Evidence-Based Complementary and Alternative Medicine

Volume 2013 (2013), Article ID 279726, 10 pages

http://dx.doi.org/10.1155/2013/279726

Research Article

Eugenia uniflora L. Essential Oil as a Potential Anti-Leishmania Agent: Effects on Leishmania amazonensis and Possible Mechanisms of Action

Klinger Antonio da Franca Rodrigues,¹ Layane Valéria Amorim,¹ Jamylla Mirck Guerra de Oliveira,¹ Clarice Noleto Dias,² Denise Fernandes Coutinho Moraes,² Eloisa Helena de Aguiar Andrade,³ Jose Guilherme Soares Maia,³ Sabrina Maria Portela Carneiro,¹ and Fernando Aécio de Amorim Carvalho¹

¹Medicinal Plants Research Center, Federal University of Piauí, 64049-550 Teresina, PI, Brazil

²Laboratory of Pharmacognosy II, Department of Pharmacy, Federal University of Maranhão, 65085-580 São Luís, MA, Brazil

³Postgraduate Program in Chemistry, Federal University of Pará, 66075-900 Belém, PA, Brazil

Received 13 October 2012; Revised 14 December 2012; Accepted 17 January 2013

Academic Editor: Liliana V. Muschietti

Copyright © 2013 Klinger Antonio da Franca Rodrigues et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Eugenia uniflora L. is a member of the Myrtaceae family and is commonly known as Brazilian cherry tree. In this study, we evaluated the chemical composition of Eugenia uniflora L. essential oil (EuEO) by using gas chromatography-mass spectrometry (GC-MS) and assessed its anti-Leishmania activity. We also explored the potential mechanisms of action and cytotoxicity of EuEO. Thirty-two compounds were identified, which constituted 92.65% of the total oil composition. The most abundant components were sesquiterpenes (91.92%), with curzerene (47.3%), γ-elemene (14.25%), and trans-β-elemenone (10.4%) being the major constituents. The bioactivity shown by EuEO against promastigotes (IC₅₀, 3.04 μg·mL⁻¹) and amastigotes (IC₅₀, 1.92 μg·mL⁻¹) suggested significant anti-Leishmania activity. In the cytotoxicity determination, EuEO was 20 times more toxic to amastigotes than to macrophages. Hemolytic activity was 63.22% at the highest concentration tested (400 μg·mL⁻¹); however, there appeared to be no toxicity at 50 μg·mL⁻¹. While the data show that EuEO activity is not mediated by nitric oxide production, they do suggest that macrophage activation may be involved in EuEO anti-Leishmania activity, as evidenced by increases in both the phagocytic capacity and the lysosomal activity. More studies are needed to determine in vivo activity as well as additional mechanisms of the anti-Leishmania activity.

1. Introduction

Protozoan parasites of the genus Leishmania are responsible for a spectrum of diseases collectively known as leishmaniasis, which affects the skin, mucous membranes, and internal organs. Over 12 million cases of leishmaniasis have been reported worldwide, with 1 to 2 million new cases being reported annually [1, 2]. Increase in the incidence of leishmaniasis is associated with urban development, deforestation, environmental changes, and increased migration to areas where the disease is endemic [3]. Despite its epidemiological importance, treatment is still performed with chemotherapeutic drugs that are delivered parenterally, require medical supervision, and have many side effects [4, 5].

The need to identify new anti-Leishmania compounds that are more effective and less toxic than conventional drugs has motivated research of substances derived from plant species. In this context, essential oils containing a group of secondary metabolites consisting mainly of monoterpenes, sesquiterpenes, and phenylpropanoids have demonstrated proven anti-Leishmania activity in vivo and in vitro on promastigote and/or amastigote forms of Leishmania. Included among these are Croton cajucara [6], Ocimum gratissimum [7], Copaifera cearensis [8], Chenopodium ambrosioides [9], Cymbopogon citratus [10, 11], and Lippia sidoides [12]. These studies have shown that essential oils can be a promising source of new drugs with anti-Leishmania activity.

Eugenia uniflora L., commonly known as “pitangueira” or Brazilian cherry tree, is a species belonging to the family Myrtaceae, which is native to South America and common in regions with tropical and subtropical climate [13]. In Brazil, it is used in the treatment of digestive disorders [14] and is thought to have anti-inflammatory and antirheumatic activities [15]. It is an aromatic species and its essential oil has pharmacological properties that are well characterized in the literature as antioxidant and antimicrobial [16]. E. uniflora has known antihypertensive [17], antitumor [18], and antinociceptive properties [19], and it shows good performance against microorganisms, demonstrating antiviral, antifungal [20], anti-Trichomonas gallinae [21], and anti-Trypanosoma cruzi properties [22].

Considering the potential pharmacological benefits of E. uniflora and the increasing interest in the discovery of essential oils with anti-Leishmania activity, the aim of this study was to investigate the anti-Leishmania activity of leaf essential oil from this species, the chemical composition of the oil, its cytotoxicity, and possible mechanisms of action.

2. Materials and Methods

2.1. Chemicals

Dimethyl sulfoxide (DMSO: 99%), anhydrous sodium sulfate, glacial acetic acid, ethanol, formaldehyde, sodium chloride, calcium acetate, zymosan, and neutral red were purchased from Merck Chemical Company (Germany). The -alkane (C₈–C₂₀) homologous series, Schneider’s medium, RPMI 1640 medium, fetal bovine serum (FBS), MTT (3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide), Griess reagent (1% sulfanilamide in H₃PO₄ 10% (v/v) in Milli-Q water), and the antibiotics penicillin and streptomycin were purchased from Sigma Chemical (St. Louis, MO, USA). The antibiotic amphotericin B (90%) was purchased from Cristália (São Paulo, SP, Brazil).

2.2. Plant Material

E. uniflora leaves were collected (January 2010) from a mature tree in the flowering stage in São Luís (2°30′45.3′′S and 44°18′1.1′′W) in the state of Maranhão in northeast Brazil. The samples were collected from a cultivated plant and its fruits have red color. A voucher specimen (no. 0998/SLS017213) was deposited at the Herbarium “Ático Seabra” of the Federal University of Maranhão, and plant identification was confirmed by botanists of the Herbarium “Murça Pires” from Museu Paraense Emílio Goeldi, Belém, PA, Brazil.

