Chemical Composition and Antimicrobial Activity of the Essential Oils from New Caledonian Citrus macroptera and Citrus hystrix

The essential oils from the leaves of Citrus macroptera and C. hystrix, collected in New Caledonia, have been analyzed by gas chromatography/mass spectrometry (GC/MS) and evaluated for their antimicrobial activity. A total of 35 and 38 constituents were identified, representing 99.1 and 89.0% of the essential oils, respectively. Both essential oils were rich in monoterpenes (96.1 and 87.0%, resp.), with β‐pinene as major component (33.3 and 10.9%, resp.), and poor in limonene (2.4 and 4.7%, resp.). Other main components of C. macroptera oil were α‐pinene (25.3%), p‐cimene (17.6%), (E)‐β‐ocimene (6.7%), and sabinene (4.8%). The essential oil of C. hystrix was characterized by high contents of terpinen‐4‐ol (13.0%), α‐terpineol (7.6%), 1,8‐cineole (6.4%), and citronellol (6.0%). The antimicrobial activity was evaluated against five bacteria and five fungi strains. Both oils were inactive against bacteria. However, the C. macroptera leaf oil exhibited a pronounced activity against Trichophyton mentagrophytes var. interdigitale, with a minimal‐inhibitory concentration (MIC) of 12.5 μg/ml.     

Chemical Characteristics,Antimicrobial, and Cytotoxic Activities of the Essential Oil of Egyptian Cinnamomum glanduliferum Bark

The essential oil isolated from the bark of Cinnamomum glanduliferum (Wall ) Meissn grown in Egypt was screened for its composition as well as its biological activity for the first time. The chemical composition was analyzed by GC and GC/MS. The antimicrobial activity of the oil was assessed using agar‐well diffusion method toward representatives for each of Gram‐positive bacteria, Gram‐negative bacteria, and fungi. The cytotoxic activity was checked using three human cancer cell lines. Twenty seven compounds were identified, representing 99.07% of the total detected components. The major constituents were eucalyptol (65.87%), terpinen‐4‐ol (7.57%), α‐terpineol (7.39%). The essential oil possessed strong antimicrobial activities against Escherichia coli, with an activity index of one and minimum inhibitory concentration (MIC) equaling to 0.49 μg/ml. The essential oil possessed good antimicrobial activities against methicillin‐resistant Staphylococcus aureus, Geotrichum candidum, Pseudomonas aeruginosa, Bacillus subtilis, Helicobacter pylori, Aspergillus fumigatus (MIC: 7.81, 1.95, 7.81, 0.98, 31.25, and 32.5 μg/ml, respectively). A considerable activity was reported against S. aureus and Mycobacterium tuberculosis (MIC; 32.5 and 31.25 μg/ml, respectively). The extracted oil was cytotoxic to colon (HCT‐116), liver (HepG2), and breast (MCF‐7) carcinoma cell lines with IC₅₀ of 9.1, 42.4, and 57.3 μg/ml, respectively. These results revealed that Egyptian Cinnamomum glanduliferum bark oil exerts antimicrobial and cytotoxic activities mainly due to eucalyptol and other major compounds.     

Chemical Composition of Hydrodistilled Essential Oil of Artemisia incana (L.) Druce and Antimicrobial Activity against Foodborne Microorganisms

The oil obtained by hydrodistillation from the aerial parts of Artemisia incana (L.) Druce from Turkey was analyzed by GC and GC/MS. Sixty‐three compounds were characterized, representing 97.2% of the total components detected, and camphor (19.0%), borneol (18.9%), 1,8‐cineole (14.5%), bornyl acetate (7.8%), camphene (4.9%), and α‐thujone (4.8%) were identified as predominant components. The essential oil was also tested for its antimicrobial activity against 44 different foodborne microorganisms, including 26 bacteria, 15 fungi, and 3 yeast species. The essential oil of A. incana exhibited considerable inhibitory effects against all bacteria, fungi, and yeast species tested. However, the oil showed lower inhibitory activity against the tested bacteria than the reference antibiotics.     

