Trata-se de um estudo “in vitro”, onde foram coletados dados
5 ARTIGOS PRODUZIDOS 5.1 Artigo 1:
Periódico: Pharmaceutical Biology - ISSN: 1388-0209. Status: a ser submetido.
Plant essential oils and their antimicrobial activity – review 2010-2013 Maiza Rocha de Abrantes1*, Edeltrudes de Oliveira Lima2, Mariana Araújo Paulo de Medeiros1, Felipe Queiroga Sarmento Guerra2, Eveline Pipolo Milan3
1Departamento de Análises Clínicas e Toxicológicas, Centro de Ciências da Saúde, Universidade Federal do Rio Grande do Norte
2Departamento de Ciências Farmacêuticas, Centro de Ciências da Saúde, Universidade Federal da Paraíba
3Departamento de Infectologia, Centro de Ciências da Saúde, Universidade Federal do Rio Grande do Norte
*Corresponding author. Mailing address: Departamento de Análises Clínicas e Toxicológicas, Centro de Ciências da Saúde, Universidade Federal do Rio Grande do Norte, R. Gal. Gustavo Cordeiro de Farias, S/N, 1o andar, Petrópolis, Natal, RN, Brazil. CEP: 59012-570. Phone: +55 (84) 3342-99797, 3342-9801. Mobile: + 55 (84) 9955-1703. E-mail: maizajrl@ufrnet.br.
ABSTRACT
The use of essential oils of vegetable origin is rooted in popular knowledge and has now been evoked by scientific studies. This study included an inventory of oils extracted from plants with antimicrobial activity, highlighting their applications and use. The literature review included any scholarly, peer- reviewed journal articles published in databases such as Google Scholar, PubMed (Medical Publications), MEDLINE (International Literature on Health Sciences), LILACS (Latin American and Caribbean Health Sciences Literature), SciELO (Scientific Electronic Library Online) as well as a wide range of academic dissertations and theses from 2010 to 2013. We found 29 essential oils of vegetable origin with antimicrobial activity, several of which from the
Lamiaceae family. This review suggests that progress has been made in the
study of essential oils.
Introduction
Essential oils (EOs) are complex mixtures of volatile, lipophilic, liquid and colorless or slightly yellowish compounds with a strong and pleasant aroma. They originate from the secondary metabolism of plants, and are very unstable, especially in the presence of air, light, heat, moisture and metals (Peixoto, 2010; Oliveira, 2011; Ehlert et al., 2013).
These oils can be found in the leaves, flowers, branches, buds, stems, fruits, seeds, bark and roots of the plants (Lavinik, 2013) and perform various necessary functions for their survival, playing a key role in the defense against
microorganisms, in attracting pollinators, in protecting the plant from heat, amongst other functions (Bassolé & Juliani, 2012; Trajano, 2012; Gomes, 2013; Silva et al., 2013).
Medicinal plants require different techniques for growing, harvesting, and postharvest processing in order to determine which methods provide higher biomass accumulation and chemical constituents of interest (Ehlert et al., 2013). The chemical and biological properties of EOs may vary according to the environment in which the plant develops, the type of cultivation technique, the collection of plant material, the season, the climate, the vegetative stage, the plant organ, age, the time of vegetative phase and the extraction method used (Zheljazkov et al., 2010; Ehlert et al., 2013; Machado, Ribeiro, Druzian, 2013; Zhaoa et al., 2013). Plants rich in essential oils should be collected in the morning or evening since sun exposure may cause loss of a significant amount of oil. Nevertheless, one can not predict or establish the use of a single standard technique, since each species reacts differently to environmental changes (Peixoto, 2010).
There are various methods for extracting essential oils, some of which include: steam distillation, hydrodistillation (Clevenger method), organic solvent extraction, microwave-assisted distillation, microwave hydrodiffusion and gravity, high-pressure solvent extraction, supercritical fluid CO2 extraction, ultrasonic extraction and solvent-free microwave extraction. However, steam distillation is the most commonly used method for commercial production scale (Okoh, Sadimenko, Afolayan, 2010).
Phytochemicals derived from EOs include terpene hydrocarbons, alcohols, terpene alcohols, aldehydes, ketones, phenols, esters, ethers, oxides,
peroxides, organic acids, lactones, coumarins and sulfur compounds. Chemically, the vast majority of EOs are derived from phenylpropanoid and predominantly from terpenoids (Lima, 2011), whereas the majority of their antimicrobial activity derive from oxygenated terpenes, particularly terpene phenolics, phenylpropanoids and alcohols (Bassolé & Juliani, 2012).
