Chemical composition and biological activities of essential oils of two new chemotypes of Glebionis Cass.

This paper includes the result of the first study of the chemical composition, antioxidant, antiinflammatory, and antidiabetic activities of the essential oils of Glebionis coronaria (L.) Cass. ex Spach and Glebionis segetum (L.) Fourr. from Turkey. In the current study, nine and twenty-eight constituents were determined in the essential oils of aerial parts of G. coronaria (GCE) (92.1%) and G. segetum (GSE) (90.0%), respectively. The main components were capillin (65.9%) in GCE, capillene (53.4%) in GSE. The essential oil compositions were evaluated and compared with previous researches. In the current study, the plants are classified as chemotypes of Glebionis species. GCE and GSE showed poor and very poor DPPH radical scavenging activity, respectively. GCE and GSE exhibited significant and strong antiinflammatory activity against the 5-lipoxygenase enzyme, respectively. Also, GCE and GSE displayed moderate and weak antidiabetic activity against the α-glucosidase enzyme, respectively. Polyacetylenes were determined as the main class of compounds in GCE and GSE and had a notable antiinflammatory activity.


Statistical analysis
The results were indicated with ± standard deviation. The statistical analysis was done by Tukey's Multiple Comparison Test with a confidence interval (CI) of 95% for each using the GraphPad Prism 5. Differences between means at p<0.05 levels were regarded as important.
The essential oils of G. coronaria and G. segetum possessed remarkable diversities in the main compounds. These diversities could be related to morphological characteristics and different geographical origins. The main compounds of the essential oil from flowers of G. coronaria grown in Sardinia-Italy were α-humulene, camphor, and γ-curcumene [4]; camphor and cis-chrysanthenyl acetate from a population in Tuscany-Italy [13]; trans-tonghaosu from populations in Sicily and Campania-Italy [16]; camphor, α-pinene and lyratyl acetate from a population Murcia-Spain [10]; trans-chrysanthenyl acetate and trans-chrysanthenyl isovalerate from a population in Korinthos-Greece [12]; camphor from a population in Attiki-Greece [12]; cis-chrysanthenyl acetate and trans-chrysanthenyl acetate from a population in Zanghouan-Tunisia [14]; camphor, cis-chrysanthenyl acetate and bornyl acetate from a population in Chile [15]; chrysanthemyl acetate and chrysanthemol from a population in Ukraine [3]; camphor, perilla aldehyde and cis-chrysanthenyl acetate from a population in Jordan [17]. The main compounds of essential oil from stems and leaves of G. coronaria were myrcene, α-bisabolol and (E,E)-α-farnesene from a population in Namyamju-South Korea [18]; (Z)-ocimene and myrcene from a population in Sicily-Italy [16]. The main compounds of the essential oil from aerial parts of G. coronaria were myrcene and (E)-β-farnesene from a population in Jordan [17]; camphor, santolinatriene, yomogi alcohol, cis-chrysanthenyl acetate, and bornyl acetate from a population in Cyprus [9]. The main compounds of the essential oil from flowers of G. segetum were (E,E)-α-farnesene and α-humulene from a population in Sardinia-Italy [4]; tonghaosu from a population in China  [19]. These main compounds were found either in low concentration or not determined in the oils of the present study. The absence of these main compounds in the present study indicates the different chemovarieties of the plants. The previous reports displayed that G. coronaria and G. segetum collected from Italy, Spain, Greece, Tunisia, Chile, South Korea, Ukraine, Jordan, China, and Cyprus had monoterpenes, oxygenated monoterpenes, sesquiterpenes, oxygenated sesquiterpenes, and acetylenes as main groups. In the present research, GCE and GSE have polyacetylenes as the main group and displayed dissimilar chemical profiles from the previous studies. The variations of the essential oil ingredients and composition may be connected to factors such as plant parts used, geographical regions, genotype, ecotype, chemotype, phenophases, and the environmental factors which can be temperature differences, relative humidity, irradiance, and photoperiod. The quantitative composition of the volatile oils of numerous aromatic plants is significantly influenced by the harvesting time, plant age, and product density [27].
There are studies on DPPH radical scavenging activity of essential oil of Chrysanthemum coronarium (Glebionis coronaria) in the literature. In a study, Polatoglu et al. reported that C. coronarium (G. coronaria) essential oil did not have significant DPPH radical scavenging activity [9]. In another study, Hosni et al. found that hydro-distilled essential oil obtained from the C. coronarium flowerheads had DPPH radical inhibition lesser than 15% at a concentration of 200 µg/ mL [14]. However, there is no study on the DPPH radical scavenging activity of the essential oil of Glebionis segetum. In the current study, GCE and GSE showed poor and very poor radical scavenging activity with IC 50 values of 1.020 and 2.525 mg/mL against DPPH radical, respectively (given in Table 2).
GCE and GSE displayed moderate and weak antidiabetic activity with IC 50 values of 0.499 and 0.967 mg/mL against the α-glucosidase enzyme, respectively (given in Table 2). There is no study on the α-glucosidase inhibitory activity of essential oils of GCE and GSE in the literature. However, there is a study on the α-glucosidase inhibitory activity of capillin obtained from CH 2 Cl 2 fraction of MeOH extract of A. capillaris. Capillin showed strong α-glucosidase inhibitory activity [38]. Thus, capillin, which was the main compound of GCE may be responsible for the antidiabetic activity of the oil.
Also, the GCE and GSE exhibited significant and strong antiinflammatory activity with IC 50 values of 0.151 and 0.017 mg/mL against 5-lipoxygenase enzyme, respectively (given in Table 2). Although there is no report on the 5-lipoxygenase enzyme inhibitory or antiinflammatory activity of GCE and GSE, there are studies on the antiinflammatory activity of the extracts of these species. In a study, Strzelecka et al. notified that ethanol extract of C. coronarium (G. coronaria) decreased cytokine or LPS-stimulated iNOS mRNA levels in MBE (Murine brain microvascular endothelial cells) and P388D1 (Murine monocyte/macrophage-like cell line cells) [45]. In another study by Mascolo et al. found the ethanol extract of C. segetum (G. segetum) inhibited carrageenin foot edema by 11% in rats (100 mg/kg p.o.) [46]. Capillin and capillene have been notified to have antiinflammatory features in previous studies [47,48]. Thus, capillin and capillene, determined as main compounds in the GCE and GSE may be responsible for the antiinflammatory activity of the oils.

Conclusion
In general, the essential oil composition of the current study showed differences in quality and quantity from the previous research. These differences of the current study may be considered as chemotypes, which can be named capillin and capillene chemotypes. As a result, polyacetylenes were the main group of the GCE and GSE and had a notable antiinflammatory activity. However, in vivo studies are required to verify our findings.