Iridoid Derivatives with Cytotoxic Activity from Pedicularis uliginosa Bunge

Three new iridoids, rel‐(4aR,7S,7aS)‐7‐hydroxy‐7‐methyl‐1,4a,5,6,7,7a‐hexahydrocyclopenta[c]pyran‐4‐carbaldehyde ( 1 ), 1‐methoxy‐7‐methyl‐1,3,5,6‐tetrahydrocyclopenta[c]pyran‐4‐carbaldehyde ( 2 ), and rel‐(1R,4S,4aS,7R,7aR)‐7‐methylhexahydro‐1,4‐(epoxymethano)cyclopenta[c]pyran‐3(1H)‐one ( 3 ), together with seven known analogues, were isolated from the 95 % EtOH extract of the whole plants of Pedicularis uliginosa Bunge . Their structures were elucidated via extensive NMR spectroscopy and mass spectral data. In terms of inhibitory effects on human tumor cells, compounds 1 , 2 , 6 , 7 , and 8 exhibited better inhibitory activities against ACHN cells than the positive control (vinblastine).     

Chemical Variability of Cleistopholis patens (Benth.) Engl. et Diels Leaf Oil from Ivory Coast

The chemical composition of 48 leaf oil samples isolated from individual plants of Cleistopholis patens (Benth .) Engl. et Diels harvested in four Ivoirian forests was investigated by GC‐FID (determination of retention indices), GC/MS, and ¹³C‐NMR analyses. The main components identified were β‐pinene (traces–59.1%), sabinene (traces–54.2%), (E)‐β‐caryophyllene (0.3–39.3%), linalool (0.1–38.5%), (E)‐β‐ocimene (0.1–33.2%), germacrene D (0.0–33.1%), α‐pinene (0.1–32.3%), and germacrene B (0–21.2%). The 48 oil compositions were submitted to hierarchical clustering and principal components analyses, which allowed the distinction of three groups within the oil samples. The oil composition of the major group (Group I, 33 samples) was dominated by (E)‐β‐caryophyllene and linalool. The oils of Group II (eight samples) contained mainly β‐pinene and α‐pinene, while those of Group III (seven samples) were dominated by sabinene, limonene, and β‐phellandrene. Moreover, the compositions of the Ivoirian C. patens leaf oils differed from those of Nigerian and Cameroonian origins.     

Chemical Composition,Antibacterial, Antioxidant and in Vitro Antidiabetic Activities of Essential Oils from Eruca vesicaria

This work describes the study of the chemical composition and bioactivity of the essential oils (EOs) of the different organs (leaves, flowers, stems and roots) from Eruca vesicaria. According to the GC and GC/MS analysis, all the EOs were dominated by erucin (4‐methylthiobutyl isothiocyanate) with a percentage ranging from 17.9 % (leaves) to 98.5 % (roots). The isolated EOs were evaluated for their antioxidant (DPPH, ABTS and β‐carotene/linoleic acid), antibacterial and inhibitory property against α‐amylase and α‐glucosidase. Most EOs exhibited an interesting α‐glucosidase and α‐amylase inhibitory potential. The roots essential oil was found to be the most active with IC₅₀ values of 0.80±0.06 and 0.11±0.01 μg mL^?1, respectively. The essential oil of roots exhibited the highest antioxidant activity (DPPH, PI=92.76±0.01 %; ABTS, PI=78.87±0.19; and β‐carotene, PI=56.1±0.01 %). The isolated oils were also tested for their antibacterial activity against two Gram‐positive and three Gram‐negative bacteria. Moderate results have been noted by comparison with Gentamicin used as positive control.     

Chemical Variability and Biological Activities of Essential Oils of Micromeria inodora (Desf.) Benth. from Algeria