Essential oils have been widely used by pharmaceutical, sanitary, cosmetic, agricultural and food industries because of their biologically active compounds, which present several pharmacological activities: antioxidant (Maskovic et al., 2013, Xu et al., 2013), anti-inflammatory (Salud et al., 2011; Ramos et al., 2013), larvicide (Govindarajan et al., 2012; Souza et al., 2012), insecticide (Salama et al., 2012; Arango et al., 2013), antibacterial (Castro, et al., 2011; Guerra et al., 2013) and antifungal activities (Oliveira et al., 2011; Tyagi et al., 2013). Moreover, EOs may be used alone or in combination with existing methods, which is considered an interesting alternative to reduce or eliminate resistant pathogens (Khan et al., 2012).
The antifungal properties of EOs of vegetable origin have been demonstrated through intensive research, driven by the growing trend towards replacing synthetic agents (Zuzarte et al., 2012). The use of natural antifungal compounds is important not only for food preservation, but also in the control of diseases that affect both plants and humans. The search for new antifungal agents is needed due to the emergence of resistant microorganisms and fatal opportunistic infections (Carmo, 2011).
The antimicrobial properties of EOs of vegetable origin have been empirically known for centuries, but only recently has science recognized their importance. Such properties have been systematically investigated by different
research groups, which study the biological activity of medicinal plants throughout the world, according to their popular use. In contrast, microorganisms that cause disease have developed resistance to most of the available antibiotics, which further fosters the search for natural antibiotics (Machado, Ribeiro, Druzian, 2013).
The mechanism of action of EOs on microorganisms is complex and not yet fully elucidated. As is well known, the hydrophobic properties of EOs and their components cause their binding to lipids in the cell membrane, altering its structure and increasing its permeability, thus leading to cell leakage and cell death (Guerra et al., 2012; Gomes, 2013; Lavinik, 2013). This mechanism of action can not be assigned to a specific target, although there may be many of them within the cell (Kacániová et al., 2012).
Essential oils of vegetable origin with antifungal action present two important characteristics: their natural origin (safe for consumers and for the environment) and lower risk of development of microbial resistance. The latter is based on the fact that EOs have a complex chemical composition and, consequently, different mechanisms of activity, making it difficult for microorganisms to adapt and mutate (Carmo, 2011).
In this retrospective study, we developed an inventory of oils extracted from plants with antifungal activity, highlighting their applications for humans.
Methods
This is a descriptive study with quantitative and qualitative approaches. The literature review included any scholarly, peer-reviewed journal articles and
academic dissertations and theses from 2010 to 2013. The following databases were used: Google Scholar, PubMed (Medical Publications), MEDLINE (International Literature on Health Sciences), LILACS (Latin American and Caribbean Health Sciences Literature) and SciELO (Scientific Electronic Library Online). The keywords used for the search were: essential oils, natural products and antimicrobials.
Results and Discussion
The sample consisted of 29 EOs with antifungal, antibacterial and antimicrobial (antifungal + antibacterial) properties. As shown in Table 1,
Lamiaceae has been the most studied family.
Studies have reported the antifungal and antibacterial properties of some Cymbopogon species. According to Carmo (2011), the EO of
Cymbopogon citratus (Gramineae - Poaceae) is indicated for the treatment of
dermatoses (urticaria, ulcers, spots and rashes), acting against clinical strains of Malassezia isolated from patients at the Hospital Universitário Lauro Wanderley (Universidade Federal da Paraíba, Brazil). Moreover, Oliveira (2011) investigated the activity of the EO of Cymbopogon winterianus (lemongrass) on
Candida albicans, Aspergillus flavus and Aspergillus fumigatus using time-kill
methodology. In this study, is was suggested that this EO had a concentration- dependent antifungal effect for all strains tested.
In order to develop an alternative therapy for candidiasis - since the one currently available has become problematic as a result of the toxicity of antifungal agents and the increasing prevalence of antibiotic-resistance -, Khan,
Malik and Ahmad (2012) studied the effect of 21 plant EOs against multidrug- resistant (MDR) strains of C. albicans. According to the study, the oil of
Cymbopogon martini showed a strong inhibitory activity against C. albicans with
Minimal Inhibitory Concentrations ranging from 90 to 100 µg/ml.
