3.1. Physical and Chemical Properties
The films presented a pleasing visual appearance and homogeneity, exhibiting a tonal range ranging from light beige to darker shades, with varying degrees of transparency. The brightness of the films was directly influenced by the amount of essential oil used. In addition, it was observed that the films were easily removed from the petri dishes. However, tests 3, 6 and 9, which did not contain glycerol, proved to be excessively fragile. There was a distinct difference in the flexibility and handling capacity of the films, and the samples with higher proportions of copaiba essential oil and glycerol, in relation to the concentration of CaCl2.2H2O, showed superior performance in these aspects, as detailed in Table 1.
Table 1
Results of the subjective evaluation for polymeric films with variations in the parameters: glycerol concentration, cross-linking and copaiba essential oil.
Tests
|
Continuity
|
Homogeneity
|
Transparency
|
Flexibility
|
1
|
+++
|
+++
|
+++
|
++++
|
2
|
++
|
++
|
++
|
+
|
3
|
+
|
+
|
++
|
+
|
4
|
+++
|
+++
|
+++
|
++
|
5
|
++++
|
++++
|
++++
|
++++
|
6
|
+++
|
+++
|
++
|
+
|
7
|
++++
|
++++
|
++
|
++++
|
8
|
++++
|
++++
|
++
|
++++
|
9
|
+++
|
+++
|
++
|
++
|
10*
|
++
|
+++
|
+++
|
++++
|
11
|
++++
|
++++
|
++++
|
++++
|
12
|
+++
|
++
|
++
|
++
|
13
|
++
|
+++
|
++
|
+++
|
14*
|
++
|
+++
|
+++
|
++++
|
15*
|
++
|
+++
|
+++
|
++++
|
* Formulations 10, 14 and 15 are the same. ++++ excellent, +++ good, ++ fair, + poor.
As detailed in section 2.2, the preparation of the biopolymers was conducted following an experimental design, and the results were recorded in Table 2. When analyzing the data presented, a significant variation in moisture content was observed, which ranged from 7.87–48.87%. These values correspond specifically to tests 6 (with 6 g of alginate, 0 ml of glycerol, 1/3% of crosslinking agent and 2/3 ml of copaiba oil) and 1 (with 6 g of alginate and 5 ml of glycerol), evidencing the influence of the components used in the formulation of the films.
It is important to highlight that the results obtained in this study showed similarities with the moisture contents found in films composed of Xanthosoma Mafaffa Schott starch enriched with copaiba oil, as reported by Rodrigues et al. [35]. However, the moisture levels obtained were lower than those reported by Paranhos et al. [27] for chitosan-based films enriched with copaiba oil.
When analyzing the data presented in Table 2, a significant variation in water content is observed, ranging from 7.87–48.87%. These values correspond to different tests, specifically, test 6 (comprising 6 g of alginate, 0 ml of glycerol, 1/3% of crosslinker, and 2/3 ml of copaiba oil) and test 1 (containing 6 g of alginate and 5 ml of glycerol). This variation evidences the influence of the components used in the formulation of the film. It is noteworthy that the results obtained in this research showed similarities with the moisture values found in films composed of babassu coconut mesocarp starch, enriched with copaiba oil, as reported by Rodrigues et al [35]. However, the moisture levels obtained in this study were lower than those reported by Paranhos et al [27] for chitosan-based films enriched with copaiba oil.
It is noteworthy that tests 6 and 9, which consisted of formulations containing 6 g of alginate, variable amounts of crosslinker and copaiba oil, did not show statistically significant differences in moisture content at the 95% confidence level. This observation can be attributed to the absence of glycerol in the compositions of these tests. In addition, it is reasonable to consider that the crosslinking process of the polymer chains may have contributed to the decrease of hydrophilicity, resulting in more hydrophobic compositions, where the copaiba essential oil did not present a significant difference in relation to the crosslinking agent. This data analysis highlights the complex interaction between formulation components and the resulting effects on the moisture properties of the produced films, emphasizing the importance of precise adjustment of these components to achieve desirable characteristics in polymer films.
In test 1 (consisting of 6 g of alginate and 5 ml of glycerol), which consisted exclusively of alginate with the highest concentration of glycerol among all the formulations examined, a significantly high moisture content was observed. This phenomenon can be attributed to the widely recognized hygroscopic properties of both alginate and glycerol, as reported by Paixão et al [26]. According to studies by Da Costa and De Oliveira [9] and Tarique and Khalina [40], polymeric films that incorporate substantial amounts of glycerol tend to exhibit significantly high moisture levels.
