Chemical Variations in the Essential Oil of Sideritis tragoriganum

• Abstract
• Materials and Methods
• References

Abstract

The essential oil composition from Sideritis tragoriganum has been investigated by capillary gas chromatography and gas chromatography-mass spectrometry. Among the 47 identified mono- and sesquiterpenes, α-bisabolol is the most prominent component. Correlation analysis of essential oil components from this population of S. tragoriganum with two other geographically distinct populations revealed the existence of unrelated chemical types.

The genus Sideritis (Lamiaceae) comprises species found throughout the Mediterranean area with medicinal properties and characterized by the presence of essential oils, flavonoids, coumarins, phenolic acids, lignans and terpenes [1] [2] [3] [4] [5] [6]. The existence of sideritoflavone and hypolaetin 8-O-β-glucoside, with anti-inflammatory and antiarthritic activities in S. tragoriganum [7] [8] [9], can explain the use of infusions and decoctions of the aerial parts of this species in folk medicine [10]. The essential oil of S. tragoriganum has antimicrobial activity against Gram-positive bacteria, yeast and mycobacteria [11]; nevertheless, within the species of this genus there can be striking differences in the essential oil composition, in part because of chemical varieties and hybrids. Environmental changes, such as the mineral status of the substrate and climatic characteristics, have well-established effects on the composition and variation of the essential oil in several genera of Lamiaceae [12]. Sideritis tragoriganum Lag. is a small polymorphic shrub [13] found in the Valenciano-Terraconense and Setabense sectors. It grows in the Thermomediterranean vegetation belt and in different types of soils (calcareous, terrarossa, rendzina. . .). Differences in the ombroclimatic index [14] have been observed in distinct locations. We were interested in analyzing the essential oil from S. tragoriganum growing in Villar del Arzobispo (ST_vi), Valencia (Spain) in order to establish its composition and compare it with plants collected in Torreblanca, Castellón (ST_cs) and in La Eliana, Valencia (ST_le). The qualitative and quantitative compositions of the latter two populations have been reported previoulsy [1].

The essential oil from aerial parts of the fresh plant was obtained by steam distillation, and analysed by capillary gas chromatography and gas chromatography-mass spectrometry after separation into fractions by column chromatography.

The gas chromatogram of the entire essential oil showed the presence of about 50 constituents, many of them present only in trace amounts (< 0.05 %). The hydrocarbon and oxygenated compounds account for about 40 % and 20 %, respectively, of the identified constituents. In the hydrocarbon constituents, 14 monoterpenoids and 15 sesquiterpenes were found. Among them δ-cadinene, β-gurjunene and germacrene D were the main compounds.

In the oxygenated fraction, 1,8-cineol, fenchone, terpinen-4-ol, α-terpineol, bornyl acetate and α-terpenyl acetate together with the sesquiterpenes caryophyllene oxide, cadinol and bisabolol were found in considerable amounts (Table [1]). At least four other unknown substances with a molecular weight of M⁺ 220 m/z and the chemical composition C₁₅H₂₄O were found in the sesquiterpene region of the chromatogram in proportions of 3.9 to 7.7 %. These oxygenated sesquiterpenes are common in the essential oils of many species from the Lamiaceae family.

On the other hand, only 22 components were identified in the ST_cs essential oil. All of these compounds were also present in the ST_vi sample. α-Pinene (17.7 %), 1,8-cineol (15.9 %), β-caryophyllene (14.6 %) and caryophyllene oxide (10.2 %) were the four main components, accounting for about 58 % of the total oil. The same compounds represented only 7 % in the ST_vi essential oil, with no individual constituent at more that 10 %. The main compound (α-bisabolol) of the sample harvested in Villar del Arzobispo was not found in the sample from Castellón. Nevertheless, the ST_vi essential oil, in which the major components are α-pinene (7.8 %), 1,8-cineol (6.8 %), fenchone (7.8 %) and cadinol II (5.3 %) is qualitatively similar to an atypical ST_le, but the quantitative composition of the two essential oils is substantially different.

