Bulgarian Chemical Communications, Volume 42, Number 1 (pp. 36-39) 2010

* To whom all correspondence should be sent:

Received December 31, 2008; Revised July 27, 2009

Essential oils from the leaves, stems and flowers of Prangos ferulacea (family Umbelliferae) growing in Esfahan, Iran, were obtained by hydrodistillation using a Clevenger-type apparatus and their chemical composition and antibacterial activity analysed by GC-MS. All the oils consisted mainly of oxygenated monoterpenes and a small percentage of sesquiterpene compounds. In the oil from the leaf, 10 components were identified, dominated by oxygenated monoterpenes. The three major constituents identified (representing 65.1% of the oil) were linalool (36.7%), caryophyllene oxide (16.3%) and α-pinene (12.1%). In the stem oil, 11 compounds were identified, with oxygenated monoterpenes again predominating. The two major constituents identified (representing 29.3% of the oil) were 1,8-cineole (19.0%) and α-pinene (10.3%). Of the 17 compounds found in the flower oil, the five main components identified (representing 74.1% of the oil) were oxygenated monoterpenes: linalool (19.0%), lavandulyl acetate (16.0%), 1,8-cineole (14.5%), α-pinene (12.4%) and geranyl isobutyrate (12.2%). The oils were tested against four Gram-positive or Gram-negative bacteria. Antibacterial activity was measured using a dilution method. It was found that oil from leaves, stems and flowers of P. ferulacea, and especially that of leaves, exhibited interesting antibacterial activity.

Key words: Prangos ferulacea, umbelliferae, essential oil, linalool, antibacterial activity.

INTRODUCTION

Of the fifteen species of the genus Prangos (family Umbelliferae) found in Iran, five are endemic: P. gaubae, P. crossoptera, P. tuberculata, P. cheilanthifolia and P. cattigonoides [1, 2]. A survey of the literature revealed that the oil compo-sition of P. latiloba [3], P. pabularia [4], P. hissa-rica, P. seraivschanica, P. fedtschenkoi [5], P. feru-lacea [6, 7], P. uechtritzii [8, 9], P. bornmuelleri [10], P. heyniae [11], P. uloptera [12], P. asperula [13] and P. platychlaena [14] have been reported. The main constituents of the aerial parts of P. uloptera were found to be β-caryophyllene (18.2%), germacrene D (17.2%) and limonene (8.7%), whereas the seed oil comprised mainly α-pinene (41.5%) and β-cedrene (4.0%) [12]. Analysis of the aerial parts of P. asperula showed δ-3-carene (16.1%), β-phellandrene (14.7%), α-pinene (10.5%), α-humulene (7.8%), germacrene-D (5.4%), δ-cadinene (4.2%) and terpinolene (4.0%) to be the major components of the oil [13]. Aerial parts of P. uechtritzii contained δ-carene (3.39%) and p-cymene (3.38%) [8, 9], while α-pinene (40.82%), nonene (17.03%), phellandrene (11.14%), δ-carene (7.39%), and p-cymene (4.90%) were identified as major components of P. platychlaena [14]. Study of the chemical composition and antibacterial activity of essential oil from aerial parts of P. ferulacea (L.) Lindl grown in Iran showed its primary constituents to be α-pinene (36.6%), β-pinene (31.9%) and β-phellandrene (11.7%) [15]. Some Prangos species have been used in folk medicine as emollient, car-minative [16], tonic, antiflatulent, anthelmintic, anti-fungal and antibacterial agents [17, 18]. Chemical investigations on the components of the genus Prangos have resulted in the isolation of various coumarins, alkaloids, flavonoids and terpenoids [19]. According to the literature, leaves, stems and flowers of P. ferulacea have not been the subject of any investigation, and this paper is the first such phytochemical study on this plant.

EXPERIMENTAL

Plant material

The sample of Prangos ferulacea was collected during the flowering stage in June 2005 from the Province of Esfahan, in the centre of Iran. Voucher specimens were deposited at the Herbarium (Voucher No. 6014) of the Research Institute of Forests and Rangelands (TARI), Tehran, Iran.

