Synthesis of novel pyrazole acetals of andrographolide and isoandrographolide as potent anticancer agents

Globally, cancer is the most prevalent chronic disease-related cause of death. Although there are many anticancer drugs, some of them have adverse effects. Due to their limited side effects, natural products are preferred over synthetic drugs. Andrographolide and its derivatives are known to be potent anticancer agents. In this context, sixteen novel 3,19-(NH-3-aryl-pyrazole) acetals of andrographolide and isoandrographolide (1a-1h, 2a-2g, 2i) from 3-aryl-1-H-pyrazole-4-carboxaldehydes (a-i) were synthesized. All the synthesized compounds were characterized using ¹H NMR, ¹³C NMR, HRMS, FT-IR, and UV-vis spectroscopy. All the compounds were evaluated against a panel of 60 different human cancer cell lines for their anticancer potential at NCI, USA. Four compounds, having promising GI₅₀s (50% growth inhibitory activity) on all 60-cell lines were selected for further in vitro studies. Out of these four compounds, compound 1g exhibited the best IC₅₀ (3.08 μM) against the colon cancer cell line, HCT-116. Cell cycle analysis, annexin V-FITC/PI, and ROS assays revealed that the apoptosis of HCT-116 cells induced by compound 1g could be mainly attributed to the elevated levels of intracellular ROS. Further, the structure-activity relationship revealed that the pyrazole moiety of andrographolide plays a key role in their anticancer properties. These compounds were further examined for in silico ADMET and Lipinski characteristics to assess their potential as lead compounds.