Volatile constituents analysis of Nepeta cataria from central Iran

Abstract

The genus Nepeta (Lamiaceae) comprises 250 species of perennial herbs that are distributed in Europe, Asia, North Africa, and the mountains of tropical Africa. These plants are commonly known as catmint [1]. The common Persian name of this genus is pune-sa, and about 67 species are recorded in Iran [2]. Many Nepeta species have some biological activity and are used in folk medicine because of their antispasmodic, diuretic, antiseptic, antitussive, antiasthmatic, and febrifuge activities [3–8]. Nepeta cataria L. (Lamiaceae) is one of the endemic species of this genus in Iran. N. cataria, commonly known as catnip, is native to Asia Minor and Southeast Europe and grows to a height of 90 cm. It is used as a fortifier, a disinfectant, and a cure against cold [1, 9]. Literature surveys reveal that most oils of Nepeta species such as N. cataria contain nepetalactones as the main component. Antibacterial, fungicidal, and antiviral activities have been attributed to nepetalactones [3, 6, 10]. According to our finding, there is no report on the chemical composition of the essential oil of N. cataria growing in central Iran, so the aim of the present research was to determine the chemical composition of N. cataria essential oil. The constituents of the volatile oil were analyzed by gas chromatography (GC) and gas chromatography–mass spectroscopy (GC–MS). The components of the oil of air-dried herbal parts of N. cataria are listed Table 1, including percentages and retention indices of the components. Constituents are listed in order of their elution from an HP-5MS column. As is shown, nine compounds were identified in the oil of N. cataria, making up 98.0% of the total oil. Among the constituents of the volatile oil, 4aα,7α,7aα-nepetalactone (87.1%), 4aα,7α,7aβ-nepetalactone (3.1%), β-caryophyllene (2.5%), and β-pinene (1.7%) were the major ones; the other constituents were present in relatively small amounts, representing only (3.6%) of the total oil. Nepetalactone isomers, which are the major constituens in our oil, were present in the essential oil of several Nepeta spp [11–20]. It was found that nepetalactones were responsible for the feline attractant properties of Nepeta species. 4aα,7α,7aα-Nepetalactone, which was the main component of our oil, has been detected as the major one in four Nepeta species growing in Turkey [21] and also in N. cataria growing in Germany [22], while caryophyllene oxide, which was abundant in N. cataria from Lebanon [23] and Lithuania [24] (6.4%, 7.3% respectively), was not found in our work. β-Caryophyllene, which was the third major component of our oil, has been reported in the oil of some Nepeta species such as N. cataria [23], N. daenensis [25], and N. fissa from Iran [26], and in N. curviflora growing in Lebanon [23]. On the other hand, 1,8-cineole, which was the most abundant component in many Nepeta species [4, 27–30], was not present in our work. Also, linalool and germacrene D have been identified in sizable amounts in other Nepeta species [4, 29, 31, 32], but traces of these compounds were found as oil constituents in this study. This is not unexpected since plants often manufacture different amounts of phytochemicals when grown in different geographical locations. The aerial parts (leaves and flowers/inflorescences) of Nepeta cataria L. growing wildly in the Kashan area (Isfahan Province, Central Iran) at an altitude of ca. 1550 m were collected in July 2007 and were dried in the shade (at room temperature). Voucher specimens of the plant were deposited in the Herbarium of Kashan Botanical Garden, Research Institute of Forests and Rangelands, Kashan, Iran. The air-dried aerial parts of the plant (130 g) subjected to volatile fractionation were isolated by hydrodistillation using an all-glass Clevenger-type apparatus for 3.5 h according to the method recommended in the European Pharmacopoeia [33]. After decanting and drying of the pale yellow oil (0.89%) over anhydrous sodium sulfate, it was stored in vials at low temperature (4°C) before analysis.