Discovery of pyrrolospirooxindole derivatives as novel cyclin dependent kinase 4 (CDK4) inhibitors by catalyst-free, green approach

•A simple, greener and highly efficient method.•Catalyst-free, ethanol is used as green solvent.•14 examples have been tested for their antiproliferative activity, compound 3n showed significant cytotoxicity with IC50 1.16 μM.•Compound 3n induces cell cycle arrest in the G0/G1 phase.•Western blot analysis suggested that reduction in Cdk4 expression level leads to apoptotic cell death.

Aiming to develop a new target for the anticancer treatment, a series of 5′H-spiro[indoline-3,4′-pyrrolo [1,2-a]quinoxalin]-2-ones has been synthesized by simple, highly efficient and environmentally friendly method in excellent yields under catalyst-free conditions using ethanol as a green solvent. A simple filtration of the reaction mixture and subsequent drying affords analytically pure products. The synthesized derivatives were evaluated for their antiproliferative activity against five different human cancer cell lines, among the congeners compound 3n showed significant cytotoxicity against the human prostate cancer (DU-145). Flow cytometric analysis revealed that this compound induces cell cycle arrest in the G0/G1 phase and Western blot analysis suggested that reduction in Cdk4 expression level leads to apoptotic cell death. This was further confirmed by mitochondrial membrane potential ((ΔΨm), Annexin V-FITC assay and docking experiments. Furthermore, it was observed that there is an increase in expression levels of cyclin dependent kinase inhibitors like Cip1/p21 and Kip1/p27.

Graphical abstractA new class of anticancer agents, pyrrolospirooxindole derivatives have been synthesized by simple, efficient and environmentally benign method has been developed for the synthesis of in excellent yields under catalyst-free condition with ethanol. The synthesized compounds evaluated for their antiproliferative activity, among them, compound 3n showed significant cytotoxicity against the human prostate cancer (DU-145). Further mechanistic studies such as cell cycle analysis, mitochondrial potential assay, annexin V-FITC assay and Western blot analysis indicated that 3n induces cell death by apoptosis.Figure optionsDownload full-size imageDownload as PowerPoint slide