Artículo original

Chemical composition and antioxidant and antibacterial activity of Ocotea quixos

Composición química y actividad antioxidante y antibacteriana de Ocotea quixos

Fredy Giovany Ortiz Calderón
Yudy Lorena Silva Ortiz
Paula Liliana Galeano García

Universidad de la Amazonia. Facultad de Ciencias Básicas. Grupo de investigación Bioprospección de los Productos Naturales Amazónicos. Florencia, Colombia.

E-mail address corresponding author: fregio1990@gmail.com

ABSTRACT

Introduction: Ocotea quixos (Lam.) Kosterm. ex O.C. Schmidt (Lauraceae) is a plant that grows in the Colombian Amazon Region. It is used in folk medicine as sweetener, eupeptic, tranquilizer, disinfectant and local anesthetic. Its bark is used for arthritis, chronic cold and hydropsy. Its antimicrobial and antifungal activity has also been reported, as well as its properties as antiplatelet, antithrombotic and vasorelaxant agent.
Objectives: Determine the chemical composition and the antioxidant and antibacterial activity of essential oils and methanolic extracts of O. quixos leaves and stems.
Methods: Essential oils from aerial parts (leaves and stems) of O. quixos (Lam.) Kosterm. ex O.C. Schmidt (Lauraceae) were obtained by hydrodistillation and analyzed by gas chromatography / mass spectrometry (GC-MS). O. quixos methanolic extracts were subjected to phytochemical analysis. Antioxidant activity, on the other hand, was evaluated by DPPH, ABTS and FRAP, lipid peroxidation by β-carotene / linoleate bleaching, and antibacterial activity by Kirby-Bauer testing on Sensi-Disc^™ paper disks using the gram-positive and gram-negative bacteria Staphylococcus aureus and Escherichia coli, respectively.
Results: Thirty-four volatile compounds were identified, the most abundant of which was trans-methyl-isoeugenol. The stem methanolic extract had a higher phenolic content and the best antioxidant activity with 65.26 ± 0.01% inhibition in the β-carotene / linoleate bleaching test, whereas the essential leaf oil exhibited the highest inhibition values against S. aureus and E. coli.
Conclusions: The methanolic extracts were found to have greater antioxidant potential and the essential oils greater antibacterial activity, due to the presence of chemical compounds such as a-terpineol and terpinen-4-ol, terpenes characterized by their antibacterial potential.

Key words: Ocotea quixos, chemical characterization, antioxidant properties, antibacterial activity.

RESUMEN

Introducción: Ocotea quixos (Lam.) Kosterm. ex O.C. Schmidt (Lauraceae) es una planta utilizada en la medicina popular como endulzante, eupéptico, tranquilizante, desinfectante y anestésico local. Su corteza ha sido empleada contra la artritis, el catarro crónico y la hidropesía. Además, se han reportado su actividad antimicrobiana y antifúngica, así como sus propiedades como antiplaquetario, antitrombótico y vasorelajante.
Objetivos: Determinar la composición química y la actividad antioxidante y antibacteriana de los aceites esenciales y de los extractos metanólicos de las hojas y los tallos de O. quixos.
Métodos: Los aceites esenciales de las partes aéreas (hojas y tallos) de O. quixos (Lam.) Kosterm. ex O.C. Schmidt (Lauraceae) se obtuvieron mediante hidrodestilación y se analizaron mediante cromatografía de gases acoplada a espectrometría de masas (CG-EM). Se estudiaron los extractos metanólicos de O. quixos mediante análisis fitoquímico. También se evaluó la actividad antioxidante mediante DPPH, ABTS y FRAP; la peroxidación lipídica mediante blanqueamiento de β-caroteno/linoleato y la actividad antibacteriana mediante la técnica de Kirby-Bauer con discos de papel Sensi-Disc™ usando las bacterias grampositiva y gramnegativa Staphylococcus aureus y Escherichia coli, respectivamente.
Resultados: Se identificaron 34 compuestos volátiles, el más abundante fue el trans-metil-isoeugenol. De todos los extractos, el extracto metanólico de los tallos presenta el mayor contenido fenólico y la mejor actividad antioxidante con 65,26 ± 0,01 % de inhibición en la prueba de blanqueamiento del β-caroteno/linoleato. El aceite esencial de las hojas presentó la mayor inhibición contra S. aureus y E. coli.
Conclusiones: Se evidenció mayor potencial antioxidante en los extractos metanólicos y mayor actividad antibacteriana en los aceites esenciales debido a sus compuestos químicos como el a-terpineol y terpinen-4-ol, terpenos que se caracterizan por tener potencial antibacterial.

