Elucidation of interaction between serum albumin and ginsenoside CK along with cytotoxic study

As a main metabolite of ginsenosides, compound K (CK) has a vast array of pharmacological effects. However, due to its low polarity and insoluble in water, its oral application has been greatly limited. In this work, the interaction between serum albumin and ginsenoside CK was elucidated by multi-spectroscopic studies. The result of ultraviolet/visible absorption spectroscopy showed that the conformation of serum albumin could be changed via binding with CK. The result of fluorescence spectroscopy suggested that CK could form complex with serum albumin. CK could quench the fluorescence and the fluorescence residues of serum albumin were located in or near the binding position. Molecular docking indicated that CK bound at Sudlow's site II of serum albumin and formed hydrogen-bonding interactions with three residues. Furthermore, the flexible side chain of CK was difficult to be stabilized at the binding site, resulting in its serious perturbation during dynamics simulation. This work also performed the cytotoxic study and the result showed that serum albumin enhanced the inhibitory effect of CK on the proliferation of both Caco-2 and HCT-116 cells. To sum up, this work revealed that serum albumin might be an appropriate carrier of hydrophobic compounds, with the advantage of improving their biocompatibility.