Current Medicinal Chemistry - Volume 32, Issue 4, 2025

The main protease (M^pro) is a crucial enzyme for the life cycle of SARS-CoV-2 and a validated target for the treatment of COVID-19 infection. Natural products have been a proper alternative for treating viral diseases by modulating different steps of the life cycle of many viruses.

This review article is designed to summarize the cumulative information of natural-derived M^pro inhibitors that are validated by experimental biological testing.

The natural-derived M^pro inhibitors of SARS-CoV-2 that have been discovered since the emergence of the COVID-19 pandemic are reviewed in this article. Only natural products with experimental validation are reported in this article. Collected compounds are classified according to their chemical identity into flavonoids, phenolic acids, quinones, alkaloids, chromones, stilbenes, tannins, lignans, terpenes, and other polyphenolic and miscellaneous natural-derived M^pro inhibitors.

These compounds could serve as scaffolds for further lead-structure optimization for desirable potency, a larger margin of safety, and better oral activity.

The molecular mechanisms regulating coronavirus pathogenesis are complex, including virus-host interactions associated with replication and innate immune control. However, some genetic and epigenetic conditions associated with comorbidities increase the risk of hospitalization and can prove fatal in infected patients. This systematic review will provide insight into host genetic and epigenetic factors that interfere with COVID-19 expression in light of available evidence.

This study conducted a systematic review to examine the genetic and epigenetic susceptibility to COVID-19 using a comprehensive approach. Through systematic searches and applying relevant keywords across prominent online databases, including Scopus, PubMed, Web of Science, and Science Direct, we compiled all pertinent papers and reports published in English between December 2019 and June 2023.

The findings reveal that the host's HLA genotype plays a substantial role in determining how viral protein antigens are showcased and the subsequent immune system reaction to these antigens. Within females, genes responsible for immune system regulation are found on the X chromosome, resulting in reduced viral load and inflammation levels when contrasted with males. Possessing blood group A may contribute to an increased susceptibility to contracting COVID-19 as well as a heightened risk of mortality associated with the disease. The capacity of SARS-CoV-2 involves inhibiting the antiviral interferon (IFN) reactions, resulting in uncontrolled viral multiplication.

There is a notable absence of research into the gender-related predisposition to infection, necessitating a thorough examination. According to the available literature, a significant portion of individuals affected by the ailment or displaying severe ramifications already had suppressed immune systems, categorizing them as a group with elevated risk.

Anti-N-methyl-d-aspartate (Anti-NMDA) receptor encephalitis is a rare autoimmune disease, which is caused by antibodies attacking NMDA receptors in the brain. Previous studies revealed that this disorder might be induced by vaccination. Vaccination is the most useful strategy to prevent human or animal infectious diseases. Although vaccines can produce immunity against diseases, at low risk, they may trigger serious adverse events. Anti-NMDA receptor encephalitis has been studied to be related to the H1N1 (influenza A virus subtype H1N1), tetanus/diphtheria/pertussis and polio vaccine, Japanese encephalitis, yellow fever, and coronavirus disease 2019 (COVID-19) vaccination. Several cases have been reported that anti-NMDA receptor encephalitis could also be triggered by the human papillomavirus (HPV) vaccine. However, there is a lack of studies to investigate the underlying mechanism.

In this paper, the association between anti-NMDA receptor encephalitis and HPV vaccination is discussed in terms of their microRNA (miRNA) biomarkers. Phylogenetic tree and distance similarity analyses are used to explore the relationship between their miRNA biomarkers.

The results show a higher degree of similarity between miRNA biomarkers associated with HPV and anti-NMDA receptor encephalitis or related vaccines when compared to the overall miRNAs. It indicates that while the risk of HPV triggering anti-NMDA receptor encephalitis is low, a connection between anti-NMDA receptor encephalitis and HPV vaccination cannot be ruled out.

This finding suggests that in cases where individuals receiving HPV vaccination experience psychiatric or neurological symptoms, it should be considered to diagnose anti-NMDA receptor encephalitis, given the exclusion of other possible complications.

P-glycoprotein, an ATP-dependent efflux transporter, plays a crucial role in eliminating cellular toxins and affects the intracellular concentration and bioavailability of CDK 4/6 inhibitors. Moreover, dietary flavonoids are natural bio-enhancers that can effectively inhibit the efflux function of these transporters. Therefore, this study aimed to assess the impact of dietary polyphenols on the inhibition of P-glycoprotein and the subsequent efflux of CDK inhibitors palbociclib and ribociclib.

A molecular docking approach was implemented to evaluate the binding interaction characteristics of CDK4/6 inhibitors in the presence of dietary polyphenols at the ATP binding site. Furthermore, the stability of the complexes was evaluated in two conformations of P-glycoprotein, followed by an ex vivo everted gut sac experiment.

The findings demonstrated that the binding of curcumin and quercetin with high affinity (-51.63 and -47.16 Kcal/mol) to ATP binding sites of P-glycoprotein-palbociclib and ribociclib inward conformation complexes resulted in good stability of complex and minimal fluctuation throughout the course of the simulation. It was evident from the everted gut sac ex vivo study that the presence of 100 µM of curcumin resulted in an increase of 1.77 and 4.20-fold in the intestinal transit of palbociclib and ribociclib, respectively.

The study emphasizes the significance of curcumin and quercetin as inhibitors of P-glycoprotein, demonstrating their potential to decrease the efflux of palbociclib and ribociclib, consequently contributing to their bioavailability enhancement.

Thrombotic disorders are among the leading causes of morbidity and mortality worldwide. Drugs used in the prevention and treatment of atherothrombosis have pharmacokinetic limitations and adverse effects such as hemorrhagic conditions, highlighting the importance of developing more effective antiplatelet agents.

In this work, we synthesized N,N'-disubstituted ureas 3a-3j and evaluated their antiplatelet profiles through in vitro, ex vivo, and in silico studies.

The synthesized derivatives exhibited a selective inhibitory profile against platelet aggregation induced by arachidonic acid (AA) in vitro, without significantly affecting other aspects of primary hemostasis and blood coagulation. The compounds that showed inhibition greater than 85% were submitted to the analysis of their potency by calculating the concentration required to inhibit 50% of platelet aggregation induced by AA (IC50). Urea derivative 3a was the most potent with IC50 of 1.45 µM. Interestingly, this derivative inhibited more than 90% of platelet aggregation induced by AA ex vivo, with a similar effect to acetylsalicylic acid. In the hemolysis assay, most of the urea derivatives presented values below 10% suggesting good hemocompatibility. Additionally, the compounds tested at 100 µM also showed no cytotoxic effects in HepG2 and Vero cells. The in silico results suggested that compound 3a may bind to the key residue of COX-1 similar to AA and known COX-1 inhibitors, and the results are also in agreement with our SAR, which suggests that the inhibition of this enzyme is the most likely mechanism of antiplatelet activity.

Therefore, these results demonstrated that N,N'-disubstituted ureas are promising candidates for the development of novel antiplatelet agents.