Mini Reviews in Medicinal Chemistry - Volume 22, Issue 15, 2022

Nuclear factor-kappa B (NF-ΚB) is one of the principal inducible proteins and a predominant transcription factor that is known to control gene expression in mammals. It plays a pivotal role in regulating cell signalling in the body under certain physiological and pathological conditions. In cancer cells, such as colon, breast, pancreatic, ovarian, melanoma, and lymphoma, the NF-ΚB pathway is active. In cellular proliferation, promoting angiogenesis, invasion, metastasis of tumour cells, and blocking apoptosis, the constitutive activity of NF-ΚB signalling has been reported. Therefore, immense attention has been given to developing drugs targeting NF-ΚB signalling pathways to treat many types of tumours. They are a desirable therapeutic target for drugs, and many studies have concentrated on recognizing compounds. They may be able to reverse or standstill the growth and spread of tumours that selectively interfere with this pathway. Recently, numerous substances derived from plants have been evaluated as possible inhibitors of the NF-ΚB pathway. These include various compounds, such as flavonoids, lignans, diterpenes, sesquiterpenes, polyphenols, etc. A study supported by folk medicine demonstrated that plant-derived compounds could suppress NF-ΚB signalling. Considering this, the present review revealed the anticancer potential of naturally occurring compounds that inhibit the NF-ΚB signalling and suppress the growth and spread of cancer.

Arginase, which converts arginine into ornithine and urea, is a promising therapeutic target. Arginase is involved in cardiovascular diseases, parasitic infections and through a critical role in immunity, in some cancers. There is a need to develop effective arginase inhibitors and therefore efforts to identify and optimize new inhibitors are increasing. Several methods of evaluating arginase activity are available, but few directly measure the product. Radiometric assays need to separate urea and dying reactions require acidic conditions and sometimes heating. Hence, there are a variety of different approaches available, and each approach has its own limits and benefits. In this review, we provide an update on arginase inhibitors, followed by a discussion on available arginase assays and alternative methods, focusing on the intrinsic biases and parameters that are likely to impact results.

Epigenetic mutations like aberrant DNA methylation, histone modifications, or RNA silencing are found in a number of human diseases. This review article discusses the epigenetic mechanisms involved in neurodegenerative disorders, cardiovascular disorders, auto-immune disorders and genomic imprinting disorders. In addition, emerging epigenetic therapeutic strategies for the treatment of such disorders are presented. Medicinal chemistry campaigns highlighting the efforts of the chemists invested towards the rational design of small molecule inhibitors have also been included. Pleasingly, several classes of epigenetic inhibitors, DNMT, HDAC, BET, HAT, and HMT inhibitors, along with RNA based therapies, have exhibited the potential to emerge as therapeutics in the longer run. It is quite hopeful that epigenetic modulator-based therapies will advance to clinical stage investigations by leaps and bounds.

The lysosomal cysteine protease enzyme, named Cathepsin B, mainly degrades the protein and manages its average turnover in our body. The Cathepsin B active form is mostly present inside the lysosomal part at a cellular level, providing the slightly acidic medium for its activation. Multiple findings on Cathepsin B reveal its involvement in neurons’ degeneration and a possible role as a neuronal death mediator in several neurodegenerative diseases. In this review article, we highlight the participation of Cathepsin B in the etiology/progress of AD, along with various other factors. The enzyme is involved in producing neurotoxic Aβ amyloid in the AD brain by acting as the β-secretase enzyme in the regulated secretory pathways responsible for APP processing. Aβ amyloid accumulation and amyloid plaque formation lead to neuronal degeneration, one of the prominent pathological hallmarks of AD. Cathepsin B is also involved in the production of PGlu-Aβ, which is a truncated and highly neurotoxic form of Aβ. Some of the findings also revealed that Cathepsin B specific gene deletion decreases the level of PGlu-Aβ inside the brain of experimental mice. Therefore, neurotoxicity might be considered a new pathological indication of AD due to the involvement of Cathepsin B. It also damages neurons present in the CNS region by producing inflammatory responses and generating mitochondrial ROS. However, Cathepsin B inhibitors, i.e., CA-074, can prevent neuronal death in AD patients. The other natural inhibitors are also equally effective against neuronal damage with higher selectivity. Its synthetic inhibitors are specific for their target; however, they lose their selectivity in the presence of quite a few reducing agents. Therefore, a humanized monoclonal antibody is used as a selective Cathepsin B inhibitor to overcome the problem experienced. The use of Cathepsin B for the treatment of AD and other neurodegenerative diseases could be considered a rational therapeutic target.

Pentacyclic triterpenoids, consisting of six isoprene units, are a kind of natural active substance. At present, numerous pentacyclic triterpenes have been identified and classified into four subgroups of oleanane, ursane, lupane, and xylene on the basis of the carbon skeleton. Among them, oleanane is the most popular due to its rich backbone and diverse bioactivities. 18β-Glycyrrhetinic acid (GA), an oleanane-type pentacyclic triterpene isolated from licorice roots, possesses diverse bioactivities, including antitumor, anti-inflammatory, antiviral, antimicrobial, enzyme inhibitor, hepatoprotective, and so on. It has received more attention in medicinal chemistry due to the advantages of easy access and rich bioactivity. Thus, numerous novel lead compounds have been synthesized using GA as a scaffold. Herein, we summarize the structure-activity relationship and synthetic methodologies of GA derivatives from 2010 to 2020, as well as the most active GA derivatives. Finally, we anticipate that this review can benefit future research on structural modifications of GA to enhance bioactivity and provide an example for developing pentacyclic triterpene-based novel drugs.