LAUSR

As rare ginsenosides, 20(R, S)-ginsenoside Rh1 [20(R, S)-Rh1] are isomers and have been reported to exhibit multiple biological effects. However, the application of 20(R, S)-Rh1 is still limited due to their poor solubilities and low bioavailabilities. Here, the complexation mechanism between 20(R, S)-Rh1 and serum albumin (SA) was explored by a combination of multi-spectroscopy and in silico investigations. Results of spectra experiments showed that 20(R, S)-Rh1 could form complexes with bovine serum albumin (BSA) and quench its intrinsic fluorescence. In addition, the influence of BSA on the anti-cancer activity of 20(R, S)-Rh1 was also evaluated in A549 cells. The result of the MTT assay indicated that anti-cancer activity of 20(R, S)-Rh1 was enhanced when combined with BSA. The results of molecular docking and dynamics simulation demonstrated that the subtle structural differences of 20(R, S)-Rh1 at the 20-carbon atom may be responsible for their different binding capacities and binding stabilities with human serum albumin. The cytotoxicity assay for 20(R, S)-Rh1 alone and their complexes with BSA demonstrated the enhancement effect of BSA for inhibition of cell proliferation. In conclusion, this work provided insight into the complexation mechanism between 20(R, S)-Rh1 and SA. PRACTICAL APPLICATION: The complexation mechanism between 20(R, S)-ginsenoside Rh1 [20(R, S)-Rh1] and serum albumin (SA) was explored by a combination of multi-spectroscopy and in silico investigations in this work. The cytotoxicity assay for 20(R, S)-Rh1 alone and their complexes with bovine serum albumin (BSA) demonstrates the enhancement effect of BSA for inhibition of cell proliferation. Hence, this work provided insight into the complexation mechanism between 20(R, S)-Rh1 and SA.