proantosyanidiinit

Proantosyanidiinit, commonly known as proanthocyanidins or condensed tannins, are a class of polyphenolic compounds belonging to the flavonoid family. They occur as oligomers and polymers of flavan-3-ol units, such as catechin and epicatechin, and are widely distributed in the plant kingdom. In foods and beverages, they contribute to astringency and color stability, notably in grapes, wine, cocoa, apples, berries, tea, and some nuts.

Chemically, proantosyanidiinit are built from flavan-3-ol building blocks linked through carbon–carbon bonds (primarily C4–C8 or C4–C6). Some molecules also contain occasional ether linkages (A-type). The degree of polymerization varies from small oligomers to large polymers, influencing solubility, bitterness, and tannin reactivity. Their structure makes them resistant to simple hydrolysis, distinguishing them from hydrolyzable tannins.

Biosynthesis and occurrence: proantosyanidiinit arise from the flavonoid biosynthetic pathway in plants, originating from phenylpropanoid metabolism. They accumulate in vacuoles and can form complex tannin matrices that participate in plant defense against herbivores and pathogens. In the food and beverage sector, their presence affects mouthfeel, astringency, and color stability, especially during fermentation and aging.

Measurement and analysis: analytical methods include phloroglucinolysis or thiolysis to determine mean degree of polymerization and monomer composition (e.g., catechin, epicatechin, gallocatechin), often coupled with HPLC or mass spectrometry.

Health and applications: studies explore antioxidant, anti-inflammatory, and potential cardioprotective effects, though human evidence remains mixed. They can interact with mineral absorption and may influence gut microbiota. Regulatory and labeling considerations vary by jurisdiction.