While studying the antifungal effect of microcapsules containing EO of
Cinnamomum zeylanicum Blume (Lauraceae) on Aspergillus flavus, Trajano
(2012) noted that in in vitro assays this EO showed fungistatic (650μg/mL) and fungicide (2600μg/mL) activities. According to the searched literature, C.
zeylanicum have some medicinal properties such as astringent, aphrodisiac,
antiseptic, aromatic, carminative, digestive, stimulant, hypertensive, sedative, tonic and vasodilator (www.plantamed.com.br).
Antifungal properties have also been found in plant species from genera
Cicuta and Eugenia. An EO extracted from the fruits of Cicuta virosa L. var.
latisecta Celak was used against four food-borne fungi: Aspergillus flavus, A.
oryzae, A. niger and Alternaria alternata. Results showed that this EO had a
strong inhibitory effect on spore production and germination in all tested fungi (Jun et al., 2011). Furthermore, Mendes (2011) evaluated the activity of the EO of Eugenia caryophyllata Thunb on strains of C. tropicalis using Minimal Inhibitory Concentration (MIC) and Minimal Fungicidal Concentration (MFC) values, and micromorphology, fungal viability (time-kill) and checkerboard methodologies. Therefore, they observed a concentration-dependent antifungal activity in the EO, which is potentialized in association with amphotericin B.
An study with Hyptis spp. (Lamiaceae) has shown the antimicrobial activity of H. suaveolens, H. rhomboidea and H. Brevipes (Xu et al., 2013), whereas Guerra-Boone et al. (2013) have shown that the EO of Magnolia
grandiflora presents an antifungal activity against dermatophyte strains.
While investigating the antifungal activity of EOs of Lavandula viridis, Zuzarte et al. (2011) showed that dermatophyte fungi and Cryptococcus
neoformans were the most sensitive to the EOs (0.32 to 0.64 mL μL⁻¹), followed
by Candida spp. (0.64 to 2.5 ml μL⁻¹). For most of these strains, MIC values were equal to MLC values, showing the fungicidal effect of the essential oils. Additionally, it has been observed that the EOs had completely inhibited the filamentation of C. albicans at concentrations sixteen times below the MIC value.
Additionally, Zuzarte et al. (2012) studied the activity of the EO of
Lavandula luisieri against dermatophyte fungi and Aspergillus strains as well as
its influence on the dimorphic transition in C. albicans, evaluated through the inhibition of germ tube formation assay. As previously reported (Zuzarte et al., 2011), the filamentation in all strains was completely inhibited at concentrations below sixteen times the MIC. The results support the use of EOs of L. luisieri for the development of new phytochemicals and food preservatives, emphasizing their antifungal properties at non-cytotoxic concentrations or at concentrations with very low negative effects on mammalian cells.
Studies with species of Mentha have made progress in reporting their antifungal properties on different pathogenic fungi. Peixoto (2010), for instance, evaluated the anti-Candida action of EOs and fractions of different accessions of Mentha spp. against C. albicans and C. dubliniensis. Four of the EOs analyzed showed strong activity with broad spectrum: M. canadensis (MC 05) - (<0,007 to 0,500 mg/mL); M. spicata (MC 30) (0,062 mg/mL to 0,500 mg/mL);
(MC 52) - (0,062 mg/mL to 0,500 mg/mL). In addition, Abdullah et al. (2010) have also investigated the antifungal activity of the EO extracted from aerial parts of Mentha spicata L. (mint) against five pathogenic fungi: Aspergillus
niger, Mucor mucedo, Fusarium solani, Botryodiplodia theobromae, and
Rhizopus solani. In this study, all tested microorganisms were strongly affected
by the EO, indicating an appreciable antimicrobial potential of spearmint oil. In a study by Castro et al. (2011), it was suggested the use of the EO of
Lippia sidoides Cham. (Verbenaceae) as an antibacterial agent in food. For this
purpose, they studied the antimicrobial activity of the EO against
Staphylococcus aureus and Escherichia coli isolated from artisanal Minas
cheese produced in Brazil and found that both strains were sensitive to its bactericidal activity.
A multiple-species approach has been used in many researches. In the
in vitro evaluation of the antimicrobial activity of EOs of Cinnamomum cassia
(Chinese cinnamon), Origanum vulgare (oregano), Piper nigrum (black pepper) and Thymus vulgaris (white thyme), Lavinik (2013) has found that only P.
nigrum showed no inhibitory effect on the growth of enteric Salmonella samples
isolated from poultry. In contrast, T. vulgaris and C. cassia were effective against 91.3% of the strains, while O. vulgare had an effectiveness of 100%. The high antimicrobial activity of Thymus and Origanum species has been associated to their phenolic components such as thymol and carvacrol (Bassolé & Juliani, 2012). Additionally, similar results were observed by Cleff et al. (2010). They studied the EO of O. vulgare against strains of Candida spp. isolated from animals and found that this oil may represent an alternative for the treatment of candidiasis.