2.3. Extraction of the Essential Oil

The plant material was air-dried for 7 days, cut into small pieces, and subjected to hydrodistillation using a Clevenger-type apparatus (300 g, 3 h) to obtain a sesquiterpene-rich essential oil. Once collected, the essential oil was dried over anhydrous sodium sulfate, filtered, and weighed, and then the oil yield was calculated in terms of % (w/w). Its percentage content was estimated based on the plant dry weight by calculating the water content by using a moisture analyzer prior to distillation. EuEO was then stored in a dark flask and refrigerated (at +5°C) until use.

2.4. Gas Chromatography-Mass Spectrometry Analysis of the Essential Oil

EuEO was analyzed using a THERMO DSQ II GC-MS instrument (Thermo Fisher Scientific, Austin, TX, USA), under the following conditions: DB-5 ms ( i.d.; 0.25 μm film thickness) fused silica capillary column, with the following temperature program: 60°C, subsequently increased by 3°C/min up to 240°C; injector temperature: 250°C; carrier gas: helium (high purity), adjusted to a linear velocity of 32 cm/s (measured at 100°C). The injection type was splitless. The oil sample was diluted 1 : 100 in hexane solution, and the volume injected was 0.1 μL. The split flow was adjusted to yield a 2 : 1000 ratio, and the septum sweep was constant at 10 mL/min. All mass spectra were acquired in electron impact (EI) mode with an ionization voltage of 70 eV over a mass scan range of 35–450 amu. The temperature of the ion source and connection parts was 200°C.

2.5. Identification and Quantification of Constituents

The quantitative data regarding the volatile constituents were obtained by peak-area normalization using a FOCUS GC/FID operated under conditions similar to those used in the GC-MS assay, except for the carrier gas, which was nitrogen. The retention index was calculated for all the volatile constituents by using an -alkane (C₈–C₂₀) homologous series. When possible, individual components were identified by coinjection with authentic standards. Otherwise, the peak assignment was performed by comparison of both mass spectrum and GC retention data by using authentic compounds previously analyzed and stored in our private library, as well as with the aid of commercial libraries containing retention indices and mass spectra of volatile compounds commonly found in essential oils [23, 24]. Percentage (relative) of the identified compounds was computed from the GC peak area.

2.6. Parasites and Mice

Leishmania (Leishmania) amazonensis (IFLA/BR/67/PH8) was used for the determination of the anti-Leishmania activity. Parasites were grown in supplemented Schneider’s medium (10% heat-inactivated fetal bovine serum (FBS), 100 U·mL⁻¹ penicillin, and 100 μg/mL streptomycin at 26°C). Murine macrophages were collected from the peritoneal cavities of male and female BALB/c mice (4-5 weeks old) from Medicinal Plants Research Center (NPPM/CCS/UFPI), located at Teresina, PI, Brazil. The macrophages were maintained at a controlled temperature (°C) and light conditions (12 h light/dark cycle). All protocols were approved by the Animal Research Ethics Committee (CEEAPI no. 001/2012).

2.7. Anti-Leishmania Activity Assay

Promastigotes in the logarithmic growth phase were seeded in 96-well cell culture plates at   Leishmania per well. Then, essential oil was added to the wells in serial dilutions of 400, 200, 100, 50, 25, 12.5, 6.25, and 3.12 μg·mL⁻¹. The plate was kept at 26°C in a biological oxygen demand (BOD) incubator, and Leishmania was observed and counted by using a Neubauer hemocytometer after 24, 48, and 72 h to monitor growth and viability [25]. Assays were performed in triplicate and were repeated 3 times on different days.

2.8. Cytotoxicity Determination

Cytotoxicity of EuEO was assessed using the MTT test. In a 96-well plate, 100 μL of supplemented RPMI 1640 medium and about macrophages were added per well. They were then incubated at 37°C in 5% of CO₂ for 2 h to allow cell adhesion. After this time, 2 washes with supplemented RPMI 1640 medium were performed to remove cells that did not adhere. Subsequently, EuEO was added, in triplicate, after being previously diluted in supplemented RPMI 1640 medium to a final volume of 100 μL for each well at the tested concentrations (100, 50, 25, 12.5, 6.25, and 3.12 μg·mL⁻¹). Cells were then incubated for 48 h. At the end of the incubation, 10 μL of MTT diluted in PBS was added at a final concentration of 5 mg·mL⁻¹ (10% of volume, i.e., 10 μL for each 100 μL well) and was incubated for an additional 4 h at 37°C in 5% CO₂. The supernatant was then discarded, and 100 μL of DMSO was added to all wells. The plate was then stirred for about 30 min at room temperature to complete formazan dissolution. Finally, spectrophotometric reading was conducted at 550 nm in an ELISA plate reader [26].

2.9. Hemolytic Activity

The hemolytic activity was investigated by incubating 20 μL of serially diluted essential oil in phosphate-buffered saline (PBS; 400, 200, 100, 50, 25, 12.5, 6.25, and 3.12 μg·mL⁻¹) with 80 μL of a suspension of 5% red blood cells (human O⁺) for 1 h at 37°C in assay tubes. The reaction was slowed by adding 200 μL of PBS, and then the suspension was centrifuged at 1000 g for 10 min. Cell lysis was then measured spectrophotometrically (540 nm). The absence of hemolysis (blank control) or total hemolysis (positive control) was determined by replacing the essential oil solution with an equal volume of PBS or Milli-Q sterile water, respectively. The results were determined by the percentage of hemolysis compared to the positive control (100% hemolysis), and the experiments were performed in triplicate [27].

2.10. Treatment of Infected Macrophages

Macrophages were collected in 24-well culture plates at a concentration of cells/500 μL in RPMI 1640, containing sterile 13 mm round coverslips. They were then incubated at 37°C in 5% of CO₂ for 2 h to allow cell adhesion. After this time, the medium was replaced with 500 μL of supplemented RPMI 1640 and incubated for 4 h. The medium was then aspirated, and a new medium containing promastigotes (in the stationary phase) at a ratio of 10 promastigotes to 1 macrophage was added to each well. After 4 h of incubation in 5% CO₂ at 37°C, the medium was aspirated to remove free promastigotes, and the test samples were added at nontoxic concentrations to the macrophages (3.12, 1.56, and 0.78 μg·mL⁻¹). This preparation was then incubated for 48 h, after which the coverslips were removed, fixed in methanol, and stained with Giemsa. For each coverslip, 100 cells were evaluated and both the number of infected macrophages and the amount of parasites per macrophage were counted [26].

