**2. Results**

*Essential Oils - Bioactive Compounds, New Perspectives and Applications*

*Staphylococcus aureus* (Staphylococcaceae) [2].

endocarditis, myocarditis, pericarditis, and meningitis [1].

are necessary in order to potentiate the action of the drug [6, 7].

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

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,

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

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

**1. Introduction**

**142**

**Figure 1.**

*(c) Highlight of flowers. (d) Leaves in senescence.*

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

#### **2.1 Chemical composition of essential oil**

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 (**Table 1**).

#### **2.2 Minimal inhibitory concentration (MIC)**

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

**Figure 2.** *Chemical structure of sesquiterpene β-caryophyllene.*


#### *Essential Oils - Bioactive Compounds, New Perspectives and Applications*

*Relative proportions of the essential oil constituents were expressed as percentages. a Retention indices experimental (based on homologous series of n-alkane C7-C30). <sup>b</sup> Retention indices from literature.*

#### **Table 1.**

*Main constituents (>1%) of* Mesosphaerum suaveolens *essential oil.*


#### **Table 2.**

*Minimal inhibitory concentration (μg/mL) of essential oil of* Mesosphaerum suaveolens *against conventional bacterial (ATCC) and multiresistant strains.*

#### **2.3 Modulation of drugs**

According to **Figure 3**, it was demonstrated that the essential oil of *M. suaveolens* does not have the capacity to modulate the antibiotics, gentamicin, imipinem, and norfloxacin, since there was no significant difference between the control group and the treatments.

**145**

#12.104.

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

of diseases related to the gastrointestinal and respiratory tract [12], it has been demonstrated that the volatile terpenes of the species are not related to this action, since in the in the present study, this product did not present antibacterial action at

However, it is possible to observe that there is antibacterial action against the standard strains of *S. aureus* multiresistants. This can be explained by the mechanisms of action that some natural products have, such as the ability to disintegrate their cytoplasmic membranes, as well as destabilization of the proton motive force, electron flow, active transport and cellular content coagulation [24]. In addition, activity against *S. aureus* can be linked to the major compound of the study oil, β-caryophyllene, since this sesquiterpene exhibits antibacterial activity,

Thus, the oil has a source of β-caryophyllene, such sesquiterpene is found to be the majority compound; however, the oil of this species shows heterogeneity according to internal (genetic) and external factors (origin, mode of collection, collection period, etc.) [26]. To avoid large variations in the chemical composition of the oil, the collections should be standardized, such as collection times, period of the year, as well as to identify if the individual is under herbivorous attack [8]. This variation in the essential oil explains why some works show the antibacterial action of the essential oil, as Tesch et al. [27], where the oil showed activity against *E. coli* ATCC 25922 (MIC 350 μL/mL), *Klebsiella pneumoniae* ATCC 23357 (MIC 300 μL/mL), *Salmonella* Typhi CDC57 (MIC 400 μL/mL). In this study, the natural product presented eucalyptol (C10H18O) and fenchone (C10H16O) as the

In addition to antimicrobial activities, the products of plant origin can have a drug modulating action, and although *M. suaveolens* does not present such action, it is seen that in members of the Lamiaceae family, some species present such action. Among the species is *Origanum vulgare* L., where its essential oil has a modulating action of the tetracycline drug against bacterial strains of *S. aureus* IS-58, which had

Fresh leaves of *M. suaveolens* were collected in the municipality of Quixelô

−39°16′14.29″W in March 2015 (**Figure 4**). The collection area is characterized as being part of the Caatinga, a seasonally dry tropical forest. The leaves were dried in an oven at 30°C. The plant material was identified and a voucher specimen was deposited in the Herbarium Caririense Dárdano of Andrade-Lima – HCDAL under

After drying, the leaves were packed in a volumetric flask containing 4 L of distilled water and subjected to constant boiling for 2 hours. Then the essential oil was collected and stored in an amber bottle under constant refrigeration until the

located in the state of Ceará (Brazil) under coordinates −6°14′22.40″S,

conduction of the chemical analyzes and microbiological tests [8].

concentrations of clinical relevance for two of the three strains used [23].

Although the leaves of *M. suaveolens* are used in folk medicine for the treatment

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

especially against Gram-positive bacteria [25].

the TetK tetracycline efflux protein [28].

**4.1 Collection of botanical material**

**4. Materials and methods**

**4.2 Extraction of essential oil**

**3. Discussion**

main compounds.

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