The theory is that, since essential oils are lipophilic, they are able to disrupt the viral membrane or “interfere with viral envelope proteins involved in host cell attachment.”
It has been demonstrated that coronavirus, which does all of its main activity inside the cell, requires certain membrane receptors in order to enter into the cell. These receptors require calcium ion channels, which are referred to as TRPs.
The researchers discovered that in cells pretreated with Sambucus nigra combined with treatment of the cells post-infection had a synergistic effect of reducing viral titers in the cells three orders of magnitude. This was much more effective than treating once the infection had occurred.