Quantitative analysis of drug–drug interactions among active components of Xuebijing in inhibiting LPS-induced TLR4 signaling and NO production

Despite the long history of Traditional Chinese Medicine (TCM) in disease treatment, the underlying "Jun-Chen-Zuo-Shi" principle remains largely unexplored. To address this gap, it is essential to elucidate the interactions between active substances in TCM through quantitative molecular and cellular pharmacology. The Chou-Talalay method is particularly effective for investigating drug combinations, making it highly relevant for TCM formulas. This study employed the Chou-Talalay method to explore the drug-drug interactions in Xuebijing (XBJ), a TCM formula used for treating sepsis. The aim was to elucidate the "Jun-Chen-Zuo-Shi" principle by investigating the interactions of the main active substances in XBJ: danshensu and salvianolic acid B (from Radix Salviae Miltiorrhizae), senkyunolide A (from Rhizoma Chuanxiong), ligustilide (from Radix Angelicae Sinensis), safflower yellow and hydroxysafflor yellow A (from Flos Carthami), and paeoniflorin (from Radix Paeoniae Rubra). We quantitatively analyzed their TLR4 antagonistic activities and used the combination index (CI) to quantify their interactions, revealing synergism (CI < 1), additive effects (CI = 1), and antagonism (CI > 1). The results show these agents inhibit nitric oxide (NO) production, with some combinations demonstrating synergistic effects at certain concentrations, while others present antagonistic effects. Understanding these interactions provides a scientific foundation for optimizing TCM formulations, enhancing quality control, efficacy, and safety.