Palabras clave: Ocotea quixos; caracterización química; propiedades antioxidantes; actividad antibacterial.

Recibido: 05/10/2016
Aprobado: 23/07/2018

INTRODUCTION

Colombian Amazonia is a region with a great variety of ecosystems and high biodiversity of animal and plant species. However, the use of these resources, in most cases, has been exploited on a big scale for commercial purposes. Especially the species of plants which possess gross and compact wood, it has been used only for timber.¹

Ocotea quixos (Lam.) Kosterm. ex O.C. Schmidt (Lauraceae) is a native and medium size tree from the Colombian and Ecuadorian Amazonia.² Traditionally, it is appreciated for its aromatic properties since Inca's times. O. quixos has been used as appetizer, eupeptic, disinfectant and local anesthetic.³ Due to its scent to cinnamon has known as "Ishpingo" in Ecuador⁴ and "Canelo de los Andaquíes" in Colombia.⁵ The calyces are traditionally used by the Amazonian indigenous people as a cinnamon spice for candies and cakes.⁴

As usually happens to many spices, a great part of the aroma and flavor is due to the presence of essential oils. The essential oils of the flowers of O. quixos are rich in phenylpropanoids compounds, such as the trans-cinnamic acid and methyl cinnamate.^6-7 Studies of the biological activity of the species are centered in its essential oils, which are related to anticoagulant, antifungal, antibacterial, antioxidant, and anti-inflammatory activities.^6,8-13

So far, only few studies about the biological activity and chemical composition of essential oils in flowers have been recognized for this specie located in Ecuador; however, there are no reports of investigations about biological activities and chemical characterization for this specie in the Colombian Amazonian region. For this reason, the aim of this paper is to determine the chemical composition, antioxidant and antibacterial activities of the essential oils and methanolic extracts of leaves and stems of O. quixos present in Colombian Amazonia.

METHODS

Obtention of essential oils and methanol extracts

To obtain the raw material of Ocotea quixos, the plants were collected in Las Lajas eco-park in Belén de los Andaquíes municipality (N: 01° 25´ 06.3 " W: 075° 52´ 24.7"). The specie was classified at the HUAZ herbarium of the Universidad de la Amazonia, voucher specimen (HUAZ 6742). The antioxidant and antibacterial analysis were performed in the Natural Products Lab at the "Macagual" Amazonia Research Center CIMAZ of the Universidad de la Amazonia, in Florencia-Caquetá (Colombia).

The essential oils were extracted by hydrodistillation of fresh vegetal material (leaves and stems) for 4 h with distilled water using a Clevenger type apparatus,¹⁴ yielded the following percentages of performance, leaves (0.96 %v/w) and stems (0.33 %v/w). The oils were then dried over anhydrous sodium sulphate and stored at -4 °C. The leaves and stems extracts were obtained by percolation in methanol for 7 days.

Chemical characterization of essential oils and methanol extracts

Essential oils from leaves and stems of O. quixos were analyzed with a gas chromatograph coupled to a mass selective detector (MSD, Agilent Technologies 5973) operated in the complete scanning mode of radiofrequencies (full scan). The column used in the analysis was DB-5MS (J & W Scientific, Folsom, CA, USA) [poly-5% diphenyl-95%-dimethyl-siloxane bonded phase column, 60 m x 0.25 mm x 0.25 µm]. The injection was performed in split mode (30:1) and volume of injection was 2 µL.¹⁵

The phytochemical analysis was performed in the methanol extracts by coloration and precipitation assays to denote the presence or absence of metabolites (alkaloids, flavonoids, tannins, coumarins, saponins, cardiac glycosides and sesquiterpene lactones).^16,17

Antioxidant activity and phenolic content

The antioxidant effect was assessed determining the capacity of removal the free radical and the reducing power of the compounds present in the methanol extracts. The antioxidant activity was compared with butylated hydroxytoluene (BHT), trolox and ascorbic acid standards. All assays were performed in triplicate. The radical scavenging assay DPPH (2,2-diphenyl-1-picrylhydrazyl)¹⁸ and radical scavenging ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) assay ¹⁹ were applied for free radical antioxidant activity and the activity was expressed as the half maximal inhibitory concentration IC ₅₀ (mmol/L).²⁰ The reducing power test (FRAP) of methanol extract was assessed according to Koehnlein and collaborators (2016) protocol.²¹ The reference curve was constructed using ascorbic acid as a primary standard. The reducing power was expressed as FRAP values (µmol ascorbic acid/g dry sample). The determination of the lipid peroxidation activity by β-carotene/linoleic acid bleaching assay described by Ozer and collaborators (2010)²² was determined using the following formula:

Where A₀ is the initial absorbance at time 0 and A_t is the final absorbance at time 120 minutes.

