Phytochemical constituents, ethnomedicinal uses, and applications of coffee (Coffea arabica) leaves in functional beverages

Traditionally, coffee-growing communities have used coffee leaves to make tea-like beverages valued for their rich phytonutrient content and ethnomedicinal properties. Among these phytonutrients, phenolic compounds, mainly mangiferin, found in Coffea arabica leaves, stands out for its potential therapeutic benefits, which may surpass those of coffee beans. Moreover, bioactive molecules in coffee leaves, such as mangiferin, trigonelline, caffeine, chlorogenic acids (CGAs), and rutin, contribute to their antioxidant, anti-inflammatory, anti-hypertensive, anti-obesity, antibacterial, antifungal, anticancer, and neuroprotective effects. However, the precise mechanisms underlying these activities remain unclear. This review offers a comprehensive overview of the phytochemical constituents, ethnomedicinal uses, and potential applications of C. arabica and C. robusta leaves in functional beverages. Additionally, it examines the mechanisms through which coffee leaves exert their therapeutic effects. It emphasizes the need for further studies to fully understand the pharmacological benefits, structure-activity relationships, and the impact of processing on bioactive compounds and bio-functional characteristics. Optimizing processing methods to preserve and enhance these bioactive compounds is crucial. Thus, this review promotes a deeper understanding of coffee leaves' potential in the functional beverage market, encouraging further exploration into their bioactive properties.