Blueberry leaves as a promising sustainable source of polyphenols: Chemical composition, functional activities and future application perspectives

Blueberry leaves are a byproduct of blueberry cultivation, often overlooked despite their potential value. As global consumption of blueberries continues to rise, the area under cultivation expands, leading to an increased production of blueberry leaves. Blueberry leaves are a rich source of polyphenols, and in recent years, extensive research has been conducted on the composition and biological functions of these compounds. However, studies on blueberry leaves are often fragmented and lack a comprehensive overview of their potential applications. This review outlines the biosynthetic pathways of polyphenols in plants and compares the variations in polyphenol content and composition in blueberry leaves, influenced by factors such as cultivars, harvesting seasons, and extraction methods. Current research indicates that the primary constituents of blueberry leaf polyphenols (BLPs) are caffeoyl quinic acids, flavonols, and flavan-3-ols. These active compounds endow blueberry leaves with a range of functional properties, including antioxidant, anti-inflammatory, antibacterial, antiviral, antitumor, and metabolic syndrome-modulating effects. As a cost-effective and potentially beneficial by-product of agricultural production, blueberry leaves represent a promising area for further development. Therefore, this review discusses the opportunities and challenges associated with the applications of blueberry leaves, offering insights into their future processing, utilization, and potential for sustainable development.