2.11. Lysosomal Activity

Measurement of the lysosomal activity was carried out according to the method of Grando et al. [28]. Peritoneal macrophages were plated and incubated with EuEO in serial dilutions of 100, 50, 25, 12.5, 6.25, and 3.12 μg·mL⁻¹. After 4 h of incubation at 37°C in 5% CO₂, 10 μL of neutral red solution was added and incubated for 30 min. Once this time had elapsed, the supernatant was discarded, the wells were washed with 0.9% saline at 37°C, and 100 mL of extraction solution was added (glacial acetic acid 1% v/v and ethanol 50% v/v dissolved in bidistilled water) to solubilize the neutral red inside the lysosomal secretion vesicles. After 30 min on a Kline shaker (model AK 0506), the plate was read at 550 nm by using an ELISA plate reader.

2.12. Phagocytosis Test

Peritoneal macrophages were plated and incubated with EuEO in serial dilutions of 100, 50, 25, 12.5, 6.25, and 3.12 μg·mL⁻¹. After 48 h of incubation at 37°C in 5% CO₂, 10 μL of zymosan color solution was added and incubated for 30 min at 37°C. After this, 100 mL of Baker’s fixative (formaldehyde 4% v/v, sodium chloride 2% w/v, and calcium acetate 1% w/v in distilled water) was added to stop the phagocytosis process. Thirty minutes later, the plate was washed with 0.9% saline in order to remove zymosan that was not phagocytosed by macrophages. The supernatant was removed and added to 100 mL of extraction solution. After solubilization in a Kline shaker, the absorbances were measured at 550 nm by using an ELISA plate reader [28].

2.13. Nitric Oxide (NO) Production

In 96-well plates, macrophages were added per well and incubated at 37°C in 5% CO₂ for 4 h to allow cell adhesion. A new medium containing promastigotes (in the stationary phase) at a ratio of 10 promastigotes per macrophage was added to half of the wells. The essential oil was added after being previously diluted in a culture medium containing different concentrations (100, 50, 25, 12.5, 6.25, and 3.12 μg·mL⁻¹) in the absence or presence of L. amazonensis, and was then incubated again at 37°C in 5% CO₂ for 24 h. After this period, the cell culture supernatant was collected and transferred to another plate for measurement of nitrite. A standard curve was prepared with 150 μM sodium nitrite in Milli-Q water at varying concentrations of 1, 5, 10, 25, 50, 75, 100, and 150 μM diluted in a culture medium. At the time of dosing, 100 μL of either the samples or the solutions prepared for obtaining the standard curve was mixed with an equal volume of Griess reagent. The analysis was performed using an ELISA plate reader at 550 nm [28].

2.14. Statistical Analysis

All assays were performed in triplicate and in 3 independent experiments. The half-maximal inhibitory concentration (IC₅₀) values and 50% cytotoxicity concentration (CC₅₀) values, with 95% confidence intervals, were calculated using a probit regression model and Student’s -test. Analysis of variance (ANOVA) followed by a Bonferroni test were performed, taking a value of <0.05 as the minimum level required for statistical significance.

3. Results

3.1. Analysis of the Essential Oil

The yield of EuEO was 0.3%. Thirty-two components were identified in this oil by GC-MS, constituting 92.65% of the total mixture. EuEO was shown to be rich in oxygenated sesquiterpenes (62.55%) and sesquiterpene hydrocarbons (29.37%). Curzerene was the major constituent (47.3%), followed by γ-elemene (14.25%) and trans-β-elemenone (10.4%). The chemical constituents are listed in Table 1.

Table 1: Chemical composition and retention indices of the constituents of Eugenia uniflora essential oil.

Constituentsa
RRI
% Ad

Cal.b
Lit.c

Myrcene
989
988
0.19

Limonene
1026
1029
0.18

Linalool
1095
1095
0.16

()-3-Hexenyl butyrate
1186
1184
0.10

Cuminaldehyde
1240
1238
0.10

δ-Elemene
1335
1338
1.32

α-Cubebene
1349
1345
0.10

β-Elemene
1390
1389
5.51

Sativene
1394
1390
0.06

(E)-Caryophyllene
1417
1417
4.33

trans-α-Bergamotene
1437
1432
0.05

γ-Elemene
1434
1434
14.25

Aromadendrene
1440
1439
0.07

α-Humulene
1455
1452
0.21

Alloaromadendrene
1462
1458
0.11

β-Chamigrene
1475
1476
0.38

Germacrene D
1482
1484
1.19

β-Selinene
1487
1489
0.70

Curzerene
1498
1499
47.3

γ-Cadinene
1513
1513
0.12

δ-Cadinene
1523
1522
0.28

Selina-3,7-(11)-diene
1546
1545
0.24

Germacrene B
1558
1559
0.45

Spathulenol
1578
1577
0.17

Caryophyllene oxide
1581
1582
0.13

Globulol
1585
1590
0.25

Viridiflorol
1590
1592
0.08

trans-β-Elemenone
1597
1601
10.4

Atractilona
1655
1657
2.38

Germacrone
1694
1693
1.51

Eudesm-7(11)-en-4-ol
1700
1700
0.33

Monoterpene hydrocarbons
0.37

Oxygenated monoterpenes
0.36

Sesquiterpene hydrocarbons
29.37

Oxygenated sesquiterpenes
62.55

Total
92.65

Compounds listed in order of elution on the DB-5ms column. bRelative retention indices (RRIs) experimentally determined against n-alkanes by using the DB-5ms column. cRRIs reported in the literature [23, 24]. dContent expressed as percentages obtained by integration of the GC peak area.

