Scaffold-Hopping of Natural Alkaloid Rutaecarpine: Synthesis and Anticancer-Apoptosis and Autophagy Effects of Indole-Based Analogs.

Natural products have been recognized as important molecular skeletons in drug discovery due to their structural diversity and promising bioactivity. In this study, a scaffold-hopping strategy was applied to Rutaecarpine, an indolo[2',3':3,4]pyrido[2,1-b]quinazolinone alkaloid with antiproliferative activity. A novel series of 2-arylamino-3-indolylethyl-amines/alcohols was prepared by an explored synthetic approach with a Buchwald-Hartwig cross-coupling key step to introduce diverse aryl/heteroaryl amines. The compounds showed notable antiproliferative properties against MCF-7, T-47D, A-549, AGS, SNU-1, HL-60, and MOLT-4 cell lines. The most potent compound, 11a, induced nuclear condensation, mitochondrial membrane depolarization, and autophagosome formation. Western blot analysis confirmed a significant reduction in expression of Pro-caspase-3 and BCL-2. The in vitro results collectively implicate the investigated molecule's significant effect on anticancer properties with simultaneous activation of intrinsic apoptosis and autophagy in cancer cells. SwissADME analysis indicated favorable drug-likeness properties. This work demonstrates the value of a natural product-inspired scaffold-hopping strategy in identifying promising new anticancer molecules with important pharmacological properties.