Phenolic content

Quantification of total phenol was performed in triplicate with Folin-Ciocalteu colorimetric method described by Tahiya and collaborators (2014),²³ and the results were expressed as mg gallic acid/g dry sample, based on a gallic acid standard curve (range: 0.12-2.03 mmol/L, r²= 0,918).

Antibacterial activity

Disc diffusion method was used to evaluate the antibacterial effects of both leaves and stems essential oils of O. quixos.²⁴ The essential oils were evaluated at different concentrations against S. aureus (Gram positive) and E. coli (Gram negative). The positive control was performed with a sensidisc of antibiotic (Tetracycline 30µg/mL) and the negative control sensidisc impregnated with solvent (DMSO).²⁵ All assays were performed in triplicate.

Statistical analysis

The antioxidant activity results were submitted to regression analysis based on its significance (F and p value) and higher coefficient of determination (R²). All tests were conducted using the statistical program InfoStat (Argentina, 2013).²⁶

The antibacterial values were submitted to a variance analysis comparing mean values with the Tukey test (p= 0.05) calculated by the Software InfoStat (Argentina, 2013).²⁶

RESULTS

Aiming to evaluate the composition and biological activities of the essential oils and methanolic extracts of the leaves and steam of O. quixos, we applied GC-MS and phytochemical characterization analysis and DPPH, ABTS, FRAP and lipid peroxidation assays for determinate the antioxidant activity of the extracts. Additionally, we determinate the antibacterial activity using disc diffusion with S. aureus and E. coli bacteria analysis.

The characterization of the volatile compound identified in the essential oils of leaves and steam of O. quixos using GC-MS analysis is summarized in the Table 1.

Table 1. Chemical composition of essential oils of leaves and stems of O. quixos

RI: Experimental retention indices from a DB-5MS column. RI^*: Theoric retention indexes
(Adams, 2007).²⁷ LEO and SEO indicate "Essential oil of leaves" and "Essential oil of steam", respectively.

In addition, the phytochemistry analysis of methanolic extracts indicates the presence of different secondary metabolites like tannins, saponins, cardiac glycosides and sesquiterpene lactones in both leaves and steam methanolic extracts. Additionally, stems methanolic extract exhibited the presence of flavonoids.

On the other hand, the Table 2 shows the antioxidant and lipid peroxidation results of the essential oils and methanolic extracts of leaves and steam of O. quixos.

LEO and SEO indicate "Essential oil of leaves" and "Essential oil of steam", respectively. LME and SME indicate "Methanol extracts of leaves" and "Methanol extracts of stems", respectively.

In terms of the antibacterial activity, a preliminary test with the leaves and steam methanol extracts reveals no inhibition activity against the bacteria (S. aureus y E. coli)). In contrast the essential oils exhibited inhibition halo, the results are summarized in Table 3.

DISCUSSION

Chemical composition

The most abundant chemicals in steam essential oil were the phenylpropanoids (97.4 %), mainly responsible for the cinnamon-like taste of the spice, including trans-cinnamaldehyde (36.70 %) and trans-methyl cinnamate (43.60 %). These results differ to previous reports about the predominance of compounds, such as, β-caryophyllene (19.00 %), α-humulene (14.20 %) and eremophyllene (11.40 %).¹³ In the other hand, trans-methyl-isoeugenol is reported in this specie second time, however in this compound is more abundant than other reports.²⁸ Compounds involved in the biosynthetic phenylpropanoids pathway accounted for a global 48.0 % in leaves essential oil and 97.4 % in stems essential oil.