3.2. Anti-Leishmania Activity Assay

The inhibitory profile of EuEO on L. amazonensis promastigotes showed a significant concentration-dependent decrease () in parasite viability, with 100% inhibition of promastigote growth at concentrations of 400, 200, and 100 μg·mL⁻¹ (Figure 1). The IC₅₀ was 1.75 μg·mL⁻¹ at 72 h of exposure (Table 2). In cultures treated with EuEO, we used an optical microscope to observe morphological changes in the promastigotes, such as cells with rounded or completely spherical shapes, as well as cellular debris, in contrast to the spindle forms present in the control (data not shown). Amphotericin B was used as a positive control and was tested at a concentration of 2 μg·mL⁻¹. The highest inhibitory effect of amphotericin B was observed after 24 h.

Table 2: Anti-Leishmania and cytotoxic effects of Eugenia uniflora essential oil.

Macrophage
Promastigote
Amastigote

CC₅₀ (μg·mL⁻¹)
IC50 (μg·mL⁻¹)
SI
IC₅₀ (μg·mL⁻¹)
SI

48 h
24 h
48 h
72 h

48 h

EuEO

14.9a

23.59b

SIpro (selectivity index) = CC₅₀ macrophages/IC₅₀ promastigote forms (48 h). bSIama (selectivity index) = CC₅₀ macrophages/IC₅₀ amastigote forms.

Figure 1: Effect of Eugenia uniflora essential oil (400, 200, 100, 50, 25, 12.5, 6.25, and 3.12 μg·mL⁻¹) or amphotericin B (Amph) (2 μg·mL⁻¹) on Leishmania amazonensis promastigotes. Cultures of log-phase promastigotes () were incubated at 26°C for 24, 48, and 72 h in different essential oil concentrations. Data represent the mean percentage of growth inhibition ± standard error of 3 experiments carried out in triplicate. .

3.3. Cytotoxicity and Hemolysis Assay

The cytotoxicity of EuEO for murine peritoneal macrophages and erythrocytes is shown in Figures 2 and 3, respectively, and in Table 2. The EO from E. uniflora significantly altered () macrophage viability at a concentration of 6.25 μg·mL⁻¹ and was able to reduce 50% of the macrophage viability (CC₅₀) at 45.3 μg·mL⁻¹. The cytotoxicity of EO from E. uniflora for human blood type O⁺ erythrocytes was 63.22% at the highest concentration tested (400 μg·mL⁻¹); however, it appeared to be nontoxic at concentrations less than 50 μg·mL⁻¹ (Figure 3).

Figure 2: Cytotoxicity of Eugenia uniflora essential oil on the viability of murine peritoneal macrophages. Peritoneal macrophages were seeded at /well in 96-well microplates and incubated for 48 h in the presence of E. uniflora L. essential oil at concentrations of 100, 50, 25, 12.5, 6.25, and 3.12 μg·mL⁻¹. Viability was determined with 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide (MTT), and the optical density was determined at 540 nm. Data represent the mean parasite density ± standard error of 3 experiments carried out in triplicate. ; ; and .

Figure 3: Hemolytic activity of Eugenia uniflora essential oil in a 4% suspension of human O⁺ red blood cells after 1 h of incubation.

3.4. Treatment of Infected Macrophages

Figures 4 and 5 show the results of EuEO treatment of macrophages infected with L. amazonensis. The values obtained revealed a significant and concentration-dependent reduction in macrophage infection at 48 h with all the 3 EuEO concentrations studied. The reduction of infection was 27%, 44.67%, and 50.67% at 0.78, 1.56, and 3.12 μg·mL⁻¹, respectively. EuEO also decreased the number of amastigotes per infected cell in a concentration-dependent manner (Figure 5). The IC₅₀ at 48 h of exposure to EuEO was 1.92 μg·mL⁻¹ (Table 2). These values and the CC₅₀ values for macrophages were used to calculate the selectivity index that is useful for assessing the safety level of EuEO in mammalian cells (Table 2). This index represents the relationship between CC₅₀ and IC₅₀ for amastigotes.

Figure 4: Effect of Eugenia uniflora essential oil on macrophage infection after 48 h of exposure. Peritoneal macrophage cells were infected with promastigotes of Leishmania amazonensis and then treated with 3.12, 1.56, or 0.78 μg·mL⁻¹ of Eugenia uniflora essential oil. Data represent the mean parasite density ± standard error of 3 experiments carried out in triplicate. .

Figure 5: Effect of Eugenia uniflora essential oil on the survival of Leishmania amazonensis amastigotes internalized in macrophages. Leishmania amazonensis-infected mouse peritoneal macrophages were treated with 3.12, 1.56, or 0.78 μg·mL⁻¹ of Eugenia uniflora essential oil. After 48 h of incubation, amastigote survival was assessed. Data represent the mean parasite density ± standard error of 3 experiments carried out in triplicate. .

3.5. Lysosomal Activity and Phagocytosis Assay

Lysosomal activity was assessed based on the retention of neutral red in macrophage lysosomes and was determined colorimetrically. The lysosomal activity of macrophages treated with EuEO showed significant reduction at concentrations of 100 and 50 μg·mL⁻¹ (Figure 6(a)) due to cytotoxicity (CC₅₀ 45.3 μg·mL⁻¹). However, we observed a statistically significant increase in lysosomal activity at concentrations from 12.5 to 3.12 μg·mL⁻¹ compared to control. Another parameter reflecting macrophage activation was the phagocytosis of stained zymosan when the cells were exposed to an external stimulus. The phagocytic ability of macrophages incubated with EuEO is shown in Figure 6(b). There was a significant increase in phagocytosis of zymosan particles in the wells treated with EuEO at concentrations ranging from 25 to 3.12 μg·mL⁻¹.

(a)

(b)

Figure 6: The influence of Eugenia uniflora essential oil on the lysosomal activity (a) and phagocytic activity (b) of peritoneal macrophages at concentrations of 100, 50, 25, 12.5, 6.25, and 3.12 μg·mL⁻¹. Data represent the mean density ± standard error of 3 experiments carried out in triplicate. and . C: control. ABS: absorbance.

3.6. NO Production

NO production was determined indirectly by measuring nitrite produced by macrophages treated with EuEO and stimulated (or not stimulated) by L. amazonensis promastigotes. Macrophages treated with EuEO, but not stimulated by Leishmania, showed significant reduction in NO production at concentrations of 100 and 50 μg·mL⁻¹ (Figure 7(a)), while macrophages stimulated by the parasite showed increased NO at a concentration of 3.12 μg·mL⁻¹, albeit without statistical significance () (Figure 7(b)).

