5H-benzo[c]fluorene derivative exhibits antiproliferative activity via microtubule destabilization

Present study aimed at a single component cyclization of 2-benzylidene-1-tetralones for the preparation of 5H-benzo[c]fluorenes and their antiproliferative activity. This ring closure reaction underwent via reductive cyclization in the presence of a sodium borohydride-aluminium chloride system. Ten diverse 5H-benzo[c]fluorene derivatives were prepared and evaluated for antiproliferative activity against three human Cancer cell lines by SRB assay. Four of these benzofluorenes exhibited significant antiproliferative effect with an IC₅₀ < 10.75 µM. The best representative compound 21, exhibited IC₅₀ against K562 leukemic cells at 3.27 µM in SRB assay and 7.68 µM in Soft agar colony assay. It exhibited a microtubule destabilization effect in tubulin kinetics and inhibited 82.9 % microtubule polymer mass at 10 µM concentration in Protein Sedimentation assay (Microtubule). Compound 21 exerted G0/G1 phase arrest in cell division cycle analysis in K562 cells. It also induced Apoptosis in K562 cells via activation of Caspase cascade pathway. Furthermore, compound 21 also possessed anti-inflammatory activity by inhibiting TNF-α and IL-6 moderately. It exhibited significant in vivo efficacy and reduced K562 tumour in xenograft mice by 47 % at an 80 mg/kg oral dose. Further, it was found to be safe and well tolerable up to 1000 mg/kg in Swiss albino mice. Compound 21 needs to be optimized for better in vivo efficacy in rodent models for further development.

Acute oral toxicity; Anticancer; Benzofluorenes; Microtubule destabilization; Reductive cyclization.