The chemical composition of the essential oils isolated from the aerial parts of Micromeria inodora (Desf .) Benth . collected in 24 Algerian localities was investigated from the first time using GC‐FID, GC/MS and ¹³C‐NMR. Altogether, 83 components which accounted for 94.7% of the total oil composition were identified. The main compounds were trans‐sesquisabinene hydrate ( 1 ; 20.9%), α‐terpinyl acetate ( 2 ; 19.8%), globulol ( 3 ; 4.9%), caryophyllene oxide ( 4 ; 4.3%), β‐bisabolol ( 5 ; 2.9%) and trans‐7‐epi‐sesquisabinene hydrate ( 6 ; 2.6%). Comparison with the literature highlighted the originality of the Algerian M. inodora oil and indicated that 1 might be used as taxonomical marker. The study of the chemical variability allowed the discrimination of two main clusters confirming that there is a relation between the essential‐oil compositions and the soil nature of the harvest locations. Biological activity of M. inodora essential oil was assessed against fourteen species of microorganisms involved in nosocomial infections using paper disc diffusion and dilution agar assays. The in vitro study demonstrated a good activity against Gram‐positive strains such as Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, and Enterococcus faecalis, and moderate activity against Candida albicans. These results might be useful for the future commercial valorization of M. inodora essential oil as a promising source of natural products with potential against various nosocomial community and toxinic infections.     

Composition,Antifungal and Antiproliferative Activities of the Hydrodistilled Oils from Leaves and Flower Heads of Pterocephalus nestorianus Nábělek

This article reports the first study of the chemical composition, and antifungal and antiproliferative properties of the volatile extracts obtained by hydrodistillation of the flower heads and leaves of the traditional Kurdish medicinal plant Pterocephalus nestorianus Nábělek , collected in the wild. A total of 55 constituents, 43 of the flower heads’ oil (PFO) and 46 of the leaves’ oil (PLO), respectively, were identified by GC/MS, constituting 99.68% and 99.04% of the two oils, respectively. The oils were obtained in 0.15% and 0.10% yields (w/w), respectively, on air‐dried vegetable material. The prevalent constituents of the PFO were α‐terpineol (2.41%), α‐linalool (6.42%), 6,10,14‐trimethylpentadecan‐2‐one (2.59%), myristic acid (24.65%), and lauric acid (50.44%), while the major components of PLO were (E)‐hex‐2‐enal (2.26%), (E)‐hex‐2‐en‐1‐ol (2.04), myristic acid (34.03%), and lauric acid (50.35%). The two oils showed significant inhibitory and fungicidal activities against the medically important fungi Candida albicans, Candida tropicalis, Microsporum canis, and Trichophyton mentagrophytes, with minimum inhibitory concentration ranging from 0.7 to 3.3 mg/ml and minimum fungicidal concentration varying from 1.4 to 6.6 mg/ml. The antiproliferative activity of the two oils was assayed against one normal and six human tumor cell lines. Both oils showed selective cytotoxic activity, with IC₅₀ values ranging from 1.4 to 3.3 μg/ml.     

Chemical Composition and Antimicrobial Activity of the Essential Oil from the Edible Aromatic Plant Aristolochia delavayi

The essential oil obtained by hydrodistillation from the aerial parts of Aristolochia delavayi Franch. (Aristolochiaceae), a unique edible aromatic plant consumed by the Nakhi (Naxi) people in Yunnan, China, was investigated using GC/MS analysis. In total, 95 components, representing more than 95% of the oil composition, were identified, and the main constituents found were (E)‐dec‐2‐enal (52.0%), (E)‐dodec‐2‐enal (6.8%), dodecanal (3.35%), heptanal (2.88%), and decanal (2.63%). The essential oil showed strong inhibitory activity (96% reduction) of the production of bacterial volatile sulfide compounds (VSC) by Klebsiella pneumoniae, an effect that was comparable with that of the reference compound citral (91% reduction). Moreover, the antimicrobial activity of the essential oil and the isolated major compound against eight bacterial and six fungal strains were evaluated. The essential oil showed significant antibacterial activity against Providencia stuartii and Escherichia coli, with minimal inhibitory concentrations (MIC) ranging from 3.9 to 62.5 μg/ml. The oil also showed strong inhibitory activity against the fungal strains Trichophyton ajelloi, Trichophyton terrestre, Candida glabrata, Candida guilliermondii, and Cryptococcus neoformans, with MIC values ranging from 3.9 to 31.25 μg/ml, while (E)‐dec‐2‐enal presented a lower antifungal activity than the essential oil.     