(a)

(b)

Figure 7: Production of nitric oxide (NO). Murine macrophages () were treated with Eugenia uniflora essential oil (100, 50, 25, 12.5, 6.25, and 3.12 μg·mL⁻¹) in the absence (a) or presence of Leishmania amazonensis (b) over 24 h. Data represent the mean density ± standard error of 3 experiments carried out in triplicate. . C: control. ABS: absorbance.

4. Discussion

The need to identify new compounds with anti-Leishmania properties that are more effective and less toxic than conventional drugs has motivated research on natural products isolated from plant species. These substances predominantly consist of alkaloids, terpenes, flavonoids, benzopyrans, phenolics, and sesquiterpene lactones and have been identified in plant species with documented anti-Leishmania activity [29, 30]. The chemical composition of EuEO obtained in this study revealed sesquiterpenes to be the dominant chemical class, corroborating the findings of many previous studies [16, 31–33]. Despite the prevalence of sesquiterpenes, the species has different chemotypes, with different major constituents being observed in different studies. The specimen analyzed in this study had curzerene as the major constituent, which again corroborated previous reported findings [32, 34]. According to Adio [35], germacrone is a heat-sensitive compound that may degrade to trans-β-elemenone during GC analysis. This may be the explanation of the presence of trans-β-elemenone among the major compounds of EuEO. Some germacrone products have shown pharmacological activity, as antitumor [35].

According to Costa et al. [20] the composition of the essential oil from E. uniflora leaves might be influenced by fruit colors. The plants with red fruit colors have curzerene as the major component as in our studied plant. In Maranhão, where the samples were collected, the majority of plants of E. uniflora have red fruit color [32]. Selina-1,3,7(11)-trien-8-one [36], germacrene B [16, 33], and α- and β-selinene [37] have been found to be the major constituents of other E. uniflora chemotypes. Genetic variability, geographical and environmental conditions, and the method of environmental management directly influence the yield and composition of essential oils [38]. It is the first report of essential oil analyzed from E. uniflora collected in São Luís, MA, Brazil and this could be an excellent source of natural product with interest for pharmaceutical industry.

The present study was conducted to evaluate the anti-Leishmania activity of EuEO on promastigotes and amastigotes of L. amazonensis, its potential mechanisms of macrophage activation, and its cytotoxicity in mammalian cells. The EuEO showed significant concentration-dependent activity against promastigotes of L. amazonensis, with an IC₅₀ of 1.75 μg·mL⁻¹. Previous studies have suggested that these classes of natural products may have potential anti-Leishmania activity. β-Caryophyllene (a sesquiterpene hydrocarbon) and nerolidol (an oxygenated sesquiterpene) are examples of terpenic substances with well-characterized anti-Leishmania activity, possibly associated with inhibition of cellular isoprenoid biosynthesis [8, 39].

It has been shown that the lipophilic components of essential oils may affect layers of polysaccharides, fatty acids, and phospholipids in plasma membranes of promastigotes of Leishmania spp. This then leads to cell lysis and release of macromolecules [40]. In the cytoplasm, these substances can disrupt the specific metabolic pathways of lipids and proteins or stimulate depolarization of mitochondrial membranes, which can lead to cell necrosis or apoptosis [41, 42].

Amphotericin B is a drug of choice for the treatment of different forms of leishmaniasis. Because of this it was used as a positive control. We observed a significant inhibitory effect on promastigote growth after 24 h of exposure to amphotericin B, but leading to an increase in viable promastigote forms at 48 and 72 h. Similar results were observed in previous studies [43]. Some Leishmania strains have shown mechanisms of resistance to amphotericin B. This may has happened with the strain used in this study. The reproduction of resistant parasites may have led to a higher cell viability after 48 and 72 h [44, 45].

Experimental models using amastigotes internalized into macrophages can produce results that more closely approximate those obtained using animal models, since these forms are responsible for the clinical manifestations of leishmaniasis [46]. Amastigotes can be found in parasitophorous vacuoles of infected macrophages; therefore, a therapeutic drug will only be effective against Leishmania spp. if it can cross the host cell membrane and act on the amastigotes inside the vacuole. Thus, assays of activity against intracellular amastigotes are the most effective way to relate the in vitro activity of a possible substance with its in vivo effectiveness [47]. The inhibition of amastigote growth was even greater at 48 h after exposure to oil, with an IC₅₀ of 1.92 μg/mL, whereas the IC₅₀ for promastigotes was 3.04 μg·mL⁻¹ for the same duration of exposure. Previous studies demonstrated greater activity against amastigotes versus promastigotes of essential oils of Artemisia absinthium and Satureja punctata [48].

Mechanisms of anti-Leishmania action on Leishmania spp. amastigotes have also been described for essential oils and their terpene compounds. Monoterpenes such as linalool, isolated from leaves of Croton cajucara (Euphorbiaceae), significantly increased NO production in macrophages infected with L. amazonensis and acts directly on the parasite, as evidenced by mitochondrial swelling and changes in the kinetoplast and the organization of nuclear chromatin [6]. In this study, the production of NO was determined by measuring nitrite. The results from macrophages treated with EuEO revealed that EuEO does not induce NO production, which demonstrates that its promising anti-Leishmania activity does not occur by this route.

Natural products that are able to activate macrophages, and are thus biological response modifiers, have been extensively studied [49, 50]. In this context, the EuEO demonstrated potential in the activation of macrophages by increasing phagocytic capacity and lysosomal activity, immunomodulatory activities possibly involved in its anti-Leishmania activity. Phagocytosis and the lysosomal system are critical to macrophage function, because of their roles in internalization, degradation, and eventually presentation of peptides derived from antigens required for host defense. In addition, antigen presentation occurs through phagocytosis and endosomal/lysosomal targeting systems [51–53].

