Abstract: The yield of the essential oil from the leaves of Eucalypt (Eucalyptus nicholii), Rosemary (Rosmarinus officinalis L.), White Cedar (Thuja occidentalis L.) and Lawson Cypress (Chamaecyparis lawsoniana) shows seasonal and diurnal variation. In order to, aerial shoots of those plants harvested in three times (6, 12 and 18) and then dried in shade condition as natural method. The essential oils obtained by hydrodistillation way. This research carried out with 5 replications in random completely design and amount of essential oils measured in any species base on dry mater and data analysis performed with LSD test. Amount of essential oils in both of Lawson Cypress and White Cedar species at 7 h were high in compared with other treatments in 1% level and non significant difference between 12 and 18 times in Lawson Cypress. The results indicated that maximum of essential oil in Eucalypt and Rosemary obtained in 12 and 18 times, respectively that have significant differences with other times in 1% level. According these results we conclude that for obtaining of more yields of essential oil and other volatile compounds, harvesting of matter plants must be accomplished at special time in one day.

INTRODUCTION

The Rosemary (Rosmarinus officinalis L.), Eucalypt (Eucalyptus nicholii), White Cedar (Thuja occidentalis L.) and Lawson Cypress (Chamaecyparis lawsoniana) genus are trees and shrubs, indigenous to the Mediterranean area (Khare, 2007) that also used as ornamental plant in landscape design in tropical and subtropical regions at Iran country. They produce a number of compounds with pharmacological properties (Khare, 2007; Coppen, 2002).

The essential oil content and its composition are one of the most important quality criteria for mentioned plant species in all purposes. Because of those powerful pharmaceutical properties, anti-inflammatory, astringent, antiseptic, stomachic, carminative, circulatory disorders (Rosemary), antiseptic, antibiotic, antiviral, antifungal, antispasmodic, decongestant, antiasthmatic, expectorant, antirheumatic, diaphoretic, bronchitis, migraine, congestive headache, neuralgia and ague, inhalant or internal medicine (Eucalypt), insecticides, anthelmintic, diuretic (White Cedar) and Tincture-vasoconstrictor, antiseptic, sedative, antispasmodic and diuretic used for cough, cold, bronchitis, varicose veins, piles, menopausal cramps, leg-cramps (Lawson Cypress) such as α-pinene, 1, 8-cineole, camphor, verbenone, borneol, linalool, citronellal, citronellol and limonene the main components, content of the essential oils are considered as a quality criterion (Khare, 2007).

Numerous studies have been conducted on these species (Moudachirou et al., 1999; Silvestre et al., 1997; Zrira et al., 2004; Gachkara et al., 2007), particularly on their volatile compounds (Zaouali et al., 2005; Flamini et al., 2002) that it’s shown in Fig. 1.

Although, synthesis of volatile compound in medicinal plants control by genetic processes, but those productions obviously influenced by environmental factors so that environmental factors cause changes in growth of medicinal plant, quantity and quality of them volatile compound (Alkaloids, Glycosides, Steroids, essential oils, Flavonoides, Phenols, Terpenoides, Tannins, Azotoides, Carbohydrates, Keton, Saponin, Biter matters, Mucilage, Salicilic acid, etc).

Fig. 1:	Structures of the major compounds identified in the essential oil of plant species examined in this experiment

The environmental factors as light (quality, intensity and duration), temperature, irrigation, elevation, soil and nutrition elements alone or in combination with to have main influence on secondary metabolite situation of plants. The temperature in day duration usually is variable from morning to night. The temperature has more effect on essential oil in medicinal plants.

There are no data concerning the diurnal variation of composition and yield of the essential oil in these species growing in Iran during specific hours of the day. Thus, this study reports the diurnal variation of the essential oil from shoots of a natural population of Eucalyptus nicholii, Rosmarinus officinalis L., Thuja occidentalis L. and Chamaecyparis lawsoniana collected at south of Tehran (Iran).

