During the ripening of almost all fruits, there occurs a disruption in the organization of chloroplasts Contains (Chlorophyll) and re-organization into Chromoplasts (Carotenoids). As the photosynthesis apparatus is dismantled and the chlorophyll is degraded, the colour of existing Carotenoids is unmasked. This causes Green banana to appear yellow after the unmasking of carotenoids. Flamingos are rich in Carotenoids diet thus their feather looks orange coloured.
There are over 600 carotenoids known till today. Carotenoids are divided into two catogories:
Carotenes are pure hydrocarbons. They are called antioxidants and they include:
- Mesoxanthin(Retina makes it with ingested lutin)
- Beta Cryptoxanthin
Foods like Carrot, Apricot, Orange, Mango and Pumpkin contains Carotenes like beta Carotene, alpha-carotene and other Carotenoids like Lutein, Zeaxanthin, beta Cryptoxanthin. Carotenoids are responsible for the orange, red, yellow colour of these foods. Other foods like Egg yolk, Corn, Bananas, Kale, Spinach etc. are also rich in Carotenoides.
Note:The color of spinach and kale are green as the Chlorophyll overrules the color of Carotenoids. Carotenoids are also the reason for the milk fat and butter to appear yellow.
- Retinol: This alcohol form of vitamin A. The original state of vitamin A found in the body and can be obtained by animal foods directly. Most abundant form of Vitamin A in our body. Can be converted to Retinal ester for storage in the liver.
Retinal: This is aldehyde form of vitamin A also called as retinaldehyde. Retinal is produced by oxidation of retinol or beta-carotene as retinol and retinal are interchangeable. Retinal reacts with opsin protein in the retinal rod cells to form rhodopsin pigment for the layer of rods and cones.
- Retinoic acid: Also called as vitamin A acid, used by the skin for making epithelial cells. Also used in acne treatment as “isotretinoin”
Deficiency of vitamin A:
- Night blindness: Inability to form Rhodopsin for rod cells(Opsin protein of rods+retinal).
- Bitot spot: Build-up of keratin on the conjunctiva as an early sign.
- Conjunctival xerosis: Lack of mucin and lacrimal tears cause dryness of conjunctiva.
- Corneal xerosis: Lack of retinoic acid to maintain corneal epithelium.
- Corneal ulcer: Infection to corneal epithelium which is eroded by xerosis.
- Corneal opacity: Opacity is formed after the stromal defects heal.
- Xerophthlmic fundus: Lack of retinoic acid cause xerosis of the epithelium of retina and no production of rhodopsin and scarcity of retinal (retinol) in the retina.
- Artificial tear drops for the xerosis of cornea and conjunctiva.
- Treatment of corneal ulcer.
- Vitamin A dose to re supply the body with retinol, so that rhodopsin is reformed and retinal (retinol) is reformed epithelial damage stops. The lacrimal gland and glands of conjunctiva starts working again.
- Women of reproductive age (Pregnant or not) is treated with a daily dose of 10,000 I.U vitamin A for 2 weeks.
- Patients above age of 1 is treated with 200,000 I.U oral or 100,000 I.U intramuscular injections in case of diarrhoea. (Not women of reproductive age)
- Child under the age of 1 or if weighs less then 17pounds (8Kilograms) is treated with the half dose of those over 1 year of Old.