# Antimicrobials from Medicinal Plants: An Emergent Strategy to Control Oral Biofilms
## 6 The Most Promising Medicinal Plant Extracts in the Control of Oral Biofilms  
The antibiotic therapy has reached its limits regarding antimicrobial resistance, threatening the effective prevention and treatment of an increasing range of infections. Thus, new therapeutic approaches based on natural phytochemicals have been the target of several research, considering their bioactive assets, namely antimicrobial properties. Knowing that the number of medicinal plants that potential possess antimicrobial/antibiofilm properties is quite large, only published works investigating the extracts obtained from plants' aerial parts, roots and seeds were considered. Hence, Table 1 presents some of the plant species whose extracts hold compounds with antimicrobial/antibiofilm activity, among others, up to 95%, against specific microorganisms, i.e., extracts with the potential to inhibit biofilm formation and/or eradicate it, with concentrations <1 mg\(\cdot\)mL\({}^{-1}\). One of the described plant species with proven antimicrobial [112], antiulcerative [113] and antifungal [114] activity is _Bacharis dracunculifolia_ D.C., considered to be the most important botanical source of South-Eastern Brazilian propolisis [115]. The antibioofilm properties against oral cavity bacteria were studied by [PERSON] et al. [9], through essential oils extracted from the aerial parts of the plant in question. These authors showed that, for a concentration of 31.2 mg\(\cdot\)mL\({}^{-1}\), _B. dracunculifolia_ extracts present 95% of inhibition growth of biofilms of \(S\). _mutans_ NCTC 1091. The ability of this extract to inhibit biofilm formation seems to be related to its composition in oxygenated sesquiterpen, such as spathulenol and trans-nerolidol, described in the literature as antibiofilm/anticriboial mediators [116; 117]. Different phenolic compounds are responsible for the wide diversity of bioactive properties of plant extracts, which, in addition to their antimicrobial assets, may also take part in the healing process. An example of this statement is the species _Camelia japonica_ L., whose extract holds antioxidant, anti-inflammatory and antimicrobial properties [118; 119; 120]. Additionally, _Chelidonium majus_ subsp. _asiaticum H.Hara_, commonly known as greater clandine, is a medicinal plant widely used in traditional medicine due to its anti-inflammatory and antimicrobial effects [121; 122], properties also attributed to the _Thuja orientalis_ L. species, a perennial conifer tree of the family Cupressaceae [123; 124]. [PERSON] et al. [125] investigated the antimicrobial and antibiofilm activities of methanolic extracts of _C. japonica_, _C. majus_ subsp. _asiaticum_, _C. flagelliferum_ and _T. orientalis_ against oral pathogens. Notably, all these plant extracts were able to inhibit the GTF function of _S. mutans_ ATCC 25175, an important virulence factor in the biofilm formation, by 99.0%, at a concentration of 1.00 mg\(\cdot\)mL\({}^{-1}\). The total phenolic compounds concentration of these extracts is quite high, which may be the reason of their superior antimicrobial effect [126; 127]. The essential oil extracted from _Cinnamomom zeylanicum_ Blume, a perennial tree from which cinnamon is obtained [128], is described in the literature as an antimicrobial agent that acts against various biofilm-forming bacteria present in the oral cavity [129; 130], such as _S. mutans_ ATCC 25175. When used in the management of biofilms of _S. mutans_, the essential oil from _C. zeylanicum_ skin was able to inhibit their formation by up to 99%, at a concentration of 0.224 mg\(\cdot\)mL\({}^{-1}\)[131]. \(\beta\)-linaload and (_E_)-cinnamaldehyde are the two main compounds present in this oil, and can be pointed out as responsible for its antibiofilm properties [132; 133]. In addition, the essential oils of _Coriandrum sativum_ L., a medicinal plant with nutritional benefits, commonly named coriander, exhibit antibacterial and antibiofilm properties against _S. mutans_, in addition to holding antioxidant and anesthetic properties [134; 135].