Chemical composition and antioxidant and antibacterial activity of Ocotea quixos

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 At 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

 

Compounds

 

RI

 

RI *

Abundance (%)

LEO

SEO

 1

Benzaldehyde

965

960

0.2

0.3

 2

Limonene

1033

1029

0.3

 3

Benzyl alcohol

1036

1032

0.2

 4

1,8-Cineol

1037

1031

0.2

0.3

 5

Hydroxy-cinnamic aldehyde

1168

1160

0.3

 6

Terpinen-4-ol

1187

1177

0.2

 7

α-Terpineol

1201

1189

0.2

0.3

 8

cis -Cinnamaldehyde

1226

1219

0.3

 9

trans -Cinnamaldehyde

1281

1270

1.3

36.7

10

trans -Cinnamyl alcohol

1311

1304

6.5

1.4

11

α-Copaene

1386

1377

0.6

12

Methyl trans-cinnamate

1393

1379

0.6

43.8

13

β-Elemene

1397

1391

0.6

14

trans -Cinnamic acid

1430

1454

1.7

15

trans -β-Caryophyllene

1435

1419

8.7

16

α-Guaiene

1446

1440

0.2

17

trans -Cinnamyl acetate

1451

1446

12.3

10

18

cis -Methyl-isoeugenol

1455

1454

0.4

19

α-Humulene

1471

1455

11.2

0.3

20

trans -Methyl-isoeugenol

1498

1492

21.7

4.6

21

β-Selinene

1504

1490

6.9

0.3

22

α-Selinene

1510

1498

3.7

23

δ-Amorfene

1528

1512

1.5

0.3

24

7-Epi-α-selinene

1535

1522

0.8

25

o -Methoxycinnamaldehyde

1536

1529

0.3

26

α-Calacorene

1555

1546

0.6

27

Espatulenol

1592

1578

3.5

28

Caryophyllene oxyde

1600

1583

5.6

29

Humulene epoxide II

1629

1608

2.9

30

Muurola-4,10(14)-dien-1-β-ol

1640

1630

0.8

31

10,10-Dimethyl-2,6-dimethylenbicicle [7.2.0]

undecan-5-β-ol

1655

1650

1.3

32

Selin-11-en-4-α-ol

1677

1660

1.2

0.3

33

Caryophylenol II

1685

1672

1.3

34

Benzyl benzoate

1782

1760

3.7

0.3

Family compound

Abundance (%)

Monoterpenes hydrocarbons

0.3

Oxygenated monoterpenes

0.6

0.9

Sesquiterpenes hydrocarbons

34.8

0.9

Oxygenated sesquiterpenes

16.4

0.3

Phenylpropanoids

48.0

97.4


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.

 

 

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Conflicto de intereses

Los autores expresan que no tienen conflicto de intereses.