## Discussion  
_S. persica_ L. roots/stems known with various names like Mustard tree, Miswak, Koyoji and Pilu have been traditionally used for maintaining oral hygiene for centuries ([PERSON] et al., 2017; [PERSON] et al., 2018). In this study, essential oils of dried (MD-1) and fresh (MF-1) roots of _S. persica_ L. were isolated and the main components from the both oils were identified as benzyl isothicarate (MD-1; 68.1% and MF-1; 85.0%). The other major compounds in these essential oils were benzyl nitrile and benzaldehyde (Table 1). A high concentration of benzyl isothiamate (73.8%) in the essential oil from _S. persica_ L. stem has also been reported previously ([PERSON] et al., 2017; [PERSON] et al., 2018), although the antimicrobial activity of compounds from _S. persica_ L., especially against oral pathogens, including _Streptococcus mutans_, _Porphyromonas gingivalis_, _Tannerella forysthia_, and _Treponema danticola_([PERSON] et al., 2017; [PERSON] et al., 2018), has been reported previously. The effects of drying on the chemical composition of essential oils from _S. perscia_ L. roots and the resulting change in their antimicrobial activity have not been reported. In particular, detailed reports on the mechanisms leading to these antimicrobial activities and comparison with the antimicrobial activities of well-known commercial oral hygiene products Chlorhexidine digluconate and clove oil are not available. It is important to study the control of oral pathogens using plants and plant-based products as the excessive and unnecessary use of antibiotics has also led to the emergence of drug resistance in oral pathogens ([PERSON] et al., 2017; [PERSON] et al., 2018). Furthermore, oral bacteria are emerging as a greater health threat than previously thought because of their involvement in other systemic diseases, in addition to oral diseases like periodontitis and gingivitis ([PERSON] et al., 2018; [PERSON] et al., 2018; [PERSON] et al., 2018). _S. mutans_ is one such pathogen of great concern, which is a leading cause of dental caries and is also involved in other diseases ([PERSON] et al., 2018; [PERSON] et al., 2018). The bacterium employs a number of mechanisms for its pathogenicity, including tolerance to pH, utilization of various carbon sources, biofilm formation and production of adhesins, proteases, haemolysins and others ([PERSON] et al., 2018). In this paper, EOs isolated from the dried and fresh roots of _S. persica_ L. (MD-1 and MF-1) showed strong antibacterial and antibofilm activities against _S. mutans_. MD-1 and MF-1 exhibit an IC\({}_{50}\) value in the range of 10-11 \(\mu\)g/mL against _S. mutans_, which is comparable to those obtained for CHX (6 \(\mu\)g/mL). These values are much lower than the values reported earlier for the water and hexane extracts of _S. persica_ L. ([PERSON] et al., 2017) and comparable to those obtained for the essential oils against other oral pathogens including _Aggregatibacter actinomycetemontinas_ and _Porphyromonas gingivalis_([PERSON] et al., 2018). In viability assays using live and dead staining and MTT assay, it was also found that the most effective essential oil was MF-1, which decreases the cellular viability by \(80\pm 5\%\) and increased the population of dead cells by \(41\pm 4\%\) at 20 and 10 \(\mu\)g/mL, respectively. These values were comparable to those obtained for CHX during this study. The mechanisms of the microbicidal activity of these EOs are not well understood. It has been demonstrated that benzyl isothirate, the main constituent of the tested essential oils, results in impaired respiration and intracellular protein aggregation in _Campylobacter jejuni_, resulting in the inhibition of various metabolic activities [22]. This is supported by the observations that in MTT assays metabolic activity of _S. mutans_ cells decreased when exposed to essential oils (Figure 5A). It was also observed that exposure to essential oils results in the lysis of the cells and deformed cells (Figure 8).