Fresh leaves (80 g), stems (90 g) and flowers (70 g) of P. ferulacea were subjected to separate hydro-distillation for 3 h using a Clevenger-type apparatus. After decanting and drying over anhydrous sodium sulphate, the corresponding yellowish coloured oils were recovered from the leaves, stems and flowers in yields of 0.9, 0.8 and 1.1% (w/w), respectively.

GC analysis of the oils was performed on a Shimadzu 15A gas chromatograph equipped with a split/splitless injector (250°C). N₂ was used as carrier gas (1 mL/min), and the capillary column used was DB-5 (50 m  0.2 mm, film thickness 0.32 m). The column temperature was maintained at 60°C for 3 min and then heated to 220°C with a 5°C/min rate and kept constant at 220°C for 5 min.

GC/MS analysis was performed using a Hewlett-Packard 6890/5973 with an HP-5MS column (30 m  0.25 mm, film thickness 0.25 m). The column temperature was maintained at 60°C for 3 min and programmed to 220°C at a rate of 5°C/min, and kept constant at 220°C for 5 min. The flow rate of helium as the carrier gas was 1 mL/min. MS was taken at 70 eV.

Identification of the constituents of each oil was made by comparison of their mass spectra and retention indices (RI) with those given in the literature and the authentic samples [20–22]. Rela-tive percentage amounts were calculated from the peak area using a Shimadzu C-R4A Chromatopac without correction factors.

A collection of four microorganisms was used, including the Gram-positive bacteria Staphylo-coccus aureus (ATCC 1112), Staphylococcus epidermidis (ATCC 1114) and Bacillus cereus (ATCC 1015) and the Gram-negative bacteria Pseudomonas aeruginosa (ATCC 1310), identified by the Research Centre of Science and Industry, Tehran, Iran.

Microorganisms (obtained from enrichment culture of the microorganisms in 1 mL of Mueller-Hinton broth, incubated at 37°C for 12 h) were cultured on Mueller-Hinton agar medium.

The following method was used to measure antibacterial activity: 40 µL of diluted essential oil (40 µL oil in 2 mL DMSO 10%) was added to a 200 µL microbial suspension (1 loop from medium in physiological serum that compared with a 0.5 McFarland standard) in well 1 in a microplate, and 100 µL from this well was add to a 100 µL microbial suspension in well 2, and this continued until 8 wells in the microplate were filled. Micro-plates were incubated at 37°C for 24 h [23].

RESULTS AND DISCUSSION

M. T. Akbari et al.: Chemical composition and antibacterial activity of essential oil

The leaf oil consisted of 10 identified com-pounds representing 81.7% of the oil composition. The main compounds were linalool (36.7%), caryophyllene oxide (16.3%) and α-pinene (12.1%). Another notable constituent was 1,8-cineole (8.9%).

In the stem oil, 11 compounds were identified, representing 43.3% of the oil composition. The main compounds were 1,8-cineole (19.0%) and α-pinene (10.3%).

Linalool (19.0%), lavandulyl acetate (16.0%), 1,8-cineole (14.5%), α-pinene (12.4%) and geranyl isobutyrate (12.2%) were the main compounds among the 17 constituents representing 98.2% of the total components detected in the flower oil.

Oxygenated monoterpenes represented the most abundant constituent of the oil of leaves, stems and flowers (63.3%, 37.4% and 74.7%, respectively). Linalool was the main constituent of the leaf and flower oils (36.7% and 19.0%, respectively), and 1,8-cineole (19.0%) of the stem oil.

The literature survey of the chemical composi-tion of P. asperula showed δ-3-carene, β-phel-landrene, α-pinene and α-humulene to be the major components of the oil [13].