The significance of the regression was assessed with a 95% confidence level (p ≤ 0.05) using the F test in ANOVA, which was statistically significant. In addition, the lack of adjustment was not considered significant at the same confidence level. The coefficient of determination (R²) corresponding to the adjusted model, which considers various combinations of glycerol, copaiba essential oil and crosslinking, reached a value of 0.9334. This result indicates that the model satisfactorily explained 93.34% of the variability present in the observed data.
In addition, it is important to note that the model simultaneously demonstrated significance in regression and insignificance in lack of fit when assessed at a 95% confidence level (Fcalculated >tabulated F). It's worth noting that a significant lack of fit may, in part, be due to the low repeatability of the center points. In this context, the discrepancy between the experimental error and the lack of fit in the model can be explained by the fact that the experimental error was considerably lower than the identified lack of fit.
Table 2
Moisture content (ω), water solubility (S), thickness (δ) and water vapor permeability (PVA) for polymeric films with variations in the following parameters: glycerol concentration, cross-linking and copaiba essential oil.
Test
|
Glycerol (ml)
|
Crosslink (%)
|
Copaiba oil (ml)
|
ω (%)
|
S (%)
|
δ(mm)
|
WVP **
|
1
|
1
|
0
|
0
|
48.879 ± 1.953F
|
44.442 ± 2.069f
|
0.080 ± 0.010A
|
4.151 ± 0.887c
|
2
|
0
|
1
|
0
|
12.329 ± 0.941b
|
16.667 ± 1.054a
|
0.060 ± 0.011a
|
2,612 ± 0,326b
|
3
|
0
|
0
|
1
|
12.857 ± 1.731b
|
15.385 ± 0.518a
|
0.060 ± 0.010A
|
1,784 ± 0.012a
|
4
|
1/3
|
2/3
|
0
|
17.460 ± 1.470c
|
25.806 ± 1.602b
|
0.130 ± 0.001c
|
4.384 ± 0.655c
|
5
|
1/3
|
0
|
2/3
|
18.750 ± 2.002CD
|
51.128 ± 0.511g
|
0.110 ± 0.003BC
|
5.597 ± 0.291d
|
6
|
0
|
1/3
|
2/3
|
7.874 ± 0.937A
|
93.128 ± 1.128i
|
0.110 ± 0.008 BC
|
4.669 ± 0.154c
|
7
|
2/3
|
1/3
|
0
|
16.854 ± 1.297c
|
45.122 ± 2.366f
|
0.070 ± 0.022a
|
2.554 ± 0.331b
|
8
|
2/3
|
0
|
1/3
|
18.919 ± 2.209cd
|
39.149 ± 0.595e
|
0.100 ± 0.006b
|
4.647 ± 0.453c
|
9
|
0
|
2/3
|
1/3
|
8.511 ± 0.754A
|
19.115 ± 2.836a
|
0.130 ± 0.004c
|
4.496 ± 0.298c
|
10*
|
1/3
|
1/3
|
1/3
|
22.222 ± 0.898d
|
34.375 ± 1.949d
|
0.150 ± 0.007d
|
4.214 ± 0.663c
|
11
|
2/3
|
1/6
|
1/6
|
32,258 ± 1,917e
|
58.670 ± 2.306h
|
0.090 ± 0.004b
|
5.060 ± 0.889c
|
12
|
1/6
|
2/3
|
1/6
|
16.667 ± 0.287c
|
27.397 ± 1.969b
|
0.165 ± 0.004d
|
8.018 ± 1.055e
|
13
|
1/6
|
1/6
|
2/3
|
17.241 ± 0.447c
|
35.795 ± 1.705d
|
0.110 ± 0.003BC
|
5,583 ± 0,020d
|
14*
|
1/3
|
1/3
|
1/3
|
21.818 ± 1.193d
|
29.630 ± 0.422c
|
0.090 ± 0.003b
|
4.347 ± 0.306c
|
15*
|
1/3
|
1/3
|
1/3
|
19.149 ± 1.038CD
|
35,897 ± 2,564d
|
0.080 ± 0.005A
|
4.437 ± 0.074c
|
*Formulations 10, 14 and 15 are the same. Mean ± standard deviation of repetitions. Means with lowercase letters in each line indicate that there was no significant difference at p < 0.05 by Tukey's test. **[(g.mm)/(m 2.dia.kPa)].
