Abstract: The essential oils of the aerial parts of two populations of Moricandia arvensis in the Setif region (Algeria) were analyzed by gas chromatography and mass spectrometry (GC-MS). Thirty compounds were identified from the oils of M. arvensis, representing 80.8% of the total essential oil of southern population and 19 compounds of the population north of Setif, representing 93% of total oil. The analysis showed that the essential oils are rich in fatty acid (34.1-22.1%). The major constituent are palmitic acid (13.2-12.9%) and the phytol (7.9-10.5%). The Setif population is characterized by 3-butenylisothiocyanate and Octadecanoic acid, 2-hydroxy-1,3-p. The effects of these oils on the growth of Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853) and Staphylococcus aureus (ATCC 25923) were investigated by the diffusion method. The oils showed no significant antibacterial activity.
INTRODUCTION
Moricandia arvensis, Brasicaceae family, includes five subspecies distributed in northern Africa; the studies on essential oils of this species are rare. The Brassicaceae is very rich in glucosinolates and sulfur compounds responsible for strong odors (Vaughn and Berhow, 2005); hydrolysis of these glucosonates can provide fatty acids (Rash et al., 2001; Jones et al., 2006). Rodriguez et al. (2006) have identified the 5-methylthiopentane-nitrile as majority component in Diplotaxis tenuifolia. The Isothiocyanates and nitrile have been identified in Lepidium coronopus by Radulovic et al. (2008) and in Arabidopsis thaliana by Rohloff and Bones (2005); Majetic et al. (2007). The major product of Lepidium meyenii is the phenyl acetonitrile (Tellez et al., 2002). The major component in oil of Raphanus sativus is the phytol (Blazevic and Mastelic, 2009), while that of the fruits of the same species is the 3-butenyl isothiocyanate (Mastelic et al. 2008; Taveira et al., 2009).
M. arvensis is rich in sulfur compounds, glucosinolates and isothiocyanates (Fahey et al., 2001). The indole glucosinolates is reported in M. arvensis (Belkhiri and Lockwood, 1990). The study of Braham et al. (2005) allowed the isolation of eight phenolic glycosides.
A number of studies have suggested that cruciferous vegetables have anticarcinogenic activity (Graham, 1983; Wattenburg, 1972). Glucosinolates are biologically active secondary metabolites found in the Brassicaceae and related families (Raybould and Moyes, 2001; Fahey et al., 2001; Tokuhisa et al., 2004; Aaron et al., 2005).
Moricandia arvensis is a dietetic species (Local Food-Nutraceuticals Consortium, 2005); it shows an important antioxidant activity and also serves as a source of various products, including polyphenols (Braham et al., 2005). The leaves of M. arvensis are used in traditional cooking. Decoctions of leaves and stems were employed in the treatment of syphilis (Le Floch, 1983) and scorbut (Cheieb and Boukhris, 1998).
The aims of the present study were to identify and compare the composition of essential oils of M. arvensis and determine the antibacterial activity.
MATERIALS AND METHODS
Plant material: The aerial parts of Moricandia arvensis were collected from two Setif regions (north and south) (Algeria) in April 2010. A voucher specimen is deposited in the Herbarium of the Biology Department of Ferhat Abbas University (Algeria). Leaves, flowers and branches were dried at room temperature for 7 days and used for analyses.
Essential oil analysis: The essential oils were extracted by hydrodistillation of dried plant material using a Clevenger-type apparatus for 3 h. The oils were stored in sealed glass vials at 4-5°C prior to analysis. Yield based on dry weight of the sample was calculated. The essential oil were analysed on a Hewlett-Packard gas chromatograph Model 5890, coupled to a Hewlett-Packard MS model 5871, equipped with a DB5 MS column (30 m X 0.25 mm; 0.25 μm), programming from 50°C (5 min) to 300°C at 5°C mn-1, 5 min hold. Helium as carrier gas (1,0 mL min-1); injection in split mode (1 : 30); injector and detector temperature, 250 and 280°C respectively. The MS working in electron impact mode at 70 eV; electron multiplier, 2500 V; ion source temperature, 180°C; mass spectra data were acquired in the scan mode in m/z range 33-450. The compounds assayed by GC in the different essential oils were identified by comparing their retention indices with those of reference compounds in the literature and confirmed by GC-MS by comparison of their mass spectra with those of reference substances (Adams, 2001).