Due to the need for anti-Leishmania substances that are more selective for the parasite and less toxic to host cells and since EuEO showed low IC₅₀ values, it was important to investigate the cytotoxic activity of EuEO against mammalian cells. EuEO showed significant toxicity in macrophages, with a CC₅₀ of 45.3 μg·mL⁻¹, but when compared with its IC₅₀ value in amastigotes, this indicates a secure selectivity index above 20. The literature recommends that for amastigotes internalized in macrophages, this index must be demonstrated as near to or greater than 20 [54]. The investigation of the toxic action of new substances with anti-Leishmania activity on macrophages is important, since they are the main cells of the vertebrate host parasitized by Leishmania spp. [55, 56]. Furthermore, various other cytotoxic assays can be conducted using animal and human cells to determine the safety of a test substance, leading to a future treatment in vivo. Tests performed with erythrocytes enable assessment of a drug’s potential to cause injury to the plasma membrane of a cell, either by forming pores or by total rupture, leading to cellular damage or changes in membrane permeability [57]. This is a model used for the preliminary study of the protective and toxic effects of substances, being a possible indicator of this type of damage to cells in vivo [58–60]. The results obtained in this test with EuEO revealed low toxicity to erythrocytes, since EuEO showed 0% hemolysis at concentrations of 50 μg·mL⁻¹ and lower.

5. Conclusions

In conclusion, the data in this study show that the essential oil of leaves from E. uniflora (EuEO), characterized by sesquiterpenes, has anti-Leishmania activity in both stages of L. amazonensis. This study also demonstrated that EuEO activity is not mediated by NO production. On the other hand, activation of macrophages may be involved in the mechanisms of EuEO anti-Leishmania activity, as evidenced by increases in both phagocytic capacity and the lysosomal compartment. Further investigation is needed to determine additional mechanisms involved in the anti-Leishmania activity of this plant species, as well as in vivo studies in models of leishmaniasis.

Conflict of Interests

The authors declare no conflict of interests.

Acknowledgments

The authors are grateful to the CAPES and FAPEMA for financial grants through the concession of scholarships and financial support.

References

S. Kaur, H. Sachdeva, S. Dhuria, M. Sharma, and T. Kaur, “Antileishmanial effect of cisplatin against murine visceral leishmaniasis,” Parasitology International, vol. 59, no. 1, pp. 62–69, 2010.

S. Azzouz, M. Maache, R. G. Garcia, and A. Osuna, “Leishmanicidal activity of edelfosine, miltefosine and ilmofosine,” Basic and Clinical Pharmacology and Toxicology, vol. 96, no. 1, pp. 60–65, 2005.

J. A. Patza, T. K. Graczykb, N. Gellera, and A. Y. Vittorc, “Effects of environmental change on emerging parasitic diseases,” International Journal of Parasitology, vol. 30, no. 12-13, pp. 1295–1304, 2000.

B. H. Alizadeh, A. Foroumadi, S. K. Ardestani, F. Poorrajab, and A. Shafiee, “Leishmanicidal evaluation of novel synthetic chromenes,” Archiv der Pharmazie, vol. 341, no. 12, pp. 787–793, 2008.

R. W. Ashford, “The leishmaniases as emerging and reemerging zoonoses,” International Journal for Parasitology, vol. 30, no. 12-13, pp. 1269–1281, 2000.

M. S. S. Rosa, R. R. Mendonça-Filho, H. R. Bizzo et al., “Antileishmanial activity of a linalool-rich essential oil from Croton cajucara,” Antimicrobial Agents Chemotherapy, vol. 47, no. 6, pp. 1895–1901, 2003.

T. Ueda-Nakamura, R. R. Mendonça-Filho, J. A. Morgado-Díaz et al., “Antileishmanial activity of eugenol-rich essential oil from Ocimum gratissimum,” Parasitology International, vol. 55, no. 2, pp. 55–59, 2006.

A. O. Santos, T. Ueda-Nakamura, B. P. Dias Filho, V. F. Veiga Junior, A. C. Pinto, and C. V. Nakamura, “Effect of Brazilian copaiba oils on Leishmania amazonensis,” Journal of Ethnopharmacology, vol. 120, no. 2, pp. 204–208, 2008.

L. Monzote, A. M. Montalvo, S. Almanonni, R. Scull, M. Miranda, and J. Abreu, “Activity of the essential oil from Chenopodium ambrosioides grown in Cuba against Leishmania amazonensis,” Chemotherapy, vol. 52, no. 3, pp. 130–136, 2006.

M. Machado, P. Pires, A. M. Dinis et al., “Monoterpenic aldehydes as potential anti-Leishmania agents: activity of Cymbopogon citratus and citral on L. infantum, L. tropica and L. major,” Experimental Parasitology, vol. 130, no. 3, pp. 223–231, 2012.

M. R. Santin, A. O. Dos Santos, C. V. Nakamura, B. P. Dias Filho, I. C. P. Ferreira, and T. Ueda-Nakamura, “In vitro activity of the essential oil of Cymbopogon citratus and its major component (citral) on Leishmania amazonensis,” Parasitology Research, vol. 105, no. 6, pp. 1489–1496, 2009.

V. C. S. Oliveira, D. M. S. Moura, J. A. D. Lopes, P. P. De Andrade, N. H. Da Silva, and R. C. B. Q. Figueiredo, “Effects of essential oils from Cymbopogon citratus (DC) Stapf., Lippia sidoides Cham., and Ocimum gratissimum L. on growth and ultrastructure of Leishmania chagasi promastigotes,” Parasitology Research, vol. 104, no. 5, pp. 1053–1059, 2009.

A. E. Consolini and M. G. Sarubbio, “Pharmacological effects of Eugenia uniflora (Myrtaceae) aqueous crude extract on rat's heart,” Journal of Ethnopharmacology, vol. 81, no. 1, pp. 57–63, 2002.

C. B. Alice, V. M. F. Vargas, G. A. A. B. Silva et al., “Screening of plants used in south Brazilian folk medicine,” Journal of Ethnopharmacology, vol. 35, no. 2, pp. 165–171, 1991.

P. Weyerstahl, H. Marschall-Weyerstahl, C. Christiansen, B. O. Oguntimein, and A. O. Adeoye, “Volatile constituents of Eugenia uniflora leaf oil,” Planta medica, vol. 54, no. 6, pp. 546–549, 1988.