Figure 1a shows the response surface for the dependent variable, humidity. When analyzed, it is evident that lower concentrations of moisture were observed in films with formulations consisting only of crosslinking and copaiba oil, as in tests 2 (6 g of alginate + 4% of crosslinking), 3 (6 g of alginate + 5 ml of copaiba oil), 6 (6 g of alginate + 0 ml of glycerol + 2/3% of crosslinking + 2/3 ml of copaiba oil) and 9 (6 g of alginate + 0 ml of glycerol + 1/3% + 1/3 ml of copaiba oil). On the other hand, the films with higher moisture content were found in the highest concentrations of glycerol and lower concentrations of copaiba oil.
Solubility plays a crucial role in water vapor permeability and film biodegradation, making it a significant property for characterization. It helps to understand the behavior of movies when they come into contact with water [5, 19]. In this context, solubility is influenced by the concentration and type of compounds present in the formulation [15], directly affecting the hydrophilicity and hydrophobicity indexes. As a result, hydrophobic films have lower solubility, while hydrophilic films have higher solubility [5].
As shown in Table 2, solubility ranged from 15.38–93.13%, corresponding to tests 3 (6 g of alginate + 5 ml of copaiba oil) and 6 (6 g of alginate + 0 ml of glycerol + 2/3% crosslinking + 2/3 ml of copaiba oil), respectively. It is evident that films composed exclusively of copaiba oil or only CaCl2.2H2O showed low solubility values. When these components were combined, the amount of CaCl2.2H2O had to be greater than the amount of copaiba oil to maintain this low solubility. This result was expected, since crosslinking promotes the closure of polymer chains, making the film less permeable to water. Copaiba oil can have a similar effect. However, when both components are present, solubility increases, as evidenced in assay 6, which showed the highest solubility among all films evaluated.
The significance of the regression and the lack of adjustment were evaluated at a significance level of 5% (p ≤ 0.05) using the F test in the analysis of variance. The R² coefficient of determination for the adjusted model was 0.7414, indicating that the model was able to explain 74.14% (R²>70%) of the variation observed in the data.
In addition, the model showed statistically significant regression at the 95% confidence level (Fcalculated > Ftabulated), while the lack of fit was not statistically significant at the same confidence level (Fcalculated > Ftabulated). This suggests that the good repeatability of the center points may have contributed to the absence of significant mismatch, resulting in a reliable response surface.
Figure 1b shows the response surface for solubility. In this figure, it is evident that films with higher solubility are characterized by a high concentration of crosslinker in relation to the amount of copaiba oil present. The reduction in solubility in aqueous environment of films incorporating copaiba oil can be attributed to its hydrophobic nature, as reported by Debone et al [12] and Paranhos et al [27].
Thickness is one of the most important properties of films, as it directly influences the rate of permeability to water vapor, as mentioned by Paixão et al [26]. However, achieving precise thickness control becomes a challenging task when employing the "casting" methodology, as also indicated by Brasil et al. [5]. The results obtained, as shown in Table 2, reveal variations in film thickness, ranging from 0.060 mm (tests 2 and 3) to 0.165 mm (test 12, characterized by the presence of ternary mixture).
The coefficient of determination, R², was calculated at 72.20%, exceeding the threshold of 70%, when considering an adjusted model that incorporates different variables, specifically the variable concentrations of glycerol, copaiba oil and crosslinking. In this context, the statistical significance of the regression is emphasized, as well as the insignificance of the lack of adjustment when evaluated at a 95% confidence level, as established by the F test applied in the analysis of variance. As a result, the R² value for the adjusted model reached 0.7220, indicating that this model was able to explain 72.20% of the variation observed in the data.
The model showed significant regression and no significant adjustment to the 95% confidence level, evidenced by the fact that the calculated F < tabulated F. This difference can be attributed, in part, to the lack of reproducibility at the pivotal points, where random error prevailed over systematic mismatch. Based on these results, it is inferred that the construction of the response surface (as presented in Fig. 1c) is a valid and justified approach.
As illustrated in Fig. 1c, it is observed that the films exhibited variability in thickness in relation to binary and ternary compositions, presenting greater thickness in contrast to those composed of a single component, which is alginate. However, the thickness of the film should not be interpreted as a disqualifying factor, as its applicability may vary depending on the specific purpose, as is the case with membrane manufacturing, where, in many cases, greater thickness is desirable.
