A class of yellow pigments derived from flavanone (2-phenylchromanone) as the parent nucleus. These include flavonoid isomers and their hydrogenated reduction products, i.e., a series of compounds with C6-C3-C6 as the basic carbon frame. Flavonoids are widely distributed in the plant world, and most of them exist in the plant in the form of glycosides or carbon glycosyl groups combined with sugars, but also in the free form. Natural flavonoids often contain hydroxyl, methoxy, hydrocarbonyloxy, isopentenoxy and other substituents on the parent nucleus. Due to the presence of these auxiliary color groups, so that the class of compounds show more yellow. And because the oxygen atom on the γ-pyrone ring in the molecule can form with strong acid? salt and behaves as a weak base, so it was once called yellow alkaloids. According to the degree of oxidation of the three-carbon bond (C3) structure and the connection position of the B ring and other characteristics, flavonoids can be divided into the following categories: flavones and flavonols; flavanones (also known as dihydroflavones) and flavonols (also known as dihydroflavonols); isoflavones; isoflavones (also known as dihydroisoflavones); chalcones; dihydrochalcones; orange ketones (also known as australia carb); flavanones and flavonols; flavanediols (3, 4) ( also known as white flower chromogen); flower (color)? [also known as 2-phenylchromen(pyran)? . There are many compounds of medicinal value in flavonoids, such as rutin in Sophora japonica and chenopodium in Chenpi, which can reduce the brittleness of blood vessels and is used to prevent and treat hypertension and cerebral hemorrhage in the elderly. Shuxinin tablets made from Ginkgo biloba contain flavonoids and biflavonoids, which are used in the treatment of coronary heart disease and angina pectoris. The fully synthetic ethoxyflavonoid, also known as cardioplegia or licoidin, has the effect of dilating coronary vessels and increasing coronary flow. Many flavonoid components have cough suppressing, expectorant, asthma calming and antibacterial activities.