Design, synthesis, and biological evaluation of potent photoaffinity probes of oleanolic acid.

To study the target proteins of oleanolic acid, a series of novel photoaffinity probes were designed and synthesized. Their affinity for the target proteins was evaluated in an enzyme inhibition assay against glycogen phosphorylase, a known target protein of oleanolic acid. Among these compounds, probe 2 exhibited the most potent activity with an IC50 value of 5.98 μM, which was about 2.5-fold more potent than its parent compound oleanolic acid. The results showed that the synthesized photoaffinity probes retained the binding affinity for their target proteins, and might be used as powerful tools to fish out the target proteins of oleanolic acid.