Design, synthesis and biological evaluation of novel indanone containing spiroisoxazoline derivatives with selective COX-2 inhibition as anticancer agents

Objective: A new family of 3'-(Mono, di or tri-substituted phenyl)-4'-(4-(methylsulfonyl) phenyl) spiroisoxazoline derivatives containing indanone spirobridge was designed, synthesized, and evaluated for their selective COX-2 inhibitory potency and cytotoxicity on different cell lines.

Methods: A synthetic reaction based on 1,3-dipolar cycloaddition mechanism was applied for the regiospecific formation of various spiroisoxazolines. The activity of the newly synthesized compounds was determined using in vitro cyclooxygenase inhibition assay. The toxicity of the compounds was evaluated by MTT assay. In addition, induction of Apoptosis, and expression levels of Bax, Bcl-2 and Caspase-3 mRNA in MCF-7 cells were evaluated following exposure to compound 9f. The docking calculations and molecular dynamics simulation were performed to study the most probable modes of interactions of compound 9f upon binding to COX-2 Enzyme.

Results: The docking results showed that the synthesized compounds were able to form hydrogen bonds with COX-2 involving methyl sulfonyl, spiroisoxazoline, meta-methoxy and fluoro functional groups. Spiroisoxazoline derivatives containing methoxy group at the C-3' phenyl ring meta position (9f and 9g) showed superior selectivity with higher potency of inhibiting COX-2 Enzyme. Furthermore, compound 9f, which possesses 3,4-dimethoxyphenyl on C-3' carbon atom of isoxazoline ring, exhibited the highest COX-2 inhibitory activity, and also displayed the most potent cytotoxicity on MCF-7 cells with an IC₅₀ value of 0.03 ± 0.01 µM, comparable with that of doxorubicin (IC₅₀ of 0.062 ± 0.012 µM). The results indicated that compound 9f could promote Apoptosis. Also, compared to the control group, the mRNA expression of Bax and Caspase-3 significantly increased, while that of Bcl-2 significantly decreased upon exposure to compound 9f which may propose the activation of mitochondrial-associated pathway as the mechanism of observed Apoptosis.

Conclusion: In vitro biological evaluations accompanied with in silico studies revealed that indanone tricyclic spiroisoxazoline derivatives are good candidates for the development of new anti-inflammatory and Anticancer (colorectal and breast) agents.

Apoptosis; Cytotoxicity; Docking; Indanone; MTT assay; Molecular dynamics simulation; Selective COX-2 inhibitors; Spiroisoxazoline; Synthesis.