Synthesis and Antiproliferative Activity of Novel Pyranocarbazoles

Development of novel 9H-carbazole-4H-chromene hybrids as dual cholinesterase inhibitors for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease affecting mental ability and neurocognitive functions. Cholinesterase enzymes affect concentration of acetylcholine in the brain, leading to dementia. Thus, there is an urgent need to develop novel dual cholinesterase inhibitors as possible anti-AD drugs. Herein, we have designed and synthesized a novel series of 9H-carbazole-4H-chromenes 4(a-l) through a one-pot three-component reaction of salicylaldehydes (1), hydroxycarbazole (2) and N-methyl-1-(methylthio)-2-nitroethenamine (3) using triethylamine as a catalyst in ethanol. Synthetic transformation involves the formation of two C-C bonds and one C-O bond in a single step to obtain desired analogs. The rapid one-pot reaction does not require chromatographic purification, proceeds under mild conditions, and exhibits good tolerance toward various functional groups with high synthetic yields. Synthesized compounds were screened for cytotoxicity using MTT assay in BV-2 microglial cells. These compounds were then in-vitro screened against acetylcholinesterase (AChE) and butyrylcholinestrase (BuChE) enzymes. Most of these ligands have shown dual cholinesterase inhibitory activity compared to the standard drug. In-vitro results showed that the compounds 4a and 4d have promising anticholinesterase response against both cholinesterase enzymes (4a, AChE IC50: 5.76 µM, BuChE IC50: 48.98 µM; 4d, AChE IC50: 3.58 µM, BuChE IC50: 42.73 µM). In-vitro results were validated by molecular docking and dynamic simulation at 100 ns. Molecular docking and molecular dynamics simulation study strongly supported structural features present in these analogs. Together, these analogs could be exploited to develop dual anti-cholinesterase candidates to treat AD in combination with other drugs.

Current status of carbazole hybrids as anticancer agents

The drug resistance and low specificity of current available chemotherapeutics to cancer cells are the main reasons responsible for the failure of cancer chemotherapy and remain dramatic challenges for cancer therapy, creating an urgent need to develop novel anticancer agents. Carbazole nucleus, widely distributed in nature, is a predominant feature of a vast array of biologically active compounds. Carbazole derivatives exhibited potential antiproliferative activity against different cancer cell lines by diverse mechanisms, inclusive of arrest cell cycle and induce apoptosis, and several anticancer agents are carbazole-based compounds. Thus, carbazole derivatives represent a fertile source for discovery of novel anticancer therapeutic agents. Over the past several years, a variety of carbazole hybrids have been developed as potential anticancer agents. The present review focuses on the recent progress, from 2016 until now, in knowledge on anticancer properties, structure-activity relationships and mechanisms of action of carbazole hybrids to provide a basis for development of relevant therapeutic agents.