Phenolic content and antioxidant activity

The phenolic content of compounds was performed only in methanol extracts because the essential oils are not soluble in the aqueous matrix of this technique. In methanolic extracts, the total phenolic content in stem methanol extract is higher than those reported in other plants of the same genre as Ocotea pretiosa.²⁹ It is likely due to the presence of flavonoids and tannins according to phytochemical analysis. This activity may be related to the high phenolic content, which proves the relationship between the antioxidant activity and total phenolic content.³⁰

Regarding the antioxidant activity, stems methanol extract showed greater radical scavenging activity (DPPH and ABTS) than leaves methanol extract, leaves and stems essential oils and BHT. Also, stems methanol extract had the highest reducing power according to FRAP assay. These results are probably due to the presence of phenylpropanoids compounds in the extract (phytochemical analysis).

Similarly, the antioxidant activity of leaves essential oil was highest than stem essential oil both in DPPH and ABTS. These activity is likely to vary according to the chemical composition (table 1); as leaves essential oil have 48.60 % phenylpropanoids, trans-methyl-isoeugenol represents 21.20% of total compounds. Several studies had reported that phenolic compounds derived from essential oils have presented strong antioxidant activity.^31-32 Generally, the essential oils of O. quixos present oxygenated monoterpenes such as 1,8-cineol, α-terpineol and terpinen-4-ol (table 1), which should influence the antioxidant activity since they have antioxidant properties.³³ Nevertheless, it is observed that the antioxidant activity of essential oils of O. quixos is lower than other essential oils, such as the calyx of the same O. quixos and the leaves ofOcotea odorífera (IC₅₀ in DPPH of 117.4 mmol/L).³⁴

The FRAP value of the leaves and stems extracts were more active than BHT. It is observed that the reducing ability of the extracts is proportional to the phenolic concentration as indicated by Oktay and collaborators (2003).³⁰ This result also asserts the phytochemical analysis, in which the stems methanol extract evidence presence of tannins and flavonoids.³⁵

In β-carotene/linoleate bleaching assay the essential oils show similar activity compared with essential oils of flowers of Ocotea bofo (75.82 ± 0.04 %).³⁶ However, the methanol extracts showed the activity more potent than BHT at the same concentration 4,538 mmol/L
(1 mg/mL). The methanol extracts have the ability for blocking the oxidation of β-carotene by active peroxyl radicals because of oxidation of linoleic acid molecules in the presence of molecular oxygen (O₂).³⁷

Antibacterial activity

In antibacterial activity, the results of these oils were relatively low compared with other essential oils reported in other species, such as in flowers of Ocotea bofo Kunth which presents an inhibition halo of 20 mm at 0.360 mmol/L against S. aureus and E. coli.³⁶ The essential oils of leaves and stems of O. quixos have oxygenated monoterpenes type compounds, such as 1,8-cineol and terpinen-4-ol in concentrations not exceeding 0.40% respectively; these compounds had been reported as good modulators of the antibacterial activity.³⁸ Recently there have been studies showing that phenolic compounds act as antimicrobials, such as derived of cinnamic acid whose activity is significant against S. aureus, L. monocytogenes, E. coli, P. aeruginosa.³⁹ In this study, leaves essential oil has 48.60 % and steam essential oil has 97.90 % phenylpropanoids compounds, they are probably the cause of this activity.

Acknowledgements

This work was supported by a grant from Colciencias, Caquetá Government and Universidad de la Amazonia. We thank to Isabel González, Biologist, for providing the plant material, we wish to thank Dr. Luis Eduardo Ortegón (RIP) for his advice and support in the trials of antibacterial activity and other people who contributed to the realization of this work.

REFERENCES

1. Salinas N, Cárdenaz D. Libro Rojo de Plantas Maderables de Colombia. Especies maderables amenazadas, parte I. Bogotá; 2006.

2. Jørgensen PM, León Yañez S. Catalogue of the Vascular Plants of Ecuador -Monographs in Systematic Botany from the Missouri Botanical Garden. Missouri; 1999.

3. Friedman J, Bolotin D, Rios M, Mendosa P, Cohen Y, Balick MJ. A novel method for identification and domestication of indigenous useful plants in Amazonian Ecuador. New York; 1993.

4. Rios M, Koziol MJ, Borgtoft P, Granda G. Plantas útiles del Ecuador: aplicaciones, retos y perspectivas. Quito; 2007.

5. Bernal R, Galeano Z, Cordero P, Cruz R, Díaz M, Gutiérrez A, Rodríguez H, Sarmiento H. Diccionario de nombres comunes de plantas de Colombia. Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Bogotá; 2006.

