# Antimicrobials from Medicinal Plants: An Emergent Strategy to Control Oral Biofilms
## 6 The Most Promising Medicinal Plant Extracts in the Control of Oral Biofilms
mutans_ DMST 1877 biofilm formation by up to 99.9%, at the highest tested concentration, 750 ug\(\cdot\)UL\({}^{-1}\). These results are in accordance with the capability of _D. reticulata_ to inhibit both sucrose-dependent and independent _S. mutans_ adherence in a concentration dependent manner, at sub-MIC concentrations (<625 ug\(\cdot\)UL\({}^{-1}\)). _Dodonaea viscosa var. angustifolia_ leaf decoction extracts have been reported to have anti-inflammatory and antimicrobial activity [156; 157], and they are traditionally used as mouthwashes for toothaches and related problems [158]. The bioactivities present in this plant can be attributed to the major compounds found in _D. viscosa_ extract, namely xylopyranoside; 2,2'-methylenebis [6-(1,1-dimethyl)]-4-methyl]; 2-(3-Hydroxy-4-methoxy-phenyl)-3,7-dimethoxy-4H-chromen-4-one; trans-3'_A_',5'-Trimethoxy-4-(methylthio)chalcone and stigmasterrol [159]. [PERSON] et al. [159] studied the inhibitory effect of this plant methanolic extract against _S. mutans_ NCTC 1091 biofilm, verifying that biofilm reduction was dependent on the exposure time and concentration. The tapered roots and rhizomes of _Glycyrrhiza glabra_ L. hold most of the bioactive components responsible for this plant medicinal and culinary features [160]. Its phytochemical compounds, namely glycyrrhizin, an oleanane-typeiterpene saponin, stands out as its major constituent with antibofilm activity [160; 161]. [PERSON] and [PERSON] [162] found that the inhibition pattern and eradication of _P. gingivalis_ biofilm by _G. glabra_ ethanol extract were concentration-dependent. At the concentration of 500 ug\(\cdot\)mL\({}^{-1}\), the extract exhibited up to 90% inhibition of _P. gingivalis_ biofilm formation. In addition, the eradication of _P. gingivalis_ biofilm was achieved at a MBEC of 62.5 ug\(\cdot\)mL\({}^{-1}\), being higher at a concentration of 500 ug\(\cdot\)mL\({}^{-1}\). The authors also found that the Rgp- and Kgp-proteinase activities of _P. gingivalis_, which are important virulence factors, were also reduced by approximately 50% [162]. Interestingly, [PERSON] et al. [163] showed that _G. glabra_ main bioactive compound, namely 18\(\alpha\)-glycyrrhetic acid, significantly inhibits the _P. gingivalis_ LPS-induced endothelial permeability, both in vitro and in vivo assays. _Lippia alba_ (Mill.) flowering plant which essential oil presents several pharmacological properties such as sedative, analgesic, antispasmodic, anti-inflammatory and antimicrobial assets [164]. In a work published by [PERSON] et al. [148], the essential oil from _L. alba_ was used as an antibacterial agent against _S. mutans_ ATCC 35668 biofilms, and it was shown that, at a concentration of 0.100 ug\(\cdot\)mL\({}^{-1}\), this natural product was able to reduce the number of viable cells present in the biofilm by 95.8%. In this case, isomeric monoterpens geraniol and citral are two of the main components found, which are known to hold antimicrobial properties [149; 165]. The _Mentha_ genus includes diverse aromatic herbs that are commonly used in herbal teas, flavoring agent, and as medicinal plants. Infusion, decoction, and distillate water of the aerial parts have been used for centuries as tonics, carminative, digestive, stomachic, antispasmodic, and anti-inflammatory preparations [166]. Traditionally, these plants have been also used for teeth whitening, and their distilled oils used to flavor toothpastes and chewing gum, until this day. Knowing this, several works were conducted in order to study the ability of these plants to eliminate oral pathogenic biofilms. As an example, [PERSON] et al. [167] investigated the effects of _Mangifera_ sp. and _Mentha_ sp. aqueous extracts towards the eradication of _S. sanguinis_ ATCC BAA-1455 and _S. mutans_ ATCC 25175 biofilms. Both extracts showed to be more effective in reducing the biofilm population of _S. mutans_ than _S. sanguinis._ At a concentration 0.50 mg\(\cdot\)mL\({}^{-1}\), _Mangifera_ sp. and _Mentha_ sp. extracts reduced 99.4% and 98.5% the _S.