Chemical constituents and antimicrobial activity of the leaf and rhizome oils of Alpinia pahangensis Ridl., an endemic wild ginger from peninsular Malaysia

The essential oils from the leaves and rhizomes of Alpinia pahangensis Ridl ., collected from Pahang, Peninsular Malaysia, were obtained by hydrodistillation, and their chemical compositions were determined by GC and GC/MS analyses. The major components of the rhizome oil were γ‐selinene (11.60%), β‐pinene (10.87%), (E,E)‐farnesyl acetate (8.65%), and α‐terpineol (6.38%), while those of the leaf oil were β‐pinene (39.61%), α‐pinene (7.55%), and limonene (4.89%). The investigation of the antimicrobial activity of the essential oils using the broth microdilution technique revealed that the rhizome oil of A. pahangensis inhibited five Staphylococcus aureus strains with minimum inhibitory concentration (MIC) values between 0.08 and 0.31 μg/μl, and four selected fungi with MIC values between 1.25 and 2.50 μg/μl.     

Chemical Composition and Antimicrobial Activity of Essential Oils from Scabiosa arenaria Forssk. Growing Wild in Tunisia

The essential oils isolated from three organs, i.e., fruits, stems and leaves, and flowers, of the endemic North African plant Scabiosa arenaria Forssk . were screened for their chemical composition, as well as their possible antibacterial, anticandidal, and antifungal properties. According to the GC‐FID and GC/MS analyses, 61 (99.26% of the total oil composition), 79 (98.43%), and 51 compounds (99.9%) were identified in the three oils, respectively. While α‐thujone (34.39%), camphor (17.48%), and β‐thujone (15.29%) constituted the major compounds of the fruit oil, chrysanthenone (23.43%), together with camphor (12.98%) and α‐thujone (10.7%), were the main constituents of the stem and leaf oil. In the case of the flower oil, also chrysanthenone (38.52%), camphor (11.75%), and α‐thujone (9.5%) were identified as the major compounds. Furthermore, the isolated oils were tested against 16 Gram‐positive and Gram‐negative bacteria, four Candida species, and nine phytopathogenic fungal strains. It was found that the oils exhibited interesting antibacterial and anticandidal activities, comparable to those of thymol, which was used as positive control, but no activity against the phytopathogenic fungal strains was observed.     

Chemical Composition and Biological Activities of the Essential Oil of Athanasia brownii Hochr. (Asteraceae) Endemic to Madagascar

The essential oil obtained from hydrodistillation of flowering aerial parts of Athanasia brownii (Asteraceae) was studied for its chemical composition by GC/FID and GC/MS, and for biological activity, namely, antioxidant, antimicrobial, and chemopreventive potential, by DPPH (=2,2‐diphenyl‐1‐picrylhydrazyl), ABTS (=2,2′‐azinobis[3‐ethylbenzothioline‐6‐sulfonic acid), and FRAP (=ferric reducing antioxidant power), disk diffusion test, and MTT (=3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay, respectively. The oil was characterized by a high content of oxygenated sesquiterpenes (71.2%), with selin‐11‐en‐4α‐ol (24.6%), caryophyllene oxide (8.7%), humulene epoxide II (5.1%), and (E)‐nerolidol (4.9%) as the predominant compounds. The oil showed a moderate activity against streptococci as well as radical‐scavenging potential, while the inhibitory effects against human cancer cells examined such as A375 (malignant melanoma) and HCT 116 (colon carcinoma) were significant, with IC₅₀ values of 19.85 and 29.53 μg/ml, respectively.     

Chemical Composition,Cytotoxic and Antibacterial Activities of Essential Oils of Cultivated Clones of Juniperus communis and Wild Juniperus Species

Needles of seven cultivated clones (C1 – C7) of Juniperus communis at lower altitude and three wild Juniperus species (J. communis, J. recurva and J. indica) at higher altitudes were investigated comparatively for their essential oils (EOs) yields, chemical composition, cytotoxic and antibacterial activities. The EOs yields varied from 0.26 to 0.56% (v/w) among samples. Sixty‐one volatile components were identified by gas chromatography‐mass spectrometry (GC/MS) and quantified using gas chromatography GC (FID) representing 82.5 – 95.7% of the total oil. Monoterpene hydrocarbons (49.1 – 82.8%) dominated in all samples (α‐pinene, limonene and sabinene as major components). Principal component analysis (PCA) of GC data revealed that wild and cultivated Juniperus species are highly distinct due to variation in chemical composition. J. communis (wild species) displayed cytotoxicity against SiHa (human cervical cancer), A549 (human lung carcinoma) and A431 (human skin carcinoma) cells (66.4 ± 2.2%, 74.4 ± 1.4% and 57.4 ± 4.0%), respectively, at 200 μg/ml. EOs exhibited better antibacterial activity against Gram‐positive bacteria than against Gram‐negative bacteria with the highest zone of inhibition against Staphylococcus aureus MTCC 96 (19.2 ± 0.7) by clone‐7. As per the conclusion of the findings, EOs of clone‐2, clone‐5 and clone‐7 can be suggested to the growers of lower altitude, as there is more possibility of uses of these EOs in food and medicinal preparations.     

