Theaflavins with health-promoting properties: From extraction, synthesis to medicinal application

Background: Theaflavins (TFs), a kind of golden-yellow pigments formed by the polymerization of catechins from black tea fermentation, have shown the potential to promote human health and obtain therapeutic efficacy in various diseases via modulating multiple bio-active factors or signaling pathways. As natural tea compounds, TFs present great value in commercial field and healthcare industries. However, the high preparation cost, poor bioavailability and unclear action mechanism in human body hinder their clinical application. A comprehensive understanding about the roles of current TFs in human health and molecular mechanism is requisite for the practical application. Scope and approach: This review summarizes the latest advancements of TFs, focusing on their extraction and synthesis technology, health benefits, bioavailability and industrial applications. Especially, it provides current synthetic methods including the extraction and purification technology. Importantly, recent advancements of the function of TFs related to human health are also discussed, unraveling the potentials of TFs in health management and diseases therapies. Key findings and conclusions: Tremendous advancements in the synthesis, extraction, and healthcare application of TFs have been investigated in vitro. Nevertheless, most research has focused on the animal level, and very few studies in vivo have adopted humans as subjects. Although the preparation and extraction process of TFs is constantly optimized and adjusted, the mechanism of the activity effect of TFs as healthy functional beverages in various organs of the human body should be the focus of future research.