# Antimicrobials from Medicinal Plants: An Emergent Strategy to Control Oral Biofilms
## 6 The Most Promising Medicinal Plant Extracts in the Control of Oral Biofilms
gingivalis_ (25.0 \(\upmu\)g\(\cdot\)mL\({}^{-1}\)) and _S. mutans_ (12.5 \(\upmu\)g\(\cdot\)mL\({}^{-1}\)). This bioactive component is a plastitial catecholic dipterpene with recognized antioxidative, anti-inflammatory and antimicrobialproperties [179; 180]. _Syzygium aromaticum_ L., another plant traditionally used as a spice and as a food preservative, holds a wide spectrum of pharmacological properties. As reported by [PERSON] et al. [151], the biofilm eradication activity of _S. aromaticum_ ethanolic extract against _P. gingivalis_ JCM 12,257 and _S. mutans_ NBRC 13,955 was observed, respectively, at a concentration of 435.5 and 871 ug\(\cdot\)mL\({}^{-1}\). Regarding its phytochemical signature, eugenol, eugenol acetate and \(\beta\)-caryophyllene are acknowledged as antimicrobial components present in this plant extract [181]. Eugenol was reported to inhibit _P. gingivalis_ and _S. mutans_ biofilms at higher concentrations, 800 and \(>\)800 ug\(\cdot\)mL\({}^{-1}\), respectively [151]. In addition, other minor compounds, such as \(\beta\)-caryophyllene, exhibited eradication activities against _P. gingivalis_ and _S. mutans_ at lower concentrations (400 and 50 ug\(\cdot\)mL\({}^{-1}\), respectively), and eugenol acetate against _S. mutans_, at 400 ug\(\cdot\)mL\({}^{-1}\)[151]. _Spirostachys africana_ Sond., a tree originally from South America, is traditionally used as a remedy for toothache [182]. Although used as an antibacterial product, its bioactive properties have not been extensively described in the literature. As an example, the dichloromethane:methanol extract from _S. africana_ leaves was used against _S. mutans_ ATCC 25175 oral pathogen, being able to inhibit the growth of _S. mutans_ biofilms by more than 97% at a concentration 0.25 mg\(\cdot\)mL\({}^{-1}\)[183]. Unfortunately, no studies have been found describing the chemical profile of _S. africana_ leaf extracts. Another plant commonly used for its interesting properties is _Thymus vulgaris_ L., commonly named thyme, whose essential oil bioactive properties include antioxidant, anti-inflammatory, antitumor, and antimicrobial effects [184]. Several studies have been conducted regarding the antibacterial activity of _T. vulgaris_ essential oil against oral pathogens, namely _S. aureus_[185]. Interestingly, when used at a concentration of 0.156 mg\(\cdot\)mL\({}^{-1}\), this essential oil was capable of inhibiting the formation of _S. aureus_ biofilms by 96%. The antibiofilm effect of _T. vulgaris_ essential oil may be due to the presence in its composition of different chemical compounds, in particular thymol, a monoterenoid phenol that is extensively described as having antibiofilm properties [186]. _Trachysperum annuli_ L., a plant rich in thymol, is a known herb with recognized medical properties, widely cultivated in the west and northwest of Iran [187]. Its seeds hold several medicinal features, including antibacterial, antioxidants and antifungal properties, among others [188; 189]. With respect to its application as an antibacterial product against oral bacteria, [PERSON] et al. [90] found that, at a 160 ug\(\cdot\)mL\({}^{-1}\) concentration, the ethanolic extract of _T. annuli_ seeds was able to reduce the number of viable cells in _S. mutans_ ATCC 700610 biofilms by 89%. On the other hand, the petroleum ether fraction of the ethanol extract, applied at 40.0 ug\(\cdot\)mL\({}^{-1}\), caused the complete inhibition of _S. mutans_ biofilms growth (100%), probably due to its higher concentration in antimicrobial compounds. As mentioned before, thymol, a monoterenoid phenol, is the major component found in ethanol extracts of _T. annuli_ seeds, which is known to exert antibiofilm effects [186].