6. Bruni R, Medici A. Chemical composition and biological activities of Ishpingo essential oil, a traditional Ecuadorian spice from Ocotea quixos (Lam) Kosterm. (Lauraceae) flower calices. Food. Chem 2004;85:415-21.

7. Sacchetti GA, Guerrini P, Noriega A, Bruni R. Essential oil of wild Ocotea quixos (Lam.) Kosterm. (Lauraceae) leaves from Amazonian Ecuador. J Flav. Frag. 2006;21:674-76.

8. Ballabeni V, Tognolini M, Bertoni S, Bruni R, Guerrini A, Moreno G, Barocelli E. Antiplatelet and antithrombotic activities of essential oil from wild Ocotea quixos (Lam.) Kosterm. (Lauraceae) calices from Amazonian Ecuador. Pharm. Res 2007;55:23-30.

9. Ballabeni V, Tognolini M, Bertoni S, Bruni R, Guerrini A, Carmini G, Barocelli E. O. quixos Lam. essential oil: in vitro and in vivo investigation on its anti-inflammatory properties. Fitoterapia 2010;81:289-95.

10. Chao LK, Hua KF, Hu HY, Cheng SS, Lin IF, Chen CJ. Cinnamaldehyde inhibits pro-inflammatory cytokines secretion from monocytes/macrophages through suppression of intracellular signaling. Food Chem. Toxicology 2008;46:220-31.

11. Lee H, Kim BS, Kim MK. Suppression effect of Cinnamomum cassia bark derived component on nitric oxide synthase. J. Agric. Food. Chem 2002;50(26):7700-3.

12. Apodaca R, Dvorak C, Xiao W, Barbier A, Boggs J, Wilson S. A new class of diamine-based human histamine H3 receptor antagonists: 4 (aminoalkoxy) benzylamines. J. Med. Chem 2003;46:3938-44.

13. Noriega P, Dacarro C. Aceite foliar de Ocotea quixos (Lam.) Kosterm.: actividad antimicrobiana y antifúngica. La Granja 2008;7(1):3-8.

14. Hesham H, Rassem A, Abdurahman H, Rosli M. Techniques for extraction of essential oils from plants: A review. Aust. J. Basic & Appl. Sci 2016;10(16):117-27.

15. Sarikurkcu C, Ozer M, Cakir A, Eskici M, Mete E. GC/MS evaluation and in vitro antioxidant activity of essential oil and solvent extracts of an endemic plant used as folk remedy in Turkey: Phlomis bourgaei Boiss. Evid. Based Complement. Altern. Med 2013;1-7.

16. Shukla SH, Mistry HA, Patel VG, Jogi BV. Pharmacognostical, preliminary phytochemical Studies and analgesic activity of Amomum. Pharm Sci. Mon 2010;1:90-102.

17. Madhav NV, Upadhyaya K, Bisht A. Phytochemical screening and standardization of polyherbal formulation for dyslipidemia. Int. J. Pharma. Pharm. Sci 2011;3:235-38.

18. Asma HS, Moza TH, Hossain MA. Comparative evaluation of total phenols, flavonoids content and antioxidant potential of leaf and fruit extracts of Omani Ziziphus jujuba L. Sci Rev A: Nat Sci Eng 2016;18:201-205.

19. Corrêa RC, Haminiuk CW, Barros L, Dias MI, Calhelha RC, Kato CG, Correa VG, Peralta RM. Stability and biological activity of Merlot (Vitis vinifera) grape pomace phytochemicals after simulated in vitro gastrointestinal digestion and colonic fermentation. J. Funct. Foods 2017,36:410-17.

20. Carbonari K. Avaliação do Potencial Antioxidante (in vitro e in vivo) e Antiinflamatório deOuratea parviflora, Polymnia sonchifolia e Marlierea obscura. Dissertação de Mestrado em Biotecnologia, Centro de Ciências Biológicas/Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brasil. 2005.

21. Koehnlein EA, Koehnlein EM, Gomes RC, Nishida VS, Correa VG, Bracht A, Peralta RM. Analysis of a whole diet in terms of phenolic content and antioxidant capacity: Effects of a simulated gastrointestinal digestion. Int. J. Food Sci. Nut 2016;67:614-23.

22. Ozer M, Sarikurkcu C, Tepe B, Can S. Essential oil composition and antioxidant activities of alkanet (Alkanna tinctoria subsp. tinctoria). Food Sci. Biotechnol 2010;19:1177-83.

