Re-exploration of tetrahydro-β-carboline scaffold: Discovery of selective histone deacetylase 6 inhibitors with neurite outgrowth-promoting and neuroprotective activities

Diverse pharmacological activities of β-carbolines: Substitution patterns, SARs and mechanisms of action

β-Carbolines, a class of indole-containing heterocyclic alkaloids, are widely distributed in nature and possess diverse bioactivities, making them promising drug candidates against a wide range of diseases. The remarkable medicinal potential of β-carbolines has spurred the pharmaceutical research community to study their derivatives extensively. This review updates the development of β-carboline derivatives in recent years (2015-2024), particularly with a focus on their anticancer, antiparasitic, antimicrobial, antiviral, and neuroprotective properties, based on the modification approaches such as substitution on indole N (ring B), pyridine or its reduced forms (ring C), and dimerization of β-carbolines. Moreover, the mechanisms of action and structure-activity relationships of these β-carboline derivatives are highlighted to offer valuable insights on the design and development of new β-carbolines with better pharmacological activities.

Multimechanism biological profiling of tetrahydro-β-carboline analogues as selective HDAC6 inhibitors for the treatment of Alzheimer's disease

With the intensive research on the pathogenesis of Alzheimer's disease (AD), inhibition of HDAC6 appears to be a potential therapeutic approach for AD. In this paper, a series of tetrahydro-β-carboline derivatives with hydroxamic acid group were fast synthesized. Among all, the most potent 15 selectively inhibited HDAC6 with IC50 of 15.2 nM and markedly increased acetylated alpha-tubulin levels. In cellular assay, 15 showed excellent neurotrophic effect by increasing the expression of GAP43 and Beta-3 tubulin markers. Besides, 15 showed neuroprotective effects in PC12 or SH-SY5Y cells against H2O2 and 6-OHDA injury through activation of Nrf2, catalase and Prx II, and significantly reduced H2O2-induced reactive oxygen species (ROS) production. In vivo, 15 significantly attenuated zebrafish anxiety-like behaviour and memory deficits in a SCOP-induced zebrafish model of AD. To sum up, multifunctional 15 might be a good lead to develop novel tetrahydrocarboline-based agents for the treatment of AD.

Design, synthesis and antiproliferative evaluation of tetrahydro-β-carboline histone deacetylase inhibitors bearing an aliphatic chain linker

The use of histone deacetylase inhibitors (HDACis) is an effective approach for cancer treatment. In this work, a series of hydroxamic acid-based HDACis with a tetrahydro-β-carboline core and aliphatic linker have been designed and synthesized. The optimal compound 13d potently inhibited HDAC1 and showed good antiproliferative activity against different tumor cell lines in vitro. Molecular docking of 13d was conducted to rationalize the high binding affinity for HDAC1. Therefore, this work provides a new structure design for HDAC inhibitors and also offers a promising treatment for solid tumors.