Another key finding from this study was the differences in antiviral activity of the essential oils between the HSV1 and SARS-CoV; strong activity against one virus did not equate to strong activity against the other. Note: IC50 determines the minimum inhibition concentration for inhibiting 50% of the pathogen and CC50 is the cytotoxic concentration of the extracts to cause death to 50% of viable cells in the host. These values are measured through dilution assays of extracts added to virus infected host cells. In the ideal situation the IC50 concentration is below the CC50 concentration and the CC50 and maximum tolerated dose (MTD) are as high as possible. This would mean the extract would kill the pathogen before killing the host; as an example - if the IC50 is 0.1g/L and the CC50 is 100g/L then the host won't suffer any adverse effects if treated with the extracts. These are important factors to consider when developing antimicrobial compounds. SI is an index value that gives us an idea about the selectivity of an extract (SI = CC50/IC50). The SI index value needs to be a high value number, indicating the virus is destroyed before the host, i.e. the compound has selectivity towards the virus and not the host. The higher the SI index value, the more selectivity the extract has. So, for this study the researchers are saying the minimum inhibition concentration (IC50) of the Laurel berry essential oil is 120mg/ml. And, this is four times smaller than the lowest cytotoxic (CC50) dose.

Excerpt of Published Paper

Introduction. – In the past decades, besides a variety of synthetic antiviral drugs with different molecular targets, a large number of phytochemicals have been recognized to control infections caused by viruses. Recently, the anti-herpes virus activity of several essential oils of different plant sources as well as of various constituents of essential oils were demonstrated [1] [2]. The severe acute respiratory syndrome (SARS) is a febrile respiratory illness primarily transmitted by respiratory droplets or close personal contact. The causative organism has been identified as a novel coronavirus, i.e., SARS-CoV [3]. The overriding clinical feature of SARS is the rapidity with which many patients develop symptoms of acute respiratory distress syndrome (ARDS). Currently, there are no approved or universally recommended therapies for SARS. Treatment for the disease is mainly supportive.