Background: Combrestastatin A-4 (CA-4) is a potent anticneoplastic and antiangiogenesis natural substance isolated from Combretum caffrum. Over the past two decades, numerous derivatives of CA-4 have been discovered. However, none of these derivatives has reached the clinical stage. Thus, continuing effort is needed in developing CA-4 analogues with improved pharmacological properties.
Methods: In this study, two series of thiazolidine-2,4-dione and 2-oxoindoline derivatives incorporating 3,4,5-trimethoxybenzyl scaffold were designed and synthesized as CA-4 analogues.
Results: Numerous CA-4 analogues bearing thiazolidine-2,4-dione/2-oxoindoline have been synthesized. These compounds were evaluated against several human cancer cell lines. It was found that a series of 5/7-substituted-1-(3,4,5-trimethoxy)benzylindoline-2,3-diones (2a-g) exhibited significant cytotoxicity. Especially compound 2d bearing a 5-bromo substituent showed the best activity with IC50 values in sub-microgram/mL scale in four human cancer cell lines tested. This compound also exhibited potent tubulin polymerization inhibitory activity. A series of (Z)-5-arylidene- 3-(3,4,5-trimethoxybenzyl)thiazolidine-2,4-diones (6a-j), on the other hand, displayed only moderate cytotoxic activities with only compound 6a showing comparable cytotoxicity to 2d. Finally, in silico molecular modeling and drug-likeness profiling revealed that five compounds 2b, 2d, 2e, 3e and 6a bound to tubulin active binding sites with strong binding affinities.
Conclusion: This study discovered some novel CA-4 analogues with cytotoxic potency and antitubulin activity acceptable to be further developed as effective anticancer drug candidates.