*2.1. Chemical Composition of O. suffruticosum Essential Oil*

The hydrodistillation of fresh aerial parts of *O. suffruticosum* gave an average essential oil yield of 0.23% (*v/w*). According to the present GC-MS analysis, sixteen components representing 85.09% of the EO in composition were identified (Table 1).


**Table 1.** GC-MS analysis of *O. suffruticosum* essential oil.

<sup>A</sup> = Adams [23], <sup>B</sup> = Babushok et al. [24], Wb = NIST Chemistry WebBook [25], MS = In addition to RI, the MS of the analyzed compound matched with the MS of the compound in [23] and/or NIST Chemistry WebBook [25], Unknown = The MS of the compound could not be matched with the available literature data.

> The major constituents of the EO were found to be the hydrocarbons and oxygenated monoterpenes amounting to 84.64%, of which the oxygenated monoterpenes were dominant by 76.49%. The only identified sesquiterpene was found to be caryophyllene oxide present as 0.45%. No hydrocarbon sesquiterpenes were detected. The major constituents were found to be oxygenated monoterpenes: camphor (31.21%), filifolone (13.98%), chrysanthenone (8.72%), 1,8-cineole (7.85%), and terpinen-4-ol (7.39%) (Figure 2).

**Figure 2.** Major components detected in *O. suffruticosum* essential oil.

As per the literature, the *O. suffruticosum* essential oil had never been studied before as it is for other plants of the same genus. However, according to the results obtained, a chemical link to its historical classification in the *Pentzia* genus was observed. Like *O. suffru-*

*ticosum* EO, the chromatographed EOs of *Pentzia incana* [26] and *Pentzia punctata* [27] have shown to possess a significant content of camphor of up to 47.9% and 27.3%, respectively. Additionally, 1,8-cineole was also found as a major compound in *Pentzia incana* with up to 16.7% [26].