23. Tahiya H, Amira M, Hossain A, Afaf R, Qasim H. Comparative study of phytochemical screening, antioxidant and antimicrobial capacities of fresh and dry leaves crude plant extracts of Datura metel L. J. King Suad Uni. Sci 2014;237-43.

24. Cockerill FR III, Wikler MA, Alder J, et al. Performance Standards for Antimicrobial Disk Susceptibility Tests; Approved Standards - Eleventh Edition. vol. 32. Wayne, PA: CLSI (Clinical and Laboratory Standards Institute); 2012, 58p.

25. Rota C, Carramiñana JJ, Burillo J, Herrera A. In vitro antimicrobial activity of essential oils from aromatic plants against selected foodborne pathogens. J. Food Prot 2004;67:1252-56.

26. InfoStat: Licencia: Di Rienzo JA, Casanoves F, Balzarini MG, Gonzalez L., Tablada M, Robledo CW. InfoStat versión 2013. Grupo InfoStat, FCA, Universidad Nacional de Córdoba, Argentina. URL http://www.infostat.com.ar

27. Adams RP. Identification of essential oil components by gas chromatography / mass spectrometry. USA. 2007.

28. Scalvenzi A, Yaguache B, Cabrera P, Guerrini A. Actividad antifúngica in vitro de aceites esenciales de Ocotea quixos (Lam) Kosterm y Piper aduncum L. Bioagro 2016;28(1):39-46.

29. Rodrigues D, Frederiksen A, Ataíde da Silva A, Franco D, Skibsted L. Sugarcane spirit extracts of oak and Brazilian woods: antioxidant capacity and activity. Eu. Food Res. Tech 2008;227:1109-16.

30. Oktay M, Gülςin I, Küfrevioglu ÖI. Determination of in vitro antioxidant activity of fennel (Foeniculum vulgare) seed extracts. Lebens-Wiss Technol 2003;36:263-71.

31. Teissedre P, Waterhouse A. Inhibition of Oxidation of Human Low-Density Lipoproteins by Phenolic Substances in Different Essential Oils Varieties. J. Agric. Food. Chem 2000;48:3801-05.

32. Zheng W, Wang S. Antioxidant activity and phenolic compounds in selected herbs. J. Agric. Food. Chem 2001;49:5165-70.

33. Tepe B, Daferera D, Sokmen M, Polissiou M, Sokmen A. The in vitro antioxidant and antimicrobial activities of the essential oil and various extracts of Origanum syriacum L. J. Sci. Food Agric 2004;84(11):1389-96.

34. Cansian RL, Mossi AJ, Paroul N, Toniazzo G, Zboralski F, Prichoa F, Kubiak GB, Lerin LA. Atividade antioxidante e antimicrobiana de extratos de canela-sassafrás (Ocotea odorifera (VELL.) ROWHER). Perspectiva, Erechim 2010;34 (127):123-33.

35. Skerget M, Kotnik P, Hadolin M, Rizner A, Simonic M, Knez Z. Phenols, proanthocyanidins, flavons and flavonols in some plant materials and their antioxidant activities. Food Chem 2005;89:191-98.

36. Guerrini A, Gianni S, Muzzoli V, Moreno M, Medici A, Besco E, Bruni R. Composition of the volatile fraction of Ocotea bofo Kunth (Lauraceae) calyces by GC-MS and NMR fingerprinting and its antimicrobial and antioxidant activity. J. Agric. Food. Chem 2006;54(20):7778.

37. Abdolrasoul H, Ebrahimabadi Asma M, Fereshteh J, Zahra D, Hossein B. Essential oil composition and antioxidant and antimicrobial properties of the aerial parts of Salvia eremophila Boiss from Iran. Food Chem Toxicol 2010;48:1371-76.

38. Pattnaik S, Subramanyam VR, Bapaji M, Kole CR. Antibacterial and anti-fungal activity of aromatic constituents of essential oils. Microbios 1997;89 (358):39-46.

39. Saavedra MJ, Borges A, Dias C, Aires A, Bennett RN, Rosa ES, Simões M. Antimicrobial activity of phenolics and glucosinolate hydrolysis products and their synergy with streptomycin against pathogenic bacteria. Med Chem 2010;6:174-83.

Conflicto de intereses

Los autores expresan que no tienen conflicto de intereses.