In the present study, the water vapor permeability (PVA) of the biopolymers ranged from 1.784 (in trial 3) to 8.018 (in trial 12), expressed in units of g.mm/m².day.kPa (as shown in Table 2). These values were lower than those obtained by Raposo et al. (2021) when using biopolymers of alginate, mesocarp starch, and babassu coconut fibers subjected to alkaline treatment. It is noteworthy that, in this study, the presence of copaiba oil possibly influenced the obtaining of lower PVP values, as observed in test 3 (composed of 6 g of alginate and 5 ml of copaiba oil), which showed the lowest permeability rate. This phenomenon may be associated with the difficulty of water passage caused by the interaction between the oil and the other components, similar to the result obtained by Nunes et al. [23] in their study on films containing lemon essential oil.
Evaluating the data and considering the significance of the regression, as well as the non-significance of the lack of adjustment to the 95% confidence level (p ≤ 0.05) by means of the F test, it was observed that the proposed model for prediction of PVF reached a coefficient of determination of 75.28% (R²>70%). The values calculated by F for regression and lack of adjustment were lower than the tabulated values (F-tabulated). Consequently, although the fitted model is not considered highly predictive, its lack of fit was not statistically significant.
In Fig. 1d, the response surface for the WVP of the films is represented. It is noteworthy that lower permeability rates can be achieved in situations where the glycerol concentration is minimized, while the concentrations of cross-linking and copaiba oil reach their maximum and minimum extremes, respectively.
The binary mixtures of formulations 5 (1/3 ml glycerol + 2/3 ml copaiba oil), 8 (2/3 ml glycerol + 1/3 ml copaiba oil), 9 (2/3% crosslink + 1/3 ml copaiba oil) and ternary mixtures of formulation 10 (1/3 ml glycerol + 1/3% crosslink + 1/3 ml copaiba oil) and 11 (2/3 ml glycerol + 1/6% crosslink + 1/6 ml copaiba oil), were selected because they presented a visual aspect with good malleability, flexibility, easy detachment from the support; in addition to presenting low solubility values and moisture and PVA intermediates (according to the optimization obtained by the response surfaces).
The selected formulations were subjected to characterizations and optical microscopy (Fig. 2), scanning electron microscopy (SEM) (Fig. 3), infrared with Forrier transform (Fig. 4), X-ray diffraction (Fig. 5), antioxidants (Table 3) and antimicrobials (Table 4). For comparison, the same analyses were also performed with copaiba essential oil.
Optical Microscopy
The optical micrographs shown in Fig. 2 illustrate the selected polymeric films, in which the presence of copaiba oil on the surface is highlighted, as evidenced by the darker color. The distribution of the oil is heterogeneous, with variation in the size of the impregnated regions, which suggests a partial incorporation during the film manufacturing process. The surface fraction of the oil is assumed to correspond to the non-emulsified portion, indicating a localized saturation and potentially a controlled release of the oil.
The films numbered 9, 10 and 11 have a more homogeneous surface, which can be attributed to the presence of the crosslinking agent, which facilitates the connection between the polymer chains, resulting in a more cohesive structure. Films 5 and 8 demonstrate a superficial heterogeneity, suggesting the absence of crosslinking agents in their composition, which may influence the structural integrity and mechanical properties of the films.
In addition, the formation of calcium crystals is observed in films 10 and 11, a phenomenon associated with the cross-linking process of alginate with calcium ions. Crystallization is particularly prominent in film 11, indicating a more intense interaction between alginate and calcium ions.
Scanning Electron Microscopy (SEM)
The investigation of the structure of alginate and copaiba oil films was studied to understand the distribution of oil droplets in the biopolymer matrix and how this can affect the physical properties of the film. Figure 3 provides a detailed view of the surface morphology of the films, allowing the analysis of the homogeneity of the oil dispersion and the identification of any droplet migration or agglomeration phenomena.
To the naked eye, the films presented a smooth, compact and continuous surface, with a homogeneous and cohesive structure. However, scanning electron microscopy (SEM) inspection allowed us to identify that the cross-linked formulations, specifically formulations 9 to 11, manifested crystals of varying morphologies and dimensions. This characteristic is probably due to the presence of calcium salts used in the crosslinking process, which is in agreement with the observations previously made by light microscopy.
The surface micrographs indicated that the copaiba oil was fully assimilated and uniformly distributed in the film matrix, resulting in no significant irregularities. The presence of surface roughness, observed in the images of films 5 and 8, is a phenomenon already documented in previous studies, such as those by Norajit, Kim, Ryu [43] and Shojaee-Aliabadi et al [44] attributed this increase in roughness to the migration of oil droplets to the surface of the films, followed by volatilization during the water evaporation process, resulting in a structure with porosity.
