ABSTRACT
COVID-19 pandemic has an enormous impact on humans, and it has disrupted daily life of people. Moreover, COVID-19 pandemic has significant negative effects on the world economics. To prevent the viral infection, vaccines are rapidly developed and available for certain strains of SARS-CoV-2 virus. However, the emerging of new variants has caused the problems for COVID-19 vaccines due to immune escape ability, challenging the vaccine development process which usually takes years. In this regard, there is a critical need of new antiviral compounds that can be used to combat SARS-CoV-2 virus safely and effectively. This review provides an overview on alkaloids and alkaloid-like compounds, which have antiviral activity against SARS-CoV-2 virus and related coronaviruses. Drug repurposing has played a crucial role for the drug discovery of COVID-19, and many effective antiviral agents against SARS-CoV-2 virus are from commonly used drugs or antiviral leads. Antiviral natural alkaloids and derivatives, which have the activity toward SARS-CoV-2 virus and related coronaviruses, are also discussed in this review. © 2022 The Japan Institute of Heterocyclic Chemistry.
ABSTRACT
This work explored the compositions of a crude extract of peels of Citrus x aurantium using a gas chromatography-mass spectrometry (GC-MS) technique. The crude extract of peels of C. × aurantium was analyzed by GC-MS revealing the presence of limonene as the major compound, accounting for 93.7% of the total. Virucidal activity of the oil of C. x aurantium peels against influenza A virus H1N1 was evaluated by the ASTM E1053-20 method. Moreover, the virucidal activity was also investigated of D-limonene, the major terpene in essential oils of C. x aurantium, and its enantiomer L-limonene. The essential oil of the C. x aurantium peels produced a log reduction of 1.9 to 2.0, accounting for 99% reduction of the virus, while D- and L-limonene exhibited virucidal activity with a log reduction of 3.70 to 4.32 at concentrations of 125 and 250.0 µg/mL, thus reducing the virus by 99.99%. Previous work found that D-limonene exhibited antiviral activity against herpes simplex virus, but L-limonene, an enantiomer of D-limonene, has never been reported for antiviral activity. This work demonstrates the antiviral activity of L-limonene for the first time. Moreover, this work suggests that concentrations of 0.0125% to 0.025% of either D- or L-limonene can possibly be used as a disinfectant against viruses, probably in the form of essential oil sprays, which may be useful disinfectants against the airborne transmission of viruses, such as influenza and COVID-19.