Phytochemistry and Pharmacological Activities of Rehmannia glutinosa: A Comprehensive Review

Rehmannia glutinosa (Orobanchaceae) has traditionally been used to control the level of blood sugar, stimulate tonification, and regenerate blood and fluid in the body. The roots can be processed by steaming, which alters the chemical profiles of the plant and helps to utilize it in various diseases. Although several review articles on R. glutinosa have been published, few have comprehensively summarized the chemical constituents isolated from this plant. Therefore, this review provides a comprehensive overview of the phytochemical components identified in R. glutinosa, which are categorized in several classes including iridoids, ionones, phenylethanoids, phenylpropanoids, flavonoids, lignans, terpenoids, alkaloids, and saccharides, together with their reported biological activities. The reviewed studies have demonstrated diverse biological activities, including antidiabetic, anti-obesity, anti-inflammatory, neuroprotective, organ-protective, cytotoxic, antioxidant, and antimicrobial activities. However, the available evidence is predominantly derived from in vitro and in vivo rodent models, and clinical evidence remains limited. Therefore, further studies are required to establish appropriate preparation methods and dosages, as well as evaluate the pharmacokinetic and pharmacodynamic profiles of R. glutinosa for its therapeutic applications.