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Antioxidant activity of essential oils from leaves of Schinus lentiscifolius Marchand
Actividad antioxidante del aceite esencial de las hojas de Schinus lentiscifolius Marchand
Eliane
Regina da Silva1* http://0000-0003-3993-3943
Ângela Pawlowski2
http://0000-0002-6098-5118
Diana Carla Lazarotto1
http://0000-0002-9811-289
Geraldo Luiz Gonçalves
Soares1 http://0000-0002-8976-1935
1Instituto de Biociências, Universidade Federal do Rio Grande do
Sul. Brasil
2Instituto
Federal de Educação, Ciência e Tecnologia Farroupilha, Campus
Santo Ângelo. Brasil
*Corresponding author: anesilva.bio@hotmail.com
ABSTRACT
Introduction:
Extracts and essential oils from Schinus spp. (Anacardiaceae) have been
evaluated for their biological activities. Some Schinus essential oils
have antioxidant properties.
Objective:
Determine the antioxidant capacity of the essential oil from leaves of Schinus
lentiscifolius Marchand (carobá).
Methods:
Antioxidant activity was determined by the 1.1-diphenyl-2-picrylhydrazyl (DPPH)
radical method. For analysis, the essential oil was dissolved in methanol at
concentrations of 20, 40, 60, 80 and 100 mg/ml. Thymol was used as standard
antioxidant.
Results:
Antioxidant activity of S. lentiscifolius essential oil was found to
depend on the dose, reaching 54.4% at 100 mg/ml. However, thymol displayed stronger
activity than S. lentiscifolius oil at a lower concentration (25 mg/ml).
Conclusions:
Essential oil from S. lentiscifolius leaves displayed moderate antioxidant
activity. This may be due to the presence of some monoterpenes in the oil.
Key words: DPPH method, free radical capture, terpenes, Anacardiaceae.
RESUMEN
Introducción:
Los extractos y aceites esenciales de Schinus spp. (Anacardiaceae) han
sido evaluados con respecto a sus actividades biológicas. Algunos aceites
esenciales de Schinus poseen propiedades antioxidantes.
Objetivo:
Determinar la capacidad antioxidante del aceite esencial de las hojas de Schinus
lentiscifolius Marchand (molle ceniciento, aroeira-cinzenta).
Métodos:
Se evaluó la actividad antioxidante por el método DPPH (1,1-difenil-2-
picrilhidrazilo). Se utilizó el aceite esencial disuelto en metanol en
concentraciones de 20, 40, 60, 80 y 100 mg/mL. Se usó timol como el antioxidante
estándar.
Resultados:
La actividad antioxidante del aceite esencial de S. lentiscifolius estuvo
en dependencia de la dosis y alcanzó 54,4 % a 100 mg/mL. Sin embargo, el
timol mostró una actividad más fuerte que el aceite de S. lentiscifolius
en una concentración más baja (25 mg/mL).
Conclusiones:
El aceite esencial de las hojas de S. lentiscifolius presentó actividad
antioxidante moderada, lo cual puede estar relacionado con algunos monoterpenos
presentes en el aceite.
Palabras clave: método DPPH; captación de radicales libres; terpenos; Anacardiaceae.
Recibido: 22/05/2018
Aprobado: 10/01/2019
INTRODUCTION
Schinus genus (Anacardiaceae) comprises 29 species, from subshrubs to tall trees. Natural distribution of the genus is generally limited to South America.(1) Schinus lentiscifolius Marchand is a tree with opaque, smooth, and glabrous leaves that is found in grasslands, especially in stony soils.(2) In folk medicine, S. lentiscifolius is used as antiseptic, antimicrobial and to treat wound healing.(3) The use of Schinus spp. in folk medicine has stimulated investigation of biological activities of their extracts and essential oils.(4) Nevertheless, little is known about biological activities of S. lentiscifolius, except by its phytotoxic(5) and antibacterial(3) effects.
