## 4 Discussion
Regarding HE, its populations occupy a wider geographical range: Crete and other Greek Islands, Central Greece, Albania, W. Turkey, Cyrenaica [15; 33]. Intraspecific-variability has been observed, in comparison to some previous studies using plant material collected from Mount Parnitha, Attica [21] and Kos Island, Aegean Sea [26]. In those studies, the plant material has also been subjected to hydro-distillation using a Clevenger apparatus [24; 26], allowing the comparison of the chemical composition of the EOs. The main compound of the EO from HE was \(\alpha\)-pinene (19.0%), a result that is consistent with previous studies for the dominant compound. However, both [PERSON] et al. [24] and [PERSON] et al. [26] reported similarly higher percentages (approx. 35%), while the latter study also describes a high amount of iswarane (30.5%), a compound totally absent in the analysis of [PERSON] et al. [21], which was revealed in small amounts (2.0%) in our study. The same compound was also identified in HA (2.3%). Generally, the most abundant group of compounds was found to be sesquiterpene hydrocarbons; however, some frequently reported constituents to other _Hypericum_ spp., such as germacrene-D and \(\beta\)-caryophyllene [9; 10], were either absent or revealed only in small amounts regarding HA and HJ. Such differences have also been found in the composition of _H. perforatum_ growing wild in Greece [11]. It is noteworthy that HJ was found to be deficient in monoterpene hydrocarbons (0.1%), while this group of compounds was present in HE (36.9%) and HA (15.1%). HA and HJ were also found to be deficient in aliphatic hydrocarbons, like n-nonane, n-decane and n-undecane, which are common compounds in other _Hypericum_ spp. [9; 10]; e.g., _H. caprifolium_ and _H. myrianthum_ are characterized by the production of n-nonane and n-undecane, 55% and 20%, respectively [34]. Similar results have been reported for _H. coris_, the type species of the section Coridium [35]. Finally, _H. ericoides_, also belonging to the section Coridium, has been studied regarding its EO; however, these studies report quite diverse results, which could be explained by the different extraction methods that have been applied: isolation of the EO from the hexane extract of the plant [36], hydro-distillation [37], and headspace solid phase microextraction [38]. Regarding their anti-microbial potential, the obtained EOs were further subjected to the evaluation of antimicrobial activity in a variety of bacteria and fungi. The selected bacteria were some clinical and food isolates. More specifically, most food-borne illness is caused by infection of _Staphylococcus aureus_, _Bacillus cereus_, _Listeria monocytogenes_, _Salmonella typhimurium_ and _Escherichia coli_, while _S. aureus_, _Pseudomonas aeruginosa_, _E. coli_ give rise to some hospital-acquired infections. The tested fungi of _Aspergillus_ and _Penicillium_ genera are plant, animal and human pathogens, food contaminators and producers of potentially carcinogenic mycotoxins. _Penicillium_ species can produce nephrotoxic, carcinogenic, teratogenic and immunotoxic metabolites, such as ochratoxin A, and contaminate cereals and cereal-based products [39]. Thus, in European countries, _P. verrucosum_, which produces this mycotoxin, is a major cause of cereal contamination [40]. Therefore, the presence of toxigenic fungi in cereals and food poses a potential risk to human and animal health. Moreover, _Aspergillus fumigatus_ can cause invasive aspergill in immunocompromised patients [41]. Regarding the selected _Candida_ species, they are responsible for the fungal infections called candidiasis. _C. albicans_ is the cause for oral and genital infections, while _C. brucei_ is the pathogen for fungemia (bloodstream infection). According to given results of the antibacterial tests, EOs showed good activity against tested strains, but in variable degree. Minimal inhibitory concentrations ranged between 0.0025-0.030 mg/mL, and minimal bactericidal concentration was 0.005-0.060 mg/mL.