The chemical variability of S. tragoriganum is further evidenced by the scarce relationship between the three populations. The Spearman correlation coefficients, determined using the SYSTAT 8.0 statistical package, are very low between ST_vi and both ST_cs (0.358) and ST_le (0.219) (Fig. [1]). Although the correlation regression between ST_le and ST_cs is greater (0.554), it is not significant. This suggests that S. tragoriganum populations can be distinguished on the basis of differences in their essential oils and geographic locations, and also illustrates the need for further work to clarify chemical and taxonomic relationships and the influences of genetics and environmental factors.

Materials and Methods

Aerial parts of Sideritis tragoriganum Lag. growing in Villar del Arzobispo, Valencia (Spain) were collected at the flowering stage. Voucher specimens were authenticated by the Department of Botany and deposited in Herbarium n^o 6609 of the Escuela Técnica Superior de Ingenieros Agrónomos de Valencia (Spain) (VALA). The fresh plant material was subjected to hydrodistillation for 2.5 h in a Clevenger-type apparatus to yield the essential oil (0.3 % v/w). The 1.56 ml distillate was dried over anhydrous sodium sulphate and fractionated on a silica gel (silica gel G-60 Merck) column using hexane (150 ml) in order to obtain the hydrocarbon fraction. The oxygenated compounds were then eluted with hexane-dichloromethane (60 : 40, 20 : 80) mixtures and dichloromethane. The oil and each fraction were analyzed by gas liquid chromatography and combined gas chromatography-mass spectrometry.

GC: Gas chromatography was performed with a Konic 2000-C gas chromatograph equipped with a Spectra Physic 4290 electronic integrator, a flame ionization detector and an SE-52 high performance capillary column (5 % phenylmethylsilicone) (25 m × 0.25 mm i.d.). The column temperature program was 60 °C for 6 min, with 5 °C increases per min to 150 °C, which was maintained for 10 min. The carrier gas was nitrogen at a flow-rate of 2 ml/min. The injector and the detector temperature were maintained at 225 °C and 250 °C, respectively. Splitless mode injection was used.

GC/MS: Gas chromatography-mass spectrometry analysis was carried out with a Hewlett-Packard 5995 B apparatus with a membrane separator coupled to a Hewlett-Packard 9825 data system. The chromatographic separations were done by a 12 m × 0.25 mm i.d. OV-1 (methylsilicone) high-performance capillary column. The same working conditions used for GC were employed except that the carrier gas was helium at a flow-rate of 2 ml/min (splitless mode). Mass spectra were taken over the m/z 28-400 range with an ionizing voltage of 70 eV. For the determination of the RIs a Varian instrument (GC model Star 3400; MS model Saturn II) and the same conditions (up to 170 °C) were used. Kovat's retention indices were calculated using co-chromatographed standard hydrocarbons. The individual compounds were identified by MS and their identity confirmed by comparison of their RIs, relative to C₈ - C₁₉ n-alkanes, and by comparing their mass spectra and retention times with those of authentic samples or with data already available in the literature [15] [16] [17].

Statistical studies: Correlations were calculated by SYSTAT 8.0, 1998. Statistical Software SPSS. Inc. Chicago.

