The composition of the essential oil from the fruit seeds of Monodora myristica Gaertn. (Annonaceae) was studied by capillary gas chromatography. The analysis using a combination of retention indices and combined Gas Chromatography/Mass Spectrometry (GC/MS) led to the identification of 30 components. The oil contains mainly monoterpenoids (93.2%) out of which 77.4% are monoterpene hydrocarbons and some sesquiterpenoids (5.8%) The major constituents were α-phellandrene (34.4%) and p-cymene (22.2%). The essential oil effects on the cardiovascular system were studied by recording the amplitude and frequency of the frog isolated heart contractions and by recording arterial blood pressure variations of the guinea pig. At the dose of 40, 80 and 120 μL kg-1 the essential oil induced a hypotensive effect on the blood pressure and at the dose of 0.01-0.05%. It reduced significantly the cardiac contractions of the isolated heart; however at 0.06% it totally stopped the cardiac contractions. Both these effects conducted in the present study could contribute to the anti hypertensive activity of the Monodora myristica essential oil.
How to cite this article:
J. Koudou, A.W. Etou Ossibi , K. Aklikokou , A.A. Abena , M. Gbeassor and J.M. Bessiere , 2007. Chemical Composition and Hypotensive Effects of Essential Oil of Monodora myristica Gaertn.. Journal of Biological Sciences, 7: 937-942.
Monodora myristica Gaertn. (Annonaceae) is a perennial tree growing in the tropical rainforest from Liberia to Angola. It is a wild plant among the most used as food and drug. In developing countries several plants give edible products: Fruits, seeds, leaves, flowers, nuts, oils, mushrooms and honey, which take a large place in the local diet and could strongly overcome or ameliorate prevailing food and health problems (Betti and Nzooh, 1998; Okwu, 2001; Tatsadjieu et al., 2003; Oboh, 2004; Okpeton et al., 2004; Tchiegang et al., 2005). The distinction between food and drug is not always clear. So, the seeds of Monodora myristica, in this case, possess these two properties and have carried us to pursue its study.
Data on Monodora myristica traditional uses are collected by personal contact with local traditional healers. In Central African Republic the seeds of fruit are used as condiment and drug in the treatment of headache and hypertension.
Earlier studies on Monodora myristica have reported the chemical composition and the evaluation of antimicrobial activities of essential oils collected in other countries (Cimanga et al., 2002; Tatsadjieu et al., 2003; Oussou et al., 2004; Nguefack et al., 2004; Odoh, 2004; Agnaniet et al., 2004).
The present study investigate to the seeds essential oil composition of Central African species with the aim of evaluating the antihypertensive activity.
MATERIALS AND METHODS
Plant: The fruit seeds of Monodora myristica were collected in September 2006 from the forest of Lobaye near Boukoko (130 km south of Bangui, Central African Republic), voucher specimens were kept in the herbarium of the faculty of Sciences, University of Bangui.
Essential oil extraction: Five hundred gram of the air-dried seeds were communited and hydrodistillated for 4 h using a Clevenger-type apparatus. The essential oil was dried after decantation over anhydrous sodium sulfate.
Analyses: GC analyses were performed on two fused silica capillary columns (25 mx0.25 mm), coated with OV-101 or Carbowax 20 M, the oven temperature was programmed from 50-200°C at 5°C min-1; helium was used as a carrier gas at a flow rate of 0.8 mL-1 min-1.
GC/MS analyses were carried out on a Hewlett Packard capillary GC-quadrupole MS system (model 5970) fitted with a (25 mx0.23 mm) fused silica column coated with DB-1 and using the same GC parameters. The volatile components were identified by comparison of their retention indices and their experimental mass spectra with those of reference compounds, further confirmation was done by referring to retention indices data generated from a series of alkanes: C9-C30 (Adams et al., 2001; Jennings et al., 1980).
Animals: Quantitative assessment of antihypertensive activity was conducted in October, 2006.
Preparation of the isolated heart: Brain and spinal of the frog were destroyed. The back of the animal was turned and pinned on cork plank. With the scissors, the frog heart was laid bare by cutting away skin, muscular tissue and pericardium. The heart was intubated through arterial trunk and carefully isolated.
Perfusion and recording of the amplitude and the frequency of the isolated heart contractions: The classical experimental model of the heart isolated from frog was used (Lompo et al., 1991).
Statistical analysis: All data are presented as means±SEM. comparisons between data were performed by Students t-test. Statistical significance was set at p<0.05.
Essential oil effects on heart contractions: Heart is initially perfused during approximately 5 min with the normal Ringer solution, then with the increasing concentrations (0.01, 0.02, 0.03, 0.04, 0.05 and 0.06%) of essential oil of Monodora myristica on the one hand, on the other hand with a solution of vérapamil at the concentrations of 0.5x10-3, 1.5x10-3, 2x10-3 and 2.5x10-3 mg mL-1 during 2 min. Effects on amplitude of the contractions and on the heart rate are recorded.
Essential oil effects on arterial blood pressure: Guinea pig weighing 300-350 g (male or female). Animals were treated under urethane 2% (1 g kg-1). The back of the animal was turned and neck region was dissected. Jugular vein was dissected and intubated with catheter supplied by syringe filled of heparinized Mac Ewen solution. Then carotid was dissected and intubated with catheter supplied with the blood pressure transducer itself connected to Gould recording system type 8000 S. After 1 h for stability, different doses of essential oil were administrated: 40, 80 and 120 μL kg-1. Arterial blood pressure variations were recorded.
The essential oil was obtained in yield of 1.2%. The compounds identified in the essential oil are shown in Table 1.
Guinea pig blood pressure was reduced by essential oil at 40, 80 and 120 μL kg-1. The blood pressure decreased in dose dependent manner. The effects were entirely or partially reversible according to the concentration used (Fig. 1).
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