Borneol acts as an adjuvant agent to enhance the oral absorption of Panax notoginseng saponins in rats: Effect of optical configuration and compatibility ratios

Ethnopharmacological relevance Panax notoginseng saponins (PNS), as the main active component of Panax notoginseng, shows broad pharmacological effects but with low oral bioavailability. Borneol (BO) is commonly used as an adjuvant drug in the field of traditional Chinese medicine, which has been proven to facilitate the absorption of ginsenosides such as Rg1 and Rb1 in vivo. The presence of chiral carbons has resulted in three optical isomers of BO commercially available in the market, all of which are documented by national standards. Aim of the study This study aimed to investigate the role of BO in promoting the oral absorption of PNS from the perspective of optical configuration and compatibility ratios. Materials and methods In this study, an ultra-performance liquid chromatography coupled with triple quadrupole-linear ion trap tandem mass spectrometry (UPLC-QTRAP-MS/MS) method was validated and applied to determine the concentrations of five main saponins in PNS in rat plasma. The kinetic characteristics of PNS was compared when co-administered with BO based on optical isomerism and different compatibility ratios. Results The results showed that BO promoted the exposure of PNS in rats. Three forms of BO, namely d-borneol (DB), l-borneol (LB), and synthetic borneol (SB), exhibited different promotion strengths. SB elevated PNS exposure in rats more than DB or LB. It is also interesting to note that under different compatibility ratios, SB can exert a strong promoting effect only when PNS and BO were combined in a 1:1 ratio (PNS 75 mg/kg; BO 75 mg/kg). As a pharmacokinetic booster, the dosage of BO is worthy of consideration and should follow the traditional medication principles of Chinese medicine. Conclusions This study shed new light on the compatible use of PNS and BO from the perspective of “configuration-dose-influence” of BO. The results provide important basis for the clinical application and selection of BO.