Dried aerial parts of Prangos uechtritzii contained δ-carene (3.39%) and p-cymene (3.38%) [8, 9], while α-pinene (40.82%), nonene (17.03%), phel-landrene (11.14%), δ-carene (7.39%), and p-cymene (4.90%) were identified as major components of P. platychlaena [14]. The main compounds of the P. ferulacea aerial parts were α-pinene (36.6%), β-pinene (31.9%) and β-phellandrene (11.7%) [15]. In our previous investigation [24] the oil of P. ferulacea collected from north of Tehran, Iran, contained α-pinene, δ-3-carene, β-pinene and epi-α-bisabolol as main compounds and was found to be rich in sesquiterpenes hydrocarbons, while in the present study, the stem, leaf and flower oils of the plant, collected from Lorestan Province, Iran, contained mostly oxygenated monoterpenes.

The oil of P. ferulacea aerial parts collected from Lorestan province, Iran, and of P. acaulis from Iran were rich in regard to oxygenated monoterpenes (77.8% and 86.2%, respectively) [15,25]. Our results, compared with our previous investigation on oils of the Prangos genus, also showed the oils of these parts to be dominated by oxygenated mono-terpenes.

The antibacterial assays showed that the oils of leaves, stems and flowers of P. ferulacea inhibited the growth of all the bacteria. Leaves, stems and flowers of P. ferulacea were further tested for Gram-positive and Gram-negative bacteria. The results of the bioassays (Table 2) showed that the three oils exhibited moderate to strong differences in anti-microbial activity.

Table 2. Antibacterial activity of leaves, stems and flowers of Prangos ferulacea oils based on dilution method and using DMSO*.

Bacterial Species	Gram +/–	Leaf Oil	Stem Oil	Flower Oil	DMSO
Staphylococcus aureus ATCC 1112	+	0.5	2	0.5	>4
Staphylococcus epidermidis ATCC 1114	+	0.25	0.5	>4	>4
Bacillus cereus ATCC 1015	+	1	2	0.5	>4
Pseudomonas aeruginosa ATCC 1310	–	0.0625	0.5	1	>4

* Values are the mean MIC (ppm).

In the antimicrobial screening, the oil of P. ferulacea leaves exhibited particularly strong activity, especially for the Gram-positive organisms, although that of stem and flower oils was also interesting. (Leaf-oil MIC values for Pseudomonas aeruginosa, Staphylococcus epidermidis, Staphylo-coccus aureus and Bacillus cereus were 0.0625 ppm, 0.25 ppm, 0.50 ppm and 1.00 ppm, respect-ively.) In previous studies, antibacterial activity of the essential oils of aerial parts of P. ferulacea in Iran appeared strong for Gram-positive bacteria, especially Staphylococcus aureus [15], while the P. ferulacea in Turkey was active against Staphylo-coccus aureus [23]. Our previous article addressed the antibacterial activity of leaf oils against a Gram-negative strain.

CONCLUSIONS

M. T. Akbari et al.: Chemical composition and antibacterial activity of essential oil

2. The leaf oil consisted of 10 identified com-pounds representing 81.7% of the oil composition. The main compounds were linalool (36.7%), caryo-phyllene oxide (16.3%) and α-pinene (12.1%). Another notable constituent was 1,8-cineole (8.9%).

In the stem oil, 11 compounds were identified, representing 43.3% of the oil composition. The main compounds were 1,8-cineole (19.0%) and α-pinene (10.3%).

Linalool (19.0%), lavandulyl acetate (16.0%), 1,8-cineole (14.5%), α-pinene (12.4%) and geranyl isobutyrate (12.2%) were the main components among the 17 constituents characterized in the flower oil, representing 98.2 % of the total com-ponents detected.

3. Oxygenated monoterpenes represented the most abundant constituents of the oil of leaves, stems and flowers (63.3%, 37.4% and 74.7%, res-pectively).

4. The oils were tested against four Gram-posi-tive or negative bacteria using a dilution method. It was found that oils from leaves, stems and flowers of P. ferulacea, and especially that of leaves, exhibited interesting antibacterial activity.

5. Comparing these results with investigations on oils of other species of the Prangos genus showed they are also dominated by oxygenated mono-terpenes.
Acknowledgements: We are grateful to Dr. V. Mozaffarian (Research Institute of Forest and Rangelands, Tehran) for his helpful assistance in the botanical identification.

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