Chemical Composition of Eremostachys labiosiformis Growing Wild in Iran and Antimicrobial Activities Against Phytopathogenic Bacteria

Abstract

Eremostachys labiosiformis (Popov) Knorring is a species of flowering plants in the Labiatae family known by the common name, Sonboleh Biabani in Iran. These species are native to Iran, Turkmenistan, and Afghanistan. It is a perennial herb with tuberculate fibrous root, lunate at base. The stem is 40–60 cm, often simple, with simple and fascicled hairs. The leaves are petiole, with basal leaves shorter than the limb, limb 8–20 5–8 cm, oblong or oval, stem leaves shortly petiolate, lower surface with stellate or simple and glandular hair. The flowers are large, yellow, verticillasters 5–7, lower distant, multiflowered, corolla 30–35 mm, upper lip 15 mm, lower lip longer than the upper lip, with hairy annulus within. The flowering period is May–June [1]. Plants produce a diverse range of bioactive molecules, making them, a rich source of different types of medicines. Approximately 20% of the plants found in the world have been submitted to pharmaceutical or biological test, and a sustainable number of new antibiotics introduced on the market are obtained from natural or semisynthetic resources [2]. It has been reported that between the years 1983 and 1994 the systematic screening of antibacterial plant extracts represents a continuous effort to find new compounds with the potential to act against multi-resistant bacteria [3]. So far, no research on phytochemical studies on this plant has been reported. The aim of our study was to evaluate the chemical composition and antimicrobial activity of E. labiosiformis. E. labiosiformis were collected at the flowering stage from the area of Bojnourd, Iran, in June 2011 and identified at the Research Center for Plant Sciences, Ferdowsi University of Mashhad, Iran. A voucher specimen has been deposited in the Environmental Department of Bojnourd Herbarium (EDBH:00108). The present study carried out on E. labiosiformis revealed the presence of medicinal active constituents. The phytochemical active compounds were qualitatively analyzed, and the results are presented in Table 1. In this screening process, alkaloid, saponin, flavonoids, and tannin gave positive results. Gas chromatographic analysis was performed on a Hewlett–Packard (HP) 6890 A instrument equipped with a flame ionization detector and Rtx-5MS (15 m 0.25 mm 0.25 m) capillary column, while the essential oil components were identified on an Agilent Technologies 5973 N mass spectrometer. The GC settings were as follows: initial oven temperature held at 35 C for 6 min and ramped at 5 C min–1 to 150 C for 0 min, then ramped at 10 C min–1 to 280 C for 3 min. The injector temperature was maintained at 250 C. The samples (1 L) were injected neat, with a split ratio of 1:10. The carrier gas was helium at a flow rate of 1.0 mL min–1. Spectra were scanned from 20 to 550 m/z at 2 scans s–1. Most constituents were identified by gas chromatography by comparison of their retention indices with those of the literature or with those of authentic compounds available in our laboratories. The retention indices were determined relative to a homologous series of n-alkanes under the same operating conditions. Further identification was made by comparison of their mass spectra on both columns with those stored in the NIST 05 and Wiley 275 libraries or with mass spectra from the literature [4, 5]. Component relative percentages were calculated based on GC peak areas without using correction factors. The average yield of chemical components of E. labiosiformis was 0.55%. The chemical composition of the plant is outlined in Table 1. Twenty-eight components were identified, accounting for 83.4% of the total oil. The various compounds were identified by comparison of their Kovats retention indexes, determined utilizing a nonlogarithmic scale on nonpolar (Rtx-5MS) columns, and by comparison of the mass spectra of each GC component with those of standards and with reported data [4].