Introduction

Genus Myosotis belongs to the Boraginaceae family and includes about 100 species occurring mainly in western Eurasia and New Zealand.

Both species differ in morphology and occupy various habitats. M. palustris is covered with straight hairs, decumbent to upright angular stem, rhizome and crown diameter of 5–8 mm. M. arvensis is also covered with hairs, crown with a diameter of 4–5 mm and petioles which are 2–3 times longer than calyx during fruiting. Hairs on the floral cup are hook shaped (Rutkowski 1998).

M. palustris prefers places with moderate light (light indicator according to Ellenberg––L7) and soil with high humidity (moisture indicator––F8). It occurs in wet meadows, at the edge of waters, wetlands. M. arvensis prefers a slightly smaller amount of light than M. palustris. It occurs in wet meadows, at the edge of waters, wetlands (light indicator––L6) on fresh and dry soils (moisture indicator––F5) like fields, fallows, roadsides, grasslands and forest edges (Jäger 2011).

According to the literature, the species of genus Myosotis contain alkaloids, saponins and higher fatty acids (Shinkarenko 2008). However, detailed reports on the chemical constituents of M. arvensis and M. palustris are scarce so far.

Folk medicine recommends M. arvensis in the treatment of malignant tumor of the oral cavity and sex organs and in tuberculosis (Shinkarenko and Vasil’ev 2008). Study conducted in mice showed that aqueous extracts of the aerial part of the M. arvensis exert anxiolytic and antidepressant activity (Polomeyeva et al. 2011). It was also proved that oil extracts of both herbs inhibit the development of bacteria microorganisms, e. g., Shigella sonnei and Candida albicans. Moreover, the extracts of M. arvensis inhibit viability of Staphylococcus aureus and Streptococcus faecalis and the M. palustris extracts inhibit the growth of Pseudomonas aeruginosa (Shinkarenko 2008).

It has already been shown that essential oils may, despite their small amounts, contribute to the therapeutic activities of the plants (Radulović et al. 2006). Among the major biological activities of essential oils antibacterial, antifungal and anti-inflammatory properties are mentioned. The aim of this study was phytochemical investigation and comparison of the components of the M. arvensis and M. palustris volatile oils. To the best of our knowledge, there are no previous reports on the essential oil profile of species belonging to genus Myosotis (Boraginaceae).

Materials and methods

Plant material

M. arvensis and M. palustris herbs were collected from the natural habitats in Central Poland (May and June 2012). Voucher specimens have been deposited in the Department of Pharmacognosy, Poznan University of Medical Sciences, Poznan.

Oil extraction

A 30 g samples of dried M. arvensis and M. palustris herbs were hydrodistillated in a Clevenger-type apparatus with 500 ml of distilled water for 3 h.

Identification of essential oils composition (GC–MS analysis)

The analysis of chemical composition of essential oils was performed using Varian 4000 GC–MS, electron energy of 70 eV and ion source temperature of 200 °C. The instrument was equipped with VF-5 ms silica column (30 m × 0.25 mm × 0.39), d f = 25 µm. Helium was the carrier gas at the flow rate of 1 mL/min and the split ratio 1:10. The oven temperature was programmed at 40 °C (held for 2 min) then gradually increased to 280 °C at the rate of 15 °C/min. The detector temperatures were: 180 °C for ion trap, 50° for manifold and 220 °C for the transfer line. Identification of components was based on comparison of their retention time, as well as mass spectra with standards from the NIST mass spectra library and literature data (Adams 2007). Semi-quantitative data were obtained from relative peak area percentages.

Results and discussion

Hydrodistillation of the herbs of M. arvensis and M. palustris yielded 0.51 and 0.54 % v/w of yellowish essential oils, respectively. The GC–MS analysis of M. arvensis volatile oil revealed the presence of at least 15 components representing 89.63 % of the total oil, while in M. palustris essential oil 21 chemical structures were identified and accounted for 93.19 % of the ingredients of the essential oil fraction. For most of the chemical structures, a good match factor of 800–900 was obtained and some of the compounds were even identified with a very good match factor of >900, while for several constituents match factor was >700 (Table 1). The constituents found in M. arvensis and M. palustris essential oils belong to various chemical groups representing primarily alcohols, aldehydes, ketones, esters, terpenes and saturated fatty acids. The 3-methyl-benzaldehyde was found to be the major constituent of both tested oils (42.76 % in M. arvensis and 45.80 % in M. palustris). Other compounds common for both species are: hexadecanoic acid, 2-hexyl-1-octanol, octanal, 2-methylcyclopentanol, 4-methyl-benzenemethanol, 3-decen-1-ol, 4-nitrophenyl ester o-toluic acid and hexahydroxyfarnesylacetone. Although the compositional data of the essential oils showed some similarities, the components present in minor amounts are quite different for the two tested species, e. g., M. palustris oil is richer in unsaturated aliphatic alcohols.

