Abstract: This study was conducted in order to study the effect of grazing on quality and quantity of Artemisia sieberi essential oil in Kerman province of Iran. Vegetation sites of Artemisia sieberi under three grazing intensity (heavy, moderate and non-grazed) with the same ecological conditions were selected based on distance of water resource and nomad tent in Khabre National Park and near rangelands. Within each sits, two individual plants sampled at random in full flowering stage. The oils were obtained by hydrodistillation of air-dried samples and were analyzed by GC-MS. The main constituents of oils were as follows: non-grazed site; 1,8cineol (29.9%), myrcene (14.1%), moderate grazed site; myrcene (15.9%), 1,8cineol (15.1%), Eudesm-7(11)-en-4-ol (11.1%) and heavy grazed site; 4-tepinyl acetate (23.3%), davanone (21.9%), p-cymene (19%).
INTRODUCTION
Artemisia sieberi Besser. belongs to the family Asteraceae (tribe Anthemideae) and is widely distributed in desert areas of Iran (Gahraman, 1997; Mozafarian, 1988, 1996). This dwarf shrub plant, which is named locally dermaneh, is a dominant species in majority step rangelands of Iran (Mesdaghy, 1993).
This plant not only has forage value but also it has medicinal properties for human. In Iranian folk medicine, Artemisia sieberi is useful for spasmolytic effects (Zargari, 1996; Mirza et al., 1998), vermicide also for strengthener and reliefing cold problem (Babakhanlo et al., 1998).
Production of secondary metabolites in plants are effected by different ecological conditions (Omidbeigi, 2005). Essential oil of A. sieberi from Semnan province of Iran have been studied previously and the main components found to be comphor (49.3%), 1,8-cineole (11.1%) and bornyl acetate (5.8%) (Sefidkon et al., 2002). Camphor (44%), 1,8-cineole (19%) and camphene (5%) were the main components of the oil of A. sieberi from north of Tehran (Weyerstahl et al., 1993). β-thujone (19.8%), camphor (19.5%), α-thujone (10.6%), verbenol (9.7%), p-mentha-1,5-dien-8-ol (6.4%) and 1,8-cineole (5.7%) were the major identified compounds of A. sieberi from south of Khorasan province of Iran (Farzaneh et al. 2006). Major compounds of Artemisia sieberi from Garmsar, Semnan, Vardavard in the southern aspect of Alborz were reported to be comphor (25.9-51.6%), 1,8-cineole (17.5-20.25) and camphen (6.39-11.64) (Azarnivand, 2003).
As essential oil of Artemisia sieberi are leached by fall rains, livestock graze it in rangeland ecosystems (Tvakoli and Ahmadnejad, 2001). Grazing process is a biotic ecological factor on natural habitats and rangelands. Permanent grazing system and overgrazing about 4 times more than allowable capacity (Mesdaghi, 1993), are ecological stresses on Iran rangelands that can effect quality and quantity of Artemisia sieberi essential oils. The effect of grazing on vegetation of Iran rangelands have been studied by several authors (Chaichi et al., 2004; Ghelichnia, 1996; Jvadi, 2003; Sanadgol, 2002; Vahabi, 1989). Walter et al. (1961) studied grazing effect and soil characteristic on abundance and growth properties of Artemisia tridenta and Artemisia cana. Mirhaji (2001) compared Artemisia sieberi yield with others Artemisia in Semnan. Tavili and Jafari (2006) compared some elemental content of Artemisia sieberi that grows on crusted and uncrushed soil of Golestan. Garehbash et al. (2001) studied forage value of Artemisia sieberi and Artemisia oucheri and reported that Artemisia sieberi has more TDN and protein than Artemisia oucheri. Researches about grazing effects on medicinal plants (with emphasize on essential oil compounds) are very a few (Shafiei, 2002; Baghalian, 2002; Lashnei, 2002). Although variety studies have reported essential oil compounds of Artemisia sieberi from different locations of Iran and other studies have considered it from different aspects, there is not any report about grazing effect on medicinal value and essential oil compounds of Artemisia sieberi. Thus the aim of this study was to look into the grazing effect on quality and quantity of Artemisia sieberi essential oil in Kerman province.
