Honeysuckle (Lonicerae japonicae) has been used in functional tea products. The chemical compositions of the water and ethanol extracts of honeysuckle were examined in the present study, along with their potential in inhibiting SARS-CoV-2 spike protein binding to ACE2, suppressing ACE2 activity, and scavenging reactive free radicals. Thirty-six compounds were tentatively identified from the honeysuckle extracts using HPLC-MS/MS, with ten reported for the first time in honeysuckle. Both honeysuckle extracts inhibited the binding of SARS-CoV-2 spike protein to ACE2, as well as ACE2 activity. The ethanol extract exhibited a 100% inhibition on binding of the SARS-CoV-2 spike protein to ACE2 at 100 mg botanical equivalent/mL, whereas the water extract had a 65% binding inhibition at the same concentration. Furthermore, the water extract exhibited 90% ACE2 activity inhibition, which was stronger than that of the ethanol extract (62% inhibition) at the same botanical weight concentration. In addition, higher total phenolic contents and greater scavenging activities against hydroxyl (HO•), DPPH•, and ABTS•+ radicals were observed in the water extract than the ethanol extract counterpart on a dry botanical weight concentration basis. These findings suggest honeysuckle has the potential to reduce the risk of SARS-CoV-2 infection and the development of severe COVID-19 symptoms.
Keywords: ACE2; COVID-19; SARS-CoV-2 spike protein; free radicals; honeysuckle.