflavin deficiency known as ariboflavinosis can occur as a result of aging and reduced efficiency in absorption. Deficiency normally occurs in combination with deficiency of other vitamins. It is characterized by cracked and red lips, inflammation of the lining of the mouth and tongue, dry scaly skin, fluid in mucous membranes, mouth ulcers, and cracks at the corners of the mouth.
The recommended daily allowance in the United States is 1.3 mg for males and 1.1 mg for females. It is best absorbed when taken between meals, since just like thiamine; riboflavin requirement also depends on the carbohydrate intake. Rich sources of vitamin B2 include cereals, meat , fish, fish and dark-green vegetables. Milk and other dairy products fortified with B2 are the largest dietary contributors in the western population. The body does not have a mechanism for storing riboflavin and as such must be replenished on a regular basis through dietary intake. There is no toxicity at higher intake as it is excreted in urine.