References

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Prof. Dr.. Mª Amparo Blázquez

Departament de Farmacologia Facultat de Farmàcia Universitat de València

Avda. Vicent Andrés Esés, s/n

E-46100 Burjassot

Spain

Email: amparo.blazquez@uv.es

Phone: +34 96 3864943

References

• 1 Mateo  C,, Sanz  J,, Calderón  J.. The essential oil of some Eastern Spain Sideritis. .  Phytochemistry. 1984;;  23 319-22
  CrossrefPubMedSearch in Google Scholar
• 2 Ezer  N,, Vila  R,, Cañigueral  S,, Adzet  T.. Essential oil composition of four Turkish species of Sideritis. .  Phytochemistry. 1996;;  41 203-5
  CrossrefPubMedSearch in Google Scholar
• 3 Laer  U,, Glombitza  K W,, Neugebauer  M.. The essential oil of Sideritis syriaca.  Planta Medica. 1996;;  62 81-2
  PubMedSearch in Google Scholar
• 4 Palomino  O M,, Gomezserranillos  P,, Carretero  E,, Villar  A.. High-performance liquid chromatography of flavonoids from Sideritis species.  Journal of Chromatography A. 1996;;  731 103-8
  CrossrefPubMedSearch in Google Scholar
• 5 Fraga  B M,, Hernández  M G,, Santana  J MH,, Terrero  D,, Galvan  M F.. A chemotaxonomical study of Sideritis-Massoniana taxa.  Biochemical Systematics and Ecology. 1995;;  23 835-42
  CrossrefPubMedSearch in Google Scholar
• 6 Gomezserranillos  P,, Palomino  O M,, Villarrubia  A I,, Cases  M A,, Carretero  E,, Villar  A.. Analysis of diterpenoids from Sideritis species by reversed-phase high performance liquid chromatography.  Journal of Chromatography. 1997;;  778 421-5
  CrossrefPubMedSearch in Google Scholar
• 7 Villar  A,, Salom  R,, Alcaraz  M J.. An approach to the anti-inflammatory activity of borjatriol.  Planta Medica. 1984;;  90-2
  PubMedSearch in Google Scholar
• 8 Villar  A,, Gascó  M A,, Alcaraz  M J.. Anti-inflammatory and anti-ulcer properties of hypolaetin-8-glucoside, a novel plant flavonoid.  Journal of Pharmacy and Pharmacology. 1984;;  36 820-3
  PubMedSearch in Google Scholar
• 9 Barberán  F AT,, Máñez  S,, Villar  A.. Identification of anti-inflammatory agents from Sideritis species growing in Spain.  Journal of Natural Products. 1987;;  50 313-4
  CrossrefPubMedSearch in Google Scholar
• 10 Peris  J B,, Stübing  G,, Vanaclocha  B.. Fitoterapie Aplicada,. M.I.C.O.F., Valencia; 1995
• 11 Villar  A,, Recio  M C,, Ríos  J L,, Zafra-Polo  M C.. Antimicrobial activity of essential oils from Sideritis species.  Pharmazie. 1986;;  41 298-9
  PubMedSearch in Google Scholar
• 12 Flück  H.. Chemical Plant Taxonomy. 167-86, Academic Press, Londres; 1963
• 13 Font i Quer P.. Treb. Museu Ciènces Naturals,. vol 4,: 30, Barcelona; 1924
  Search in Google Scholar
• 14 Rivas-Martínez  S.. Etáges Bioclimatiques, Secteurs Chorologiques et Séries de Végétation de l'Espagne Mediterranéénne.  Ecologia Mediterránea. 1982;;  8 1-2
  PubMedSearch in Google Scholar
• 15 Cornu  A,, Massot  R.. Compilation of Mass Spectral Data;. Heyden, London; 1975
• 16 Noever de Brauw  H C,, Bouwman  J,, Tas  A C,, Las Vos  G.. Compilation of Mass Spectra of Volatile Compounds in Food;. TNO Zeist, Utrecht; 1979
• 17 Stenhagen  E,, Abrahamsson  S,, McLafferty  F W.. Registry of Mass Spectral Data;. Wiley, New York; 1974

Prof. Dr.. Mª Amparo Blázquez

Departament de Farmacologia Facultat de Farmàcia Universitat de València

Avda. Vicent Andrés Esés, s/n

E-46100 Burjassot

Spain

Email: amparo.blazquez@uv.es

Phone: +34 96 3864943