Photopharmacology of Azo-Combretastatin-A4: Utilizing Tubulin Polymerization Inhibitors and Green Chemistry as the Key Steps

Abstract

: Tubulin Polymerization Inhibitors (TPIs) are promising ligands utilized in chemotherapy for modern cancer treatment. However, the current TPIs exhibit many serious side effects that may pose limitations in chemotherapy. Combretastatin A-4 (CA-4) is a natural TPI that binds at the colchicine binding site located on microtubules. The only cis isomer of CA-4 is bio-active; however, due to its short half-life, it isomerizes quickly to its bio-inactive trans geometric isomer. For preventing shortcomings of CA-4, azobenzene based CA-4, called azo-CA-4 (azo-CA-4) is identified as a novel TPI. The geometric isomerization of azo- CA-4 can be controlled upon exposure to ultraviolet (UV) light to remotely control its bioactivity. Cis-azo-CA-4 is 200-500 times more active (IC50 = 0.2-10 μM) than trans-azo-CA-4 (IC50 = 50-110 μM) against various cancer cell lines. Photo-pharmacology uses light to control drug activity, introducing a unique mechanism to develop novel photo-responsive TPIs. Further, the green chemistry approach using ethanol and water as a green solvent in the synthesis of azo-CA-4 delivers advanced methodology in novel TPI development.