By investigating the antibacterial activity of EOs from Coriandrum
sativum L. (coriander), Ocimum basilicum L. (sweet basil), Origanum majorana
L. (marjoram) and Rosmarinus officinalis L. (rosemary), Guerra et al. (2012) found that they presented an effective antibacterial activity against MDR strains of Acinetobacter spp., except for coriander, which presented lower activity. A latter study by Guerra et al. (2013) suggested that the EO of Citrus limonun is also effective against MDR strains of Acinetobacter spp.
Following the multiple-species approach, Silveira et al. (2012) studied the antimicrobial activity of EOs of herbs grown in the southern Brazil against 12 important bacterial species in food. They noted that the EOs with greater activity against the bacteria tested were, in descending order, Cymbopogon flexuosus (lemongrass), Ocimum basilicum L. (sweet basil), Origanum vulgare (oregano),
Cinnamomum zeylanicum (cinnamon) and Laurus nobilis (bay laurel). The
bacterium Yersinia enterocolitica was the most sensitive pathogen to all EOs tested (MIC 0.62 mg mL-1).
Furthermore, Rana et al. (2011) investigated the antibacterial activity of 19 EOs against four species of bacteria: Pseudomonas aeruginosa,
Staphylococcus aureus, Salmonella typhimurium and Bacillus subtilis. Various
degrees of antibacterial activity were found: Cinnamomum zeylanicum, with the most prominent antibacterial activity, was followed, respectively, by
Cymbopogon ciatrus and Carum copticum.
Recent researches have aimed to detect in vitro antifungal action of EOs extracted from plant species native to other biomes. Cyclotrichium
leucotrichum (Lamiaceae), a plant species native to Iran, and Thymus
Candida albicans (Mirjalili et al., 2013; Bellete et al., 2012). The latter was
further suggested to have an antifungal action against Aspergillus fumigatus and dermatophytes (Bellete et al., 2012).
Calamintha nepeta L (Lamiaceae) Savi subsp. nepeta and Smyrnium
olusatrum L. (Apiaceae), two species native to the Mediterranean coast (Island
of Sardinia, Italy) and to Portugal’s Atlantic coast, were used by Marongiu et al. (2010, 2012) in order to evaluate the antifungal activity of their EOs against five species of Candida (C. albicans, C. tropicalis, C. krusei, C. guillermondii, C.
parapsilosis), three species of Aspergillus (A. niger, A. fumigatus, A. flavus), two
species of Microsporum (M. canis, M. gypseum), two species of Trichophyton
(T. rubrum, T. mentagrophytes), Cryptococcus neoformans and
Epidermophyton floccosum. Using MIC and MLC values, it was observed that C. nepeta L populations rich in pulegone exhibited significant antifungal activity
against Aspergillus and dermatophyte strains (MIC = 0.32 to 1.25 mL mL⁻¹). In the other hand, S. olusatrum L. oils were particularly active against dermatophytes strains and C. neoformans (MIC = 0.32 to 0.64 mL mL⁻¹).
Concerning the cell wall structure of bacteria, some studies have reported that EOs show better activity against Gram-positive bacteria rather than Gram-negative bacteria. Marzoug et al. (2010), for example, observed this phenomenon by studying the antimicrobial activity of the EO of Eucalyptus (E.
gracilis, E. oleosa, E. salubris, and E. salmonophloia). Furthermore, Zarai et al.
(2011) reported the same antimicrobial activity while studying the EO of
Marrubium vulgare.
Finally, after analyzing all data collected in this literature review and as pointed out in a previous study by Lavinik (2013), we noted that it is difficult to
compare results from different studies because of the considerable variation among the methods used to evaluate the inhibitory effect of EOs on different microorganisms, such as: exposure of the microorganism to the oil, amount of emulsifier used, oil solubility and the type of microorganisms used in different tests.
Conclusion
This review suggests that there has been an improvement in the study of essential oils of vegetable origin and in the elucidation of their antimicrobial activity. Undoubtedly, essential oils have proven to be a promising source of biologically active compounds. Hence, further studies are needed in order to understand their therapeutic potential and to establish new treatments for pathogenic diseases.
Declaration of interest
The authors report no declarations of interest
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