The antioxidant activity of some Schinus essential oils and extracts has been reported. Regarding essential oils, antioxidant activity was observed for leaf and fruit oils of S. molle L. and S. terebinthifolius Raddi.(6-8) In addition, studies reported the activity of S. areira L., S. longifolius (Lindl.) Speg., S. fasciculatus (Griseb.) I.M. Johnst. and S. praecox (Griseb.) Speg. essential oils.(4,9) However, no study has investigated the potential antioxidant effects of S. lentiscifolius. Hence, this study aimed to evaluate the antioxidant activity of S. lentiscifolius leaf essential oil.
METHODS
Leaves of S. lentiscifolius were collected in the city of Encruzilhada do Sul (30° 31' S, 52° 31' W), Rio Grande do Sul State, Brazil. Samples were identified and a voucher (164708) was deposited in the herbarium ICN of the Universidade Federal do Rio Grande do Sul, Brazil. Leaves were dried at room temperature. The essential oil was obtained by hydrodistillation in a modified Clevenger apparatus and stored at -80 °C. Chemical characterization of this essential oil was carried out in a previous study.(5)
Antioxidant activity was evaluated by the DPPH (1,1-diphenyl-2-picrylhydrazyl) method, which is based in evaluating the ability of compounds to scavenge the stable free radical DPPH. Schinus lentiscifolius leaf essential oil was diluted in methanol at the concentrations of 0 (control), 20, 40, 60, 80 and 100 mg/mL. The positive control was thymol, which was diluted in methanol at the concentrations of 1, 5, 10, 15, 20 and 25 mg/mL. Tests were conducted as described by Silva et al., (10) and all measurements were performed in triplicate. Antioxidant activity (%) was calculated according to the equation: Antioxidant activity (%) = [(Ac - As)/(As)] * 100, where Ac is the absorbance of control and As is the absorbance of the sample.
RESULTS
Chemical characterization of the S. lentiscifolius essential oil has been previously reported(5) (exactly the same essential oil sample used herein). The essential oil was mostly composed by sesquiterpene hydrocarbons (41.5 %), followed by monoterpene hydrocarbons (27.7 %), oxygenated sesquiterpenes (26.2 %), and oxygenated monoterpenes (4.6 %). Some compounds present in representative amounts were δ-cadinene (14.4 %), limonene (8.14 %), sabinene (5.08 %), α-cadinol (4.91 %), α-pinene (4.80 %) and terpinen-4-ol (3.85 %).
Schinus lentiscifolius leaf essential oil showed dose-dependent antioxidant activity (fig.), with 54.4 % activity at 100 mg/mL, the highest concentration in methanol (Fig. A). Thymol reached 91.6 % antioxidant activity at 25 mg/mL (Fig. B), which demonstrates about 37.2 % more effectiveness than the highest concentration of S. lentiscifolius essential oil.
DISCUSSION
Antioxidant activity of S. lentiscifolius may be related to some of the main components of the essential oil that present antioxidant activity, such as the monoterpenes sabinene (strong activity), limonene and terpinen-4-ol (moderate activity). The monoterpene hydrocarbons α-terpinene, γ-terpinene and terpinolene, which are present in minor amounts in the oil, also possess strong activity.(11) Nevertheless, S. lentiscifolius oil was not very effective compared to thymol, the standard antioxidant.
The activity of S. lentiscifolius essential oil observed herein was not as strong as of essential oils of other Schinus species. However, in some cases, Schinus species that showed effective antioxidant properties, such as S. terebinthifolius andS. molle, presented weak activity in other studies.(8,12) Differences in activity level can occur because composition of essential oils may vary according to climatic factors(13), fertility regime(14), location, plant density(15), soil type(16) and methods for drying plant material.(17) Therefore, antioxidant activity of S. lentiscifolius should not be completely disregarded yet. Further studies should use other tissues of S. lentiscifolius, as well as other chemotypes that could present higher amounts of monoterpenes with strong antioxidant activity.
Acknowledgments
The authors thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for the Ph.D. scholarship granted to the first author.
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Conflicto de intereses
Los autores expresan que no tienen conflicto de intereses.
Contribución de los autores
E.
R. Silva defined the experimental design, performed the experiments and
wrote the manuscript.
 Pawlowski
and D.C. Lazarotto defined the experimental design, performed the experiments
and revised the manuscript.
G. L. G. Soares
defined the experimental design and revised the manuscript.