Nearly 70% of beta carotene is absorbed from spirulina.
Retinol (alcohol form), retinal (retinaldehyde), and retinoic acid.
Retinoids.
Vitamins are organic substances necessary in trace amounts for normal metabolic functioning, acting as coenzymes and regulators of metabolic processes.
The term 'vitamine' was coined by biochemist Casimir Funk in the early 1900s.
70-90% of retinol is absorbed, while only 20-50% of beta carotene is absorbed.
Retinol functions as a storage form of Vitamin A and can be converted to retinal.
E. V. McCollum initially named it 'fat-soluble factor A' in 1918.
True carotenes are pure hydrocarbon molecules, while xanthophylls contain oxygen in various forms.
Retinol and retinyl esters account for virtually all of the preformed Vitamin A available in the diet, obtained exclusively from animal foods.
Carotenoid absorption from the diet ranges from about 20-50%, while absorption of other carotenoids may be as low as 3 to 10%.
Common plant sources of provitamin A include β-carotene and β-cryptoxanthin, found in green leafy vegetables, yellow vegetables, and orange fruits.
They must be hydrolysed to free retinol and an organic acid.
It is incorporated into a micelle and absorbed across the brush border into the enterocytes.
To the liver.
In 1877, W. Kuhne discovered that the purple retinas of dark-adapted frogs turned yellow when exposed to light, and that vitamin A restored the purple color, enabling vision.
Carotenoids are red, yellow, and orange pigments found naturally in a variety of fruits and vegetables, synthesized by plants.
Retinyl esters, with retinyl palmitate being the most common.
Researchers discovered that vitamin A is formed by the conversion of beta-carotene in the intestinal mucosa of animals and humans.
They package newly formed products and precursors for transport throughout the body.
β-carotene is better absorbed from papaya and carrots than from amaranth.
The scientific term for vitamin A is retinol, because it is found in the retina of the eyes.
Vitamins are classified as water-soluble (e.g., Vitamin B-complex and Vitamin C) or fat-soluble (e.g., Vitamins A, D, E, and K).
M. Mori treated xerophthalmia with liver and cod liver oil, finding that cod liver oil was more effective in restoring visual function.
Preformed vitamin A, also known as retinol, is primarily found in animal sources such as egg yolks, liver, fish oil, and dairy products.
The term 'carotenoid' was coined in 1831 by Wackenroder.
Retinol and provitamin A carotenoids such as alpha-carotene, beta-carotene, gamma-carotene, and beta-cryptoxanthin.
Approximately 70-90% of retinol from the diet is absorbed as long as the diet is adequate in fat.
Most retinoids are soluble in organic solvents and fat.
Eduard Schwarz cured night blindness among sailors by feeding them a regular diet of ox or pork liver.
The common structural link is its β-ionone ring and isoprenoid chain.
Retinyl palmitate, which is converted to retinol in the small intestine.
Cows fed on wheat did not thrive, became blind, and gave birth to dead calves.
Alpha-carotene, gamma-carotene, and beta-cryptoxanthin possess vitamin activity in humans.
It cleaves beta-carotene in the intestinal mucosa and converts it to retinol.
Reduced secretion of bile or obstruction in the bile duct can lead to decreased absorption of Vitamin A from the diet.
No, retinoids are insoluble in water.
Lycopene is the red carotenoid commonly found in tomatoes.
Over 80% of the daily supply of vitamin A in Indian diets is derived from its precursors found in many plant foods.
It increases to 60-80%.
Vitamin A was first synthesized in 1947 by two Dutch chemists.
Free carotenoids and retinols integrate into micelles and likely traverse the enterocyte plasma membrane by passive diffusion.
The absorption range of beta carotene from green leafy vegetables is 50-99%.
Provitamin A carotenoids are less biologically available but more affordable than animal products, contributing to most of the vitamin A activity in these diets.
The existence of vitamin A was first clearly recognized in 1913.
An intake of at least 5g of fat is necessary for β-carotene absorption.
Seventy to ninety percent.
Harry Holmes and Ruth Corbet isolated and crystallized vitamin A.
Normal digestive processes.
Historically, liver has been used to treat various types of blindness, with practices recorded in ancient Egypt and by Hippocrates, who treated malnourished children with liver soaked in honey.
Vitamin A is essential for the normal functioning of the visual system, growth and development, and maintenance of epithelial cellular integrity.
11-cis-retinal.
Retinyl palmitate.
They are converted to the active forms of vitamin A.
They are embedded in complex cellular structures such as the cellulose containing matrix of chloroplasts.
Retinoids are relatively stable to heat, acid, and alkalies but are easily oxidized at high temperatures in the presence of air and rapidly destroyed by UV rays or in rancid fats.
Retinols present in animal foods and carotenoids found in plant foods.
Elmer V. McCollum and Marguerite Davis proved that all fats do not have similar nutritional value.
Harry Steenbock proposed a relationship between yellow plant pigments (beta-carotene) and vitamin A in 1919.
They differ in the location of a double bond in a ring, influencing their efficiency of conversion to Vitamin A.
β-carotene is converted to retinol in the body.
Diets critically low in dietary fat (under about 5-10 g daily) or disease conditions that interfere with normal digestion and absorption, such as pancreatic and liver diseases and frequent gastroenteritis.
Bile salts are essential for effective absorption as they are surface active agents that activate lipase enzyme and help in the digestion of fat-soluble vitamins.
It is believed that only 10% of the pigments have 'vitamin A activity', with beta-carotene having the greatest activity.
Beta-carotene consists of two connected retinyl groups.
Vitamin A deficiency was linked to xerophthalmia, abnormal tissue differentiation, and impaired immune functions.
The double bonds play a unique role in multiple vision processes.
Their research confirmed that cod liver oil produced the same results as butter in rat studies.
Swiss chemist Paul Karrer described the chemical structure of vitamin A in 1931.
Retinol is a pale yellow crystalline solid and exists in nature as various isomers.
