Essential oil composition of four Hypericum species from Iran

Abstract

L., is used as a valuable medicinal plant for nervous exhaustion, depression, and seasonal affective disorders [3]. This genus contains a wide range of different natural product classes, including naphthodianthrones (e.g., hypericin), prenylated phloroglucinols (e.g., hyperforin), xanthones, flavonoids, biflavonoids, tannins, proanthocyanidins, and phenolic acids [4]. Hypericum helianthemoides (Spach) Boiss., H. hirtellum (Spach) Boiss., H. scabrum L., and H. dogonbadanicum Assadi. are four Hypericum species whose oils have been subjected to analysis in this article. H. dogonbadanicum, the only member of the section Campylusporus in Iran, is a narrow endemic plant confined to mountainous regions NE of Gachsaran city, SW of Iran; the other three species belong to the Hirtella section and are distributed W and NW of Iran [2]. Here we report on the chemical composition of these four species, two of which, Hypericum helianthemoides and H. hirtellum, have not been subjected to any previous phytochemical analysis. Data on the constituents of the four Hypericum oils are shown in Table 1. According to Table 1, monoterpenes are the major constituents of H. scabrum (Fars, Doshman Ziari, 2005; 73.7%) and H. dogonbadanicum (Kohkilooyeh, Gachsaran, 2006; 59.4%), while the major compounds in H. helianthemoides (Fars, Hesami, Roshan Kuh, 2005) and H. hirtellum (Fars, Neyriz, 2006) are sesquiterpenes with 74.1% and 53.0% of the total oils, respectively. The first major compound of H. scabrum and H. dogonbadanicum is α-pinene, which is a major and characteristic constituent of many Hypericum species like H. perforatum [5], H. forrestii [6], H. perfoliatum [7], H. triquetrifolium [8], H. hircinum [9], H. hyssopifolium, and H. heterophyllum [10]. In three previous works on H. scabrum oil, α-pinene was also shown to be the first major compound and in two of them, like ours, α-pinene constituted more than 40% of the total oil [11, 12]. However, in the other report α-pinene only comprised 11.2% of the total oil [13]. Comparison of the other constituents of these reports and ours show that the other major compounds are completely different from each other, which could be attributed to different localities where the plant materials were collected. The major constituents of H. dogonbadanicum oils of our work and previous work [14] were the same but differ in order and percentage. α-Pinene (34.7%), β-pinene (32.1%), limonene (12.1%), and camphene (6.6%) were the first four major compounds of previous work that were the first (12.8%), third (4.7%), second (8.2%), and sixth (3.9%) majors of ours. Major compound percentages in our work were totally less than the previous work. Because of the very limited distribution range of this species, locality could not be an important factor in this difference. Our plant material was collected before bud blooming; different stages of flowering may resulted in different chemical compositions of these two oils. Two first major compounds of H. helianthemoides and H. hirtellum are the same; β-caryophyllene (23.3%, 14.1%) and spathulenol (17.4%, 12.3%) with respective percentage. β-Caryophyllene was also among the major constituents of H. perforatum [5], H. triquetrifolium [8], H. bupleuroides [15], H. carinatum [16], H. maculatum [17], H. foliosum [18], and H. brasiliense [19]; and spathulenol was one of the main compounds of H. perforatum [5], H. hissopifolium [20] and H. linarioides [21]. α-Pinene is also the fourth and third major compounds of H. helianthemoides (6.7%) and H. hirtellum (9.8%), respectively. The third major constituent of H. helianthemoides is 14-hydroxy-9-epi-(E)-carophyllene, with the caryophyllene skeleton. Compounds with this skeleton comprise 47.9% of H. helianthemoides total oil. Nonane was a characteristic constituent of H. perfoliatum [7], H. triquetrifolium [8], H. hircium [9], H. scabrum [11], H. caprifoliatum [16], H. foiosum [18], and H. richeri [22] oils, the amount of which was not considerable in the four Hypericum oils of our work.