Procyanidins are polyphenolic compounds, which are precursors of anthocyanins, which can be produced by heating in acidic media. Proanthocyanidins widely exist in plants and can be said to be secondary metabolites of plants. It is not a single compound, but is composed of a series of compounds. The basic structure is flavan-3-ol-catechin and epicatechin. Elements are monomers to form dimers, trimers, tetramers and other polymers. The structure is divided into A-type and B-type due to the polymerization method. Usually dimer-pentamers are called oligomeric proanthocyanidins, or OPC for short. , its physiological activity is the best, it is currently recognized internationally as an effective natural antioxidant for scavenging free radicals in the human body. Proanthocyanidins mainly exist in grape seeds, pine bark, apple, hawthorn, peanut, ginkgo, custard apple, wild strawberry and other plants, and the proanthocyanidin extracts currently on the market are mainly derived from grape seeds and pine bark.

Anthocyanins, also known as anthocyanins, are flavonoids. It is a kind of water-soluble natural pigment that widely exists in plants in nature. It is obtained from the hydrolysis of anthocyanins and exists in many fruits and vegetables, such as blueberries, cherries, strawberries, grapes, black currants, bilberries, etc., in the vacuoles of plant cells. Under different pH conditions, anthocyanins make plants show colorful colors, the cell fluid is acidic and reddish, and the cell fluid is alkaline and blue. All anthocyanins in their natural state exist in the form of glycosides, called anthocyanins, and few free anthocyanins exist. It is mainly used in food coloring, and can also be used in dyes, medicine, cosmetics and so on. Anthocyanins are widely found in plants, and there are more than 300 different anthocyanins in nature.

Both proanthocyanidins and anthocyanins are strong oxidizing substances, but there are obvious differences between them, mainly in terms of color, chemical structure, source and function.

1. Color: Proanthocyanidins are colorless and can be converted into colored substances during food handling and processing. Anthocyanins are water-soluble pigments and are one of the sources of plant fruit and petal color.

2. Chemical structure: Procyanidins are polyphenolic compounds, while anthocyanins are flavonoids. The reason for the similarity in the names of the two is that anthocyanins can be produced by heating procyanidins at high temperatures in an acidic medium.

3. Source: Proanthocyanidins are widely found in plant cores, skins, and seeds, including pine bark, grape seeds, cinnamon bark, etc. Anthocyanins mainly come from the flowers, leaves, and fruits of plants. Fruits and vegetables containing anthocyanins include blueberries, grapes, eggplants, etc.;

4. Function: Proanthocyanidins have the functions of resisting myocardial ischemia, regulating blood lipids, protecting the skin, etc., and can interact with proteins to form polymers, affecting protein digestion and absorption. Anthocyanins have a wide range of biochemical and pharmacological effects, such as anti-inflammatory, antimicrobial, and can prevent low-density lipoprotein oxidation.