Vitamin A ester derivatives mainly refer to its alkyl acid esters, such as vitamin A acetate, vitamin A palmitate, etc. Due to the instability of vitamin A, commercial vitamin A is available in the form of its ester. However, vitamin A acetate easily absorbs water and gets damp, while vitamin A palmitate is more stable than vitamin A acetate. Vitamin A, commonly known as retinol, is an unsaturated monohydric alcohol with an ester ring. It is a yellow flaky crystal or crystalline powder. It is a fat-soluble vitamin. It is insoluble in water and glycerol, and soluble in alcohol, ether, hydrocarbon, Most organic solvents such as halogenated hydrocarbons. Retinol palmitate is an ester of retinol combined with palmitic acid, a saturated fatty acid that is the main component of palm oil. Retinyl palmitate is easily absorbed by the skin and then converted into retinol. It is a yellow or yellow-red solid or oily substance.