Extract Analyses of Satureja thymbra L. and Thymbra spicata L. Aromatic Plants of the Holy Land and the Sinai. Part XVII

Journal of Essential Oil Research: JEOR, Jan/Feb 2005 by Fleisher, Zhenia, Fleisher, Alexander

Abstract

The extracts from individual specimens of Satureja thymbra L. and Thymbra spicata L. were analyzed in detail by GC and GC/MS. This study confirms the existence of thymol- and carvacrol-containing chemotypes of both species, which have been found to grow in rather small and compositionally segregated populations.

With the exception of the thymol/carvacrol ratio, the volatile constituent compositions of both species were found to be very similar. In addition to the biosynthetically interrelated thymol, carvacrol, γ-terpinene and p-cymene, the other major volatiles of both species were β-caryophyllene, caryophyllene oxide, thymohydroquinone and thymoquinone.

Key Word Index

Satureja thymbra, Thymbra spicata, Labiatae, extract composition, thymol, carvacrol, p-cymene, γ-terpinene, chemotypes.

Plant Names

Satureja thymbra L., Thymbra spicata L.

Source

Fresh plant material from individual specimens of S. thymbra have been collected from three small isolated populations on Mt. Netufa in Upper Galilee (eight specimens), near Usafia on Mt. Carmel (10 specimens), and in Beit Gainai, Western Judea (seven specimens), while samples of T, spicata have been taken from Daliat el Carmel on Mt. Carmel (seven specimens) and from Beit Gamal, Western Judea (six specimens).

Plant Part

The existence of S. thymbra and T. spicata chemotypes has been established before (1). In order to determine a true compositional range of each chemotype, we opted to analyze individual specimens and not mixed representative samples of plant populations. Branches (about 5 g) were taken from most plants of small, isolated populations, packed in glass bottles, and immediately preserved with methylene chloride.

The methylene chloride extracts were gently concentrated under nitrogen stream and used directly for the GC and GC/MS analysis. The yields of extracts were not determined.

Previous Work

Satureja thymbra, Thymbra spicata and also Coridothymus capitatus are finding some use in the preparation of Za'atar (popular Middle Eastern condiment), along with the true Za'atar plant - Origanum syriacum L. (2). The same four species have been thoroughly discussed (2,3) in the description of the Biblical purification ritual involving the plant called hyssop (Num. 19:6). Satureja thymbra, Thymbra spicata and also Coridothymus capitatus were considered to be pseudo-hyssops (3,4). The only true hyssop of the Bible, which was the carvacrol-containing chemotype of Origanum syriacum L. (2), was allowed to be used in purification rites (4).

Previously, it was demonstrated that the similarity in the composition of volatiles and, consequently, similarity of flavor profiles of these four species is the most probable cause for the historic confusion in the identification of the biblical hyssop (2). Indeed, the compositions of respected chemotypes of O. syriacum and C, capitatus are very similar (5,6).

The essential oils of S. thymbra and T. spicata have been widely investigated during last decades. Kokkini and Vokou (7) list S. thymbra among the carvacrol-rich Labiatae species of Greek origin. Other studies show that mostly the thymolcontaining chemotype of S. thymbra can be found growing in Greece (8,9) and Sardinia (10,11). The same is true for S. thymbra found in Turkey (12).

On the other hand, the literature indicates that wild populations of T. spicata in Turkey is almost exclusively represented by the carvacrol-containingchemotype ( 13,14). More specifically, detailed studies of Turkish Thymbra spicata L. van spicata indicated only one carvacrol-containing chemotype (15,16), while endemic to Turkey Thymbra spicata L. var. intricata is represented by both carvacrol- and thymol-containing chemotypes (16).

Both S. thymbra and T. spicata from Israel were also studied previously (1,17-20); however, a detailed composition of their volatiles has not been reported.

It appears that previous studies did not pay special attention to the methodology of collecting plant material samples. Different chemotypes of aplant species often coexist within the same population (2,6) in unpredictable proportions. Random collection of plants from mixed population variably impacts the volatiles, thus undermining the validity of compositional data.

We believe that the screening of individual plant specimens is necessary for obtaining reliable data for the composition of volatile constituents of individual chemotypes.

Present Work

Methylene chloride extracts of individual S. thymbra and T. spicata specimens were first "fingerprinted" by GC. It was found that the GC profiles of individual samples within a population were very similar. As a result, extracts were combined according to the types and subjected to a detailed GC/MS analysis. The qualitative analysis of the oils was performed using the 6970 Hewlett-Packard gas Chromatograph coupled with 5973 mass-selective detector. A Supelco SPB-1 30 m × 0.25 mm non-polar column with a 0.25 µm film thickness was employed in the analysis. The temperature was programmed from 70°-320°C at the 6°C/min with 10 min hold at 320°C. Helium was used as a carrier gas at 1.5 mL/min with 1:80 split ratio. The identity of each component was determined by MS and confirmed by retention indices using the authors own database.