The chemical composition and the antimicrobial and antioxidant activity of essential oils from two Helichrysum italicum (Roth) G.Don subspecies grown in Bulgaria were investigated. As a result, 95 compounds with concentrations above 0.05% were detected by GC/MS and 46 of them, mainly mono-and sesquiterpenes, representing 79.81% and 85.51% of the total content of the samples, were identified. The main constituents of the essential oil from Helichrysum italicum subsp. microphyllum (plant origin from Bosnia) were monoterpene α-pinene (20.84%) and sesquiterpene γ-curcumene (16.53%), followed by β-selinene (5.59%), ar-curcumene (4.39%), trans-caryophyllene (4.35%), β-diketone italidione I (4.32%), α-selinene (4.28%), and neryl acetate (3.81%). The sesquiterpene hydrocarbons were the dominant groups of chemical constituents in the essential oil, followed by the oxygenated aliphatic hydrocarbons. The main constituents in the H. italicum essential oil (plant origin from France) were neryl acetate (33.87%), γ-curcumene (8.84%), rosifoliol (5.46%), geranyl propionate (4.98%), αr-curcumene (4.31%), italidione I (3.56%), α-eudesmol (3.19%), and limonene (3.02%). The main class of chemical compounds was the oxygenated monoterpenes, followed by sesquiterpene hydrocarbons. H. italicum essential oil from France showed more pronounced antimicrobial activity against the Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis, and the fungus Aspergillus brasiliensis, as well as stronger antioxidant potential.

The genus Nepeta, belonging to the family Lamiaceae, includes about 300 species, most of which are used in folk medicine due to their pronounced biological properties. The aim of the present study was to evaluate the agrobiological characteristics of Nepeta transcaucasica (N. transcaucasica) Grossh. and Nepeta cataria (N. cataria) L., cultivated in Bulgaria, and obtain their essential oils and determine their antimicrobial and antioxidant activities. The agrobiological characteristics of the two species growing in Kazanlak were analyzed; therefore, high variability in the population of N. transcaucasica and comparative homogeneity in N. cataria was shown. The species N. transcaucasica contained 0.28% essential oil with main components β-citronellol (52.05%), eucalyptol (7.34%), β-citronellal (6.06%), germacrene D (5.45%), (Z)-β-ocimene (5.14%), and β-caryophyllene (3.06%). The species N. cataria consisted of 0.19% essential oil with main components β-citronellol (26.31%), geraniol (15.92%), neral (11.45%), nerol (9.56%), carvacrol (6.04%), and β-citronellal (5.35%). The antibacterial activity against Gram-positive bacteria Listeria monocytogenes and Staphylococcus aureus and Gram-negative bacteria Escherichia coli (E. coli) and Salmonella enterica subsp. enterica serovar Abony was determined. The essential oils showed antimicrobial activity only against E. coli. The diameters of the inhibition zones were found to be 26 mm for the species N. transcaucasica and 10 mm for the species N. cataria. The antioxidant activity of the two essential oils was also determined by four different methods, DPPH, ABTS, FRAP, and CUPRAC, with the highest values for the ABTS radical, for the species N. transcaucasica (48.72 μM TE/mL), and the species N. cataria (310 μM TE/mL).