Development and validation of RP-HPLC method for simultaneous quantification of metformin and oleanolic acid in rabbit and human plasma: application to pharmacokinetic study

Abstract Metformin has long been used in diabetes therapy, and recent studies suggest that combining it with oleanolic acid enhances its effectiveness. Research in animals has shown that this combination outperforms the individual drugs in combating diabetes. However, no method has yet been developed to simultaneously analyze both drugs. A validated HPLC spiked plasma method was developed and employed in a pharmacokinetic study. Using a C18 BDS column (250 × 4.6, 5 μm) with a mobile phase composed of 1% aqueous ammonium acetate solution, acetonitrile, and methanol (20:56:24) at 210 nm, metformin and oleanolic acid were separated at 4.21 min and 7.78 min, respectively. The limit of detection (LOD) and limit of quantification (LOQ) for metformin were 0.01826 µg/mL and 0.05533 µg/mL, respectively, and 0.02308 µg/mL and 0.06996 µg/mL for oleanolic acid. The accuracy and precision were within acceptable ranges. Moreover, the sensitivity, recovery, and stability assessments of quality control samples validated the robustness of the method. This developed method was successfully employed for pharmacokinetic studies of metformin and oleanolic acid after simultaneous oral administration. The HPLC method could be used for routine analytical testing of metformin and oleanolic acid, either alone or in combination with other drugs.