Composition of Essential Oils from Fir (Abies) Wood Species Grown in Turkey

Abstract

Abies species naturally grown in Turkey are represented by four species and two subspecies. Abies equi-trojani (Aschers & Sint.) and Abies bornmulleriana (Mattf.) occur in western and northwestern regions. Abies cilicica subsp. isaurica (Coode & Cullen) and Abies cilicica subsp. cilicica (Antoine & Kotschy) Carr. are widespread in the southern part of the country (on Taurus mountains), and Abies nordmanniana (Steven) Spach is native in the eastern Black Sea region of Anatolia [1]. The main cell wall constituents (lignin, polysaccharides) of the woods from these species were studied by Ozdemir [2]. However, there have been no reports on the constituents of wood essential oils of Anatolian Abies species. On the other hand, Abies woods characteristically contain juvabiones, which are insect juvenile hormone related compounds. As a group of sesquiterpenoids, juvabiones and dehydrojuvabiones have been investigated in some fir woods [3–9]. In the present study, the components of the essential oils isolated from the woods of Anatolian fir species by hydrodistillation were analyzed and compared with one another. Two representative trees from each of a total of ten regions were felled to collect wood samples; A. bornmulleriana: Bolu and Uludag; A. equi-trojani: Kalkim and Gurgen; A. cilicica subsp. cilicica: Andirin and Goksun; A. cilicica subsp. isaurica: Bucak and Akseki; A. nordmanniana: Artvin and Torul. The essential oil yields of Anatolian fir woods were remarkably low, in the range 0.01–0.02%. GC-MS results of the essential oils from fir woods are shown in Table 1. Generally, fir essential oils exhibited large differences in both the composition and percentages of compounds between species and from tree to tree. Even within the same region and species, the essential oil composition could vary greatly. Therefore, in this study the composition of fir wood essential oils is given in the compound classes with special emphasize on juvabiones. As can be seen from Table 1, sesquiterpenes are present in the highest percentages in many fir woods. In particular, juvabiones and nerolidol were the main compounds among the sesquiterpenes, and these compounds together with fatty acids constitute a high percentage in some fir species. The monoterpenes often occur in small quantities, and some diterpene related compounds in trace amounts were recorded in fir woods. The monoterpenes varied widely both in their content and chemical structures. It is well known that juvabiones are characteristic compounds for Abies species. As expected, juvabione, dehydrojuvabione, and dihydrojuvabione were detected also in the essential oils of Anatolian fir woods. Both juvabione and dehydrojuvabione concentrations had large variations among the tested trees. This finding is in good agreement with the literature showing that the juvabiones in fir woods can vary considerably in a qualitative and quantitative manner among trees within the same species [3–6, 10]. In our case, juvabione was present in larger amounts than dehydrojuvabione in all 20 trees. This finding is contradictory to the data of [11] who reported that the extract of A. fraseri had a higher amount of dehydrojuvabione than juvabione. It is of interest to note that the Table 1 shows larger variations in juvabione, dihydrojuvabione, and dehydrojuvabione concentrations in fir woods. Similar results were reported for A. balsamea [3], A. alba [4], A. lasiocarpa [5], A. sachalinensis [6], and A. bifolia [10]. These authors studied the juvabiones isolated from hexane or petroleum ether extracts of fir woods and elucidated the structure of these compounds by different techniques. However, in our study the juvabiones were isolated from the oily layer of the water distillates obtained by hydrodistillation. The juvabione content of Abies fraseri woods under intact and infested condition attacked by balsam woody adelgid was studied. The results showed that infested firs had higher mean juvabione levels than uninfested trees [11].