F. N. Victoria, E. J. Lenardão, L. Savegnago et al., “Essential oil of the leaves of Eugenia uniflora L.: antioxidant and antimicrobial properties,” Food and Chemical Toxicology, vol. 50, no. 8, pp. 2668–2674, 2012.

A. E. Consolini, O. A. N. Baldini, and A. G. Amat, “Pharmacological basis for the empirical use of Eugenia uniflora L. (Myrtaceae) as antihypertensive,” Journal of Ethnopharmacology, vol. 66, no. 1, pp. 33–39, 1999.

I. A. Ogunwande, N. O. Olawore, O. Ekundayo, T. M. Walker, J. M. Schmidt, and W. N. Setzer, “Studies on the essential oils composition, antibacterial and cytotoxicity of Eugenia uniflora L.,” International Journal of Aromatherapy, vol. 15, no. 3, pp. 147–152, 2005.

A. C. L. Amorim, C. K. F. Lima, A. M. C. Hovell, A. L. P. Miranda, and C. M. Rezende, “Antinociceptive and hypothermic evaluation of the leaf essential oil and isolated terpenoids from Eugenia uniflora L. (Brazilian Pitanga),” Phytomedicine, vol. 16, no. 10, pp. 923–928, 2009.

D. P. Costa, E. G. A. Filho, L. M. A. Silva et al., “Influence of fruit biotypes on the chemical composition and antifungal activity of the essential oils of Eugenia uniflora leaves,” Journal of the Brazilian Chemical Society, vol. 21, no. 5, pp. 851–858, 2010.

G. F. Ibikunle, A. C. Adebajo, F. G. Famuyiwa, A. J. Aladesanmi, and C. O. Adewunmi, “In-vitro evaluation of anti-trichomonal activities of Eugenia uniflora leaf,” African Journal of Traditional, Complementary and Alternative Medicines, vol. 8, no. 2, pp. 170–176, 2011.

K. K. Santos, S. R. Tintino, C. E. Souza et al., “Anti-Trypanosoma cruzi and cytotoxic activities of Eugenia uniflora L.,” Experimental Parasitology, vol. 131, no. 1, pp. 130–132, 2012.

NIST 05, Mass Spectral Library (NIST/EPA/NIH), National Institute of Standards and Technology, Gaithersburg, Md, USA, 2005.

R. P. Adams, Identification of Essential Oil Components By Gas Chromatography/Mass Spectrometry, Allured, Carol Stream, Ill, USA, 4th edition, 2007.

S. M. P. Carneiro, F. A. A. Carvalho, L. C. L. R. Santana, A. P. L. Sousa, and M. H. Chaves, “The cytotoxic and antileishmanial activity of extracts and fractions of leaves and fruits of Azadirachta indica (A Juss.),” Biological Research, vol. 45, no. 2, pp. 111–116, 2012.

M. D. G. F. de Medeiros, A. C. da Silva, A. M. D. G. L. Citó et al., “In vitro antileishmanial activity and cytotoxicity of essential oil from Lippia sidoides Cham,” Parasitology International, vol. 60, no. 3, pp. 237–241, 2011.

S. E. Löfgren, L. C. Miletti, M. Steindel, E. Bachère, and M. A. Barracco, “Trypanocidal and leishmanicidal activities of different antimicrobial peptides (AMPs) isolated from aquatic animals,” Experimental Parasitology, vol. 118, no. 2, pp. 197–202, 2008.

F. C. C. Grando, C. A. Felício, A. Twardowschy et al., “Modulation of peritoneal macrophage activity by the saturation state of the fatty acid moiety of phosphatidylcholine,” Brazilian Journal of Medical and Biological Research, vol. 42, no. 7, pp. 599–605, 2009.

M. M. Iwu, J. E. Jackson, and B. G. Schuster, “Medicinal plants in the fight against leishmaniasis,” Parasitology Today, vol. 10, no. 2, pp. 65–68, 1994.

L. G. Rocha, J. R. G. S. Almeida, R. O. Macêdo, and J. M. Barbosa-Filho, “A review of natural products with antileishmanial activity,” Phytomedicine, vol. 12, no. 6-7, pp. 514–535, 2005.

S. M. De Morais, A. A. Craveiro, M. I. L. Machado, J. W. Alencar, and F. J. A. Matos, “Volatile constituents of Eugenia uniflora leaf oil from northeastern Brazil,” Journal of Essential Oil Research, vol. 8, no. 4, pp. 449–451, 1996.

J. G. S. Maia, E. H. A. Andrade, M. H. L. Da Silva, and M. G. B. Zoghbi, “A new chemotype of Eugenia uniflora L. from North Brazil,” Journal of Essential Oil Research, vol. 11, no. 6, pp. 727–729, 1999.

J. H. G. Lago, E. D. Souza, B. Mariane et al., “Chemical and biological evaluation of essential oils from two species of myrtaceae—Eugenia uniflora L. and Plinia trunciflora (O. Berg) Kausel,” Molecules, vol. 16, no. 12, pp. 9826–9837, 2011.

R. Chang, S. A. L. de Morais, D. R. Napolitano, K. C. Duarte, V. B. Guzman, and E. A. do Nascimento, “A new approach for quantifying furanodiene and curzerene. A case study on the essential oils of Eugenia uniflora (pitangueira) leaves,” Brazilian Journal of Pharmacognosy, vol. 21, no. 3, pp. 392–396, 2011.

A. M. Adio, “Germacrenes A-E and related compounds: thermal, photochemical and acid induced transannular cyclizations,” Tetrahedron, vol. 65, no. 8, pp. 1533–1552, 2009.

D. P. Costa, S. C. Santos, J. C. Seraphin, and P. H. Ferri, “Seasonal variability of essential oils of Eugenia uniflora leaves,” Journal of the Brazilian Chemical Society, vol. 20, no. 7, pp. 1287–1293, 2009.

A. T. Henriques, M. E. Sobral, A. D. Caudaro, E. E. S. Schapoval, V. L. Bassani, and G. Lamaty, “Aromatic plants from Brazil II. The chemical composition of some Eugenia essential oils,” Journal of Essential Oil Research, vol. 5, no. 5, pp. 501–505, 1993.

