Chemical Composition and Aromatic Profiles of Essential Oil from Rosa laevigata by GC-MS / GCO Analysis

Chemical composition and aroma of essential oil from the fruit of Rosa laevigata obtained by steam distillation was analyzed by Gas Chromatography-Mass Spectrumeter (GC-MS) and Gas ChromatographyOlfactometry (GC-O). Sixty seven compounds in the essential oil, accounting for 99.97%, were identified, in which palmitic acid (16.49%), cis-13-Octadecenoic acid (16.31%) and Linoleic acid (13.93%) were the main compounds. The overall aroma of the oil was comlex, smelled waxy, heavy refreshing and sweet and strong woody with a tiny tea. 24 aroma compounds were identified by the technique of GC-O with a posterior intensity method. The key active odor compound in this essential oil is myristic acid.


INTRODUCTION
Rosa laevigata Michx, belonging to the family of Rosaceae, is an evergreen climbing shrub which abundantly distributed in China.The fruit of this plant had a long history to be used for food and herbal medicines.Some studies have been reported that the fruit of Rosa laevigata has an influence on treating nocturnal emission, enuresis, frequent urination, vaginal discharge metrorrhagia, chronic diarrhea and other diseases (Zhang et al., 2004;Zou et al., 2006).The fruit was also used to make wine for a long time and this plant comes to be a remarkable fruit recently.
It is known that the fruit of Rosa laevigata contains abundant polysaccharides, saponins and flavonoids, which have strong abilities for eliminating active oxygen, anti-inflammatory and anti-tumor (Chen and Zhang, 2005;Wu et al., 2009;Xiao and Liu, 2006;Zhao et al., 2003).Moreover, it has been found that the total flavonoids from the fruit had hepatoprotective activity in mice treated by paracetamol (Dong et al., 2013;Liu et al., 2011).Natural essential oil has been widely and effectively applied in medicine, additive, cosmetics and so on.Therefore, it is necessary to study the essential oil from the fruit of Rosa laevigata.
Gas Chromatography-Olfactometry (GC-O) is a valuable technique for selection of odor active compounds from a complex mixture, (Grosch, 1993) which was developed by Fuller et al. (1964).Several methods have been developed to collect and process GC-O data and to estimate the sensory contribution of single odor active compound (Dravnieks and O'Donnell, 1971).One of the GC-O techniques is posterior intensity methods, which proposes the odor intensity measurement of a compound and its posterior scoring on a previously determined scale (Zellner et al., 2008).This method has been reported in some literatures (Van Ruth and O'Connor, 2001).It has been applied to evaluate volatile compounds of fruits (Casimir and Whitfield, 1978) and dairy products (Arora et al., 1995;Cadwallader and Howard, 1998).Nowadays, in order to identify the odor active volatile compounds more accurately, GC-O was always combined with GC-MS (Goodner et al., 2006;Marquez et al., 2013).
Aim of this study was to identify chemical compositions and main aromatic active compounds of the essential oil from fruit of Rosa laevigata.

MATERIALS AND METHODS
Plant materials: Rosa laevigata fruits were harvested from Zhejiang province of China, in September 2014.They were roughly processed in Anhui province of China (Tongling Hetian medicine Pieces Ltd), in October 2014.Those fruits were semi-crushed for oil extraction.Extraction of the essential oil: An ultrasonic bath at 400 W was used to treat with 300 g of semi-crushed Rosa laevigata fruits for 30 min.Then the fruits were hydrodistilled for 3 h, using a modified Clevenger apparatus with 400 mL water to yield about 0.1% of essential oil.Anhydrous sodium sulphate (Na 2 SO 4 ) was used to remove water from the oil.The treated oil was stored in a sealed brown glass vial at 4°C for the following use.

GC-MS analysis:
Chemical compositions of the essential oil were analyzed by GC-MS (Agilent 7890-5975, Agilent Technologies Inc, USA).DM-WAX MS column (0.25 mm×30 m ID, 0.25 μm film thickness, Dikma Technologies Inc, USA) was used.The column temperature was programmed from 100 to 235°C at a 3°C/min first and then from 235 to 245°C at a 10°C/min, finally kept the final temperature for 10 min.The injector temperature was 250°C and flow rate of the carrier gas (He) was 0.8 mL/min.The essential oil was diluted with ethanol of 1:50.The volume of injected solution was 1 μL, splitless.Mass spectrometry analysis was performed in the Electron Impact (EI) ionization mode (70 eV) in the m/z range of 35-400 amu.The ion source temperature was 230°C and the interface line temperature was 280°C.

GC-O analysis:
Aromatic profile of the essential oil was analyzed by GC-O instrument (Agilent 7890, Agilent Technologies Inc, USA).The column model, program temperature, injector temperature and other parameters were set the same as these in GC-MS analysis.
The essential oil was diluted with ethanol at 1:5 and 1:10 for injection, respectively.The aroma profiles, retention time and intension were recorded during the analysis process manually by three scent guiders.Posterior intensity analysis: Posterior intensity method involves recording the odor intensity on a scale after a peak has eluted from the column (Van Ruth, 2001).The experienced experts measured and recorded the intensity of every aroma components by using five odor intensity notations, shown in Table 1.This posterior registration of the perceived intensity may cause a considerable variance between assessors (Zellner et al., 2008).However, this is a fast accurate method to find characteristics of aroma components from the essential oil.

Identification of compositions:
Compositions of the oil were identified by direct comparison with authentic samples in some literatures (Adams, 2007;Miyazawa et al., 2007).

RESULTS AND DISCUSSION
The essential oil was obtained by steam distillation from the fruits of Rosa laevigata and achieved the yield of about 0.1%.In GC-MS, 67 compounds in the oil were detected, as shown in Fig. 1. 58 components were identified, as shown in Table 2, which took up about 99.97% of the total oil .In these compounds, long carbon chain acids predominated with about 51.69%, followed by esters (27.48%) and alcohol (1.40%).Some main compounds identified in the essential oil were palmitic acid (16.49%), cis-13-Octadecenoic acid (16.31%), linoleic acid (13.93%), ethyl linoleate (7.05%), ethyl palmitate (6.39%), ethyl oleate (6.39%),The overall aroma of the oil was complex, smelled waxy, heavy refreshing and sweet and strong woody with a tiny tea.24 aroma compounds in essential oil were identified by three scent guiders, as shown in Table 1.In these aromatic compounds, myristic acid had a strong refreshing and heavy burnt aroma accompanying with fishy smell.Therefore, it played an important role in the characteristic aroma of the essential oil.Using the value of Dilution Factor (FD) and Odor intensity, two histograms were obtained, as shown in Fig. 2 and 3, respectively.In Fig. 2, the odor intensity of myristic acid is the biggest of all the compounds.Octanoic acid, 6, 10, 14-trimethyl-2pentadecanone, ethyl palmitates and two unknown compounds also have a relatively large odor intensity.All these compounds are the main ingredients for the odor of this essential oil.In Fig. 3, five compounds, ethyl oleate, ethyl linoleate, ethyl linolenate, palmitic acid and 4, 8, 12, 16-tetramethyl heptadecan-4-olide, whose FD factor reached 50 were considered to be the major impact for the odor of the essential oil.Structures of the five main aromatic compositions have been shown in Fig. 4.

Fig. 1 :
Fig. 1: Total ion chromatogram of the essential oil from R. laevigata

Table 1 :
Five odor intensity notation

Table 2 :
Chemical compositions and aromatic profiles of the essential oil from R. laevigata