Origanum bastetanum Soc. Cultivated Specimens: Characterization of Its Essential Oil

Journal of Essential Oil Research: JEOR, Nov/Dec 2005 by Pérez-Galindo, Pilar, Martínez-Raya, Armando, Francia, José Ramón, Jiménez, José, Navarro, Concepción

Abstract

Through a combination of GC and GC/MS, we studied the Origanum bastetanum Soc. essential oil obtained from the aerial parts submitted to three different cut-off heights of three-year-old plants, established from micropropagated specimens. Over 80 components were identified, the major ones, in all cases, being γ-terpinene (32.0-37.0%), thymol (29.5-31.6%), p-cymene (7.0-8.8%) and β-caryophyllene (5.0-6.9%). Therefore, this Spanish Origanum species can be classified as belonging to the terpenphenolic oregano group, in contrast to the wild specimens, the main component of which is cis-sabinene hydrate (cis-thujanol).

Key Word Index

Origanum bastetanum, Lamiaceae, essential oil composition, thymol, γ-terpinene.

Introduction

Interest among consumers in products derived from aromatic/medicinal plants is expanding. The growing demand has given rise to an increase in the number of specialized industries that utilize these plants. The availability of the appropriate raw materials for processing and handling can be based on controlled cultivation or on harvesting wild plants. The latter solution is the most common in areas where this tradition already exists. Harvesting of these wild species is not usually carried out using the most adequate methods, as frequently the plants are pulled out of the ground by hand.

Traditionally, the genus Origanum (Lamiaceae) was used both in food and medicine for treating various ailments, its effectiveness having been scientifically proven as anti-fungal (1-4), anti-bacterial (5,6), depressor of the central nervous system (7), spasmolytic (8), anti-diabetic (9,10), anti-mutagenic (11), antioxidant (12), etc. Among the Origanum species that grow spontaneously in the Iberian Peninsula, Origanum hastetanum is an endemic species in the northeastern part of Granada province (Andalucía, Spain) (13), a region which suffers a severe desertitation process. Our research is aimed at encouraging cultivation of O. hastetanum to meet the demand for use in food and phytotherapy, and therefore to establish the quality of its oil and identify harvest techniques that would make sustainable production possible. Among these techniques we have investigated the influence of cut-off levels on the quality and quantity of the essential oils.

Experimental

Plant material: Micropropagated plants of O. bastetanum were obtained from seeds of wild specimens collected in Benamaurel (Granada) during the ripening period and a voucher specimen was deposited in the Herbarium of the Faculty of Pharmacy (Granada). Germination, propagation, growth and acclimatization were carried out according to the method described by Socorro et al. (14). Subsequently, the micropropagated specimens were transplanted into four different plots in Lanjarón (Granada, Spain), and cultivated for three years. They were collected during the flowering period. The samples corresponded to three different cut-off levels: 25%, 50% and 75% of the aerial parts.

Oil isolation: The material was air-dried at 20°-22°C for 10-15 days, broken up and put into cold storage (-4°C) until distillation. For each cut-off level, 200 g of the dried plant material was hydrodistilled for 3 h in a Clevenger-type apparatus, according to the method recommended by the Real Farmacopea Española (15). The isolated oils were dried over anhydrous sodium sulfate and stored at 4°C.

Qualitative and quantitative analyses: Qualitative data were determinated by GC and GC/MS. GC analysis was carried out on a Hewlett-Packard 5890 gas chromatograph fitted with a methyl silicone DB-5 (cross linked 5%-PH-95%- ME Siloxane) fused silica capillary column (30 m x 0.25 mm, 0.25 µm film thickness). Oven temperature was kept at 65°C for 3 min and programmed to 210°C at a rate of 3.5°C/min, then kept at 210°C for 30 min. Injector temperature was 250°C. Carrier gas (He) flow rate was 1 mL/min. Detection was performed by FID, at 250°C; 0.1 µL of sample was injected.

GC/MS analyses were carried out using the Hewlett-Packard GC/MS 5973/6890 system. Both DB5 cross linked 5%-PH-95% ME siloxane (HP-5MS 30 m x 0.25 mm, 0.25 µm film thickness) and polyethylene glycol (HP-Innowax 30m x 0.25mm, 0.25 µm film thickness) fused capillary columns were used with helium as a carrier gas (flow rate = 1.2 mL/min). Oven temperature was kept at 65°C for 3 min and programmed to 210°C at a rate of 3.5°C/min, then kept at 210°C for 30 min. Split ratio was adjusted at 1:70. Injector and detector temperatures were 250°C. Mass spectra were taken on EI mode (70 eV). Scanning speed was 2 scan/sec from m/z 35 to 300 amu.

Component identification was done on the basis of mass spectral fragmentation, comparison of retention indices calculated by application of the Kovats method (16) with those of authentic constituents or with those in close agreement with reference (17) and mass spectral matching library search system with commercial libraries (17,18).

Quantitative values were calculated directly from the GC peak areas without correction factors.