Table 1 Compounds identified in the essential oils of M. arvensis and M. palustris
Full size table

Some of the identified constituents have already been described in many plant species and were demonstrated to possess medicinal properties, e. g., α-bisabolol oxide B characteristic for M. palustris and methyl salicylate characteristic for M. arvensis. α-Bisabolol is (α,4-dimethyl-α-(4-methyl-3-pentenyl)-3-cyclohexene-1-methanol) monocyclic sesquiterpene alcohol. Its oxidation products are mainly bisabolol-oxide A and B (Kamatou 2010). The compound is also present in some species belonging to Boraginaceae, e.g., Auxemma glazioviana Taub. (Costa et al. 2007). In tested M. palustris essential oil α-bisabolol is present in an oxidized form as α-bisabolol oxide (B). A particularly important medicinal activity of α-bisabolol includes anti-inflammatory, antibacterial and anti-irritant properties. Due to the non-allergenic activity it is widely used in dermatology and cosmetology as an ingredient of different kinds of cosmetics including deodorants, hand, body and after-shave creams, lipsticks, after-sun products, as well as baby care cosmetics (Kamatou 2010; Anonymous 2008).

Methyl salicylate present in M. arvensis oil is a well-known organic ester which exerts anti-inflammatory, analgesic and rubefaction activity. It commonly occurs in many plants, especially belonging to families: Betulaceae (genus Betula) and Rosaceae (genus Spiraea) (Zhang et al. 2011).

A lot of fatty acids exhibit antibacterial and antifungal activity (Dilika et al. 2000) among other hexadecanoic acid (palmitic acid) (McGraw et al. 2002) present in large quantities in the M. arvensis and M. palustris essential oil. The compound is widely distributed in plants including Boraginaceae family, e.g., M. ramosissima, M. sicula, (Özcan 2008) and other like Asteraceae, i. a., Taraxacum officinale F. H. Wigg. (Bylka et al. 2010), Ranunculaceae, e. g., Trollius europaeus L. (Witkowska-Banaszczak 2013), Lamiaceae (Salvia species, Stachys species) (Azcan et al. 2004; Skaltsa et al. 2003). One of the most interesting properties of palmitic acid is the supposed inhibition of HIV-1 infection (Paskaleva et al. 2010). In addition, the constituent exerts antitumor activity against human leukemic cells (Harada et al. 2002). Other compound with anticancer potential is β-ionone, unsaturated cyclic ketone present in M. palustris oil. Its ability of mammary cancer suppression was proved in the study conducted in rats (Liu et al. 2008).

Some of the chemical structures common for both species tested in this study present antibacterial activity. Octanal widely used in perfumery exhibits antimicrobial activity against E. coli, S. cerevisiae, S. aureus and A. niger. It is also a strong antioxidant agent (Liu et al. 2012).

Hexahydroxyfarnesylacetone (6,10,14-trimethyl-2-pentadecanone) may repel insects, while according to some studies aliphatic methyl ketones with long chains exert such activity (Innocent et al. 2008). Also, identified aliphatic alcohols including 2-nonen-1-ol, 2-tetradecen-1-ol, 7-tetradecen-1-ol, and 2-hexyl-1-decanol are common components of essential oils extracted from different plants and for which antimicrobial activity was demonstrated (Manilal et al. 2009; Üçüncü et al. 2010; Ogunlesi et al. 2010; Rahmat et al. 2006).

In conclusion, the identification of M. arvensis and M. palustris components of essential oils may contribute to extending the knowledge of the chemical composition of these two species at the same time revealing species differences. The presence of components possessing proven biological properties may partly justify the use of plant from genus Myosotis in folk medicine.

Author contribution

Authors collected the material to be tested, obtained the essential oils and developed the results of GC–MS analysis. The authors prepared the documentation and described the results of the research in this paper.