*3.4. Essential Oil Yield, Composition and Antioxidant Activity*

The essential oil yield in terms of dry weight basis, in general, for all *Sideritis* genus species is considerably low, in contrast with other Lamiaceae family genera [1]. There is a reported yield of *S. perfoliata* from Turkey as low as 0.08% [68]. Kirimer et al. [69] reported the yield of many *Sideritis* species varying from traces to 0.85%, with *S. perfoliata* ranging from 0.12% to 0.36%. When *S. perfoliata* subjected to drought stress (deficit irrigation) which is considered as an abiotic stress factor, EO yield increased up to 0.75% and 0.83% at a conventional and organic cultivation [32]. In the present study the yield was 0.30% ± 0.08%, in accordance with the species records (Table 3). The lower EO yield could be related that the collection of plant material in our study was from an organic plantation for seed/seedling production (''mother" plants) and not a commercial plantation as in previous studies [32]. They have also reported the connection between the yield and the percentage of total monoterpenes or sesquiterpenes in the oils.

**Table 3.** Composition (%) of essential oils of *S. perfoliata* aerial parts, after GC/MS analysis and compound identification. Values are mean percentage (%) of three replicates ±SD.


Not many reports are available in literature characterizing the components of the essential oil of *S. perfoliata* subs *perfoliata*, particularly from plants collected in Cyprus. The essential oil analysis revealed 34 identified compounds, representing the 98.10% of the total chromatogram of the oil profile. The most abundant components were α-pinene (27.92%), β-phelladrene (26.59%), valeranone (11.21%), β-pinene (7.12%), sabinene (4.59%), and α-myrcene, terpinolene, careen, β-caryophyllene with percentages 2–3%. Plants from the Eastern Mediterranean Region of Turkey also revealed the similar oil profile, with high percentage of α and β-pinene and β-phelladrenne [70]. Loizzo et al. [67] also found high percentages of β-phelladrene (32.85%), sabinene (12.76%), α and β-pinene (8.66% and 8.90%) when essential oils from *S. perfoliata* sampled in Lebanon were analyzed, in accordance with the analysis presented here. However, there are studies on *Sideritis* reporting differences between the components and their participation in the oil chromatograph [55,68].

The antioxidant activity of the *S. perfoliata* oils is reported in this study for the first time. The EO exhibited high antioxidant activity, with a two-fold increase of ABTS scavenging activity and Reducing Power whereas a four-fold increase for β-carotene activity was observed, when compared to their respective positive controls (Table 4). A study comparing the antioxidant activity of *S. italica* prepared from the leaves and flower heads reported higher in the EO extracted from the leaves [52].

**Table 4.** Total phenolics, flavonoids, and antioxidants in the leaf essential oil extracted from *Sideritis perforata*.


<sup>a</sup> Butylatedhydroxytoluene, <sup>b</sup> Ascorbic acid.
