7-methoxycryptopleurine and Coronavirus-Infections

Several corona viral infections have created serious threats in the last couple of decades claiming the death of thousands of human beings. Recently, corona viral epidemic raised the issue of developing effective antiviral agents at the earliest to prevent further losses. Natural products have always played a crucial role in drug development process against various diseases, which resulted in screening of such agents to combat emergent mutants of corona virus. This review focuses on those natural compounds that showed promising results against corona viruses. Although inhibition of viral replication is often considered as a general mechanism for antiviral activity of most of the natural products, studies have shown that some natural products can interact with key viral proteins that are associated with virulence. In this context, some of the natural products have antiviral activity in the nanomolar concentration (e.g., lycorine, homoharringtonine, silvestrol, ouabain, tylophorine, and 7-methoxycryptopleurine) and could be leads for further drug development on their own or as a template for drug design. In addition, a good number of natural products with anti-corona virus activity are the major constituents of some common dietary supplements, which can be exploited to improve the immunity of the general population in certain epidemics.

Topics: Alkaloids; Animals; Antiviral Agents; Biological Products; Coronavirus; Coronavirus Infections; Drug Development; Humans; Indolizines; Ouabain; Phenanthrenes; Plant Extracts; Quinolizines; Triterpenes; Viral Proteins; Virus Replication

The discovery and development of new, highly potent anti-coronavirus agents and effective approaches for controlling the potential emergence of epidemic coronaviruses still remains an important mission. Here, we identified tylophorine compounds, including naturally occurring and synthetic phenanthroindolizidines and phenanthroquinolizidines, as potent in vitro inhibitors of enteropathogenic coronavirus transmissible gastroenteritis virus (TGEV). The potent compounds showed 50% maximal effective concentration (EC₅₀) values ranging from 8 to 1468 nM as determined by immunofluorescent assay of the expression of TGEV N and S proteins and by real time-quantitative PCR analysis of viral yields. Furthermore, the potent tylophorine compounds exerted profound anti-TGEV replication activity and thereby blocked the TGEV-induced apoptosis and subsequent cytopathic effect in ST cells. Analysis of the structure-activity relations indicated that the most active tylophorine analogues were compounds with a hydroxyl group at the C14 position of the indolizidine moiety or at the C3 position of the phenanthrene moiety and that the quinolizidine counterparts were more potent than indolizidines. In addition, tylophorine compounds strongly reduced cytopathic effect in Vero 76 cells induced by human severe acute respiratory syndrome coronavirus (SARS CoV), with EC₅₀ values ranging from less than 5 to 340 nM. Moreover, a pharmacokinetic study demonstrated high and comparable oral bioavailabilities of 7-methoxycryptopleurine (52.7%) and the naturally occurring tylophorine (65.7%) in rats. Thus, our results suggest that tylophorine compounds are novel and potent anti-coronavirus agents that may be developed into therapeutic agents for treating TGEV or SARS CoV infection.

Topics: Alkaloids; Animals; Antiviral Agents; Apocynaceae; Chlorocebus aethiops; Coronavirus Infections; Cytopathogenic Effect, Viral; Dose-Response Relationship, Drug; Gastroenteritis, Transmissible, of Swine; Indolizines; Phenanthrenes; Phenanthrolines; Quinolizines; Rats; Rats, Sprague-Dawley; Severe Acute Respiratory Syndrome; Severe acute respiratory syndrome-related coronavirus; Structure-Activity Relationship; Swine; Transmissible gastroenteritis virus; Tylophora; Vero Cells