Composition and Activity against Oral Pathogens of the Essential Oil of Melampodium divaricatum (Rich.) DC.

The chemical composition of the essential oil isolated from the aerial parts of Melampodium divaricatum (Rich .) DC. (Asteraceae) was characterized by GC‐FID and GC/MS analyses. (E)‐Caryophyllene (56.0%), germacrene D (12.7%), and bicyclogermacrene (9.2%) were identified as the major oil components. The antimicrobial activity of the oil against seven standard strains of oral pathogens from the American Type Culture Collection (ATCC) was evaluated by determining minimum inhibitory concentrations (MICs) using the microdilution method. MIC Values below 100 μg/ml were obtained against Streptococcus sobrinus (90 μg/ml), Lactobacillus casei (30 μg/ml), S. mutans (20 μg/ml), and S. mitis (18 μg/ml). In contrast, the MIC values of the major oil compound (E)‐caryophyllene were higher than 400 μg/ml against all pathogens, suggesting that the activity of the oil might depend on minor oil components and/or on synergistic effects. The M. divaricatum essential oil is a promising agent to include in anticariogenic oral rinse formulations for the control of oral pathogens.     

Composition and Antimicrobial Activity of the Essential Oils of Laserpitium latifolium L. and L. ochridanum Micevski (Apiaceae)

The chemical composition and antimicrobial activity of essential oils of Laserpitium latifolium and L. ochridanum were investigated. The essential oils were isolated by steam distillation and characterized by GC‐FID and GC/MS analyses. All essential oils were distinguished by high contents of monoterpenes, and α‐pinene was the most abundant compound in the essential oils of L. latifolium underground parts and fruits (contents of 44.4 and 44.0%, resp.). The fruit essential oil was also rich in sabinene (26.8%). Regarding the L. ochridanum essential oils, the main constituents were limonene in the fruit oil (57.7%) and sabinene in the herb oil (25.9%). The antimicrobial activity of these essential oils as well as that of L. ochridanum underground parts, whose composition was reported previously, was tested by the broth‐microdilution method against four Gram‐positive and three Gram‐negative bacteria and two Candida albicans strains. Except the L. latifolium underground‐parts essential oil, the other investigated oils showed a high antimicrobial potential against Staphylococcus aureus, S. epidermidis, Micrococcus luteus, or Candida albicans (minimal inhibitory concentrations of 13.0–73.0 μg/ml), comparable to or even higher than that of thymol, which was used as reference compound.     

Repellent activity of catmint, Nepeta cataria, and iridoid nepetalactone isomers against Afro-tropical mosquitoes, ixodid ticks and red poultry mites