Evaluation of the antibacterial activity: The antibacterial activity of the oil was carried out by the disc diffusion method, according to the National committee of clinical laboratory standards against three of American Type Culture Collection (ATCC) namely: Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Staphylococcus aureus (ATCC 25923) which were obtained from the Microbiology and Parasitology Laboratory of Ferhat Abbas University Hospital. It was performed using an 20 h culture growth at 37°C and adjusted to approximately 105 CFU mL-1. Five hundred microliters of the bacterial suspension was spread on the surface of Muller-Hinton Agar plates. Sterile filter paper disks (Whatman No. 1.6 mm in diameter) containing 10 μL of each dilution of the oil (half, 1/4 and 1/8 v/v in the absolute ethanol) were placed on the surface of the media. The plates were left 30 min at room temperature to allow the diffusion of the oil and then they were incubated at 37°C for 24 h. At the end of this period, the inhibition zones were measured. All the experiments were performed in triplicate. Positive (Gentamycin, 10 μg disc-1) and negative controls (10 μL ethanol) were also included in the test.
RESULTS AND DISCUSSION
The extraction of essential oils of two populations of Moricandia arvensis (L.) DC., presents an average yield of 0.065%. This yield is 0.07% for the southern population of Setif and 0.06% for the north population.
The analysis of essential oils by GC and GC/MS enabled the identification of 4 alkanes, one alkene, 7 fatty acids, six alcohols, one aldehyde, three ester and two derivatives of glucosinolates, which 2 sulfur compounds and one isothiocyanate. In total, 30 compounds were identified in the population of southern Setif and 19 in the population of the north (Table 1). Fatty acids are predominant in the essential oil of M. arvensis, to 34.1% for the population of southern Setif and 22.1% for the population of the north, followed by the glucosinolates (23.5-12%). The two dominant compounds in the essential oil of M. arvenssis are palmitic acid (13.2-12.9%) and phytol (7.9-10.5%). The population of southern Setif differs from the north of Setif by the presence of 3-butenylisothiocyanate (11.9%), the octadecanoic acid (10.3%), the heptacosane and the pentadecanoic acid (2%).
Many essential oils, derived of plant, are known to exhibit antimicrobial activity against a wide range of bacteria and fungi. The in vitro antibacterial activity of the Moricanda arvensis essential oil in comparison with Gentamicin is shown in Table 2. The bacteria tested were resistant to all concentrations of essential oils studied, except for the half dilution of the essential oil of population of northern Setif which has showed a moderate activity against Escherichia coli and Staphylococcus aureus, with a diameter of 9 and 15 mm, respectively.
The result yield of M. arvensis is similar to that obtained by Rodriguez et al. (2006) for Diplotaxis tenuifolia (0.079%). This performance can be considered low compared to other species of Brassicaceae, such as Raphanus sativus (0.18%) (Blazevic and Mastelic, 2009).
The components identified in our study characterizes almost all species of Brasicaceae. The studies conducted on the phytochemical M. arvensis shows that this species contains phenolic glycosides, indoles, derivatives of glucosinolates and the fatty acid (Belkhiri and Lockwood, 1990; Bennett et al., 2004; Braham et al., 2005). Glucosinolates are compounds containing sulphur and nitrogen, they characterize the Brassicaceae family and neighboring families of Caparales order (Chen and Andreasson, 2001; Hopkins and Evrard, 2003; Yan and Chen, 2007).
Twenty Two chemical components identified in M. arvensis essential oils are identical to those found in other species of the Brassicaceae cited by Rohloff and Bones (2005), Mastelic et al. (2008) and Blazevic and Mastelic (2009).
| Table 1: | Chemical composition of M. arvensis essential oil |
| Table 2: | Antibacterial activity of Moricandia arvensis oil in vitro |
| P1: Setif south, P2: Setif north, Gen.: Gentamicine (10 μg disk-1); Inhibition zone (diameter of the disk, 6 mm, include), values represent average of three determination | |
Glucosinolates and these derivatives have various applications due to their antibacterial properties (Al-Gendy et al., 2010), antifungal (Rodriguez et al., 2006), antioxidants (Skandrani et al., 2008) and anti-nutrients in food (Hopkins and Evrard, 2003; Jahangir et al., 2009) but present results show that the oil of Setif populations has no bacterial activity.
In brief, essential oils analysis carried out on the populations of M. arvensis showed both inter-specific variability in their essential oil composition; but the abundance of majorities’ compounds were emphasized.
ACKNOWLEDGMENT
This study was supported, in part, by the Chemi. and Hetero. Laboratory, Blaise Pascal University and MESRS of Algeria.