A stabilized enrichment method for rosemary diterpenoids and their therapeutic potential in diabetic kidney disease

Abstract Background As a traditional medicinal herb, rosemary leaves have shown potential for the treatment for diabetic kidney disease (DKD). However, the bioactive compounds responsible for its anti-DKD effects remain unidentified, and the instability of its primary phytochemicals limits its practical application. Methods This study investigated the active components of rosemary leaves and characterized their degradation pathways using UPLC-Q/TOF–MS/MS. Four solvent-extracted fractions were evaluated using an in vitro DKD model to identify the major anti-DKD constituents. A targeted enrichment method was then developed to isolate these bioactive compounds. Finally, a DKD model was established in C57BL/6J mice using high-fat diet combined with streptozotocin injection to evaluate the therapeutic effects of the enriched extracts. The pharmacokinetic profiles of the major components of TD were further investigated. Results 38 chemical constituents were characterized with diterpenoids were identified as the primary anti-DKD constituents by in vitro DKD model. Considering their pronounced susceptibility to oxidative degradation, a novel enrichment strategy for total diterpenoids (TD) was developed based on water and ethanol. Vitamin C served as a stabilizer to improve TD stability, leading to a TD extraction yield of 40.12% and the diterpenoid content of 81.80%. In vivo studies revealed that TD attenuated renal injury, improved glucose and lipid dysmetabolism, and reduced renal oxidative stress in DKD mice. The in vivo absorption profiles showed that TD also exhibited good bioavailability. Conclusion This study provides an effective method for TD enrichment and demonstrates the renoprotective effects of TD. These findings offer new insights on the broader use of rosemary leaves and the development of natural product-based therapies for DKD. Graphical Abstract