Betulin-Hippuric Acid Conjugates: Chemistry, Antiproliferative Activity and Mechanism of Action

The structure of betulin enables the formation of conjugates that offer improved activity, selectivity, or pharmacokinetic parameters. It was assumed that combining betulin with hippuric acid could produce a product with favorable biological properties. The bond connecting the conjugate elements was an ester group introduced using a method ensuring mild reaction conditions (Steglich method). In this way, betulin and its acetyl derivatives were converted into conjugates with hippuric acid, with good yields. The obtained compounds were assessed for their in vitro antiproliferative activity against seven different human cancer cell lines (MTT and SRB assays), preceded by in silico prediction (PASS online). Lipophilicity (logPTLC), a significant parameter influencing all stages of the ADME process, was experimentally determined using RP-TLC. LogPTLC values were compared with logP results obtained from available online computational programs. Antiproliferative activity studies demonstrated the significant sensitivity of MV4-11 cells to the tested compounds. The IC50 values ranged from 4.2 to 31.4 µM. The mechanism of anticancer action was investigated for the most active derivatives 4, 5, and 7. For derivative 7, molecular docking revealed the highest affinity for the FLT3 protein binding site.