Despite the variations in the microstructure of some formulations, the results indicate that the copaiba oil formed a stable emulsion system, and there was no collapse of the nanometric droplets during the drying process of the films. This implies that the mechanical and barrier properties of the films can be preserved, ensuring the integrity of the polymer matrix and the efficacy of copaiba oil as a functional agent.
Fourier transform infrared spectroscopy (FTIR)
Infrared Fourier transform spectroscopy (FTIR) was used to investigate the interactions between copaiba oil, glycerol, alginate, and calcium chloride. The corresponding spectra are shown in Fig. 4.
The FTIR spectra of the polymeric films revealed vibratory bands at 3415 cm-1, associated with the O-H stretching of the water molecules and hydroxyl groups present in the alginous matrix. The band at 2926 cm-1 corresponds to the stretch of the C-H bonds of the carbons of the pyranoid ring. Vibration at 1685 cm-1 is related to the C = O stretching of carboxylic groups and esters. Vibration bands less than 1050 cm-1 make up the "fingerprint" region of the polysaccharide. Two additional bands were also observed at 1634 cm-1 and 1415 cm-1, pertinent to the asymmetrical and symmetrical stretching of the carboxylic groups in the form of carboxylate, respectively. The spectral range of 1200–1000 cm-1 is associated with C–O and C–C vibrations, characteristics of glycosidic bonds, and pyranose rings [44].
The infrared spectra highlighted characteristic bands of the components of copaiba oil, emphasizing the regions between 2926 cm-1, 2858 cm-1 and 887 cm-1, attributed to the axial deformations of the C-H bonds in aliphatic hydrocarbons, such as sesquiterpenes [45]. The 1693 cm-1 and 1637 cm-1 bands were associated with axial deformation of carboxylic acid, while the 1445 cm-1 and 1369 cm-1 bands refer to axial deformations of the C-H connections.
It is noteworthy that the appearance of a peak at 887 cm-1 (β-caryophyllene) and the increase in the intensity of the bands at 2921 cm-1 and 2858 cm-1 (sesquiterpenes) indicate that the films maintained the components responsible for the antimicrobial action of copaiba oil. Similar results were reported by de Lima et al [46].
As for light transmission, it was observed that some films allowed light to pass through more easily than others. Formulations 8 and 11 showed transmittance lower than 10%, while formulations 10 and 5 showed better transmittance results, as illustrated in Fig. 4. It is postulated that this difference is due to the variation in the proportion of the components, especially in the relationship between glycerol and crosslinking agent. Films with high transmittance showed minimal or no interaction between glycerol and crosslinker.
X-ray diffraction (XRD)
X-ray diffraction analysis (XRD) revealed the presence of a limited crystalline region in the films, with well-defined diffraction peaks at the 2θ positions of 31.88°, 45.49°, 56.52° and 66.26°, as illustrated in Fig. 5. These tips are characteristic of sodium chloride, suggesting that it may have formed due to interactions between the components of the mixture or as an impurity.
No significant difference was observed in the crystalline region between the films. However, there was a decrease in peak intensity at 45.46° for films 9, 10 and 11, which contain crosslinkers in their formulations, compared to films 5 and 8, which do not have crosslinking. The opposite was observed in the region of 31.88°.
The spectral region below the peaks, ranging from approximately 10° to 50°, is dominated by the amorphous form of the material, indicating that most of the film matrix is amorphous. This amorphous characteristic is typical of polymeric materials and can influence the mechanical and barrier properties of films, such as flexibility and permeability.
Table 3 shows the results of the oxidative potential evaluated by the DPPH and ABTS methods. It was observed that the copaiba oil examined showed significant oxidative capacity, which is in accordance with the expectations of the literature, in addition to good inhibitory capacity of bacteria. The analyses revealed favorable results, with an IC50 value of 11.60 µg/ml for the oil. This value was similar to the results of Pereira et al. [29], who performed similar analyses in relation to the species Copaifera multijuga (Fabaceae), belonging to the same family as Copaifera Langsdorffii, the object of study of this research.
Table 3
Oxidative potential of copaiba essential oil and films selected by DPPH and ABTS methods.