The repellent activity of the essential oil of the catmint plant, Nepeta cataria (Lamiaceae), and the main iridoid compounds (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone, was assessed against (i) major Afro-tropical pathogen vector mosquitoes, i.e. the malaria mosquito, Anopheles gambiae s.s. and the Southern house mosquito, Culex quinquefasciatus, using a World Health Organisation (WHO)-approved topical application bioassay (ii) the brown ear tick, Rhipicephalus appendiculatus, using a climbing repellency assay, and (iii) the red poultry mite, Dermanyssus gallinae, using field trapping experiments. Gas chromatography (GC) and coupled GC-mass spectrometry (GC-MS) analysis of two N. cataria chemotypes (A and B) used in the repellency assays showed that (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone were present in different proportions, with one of the oils (from chemotype A) being dominated by the (4aS,7S,7aR) isomer (91.95% by GC), and the other oil (from chemotype B) containing the two (4aS,7S,7aR) and (4aS,7S,7aS) isomers in 16.98% and 69.83% (by GC), respectively. The sesquiterpene hydrocarbon (E)-(1R,9S)-caryophyllene was identified as the only other major component in the oils (8.05% and 13.19% by GC, respectively). Using the topical application bioassay, the oils showed high repellent activity (chemotype A RD₅₀ = 0.081 mg cm⁻² and chemotype B RD₅₀ = 0.091 mg cm⁻²) for An. gambiae comparable with the synthetic repellent DEET (RD₅₀ = 0.12 mg cm⁻²), whilst for Cx. quinquefasciatus, lower repellent activity was recorded (chemotype A RD₅₀ = 0.34 mg cm⁻² and chemotype B RD₅₀ = 0.074 mg cm⁻²). Further repellency testing against An. gambiae using the purified (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone isomers revealed overall lower repellent activity, compared to the chemotype A and B oils. Testing of binary mixtures of the (4aS,7S,7aR) and (4aS,7S,7aS) isomers across a range of ratios, but all at the same overall dose (0.1 mg), revealed not only a synergistic effect between the two, but also a surprising ratio-dependent effect, with lower activity for the pure isomers and equivalent or near-equivalent mixtures, but higher activity for non-equivalent ratios. Furthermore, a binary mixture of (4aS,7S,7aR) and (4aS,7S,7aS) isomers, in a ratio equivalent to that found in chemotype B oil, was less repellent than the oil itself, when tested at two doses equivalent to 0.1 and 0.01 mg chemotype B oil. The three-component blend including (E)-(1R,9S)-caryophyllene at the level found in chemotype B oil had the same activity as chemotype B oil. In a tick climbing repellency assay using R. appendiculatus, the oils showed high repellent activity comparable with data for other repellent essential oils (chemotype A RD₅₀ = 0.005 mg and chemotype B RD₅₀ = 0.0012 mg). In field trapping assays with D. gallinae, addition of the chemotype A and B oils, and a combination of the two, to traps pre-conditioned with D. gallinae, all resulted in a significant reduction of D. gallinae trap capture. In summary, these data suggest that although the nepetalactone isomers have the potential to be used in human and livestock protection against major pathogen vectors, intact, i.e. unfractionated, Nepeta spp. oils offer potentially greater protection, due to the presence of both nepetalactone isomers and other components such as (E)-(1R,9S)-caryophyllene.     

Chemical composition and larvicidal activity of edible plant‐derived essential oils against the pyrethroid‐susceptible and ‐resistant strains of Aedes aegypti (Diptera: Culicidae)

The chemical compositions and larvicidal potential against mosquito vectors of selected essential oils obtained from five edible plants were investigated in this study. Using a GC/MS, 24, 17, 20, 21, and 12 compounds were determined from essential oils of Citrus hystrix, Citrus reticulata, Zingiber zerumbet, Kaempferia galanga, and Syzygium aromaticum, respectively. The principal constituents found in peel oil of C. hystrix were β‐pinene (22.54%) and d‐limonene (22.03%), followed by terpinene‐4‐ol (17.37%). Compounds in C. reticulata peel oil consisted mostly of d‐limonene (62.39%) and γ‐terpinene (14.06%). The oils obtained from Z. zerumbet rhizome had α‐humulene (31.93%) and zerumbone (31.67%) as major components. The most abundant compounds in K. galanga rhizome oil were 2‐propeonic acid (35.54%), pentadecane (26.08%), and ethyl‐p‐methoxycinnamate (25.96%). The main component of S. aromaticum bud oil was eugenol (77.37%), with minor amounts of trans‐caryophyllene (13.66%). Assessment of larvicidal efficacy demonstrated that all essential oils were toxic against both pyrethroid‐susceptible and resistant Ae. aegypti laboratory strains at LC₅₀, LC₉₅, and LC₉₉ levels. In conclusion, we have documented the promising larvicidal potential of essential oils from edible herbs, which could be considered as a potentially alternative source for developing novel larvicides to be used in controlling vectors of mosquito‐borne disease.     

