Chemical composition of the essential oil from carnation coniferous (Dianthus acicularis Fisch. ex Ledeb) growing wild in Northern Kazakhstan

Abstract The aim of the study was to investigate volatile compounds from the aerial parts of Dianthus acicularis of the genus Dianthus of the family Caryophyllaceae grown wild in Northern Kazakhstan for the first time. D. acicularis is a typical Trans-Volga-Kazakhstani endemic. D. acicularis has high resistance to the bacterial wilt, a serious disease caused by Burkholderia caryophylli. The qualitative and quantitative compositions of the specimens of the essential oils were analysed by the method of GC–MS. The main constituents of D. acicularis essential oil were methyl ketones - 2-pentadecanone (26.9–32.2%) and 2-tridecanone (4.7–17.7%), identified for the first time in the Dianthus genus. The methyl ketone activity provides protection of the plants from herbivores and fungal pathogens. One can suppose that the presence of 2-pentadecanone and 2-tridecanone in the essential oil of carnation coniferous provides its resistance to different insects and pathogens, including the resistance to the bacterial wilt.


Introduction
The genus Dianthus belongs to the Caryophyllaceae family which comprises over 300 species of herbaceous plants, annuals, biennials and perennials, spread over a vast area, which includes warm temperate zones of europe, North America and Asia, and contains many important ornamental species (Shiba & Mii 2005b;Casiglia et al. 2014a). In Kazakhstan the genus Dianthus includes 28 species.
Dianthus acicularis (Supplementary Figure S1 (online only)) -it is a perennial plant forming dense root mat; the leaves are 2-6 cm in length, adjacent to the caulis or remote from it, but not deflexed (Pavlov 1960).
D. acicularis is a typical Trans-Volga-Kazakhstani endemic (Rachkovskaya & Bragina 2012). D. acicularis grows in the far east of europe, in West Siberia, Central Asia (Kazakhstan), in the Far east, in China (Xinjiang). In european Russia, this plant occurs in nature only in the eastern part. D. acicularis is considered to be a rare species in Samara Region and in the Urals. Gorchakovskiy P. l. characterises this species as the Ural rocky and steppe subendemic (Gorchakovskiy & Stepanova 1994).
Paleoendemism and relatively low competitiveness of D. acicularis are the natural reasons of the reduction in its populations. D. acicularis grows in the communities with low projecting cover of the grass and subshrub layer where the competitiveness on the part of the other plants is weakened. The given species can exist over a long period of time by small in number populations on the sites with favourable edaphic conditions. It grows on rocks, stony slopes, in stony steppes and sandy pine forests. The plant blooms in June-July. D. acicularis is a vegetative non-motile plant, propagating only by the seed way. This plant is characterised by gynodioecy. According to the way of pollination, D. acicularis belongs to the entomophilic plants. The white flowers of the plant, well noticeable at night, are pollinated in the evening and nocturnal butterflies of the families of Noctuidae and Sphingidae. The flower scent composition of Dianthus species has relevance for pollination biology and taxonomy (Jürgens et al. 2003).
D. acicularis Fischer ex ledeb has high resistance to the bacterial wilt, a serious disease caused by Burkholderia caryophylli (Pseudomonas caryophylli) (Onozaki et al. 1999). D. acicularis is highly resistant to the hot and humid climate in summer as well as to the cool climate of winter in Japan. Because this wild species has a dwarf nature with beautiful white flowers, its use is now anticipated in breeding programmes for the genus Dianthus as an important germ plasm with bacterial resistance (Shiba & Mii 2005a, 2005b.
D. acicularis is recommended for cultivation as an ornamental plant, having a pleasant aroma of the white flowers, thick pillow-like root mat, abundant and long-continued blossoming. D. acicularis has a great potential for the use in landscape gardening of parks and gardens. It can be grown on flower beds and it can be used as a border plant. It is possible to transplant D. acicularis into a rock garden with other species.
The aim of the study was to investigate volatile compounds from the aerial parts of carnation coniferous (D. acicularis Fisch. ex ledeb) grown wild in Northern Kazakhstan for the first time.

Results and discussion
The chemical composition of the essential oil of D. acicularis growing wild in Northern Kazakhstan was determined. Characteristic of the places of collection of the plant material is given in Supplementary Table S1 (online only). The GC and GC/MS analyses allowed determining the 63 components which amounted to 82.7-85.7% of the oil. The composition of essential oil obtained by hydrodistillation of the dried material was presented in Supplementary Figures S2-S4 and Supplementary Table S2 (online only).
2-tridecanone has broad pest control activity. Pest repellency is a potentially valuable mechanism for protecting plants from arthropod damage. Crops such as fruits and vegetables having low economic injury thresholds, and the crops susceptible to insect-transmitted viruses can especially benefit from protection by repellents (Jones 1987).
According to Forney and Markovetz (Forney & Markovetz 1971), methyl ketones do contribute to the olfactory stimuli evoked in insects by the essential oil in which they are present. Individual methyl ketones in plant essential oils may eventually be found to evoke subtle specific stimuli in insects which resemble those evoked by the same specific compounds synthesised by insects themselves.
2-tridecanone and 2-pentadecanone were found at lower levels in preen oil secretions of the dark-eyed Junco (Junco hyemalis) (both the male and the female juncos). In birds, methyl ketones may be promoting healthy feather conditions by acting as the chemical defence compounds. Perhaps they provide similar protection for feathers (Soini et al. 2007). 2-pentadecanone was revealed in secretion of the spinal glands of springboks and in secretion of the perineal glands of Guinea pigs (Burger et al. 1981).
There are no significant differences in the essential oil composition between plants of D. acicularis grown in dry and very dry conditions. However, the content of major components (2-pentadecanone and 2-tridecanone) in the essential oil of D. acicularis grown in very dry conditions lower in comparison with the essential oil of D. acicularis grown in dry conditions.
The chemical composition of the oil we studied is different from that of the oils from other Dianthus species. As can be seen from Supplementary Table S3 (online only), neither 2-pentadecanone nor 2-tridecanone, forming a part of the essential oil of D. acicularis, are present at composition of the main constituents of the essential oil and floral scent of different species of Dianthus.

Conclusion
The chemical composition of the essential oil of D. acicularis Fisch. ex ledeb from Northern Kazakhstan was studied for the first time. The major components of the oil were 2-pentadecanone (26.9-32.2%) and 2-tridecanone (4.7-17.7%). One can suppose that the presence of methyl ketones of 2-pentadecanone and 2-tridecanone in the essential oil of carnation coniferous (D. acicularis Fisch. ex ledeb) provides its resistance to different insects and pathogens, including the resistance to the bacterial wilt, a serious disease caused by B. caryophylli (P. caryophylli). In the future, it is possible to test the essential oil of D. acicularis for its ability to attract or repel insects.

Supplementary material
experimental details relating to this paper are available online, alongside Figures S1-S4 and Tables S1-S3.

Disclosure statement
No potential conflict of interest was reported by the authors.