Secondary Metabolites from Rehmannia glutinosa Protect Mitochondrial Function in LPS-Injured Endothelial Cells

Background: Rehmannia glutinosa, a traditional Chinese herb, is commonly used to treat vascular-related disorders. Sepsis-associated vascular endothelial dysfunction is closely associated with mitochondrial damage. This study investigated the protective effects of secondary metabolites from R. glutinosa against LPS-induced mitochondrial dysfunction in endothelial cells, providing potential therapeutic insights into sepsis-related vascular complications. Methods: Phytochemical profiling of fresh R. glutinosa roots was conducted, and the structures of new secondary metabolites (1 and 2) were elucidated through comprehensive spectroscopic analysis and ECD calculations. UPLC-Q-TOF-MS/MS characterized phenylethanoid glycosides. Mitochondrial function was assessed by measuring the membrane potential, ROS levels, and TOM20/DRP1 expression in LPS-injured HUVECs. Results: Two novel eremophilane-type sesquiterpenes, remophilanetriols J (1) and K (2), along with five known phenylethanoid glycosides (3–7), were isolated from the fresh roots of R. glutinosa. UPLC-Q-TOF-MS/MS analysis revealed unique fragmentation pathways for phenylethanoid glycosides (3–7). In LPS-injured HUVECs, all compounds collectively restored the mitochondrial membrane potential, attenuated ROS accumulation, and modulated TOM20/DRP1 expression. In particular, remophilanetriol K (2) exhibited potent protective effects at a low concentration (1.5625 μM). Conclusions: This study identifies R. glutinosa metabolites as potential therapeutics for sepsis-associated vascular dysfunction by preserving mitochondrial homeostasis. This study provides a mechanistic basis for the traditional use of R. glutinosa and offers valuable insights into the development of novel therapeutics targeting mitochondrial dysfunction in sepsis.