Chemical Variability of the Essential Oil of Juniperus phoenicea var. turbinata from Algeria

The chemical composition of 50 samples of leaf oil isolated from Algerian Juniperus phoenicea var. turbinata L. harvested in eight locations (littoral zone and highlands) was investigated by GC‐FID (in combination with retention indices), GC/MS, and ¹³C‐NMR analyses. The composition of the J. phoenicea var. turbinata leaf oils was dominated by monoterpenes. Hierarchical cluster and principal component analyses confirmed the chemical variability of the leaf oil of this species. Indeed, three clusters were distinguished on the basis of the α‐pinene, α‐terpinyl acetate, β‐phellandrene, and germacrene D contents. In most oil samples, α‐pinene (30.2–76.7%) was the major compound, associated with β‐phellandrene (up to 22.5%) and α‐terpinyl acetate (up to 13.4%). However, five out of the 50 samples exhibited an atypical composition characterized by the predominance of germacrene D (16.7–22.7%), α‐pinene (15.8–20.4%), and α‐terpinyl acetate (6.1–22.6%).     

Myrtus communis Essential Oil: Chemical Composition and Antimicrobial Activities against Food Spoilage Pathogens

Myrtus communis is a typical plant of the Mediterranean area, which is mainly used as animal and human food and, in folk medicine, for treating some disorders. In the present study, we evaluated in vitro antibacterial and antifungal properties of the essential oils of Myrtus communis (McEO), as well as its phytochemical composition. The GC/MS analysis of the essential oil revealed 17 compounds. Myrtenyl acetate (20.75%), 1,8‐cineol (16.55%), α‐pinene (15.59%), linalool (13.30%), limonene (8.94%), linalyl acetate (3.67%), geranyl acetate (2.99%), and α‐terpineol (2.88%) were the major components. The antimicrobial activity of the essential oil was also investigated on several microorganisms. The inhibition zones and minimal inhibitory concentration (MIC) values of bacterial strains were in the range of 16–28 mm and 0.078–2.5 mg/ml, respectively. The inhibitory activity of the McEO against Gram‐positive bacteria was significantly higher than against Gram‐negative. It also exhibited remarkable activity against several fungal strains. The investigation of the mode of action of the McEO by the time‐kill curve against Listeria monocytogenes (food isolate) showed a drastic bactericidal effect after 5 min using a concentration of 312 μg/ml. These results evidence that the McEO possesses antimicrobial properties, and it is, therefore, a potential source for active ingredients for food and pharmaceutical industries.     

Essential Oil from Blackcurrant Buds as Chemotaxonomy Marker and Antimicrobial Agent

Dormant buds are recognized as valuable side product of the blackcurrant cultivation. Four blackcurrant varieties cultivated in Serbia, i.e., Ben Sarek, Ometa, Ben Lomond, and Ben Nevis, were evaluated for the content, chemical composition, and antimicrobial activity of their bud essential oils. The oil yields of buds harvested during two different growth periods ranged from 1.2–2.0%, and the variety Ometa had the highest yield among the tested varieties. GC‐FID and GC/MS analysis of the oils allowed the identification of eight main components, i.e., α‐pinene (1.6–5.4%), sabinene (1.9–38.4%), δ‐car‐3‐ene (13.0–50.7%), β‐phellandrene (2.9–18.0%), terpinolene (6.6–11.9%), terpinen‐4‐ol (0.9–6.6%), β‐caryophyllene (3.8–10.4%), and α‐humulene (0.2–4.1%). In addition, the similarity degree of the essential‐oil compositions of buds harvested from the upper and lower parts of the shrubs was investigated by hierarchical clustering. All essential oils originating from the same genotype were grouped in the same cluster, indicating the reliability of essential oils as chemotaxonomic markers. For more detailed chemotaxonomic investigations, the three compounds with the greatest variance were chosen, i.e., sabinene, δ‐car‐3‐ene, and β‐phellandrene, which proved to be efficient for the variety distinction. Factor analysis showed that the essential‐oil composition as chemotaxonomic marker in blackcurrants was more reliable for variety Ben Sarek than for variety Ben Nevis. Moreover, it was demonstrated that the essential oils had very strong inhibitory activity against all tested microorganisms. Fungi were more sensitive than bacteria; indeed their growth was completely inhibited at much lower concentrations. In comparison to commercial antibiotics, significantly lower concentrations of the oils were necessary for the complete inhibition of fungal growth.