MATERIALS AND METHODS

Plant matter and extraction of essentials oils: Aerial parts of Eucalypt (leaves), Rosemary (shoots and flowers), Lawson cypress (leaves) and White cedar (leaves) plants harvested in the 2006 year at three times (6, 12 and 18 h) in one day in July from landscape plants of the Shahed University (35°32'N, 51°20'E, 1028 m), Tehran, Iran. Aerial parts of investigated plants were air dried at room temperature (<25°C) in shady place for 10-16 days dependent on plant species. The dried herb of all species was subjected to water distillation (hydro-distillation) for 3 h using an all glass Clevenger-type apparatus, to produce oil according to the method recommended by the European Pharmacopoeia.

The oil volume was measured directly in the extraction burette. Yield percentage was calculated as volume (mL) of essential oil per 1000 g of plant dry matter. The obtained oil were dried over anhydrous sodium sulphate and stored in sealed vial at low temperature.

Statistical analysis: The experiments were arranged as a completely randomized design with 5 replications of each treatment. The significance of differences (p<0.05, 0.01) between treatments was determined by tukey multiple range tests. All the statistical analysis was performed using SPSS/PC software version 13.

RESULTS AND DISCUSSION

Differences in the yield of the essential oils under the influence of the harvest time have been reported for several plants (Lopes et al., 1997; Duschatzky et al., 1999; Moudachirou et al., 1999; Schwob et al., 2004; Msaada et al., 2007; Argyropoulou et al., 2007; Hussain et al., 2008; Angelopoulou et al., 2002; Marcum and Hanson, 2006; Ebrahimi et al., 2008; Chericoni et al., 2004; Callan et al., 2007). Also, our results indicated that various hours of diurnal have much influence on amount of Rosemary, Eucalypt, Lawson cypress and White cedar essential oils.

In this study, the essential oil content of Rosemary, Eucalypt, Lawson cypress and White cedar varied from 31-42, 34-46, 20-24 and 19.3-24.5 mL kg^-1 dry matter according to the time of day, respectively (Table 1).

In our study the maximum yield of Rosemary essential oils from leaves was obtained in 12 h treatment (42 mL kg^-1 dry matter) so that was significant difference at 5% level in comparing with 6 and 18 h treatments (31 and 34 mL kg^-1 dry matter, respectively).

Table 1:	The effect of harvest time in day duration on essential oil yield of Rosemary, Eucalypt, Lawson cypress and White cedar species in Iran
Means followed by the same letter within each Row are not significantly different, as indicated by Tukey test

Fig. 2:	The effect of harvest time in day duration (6, 12, 18) on essential oil yield of Rosemary (left) and Eucalypt (right) in Iran

Amount of essential oil obtained from leaves of Eucalypt at various times indicated that harvest at 18 h resulted in the greatest yield of essential oil (46 mL kg^-1 dry matter). There were significant difference at 5% level with 6 and 12 treatments (34 and 35 mL kg^-1 dry matter, respectively) that shown in Fig. 2.

Maximum quantity of essential oil in both of Lawson cypress and White cedar were obtained at 7 h treatment (24 and 24.5 mL kg^-1 dry matter, respectively) and no significant differences were observed between 12 and 18 treatments. Thus, 7 h introduced as the best time for harvesting of Lawson cypress and White cedar for extraction of greatest part of essential oil (Fig. 3).

Fig. 3:	The effect of harvest time in day duration (6, 12, 18) on essential oil yield of Lawson cypress and White cedar in Iran

CONCLUSON

Rosemary and Eucalypt are widely collected from nature and also cultivated especially in the southern regions of Iran. The harvest time of these species is very important for all kinds of usage.

It is known that genetic constitution and environmental conditions influence the yield and composition of volatile oil produced by medicinal plants. (Omidbaigi, 2007).

Volatile compounds in various plant species are different that this is resulted in variation yield of essential oils to environmental factors such as temperature and light, so that synthesis of these compound in various hours of diurnal will be vary.

As a conclusion of the present study, it could be stated that 12, 18, 7 and 7 harvests in Rosemary, Eucalypt, Lawson Cypress and White Cedar, respectively may result in higher values of essential oil content.

ACKNOWLEDGEMENT

We thank the contribution of Dr. Habibi, Dr. Rezaei, Shahed university horticulture laboratory especially Mr. Aghaeizadeh and Mrs. Fatemeh Bina for their help.