B. Teixeira, A. Marques, C. Ramos et al., “European pennyroyal (Mentha pulegium) from portugal: chemical composition of essential oil and antioxidant and antimicrobial properties of extracts and essential oil,” Industrial Crops and Products, vol. 36, no. 1, pp. 81–87, 2012.

D. C. Arruda, F. L. D'Alexandri, A. M. Katzin, and S. R. B. Uliana, “Antileishmanial activity of the terpene nerolidol,” Antimicrobial Agents and Chemotherapy, vol. 49, no. 5, pp. 1679–1687, 2005.

R. Di Pasqua, G. Betts, N. Hoskins, M. Edwards, D. Ercolini, and G. Mauriello, “Membrane toxicity of antimicrobial compounds from essential oils,” Journal of Agricultural and Food Chemistry, vol. 55, no. 12, pp. 4863–4870, 2007.

Y. Tariku, A. Hymete, A. Hailu, and J. Rohloff, “Essential-oil composition, antileishmanial, and toxicity study of Artemisia abyssinica and Satureja punctata ssp. punctata from Ethiopia,” Chemistry and Biodiversity, vol. 7, no. 4, pp. 1009–1018, 2010.

J. S. Armstrong, “Mitochondrial membrane permeabilization: the sine qua non for cell death,” BioEssays, vol. 28, no. 3, pp. 253–260, 2006.

A. L. Silva, C. M. Adade, F. M. Shoyama et al., “In vitro leishmanicidal activity of N-dodecyl-1, 2-ethanediamine,” Biomedicine and Pharmacotherapy, vol. 66, no. 3, pp. 180–186, 2012.

B. Purkait, A. Kumar, N. Nandi et al., “Mechanism of amphotericin B resistance in clinical isolates of Leishmania donovani,” Antimicrobial Agents and Chemotherapy, vol. 56, no. 2, pp. 1031–1141, 2012.

M. Vermeersch, R. I. Da Luz, K. Toté, J. P. Timmermans, P. Cos, and L. Maes, “In vitro susceptibilities of Leishmania donovani promastigote and amastigote stages to antileishmanial reference drugs: practical relevance of stage-specific differences,” Antimicrobial Agents and Chemotherapy, vol. 53, no. 9, pp. 3855–3859, 2009.

C. Di Giorgio, F. Delmas, V. Akhmedjanova et al., “In vitro antileishmanial activity of diphyllin isolated from Haplophyllum bucharicum,” Planta Medica, vol. 71, no. 4, pp. 366–369, 2005.

H. Martinez-Rojano, J. Mancilla-Ramirez, L. Quiñonez-Diaz, and N. Galindo-Sevilla, “Activity of hydroxyurea against Leishmania mexicana,” Antimicrobial Agents and Chemotherapy, vol. 52, no. 10, pp. 3642–3647, 2008.

Y. Tariku, A. Hymete, A. Hailu, and J. Rohloff, “Essential-oil composition, antileishmanial, and toxicity study of Artemisia abyssinica and Satureja punctata ssp. punctata from Ethiopia,” Chemistry and Biodiversity, vol. 7, no. 4, pp. 1009–1018, 2010.

A. H. Klimp, E. G. E. De Vries, G. L. Scherphof, and T. Daemen, “A potential role of macrophage activation in the treatment of cancer,” Critical Reviews in Oncology/Hematology, vol. 44, no. 2, pp. 143–161, 2002.

M. R. Piemonte and D. F. Buchi, “Analysis of IL-12, IFN-γ and TNF-α production, a5b1 integrins and actin filaments distribution in peritoneal mouse macrophages treated with homeopathic medicament,” Journal of Submicroscopic Cytology and Pathology, vol. 33, no. 1, pp. 255–263, 2002.

F. Niedergang and P. Chavrier, “Signaling and membrane dynamics during phagocytosis: Many roads lead to the phagos(R)ome,” Current Opinion in Cell Biology, vol. 16, no. 4, pp. 422–428, 2004.

W. L. Lee, R. E. Harrison, and S. Grinstein, “Phagocytosis by neutrophils,” Microbes and Infection, vol. 5, no. 14, pp. 1299–1306, 2003.

S. J. Green, M. S. Meltzer, J. B. Hibbs, and C. A. Nacy, “Activated macrophages destroy intracellular Leishmania major amastigotes by an L-arginine-dependent killing mechanism,” Journal of Immunology, vol. 144, no. 1, pp. 278–283, 1990.

E. Osorio, G. J. Arango, N. Jiménez et al., “Antiprotozoal and cytotoxic activities in vitro of Colombian Annonaceae,” Journal of Ethnopharmacology, vol. 111, no. 3, pp. 630–635, 2007.

S. Kamhawi, “Phlebotomine sand flies and Leishmania parasites: friends or foes?” Trends in Parasitology, vol. 22, no. 9, pp. 439–445, 2006.

P. Tripathi, V. Singh, and S. Naik, “Immune response to leishmania: paradox rather than paradigm,” FEMS Immunology and Medical Microbiology, vol. 51, no. 2, pp. 229–242, 2007.

L. V. Costa-Lotufo, G. M. A. Cunha, P. A. M. Farias et al., “The cytotoxic and embryotoxic effects of kaurenoic acid, a diterpene isolated from Copaifera langsdorffii oleo-resin,” Toxicon, vol. 40, no. 8, pp. 1231–1234, 2002.

R. M. Aparicio, M. J. García-Celma, M. Pilar Vinardell, and M. Mitjans, “In vitro studies of the hemolytic activity of microemulsions in human erythrocytes,” Journal of Pharmaceutical and Biomedical Analysis, vol. 39, no. 5, pp. 1063–1067, 2005.

L. A. Lexis, R. G. Fassett, and J. S. Coombes, “α-tocopherol and α-lipoic acid enhance the erythrocyte antioxidant defence in cyclosporine A-treated rats,” Basic and Clinical Pharmacology and Toxicology, vol. 98, no. 1, pp. 68–73, 2006.

J. R. Muñoz-Castañeda, J. Muntané, M. C. Muñoz, I. Bujalance, P. Montilla, and I. Tunez, “Estradiol and catecholestrogens protect against adriamycininduced oxidative stress in erythrocytes of ovariectomized rats,” Toxicology Letters, vol. 160, no. 3, pp. 196–203, 2006.