MATERIALS AND METHODS
Plant material: Vegatations sites of Artemisia sieberi under three grazing intensity (heavy, moderate and non-grazed) with the same ecological conditions were selected based on distance of water resource and nomad tents (Li and Wang, 1977) in Khabre National Park and near rangelands. Khabre National Park has not been grazed for the last 10 years. After determining the grazing sites, arial parts of Artemisia sieberi were collected at the full flowering stage in 2005 from three sites. Within each sites, two individual plant sampeled at random. Plant materials were dried at ambient temperature and shade condition. Voucher specimen have been deposited in herbarium of Baft Islamic Azad University, Kerman, Iran.
Oil isolation procedure: The essential oil of air-dried samples (100 g) of each species was isolated by hydrodistillation for 3 h, using a Clevenger-type apparatus. The distillated oils were dried over anhydrous sodium sulfate and stored in tightly closed dark vials at 4°C until the analysis and tests.
GC analysis: GC analysis was performed by using a Thermoquest gas chromatograph with a Flame Ionization Detector (FID). The analysis was carried out using fused silica capillary DB-1 column (60 mx0.25 mm i.d., film thickness 0.25 μm). The operating conditions were as follows: injector and detector temperatures were 250 and 300°C, respectively. Nitrogen was used as carrier gas at a flow rate of 1 mL min-1; oven temperature programme, 60-250°C at the rate of 5°C min-1 and finally held isothermally for 10 min.
GC-MS analysis: GC-MS analysis was performed by using Thermoquest-Finnigan gas chromatograph equipped with above mentioned column and coupled to a TRACE mass quadrapole detector. Helium was used as carrier gas with ionization voltage of 70 ev. Ion source and interface temperatures were 200 and 250°C, respectively. Mass range was from m/z 43-456. Gas chromatographic conditions were as given for GC.
Identification of compounds: The constituents of the essential oil were identified by calculation of their retention indices under temperature-programmed conditions for n-alkanes (C6-C24) and the oil on a DB-1 column under the same chromatographic conditions. Identification of individual compounds was made by comparison of their mass spectra with those of the internal reference mass spectra library or with authentic compounds and confirmed by comparison of their retention indices with authentic compounds or with those of reported in the literature (Vajs et al., 2004). For quantification purpose, relative area percentages obtained by FID were used without the use of correction factors.
RESULTS
The analysis of essential oils (Table 1) showed that there were significant quantitive and also qualitative differences within natural population under three grazing different sites in Kerman province. The main constituents of oils were as follows: non-grazed site; 1,8cineol (29.9%), myrcene (14.1%), moderate grazed site; myrcene (15.9%), 1,8cineol (15.1%), Eudesm-7(11)-en-4-ol (11.1%) and heavy grazed site; 4-tepinyl acetate (23.3%), davanone (21.9%), p-cymene (19%).
| Table 1: | Percentage of essential oil compositions of Artemisia sieberi under three different grazing sites from Iran (Kerman province) |
DISCUSSION
This study allowed the identification of 64 constituents (accounting for 93.9-98.9) in the oils, under three different grazing sites that 35 of this components have been previously reported in the oil of Artemisia sieberi from Iran (Sefidkon et al., 2002; Weyerstahl et al., 1993; Farzaneh et al., 2006; Azarnivand, 2003). There are considerable differences between oil composition of Artemisia sieberi under three sites due to grazing factor. We found that grazing in moderate and heavy level have eliminated 8 components and added 19 new components in comparsion with non-grazed sites. Among these compounds (were highlighted in Table 1), 4-thepenyl acetat allocated highest amount in heavy grazing sites.
According to this study, overgrazing influences medicinal importance of Artemisia sieberi rangeland ecosystems. Therefore grazing management is necessary for multiple use of this ecosystems.