**1. Introduction**

Bacterial infections are major problems in medicine due to the indiscriminate use of antibiotics that eventually select resistant microorganisms, which in turn proliferate [1]. Among the bacteria that cause infections stand out *Pseudomonas aeruginosa* (Pseudomonadaceae), *Escherichia coli* (Enterobacteriaceae) and *Staphylococcus aureus* (Staphylococcaceae) [2].

The bacterium, *P. aeruginosa*, is a gram-negative bacterium that is responsible for causing hospital infections, especially in patients who have compromised immune systems, and in rarer cases, it can lead to pneumonia, resulting in the death of 60% of infected [3, 4]. Although strains of *E. coli* colonize the human digestive tract, in large quantities they are capable of causing intestinal problems such as diarrhea. While *S. aureus* causes several acute infections such as pneumonia, osteomyelitis, endocarditis, myocarditis, pericarditis, and meningitis [1].

It has been reported that the mechanisms of bacterial resistance include the efflux pumps, which expel the antibiotic, in addition, the bacteria are capable of altering the target of the antibiotic for mutation or enzymatic inactivation and alteration of the permeability of the bacterium to the drug [5]. Thus, antibiotics alone cannot inhibit bacterial growth so that substances that modulate their effect are necessary in order to potentiate the action of the drug [6, 7].

These substances capable of modulating standard drugs can be found in plants, since these have constituents with antibacterial actions derived from their secondary metabolism, mainly the aromatic herbs, because their essential oils have diverse biological and pharmacological activities [8, 9]. Among the botanical families most

#### **Figure 1.**

Mesosphaerum suaveolens*. (a) Leaves and stem. (b) Population of* M. suaveolens *in Quixelô—CE, Brazil. (c) Highlight of flowers. (d) Leaves in senescence.*

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**Figure 2.**

*Chemical Composition and Antibacterial Activity of the Essential Oil of* Mesosphaerum…

rich in aromatic plants is Lamiaceae, which is well known for its representatives as sources of essential oils used in cooking, aromatherapy and medicine [10, 11]. Among the species of this family, the species *Mesosphaerum suaveolens* (L.) Kuntze (**Figure 1**), known in Brazil as "bamburral" and "alfazema-brava," is popularly used in the treatment of diseases related to gastrointestinal and respiratory tract [12], so that we hypothesize that the species is abundant in phytochemical constituents, which present biological activity against strains of pathogenic microorganisms, such as bacteria. This hypothesis is supported by the pharmacological and biological activities of these species already evidenced in the literature, such as antioxidant activity [13], neuroprotective [14], gastro-protective [15], antitumor [16], antinociceptive [17], anti-inflammatory [18], antifungal [19], anti-bacterial

Thus, due to increasing bacterial resistance to drugs and the search for new bioactive sources, this research aims to evaluate the *in vitro* antibacterial and modulatory activity of *M. suaveolens* essential oil as well as to characterize its chemical

The essential oil of *M. suaveolens* presented a total of 44 phyto-constituents, with β-caryophyllene (20.37%) being the major constituent (**Figure 2**). Following this, the oil presented as secondary compounds were sabinene (15.94%) and espatulenol (11.09%). As constituents traces (<1%), 26 constituents were found

According to **Table 2**, the essential oil of *M. suaveolens* showed no activity against gram-negative bacteria (*P. aeruginosa* and *E. coli*), both standard strains and multiresistant strains, since they have MIC ≥1024 μg/mL. However, the oil presented antibacterial action against *S. aureus* with MIC of 64 μg/mL for the standard

[20], insecticide [21], larvicide [8], and allelopathic action [22].

*DOI: http://dx.doi.org/10.5772/intechopen.92704*

**2.1 Chemical composition of essential oil**

**2.2 Minimal inhibitory concentration (MIC)**

*Chemical structure of sesquiterpene β-caryophyllene.*

strain (ATCC) and 256 μg/mL for the multiresistant strain.

compounds.

**2. Results**

(**Table 1**).

*Chemical Composition and Antibacterial Activity of the Essential Oil of* Mesosphaerum… *DOI: http://dx.doi.org/10.5772/intechopen.92704*

rich in aromatic plants is Lamiaceae, which is well known for its representatives as sources of essential oils used in cooking, aromatherapy and medicine [10, 11]. Among the species of this family, the species *Mesosphaerum suaveolens* (L.) Kuntze (**Figure 1**), known in Brazil as "bamburral" and "alfazema-brava," is popularly used in the treatment of diseases related to gastrointestinal and respiratory tract [12], so that we hypothesize that the species is abundant in phytochemical constituents, which present biological activity against strains of pathogenic microorganisms, such as bacteria. This hypothesis is supported by the pharmacological and biological activities of these species already evidenced in the literature, such as antioxidant activity [13], neuroprotective [14], gastro-protective [15], antitumor [16], antinociceptive [17], anti-inflammatory [18], antifungal [19], anti-bacterial [20], insecticide [21], larvicide [8], and allelopathic action [22].

Thus, due to increasing bacterial resistance to drugs and the search for new bioactive sources, this research aims to evaluate the *in vitro* antibacterial and modulatory activity of *M. suaveolens* essential oil as well as to characterize its chemical compounds.
