原花青素（PAs）是由类黄酮-3-醇单体组成的聚合物，具有多种生物活性，可应用于食品、药物和化妆品中作为天然生物制剂。PAs广泛存在于水果和蔬菜中，并且通常从其果肉和皮中提取。为了降低提取成本并增加可商业化的PAs来源，可以利用植物的副产品。叶子是水果和蔬菜农业生产的主要副产品，虽然它们的比例尚未精确量化，但它们占植物的比例不少于20%，叶子可能是生产和加工过程中的一个有趣资源。各种植物叶子中具有特定结构的PAs往往容易被忽视，其稳定含量和聚合度也是显著特征。本综述研究了各种因素（如加工条件、环境、气候、物种和成熟度）对叶子中PAs含量和结构的影响，并强调了它们的生物活性（如抗氧化、抗炎、抗菌、抗癌和抗肥胖作用），以及它们与肠道微生物群和其他生物分子（如多糖和蛋白质）的相互作用。未来的研究还需要集中关注其精确提取、高聚物天然或修饰PAs的生物活性以及更好的应用形式。

Proanthocyanidins (PAs) are a class of polymers composed of flavan-3-ol units that have a variety of bioactivities, and could be applied as natural biologics in food, pharmaceuticals, and cosmetics. PAs are widely found in fruit and vegetables (F&Vegs) and are generally extracted from their flesh and peel. To reduce the cost of extraction and increase the number of commercially viable sources of PAs, it is possible to exploit the by-products of plants. Leaves are major by-products of agricultural production of F&Vegs, and although their share has not been accurately quantified. They make up no less than 20% of the plant and leaves might be an interesting resource at different stages during production and processing. The specific structural PAs in the leaves of various plants are easily overlooked and are notably characterized by their stable content and degree of polymerization. This review examines the existing data on the effects of various factors (e.g. processing conditions, and environment, climate, species, and maturity) on the content and structure of leaf PAs, and highlights their bioactivity (e.g. antioxidant, anti-inflammatory, antibacterial, anticancer, and anti-obesity activity), as well as their interactions with gut microbiota and other biomolecules (e.g. polysaccharides and proteins). Future research is also needed to focus on their precise extraction, bioactivity of high-polymer native or modified PAs and better application type.