IC50 (µg/ml)
|
Tests
|
DPPH
|
ABTS
|
Copaiba oil
|
11.6
|
74.1
|
5
|
49.7
|
17.6
|
8
|
50.6
|
30.2
|
9
|
45.4
|
15.1
|
10
|
29.9
|
25.0
|
11
|
56.0
|
45.4
|
Regarding the formulations of the films, it is important to emphasize that these films showed satisfactory inhibition when compared to the inhibition observed with the isolated use of the oil. This indicates a significant increase in inhibitory capacity, possibly attributed to the presence of other components, such as alginate, which also acts as an inhibitory agent and is commonly used in dressings. Notably, formulations 5, 8 and 11 outperformed the others in the DPPH method, possibly due to their low or absent crosslinking agent content.
The oxidative potential in the ABTS method remained satisfactory, with IC50 of 74.1 µg/ml for copaiba oil. However, there is a notable reduction in this potential when considering the formulations of the films, probably due to the components used.
According to the results in Table 4, the films showed reduced antimicrobial capacity in relation to the values documented in the literature for the corresponding oil. Although this reduction may be advantageous for preserving dermal lesions without microbial contamination, it is ineffective for wounds already colonized by pathogenic microorganisms.
An interesting aspect that deserves to be highlighted is that pure copaiba oil did not show reactivity against the bacterial strains Pseudomonas aeruginosa and Bacillus cereus. However, it is intriguing to note that when copaiba oil is combined with other formulations, modest but noteworthy antimicrobial activity emerges. The importance of this finding lies in the fact that copaiba oil, when used alone, did not demonstrate any noticeable antimicrobial effect. Consequently, it can be safely inferred that the combinations employed in this study increased the antimicrobial properties of copaiba oil, as shown in Table 5.
Table 4
Antimicrobial action for selected films.
Microorganisms
|
Tests
|
5
|
8
|
9
|
10
|
11
|
|
IHL(mm)
|
Escherichia coli
|
8.3
|
9.3
|
10.3
|
12.3
|
8.3
|
Salmonella typhi
|
6.3
|
7.3
|
8.3
|
10.3
|
6.3
|
Pseudomonas aeruginosa
|
2.7
|
3.7
|
4.7
|
6.7
|
2.7
|
Bacillus cereus
|
1.7
|
2.7
|
3.7
|
5.7
|
1.7
|
Staphylococcus aureus
|
1.7
|
2.7
|
3.7
|
5.7
|
1.7
|
|
MIC (µ g.ml−1)
|
Escherichia coli
|
100.2
|
111.0
|
109.0
|
130.1
|
87.9
|
Salmonella typhi
|
67.6
|
78.5
|
87.9
|
109.0
|
66.8
|
Pseudomonas aeruginosa
|
24.2
|
35.1
|
49.2
|
70.3
|
28.1
|
Bacillus cereus
|
13.4
|
24.2
|
38.7
|
59.8
|
17.6
|
Staphylococcus aureus
|
24.2
|
35.1
|
38.7
|
59.8
|
17.6
|
|
CBM (µ g.ml−1)
|
Escherichia coli
|
364.9
|
404.6
|
545.0
|
650.5
|
439.5
|
Salmonella typhi
|
245.9
|
285.5
|
439.5
|
545.0
|
334.0
|
Pseudomonas aeruginosa
|
87.2
|
126.9
|
246.1
|
351.6
|
140.6
|
Bacillus cereus
|
47.5
|
87.2
|
193.4
|
298.9
|
87.9
|
Staphylococcus aureus
|
87.2
|
126.9
|
193.4
|
298.9
|
87.9
|
IHL: Diameter of Inhibition Halos; MIC: Minimum Inhibitory Concentration; CBM: Minimum bactericidal concentration.
Table 5
Antimicrobial action of copaiba essential oil.
Microorganisms
|
IHL(mm)
|
MIC (µ g.ml−1)
|
CBM (µ g.ml−1)
|
Escherichia coli
|
12 / 11 / 2012
|
625 / 700 / 625
|
1250 / 1250 / 1200
|
Staphylococcus aureus
|
14 / 13 / 14
|
625 / 700 / 625
|
625 / 700 / 625
|
Staphylococcus epidermis
|
12 / 12 / 2013
|
700 / 700 / 750
|
700 / 700 / 800
|
Salmonella typhi
|
09 / 07 / 2009
|
1250 / 1250 / 1200
|
1250 / 1250 / 1200
|
Pseudomonas aeruginosa
|
-
|
-
|
-
|
Bacillus cereus
|
-
|
-
|
-
|
IHL: Diameter of Inhibition Halos; MIC: Minimum Inhibitory Concentration; CBM: Minimum bactericidal concentration.