Ethnopharmacological relevanceAidi injection (AD) is a traditional medical preparation that has a Chinese origin. It is extensively used particularly in combination with doxorubicin (DOX) for the management of hepatocellular carcinoma (HCC). However, the combination's synergistic mechanism has not yet been clarified. Aim of the studyTo investigate the anti-tumor impact of AD in combination with DOX and their synergistic mechanism in HCC. Materials and methodsAn H22 mouse xenograft model was utilized to study the impact of AD, DOX, and their combination on HCC in vivo. Their effects on cell vitality, apoptosis, mitochondrial membrane potential, reactive oxygen species (ROS) production, caspase-3, and cleaved caspase-3 protein expression were also investigated in H22 cells in vitro. Subsequently, human umbilical vein endothelial cells (HUVECs) were utilized to investigate the impacts of AD, DOX, and their combination on cell viability, migration, invasion, tube formation, and vascular endothelial growth factor (VEGF) protein expression. ResultsThe study established that the tumor inhibition rate of AD combined with DOX reached 79.51%, which was significantly higher than that of AD (25.14%) or DOX (49.48%) alone. Additionally, the Q-value characterizing the synergy between AD and DOX was 1.72, demonstrating a strong synergistic effect. Furthermore, compared to AD or DOX administration alone, the combined administration group significantly decreased the alpha-fetoprotein (AFP) level in the serum, increased the tumor necrosis area, increased the Bax/Bcl-2, Cyt-c, caspase-9, Fas, Fasl, caspase-8, and caspase-3 protein expression, and significantly increased the CD31 and Ki67 protein expression in tumor tissue. Compared to AD or DOX alone, AD combined with DOX treatment had a synergistic effect on H22 cells (combination index values < 0.9), which inhibited cell viability, reduced mitochondrial membrane potential (MMP), induced apoptosis, promoted MMP loss, and increased ROS generation, cleaved caspase-3/caspase-3 levels, and caspase-3 activity. Moreover, combined administration showed a more pronounced inhibition of cell viability, migration, invasion, tube formation, and VEGF protein expression in HUVECs. ConclusionsAD enhances the anti-tumor effect of DOX by promoting apoptosis and inhibiting angiogenesis and cell proliferation. The findings of this study lay experimental foundations for the clinical combination of AD and DOX.