In vitro antiviral effect of cinnamon oil, Moringa oleifera extract, Manuka honey, and Nigella sativa oil against SARS-CoV-2 compared to remdesivir

Background Severe acute respiratory syndrome coronavirus 2 ( SARS - CoV - 2 ) is of a public health importance as it is continually evolving due to random mutations. New mutations can potentially affect the degree of infectiousness, virulence, and can increase the virus’ capability to evade adaptive immune responses of the body. Immunity is one of the key factors determining the extent of severity of SARS-CoV-2 patients. Therefore, thinking about natural remedies is the way to boost immunity, keep the body protected, and able to fight the SARS-CoV-2 virus. We aimed to make progress in the field of anti- SARS-CoV-2 nutraceuticals, thus providing a safe and natural alternative to traditional chemically manufactured medications. Methods The cytotoxic activity (CC 50 ) of the natural products was tested experimentally in vitro on the VERO-E6 cells using a crystal violet assay. The cells were then treated with different concentrations of the natural products of Moringa oleifera leaves extract, cinnamon bark oil extract, Manuka honey, and Nigella sativa oil. The inhibitory concentration 50 (IC 50 ) value and the CC 50 value were calculated in order to measure the antiviral effect of on SARS-CoV-2 virus compared to antiviral Remdesivir drug. Results The tested natural products of honey and extracts exhibited pronounced virucidal effect against one of the most challenging viruses worldwide which is the SARS-CoV-2 virus. The results showed that the highest selectivity index was the Manuka honey + 20 UMF with SI of 10.23. The second sample following Manuka honey regarding its efficiency was the mixture of the three extracts with the honey (SI = 7.12), then followed by Remdesivir antiviral drug (SI = 3.3), then Moringa oleifera leaves extract (SI = 2.1). The last two products showing the least SI were Nigella sativa oil (SI = 1.6) and cinnamon bark oil (SI = 1.08), respectively. Conclusions Manuka honey + 20 UMF alone or combined with other three extracts of Moringa oleifera , Nigella sativa , and cinnamon bark oil have a much stronger in vitro antiviral effect on SARS-CoV-2 virus than the traditional antiviral drug Remdesivir. Further research will be needed to test the effectiveness of these natural products in vivo as an antiviral remedy against SARS-CoV-2 virus.