Major Constituents Of Essential Oil Research Articles

Insecticidal and Repellent Activity of Essential Oils from Copaifera reticulata, Citrus paradisi, Lavandula hybrida and Salvia sclarea Against Immature and Adult Stages of Ctenocephalides felis felis.

The flea Ctenocephalides felis (Siphonaptera: Pulicidae), parasitizes dogs and cats globally, acting as a vector for various pathogens affecting both animals and humans. Growing interest in environmentally friendly, plant-based products prompted this study. The aim of the study was to determine the chemical composition of essential oils (EOs) from Copaifera reticulata, Citrus paradisi, Lavandula hybrida and Salvia sclarea, assessing their insecticidal and repellent properties, determining lethal concentrations (LC50 and LC90), and evaluating residual efficacy in vitro against Ctenocephalides felis felis. Gas Chromatography with Flame Ionization Detector analyzed EO composition. In vitro tests involved preparing EO solutions at various concentrations. Ten specimens from each life stage (egg, larva, pupa, adult) were used for insecticidal activity assessment. Adulticidal activity was assessed using 10cm2 filter paper strip, each treated with 0.200mL of the test solution. Immature stages activities were evaluated using 23.76cm2 discs of the same filter paper, each treated with 0.470mL of the test solution. Mortality percentage was calculated using (number of dead insects × 100) / number of incubated insects. Probit analysis calculated LC50 values with a 95% confidence interval. Major EO constituents were β-caryophyllene (EOCR), linalool (EOLH), linalyl acetate (EOSS), and limonene (EOCP). LC50 values were obtained for all stages except for the essential oil of C. paradisi. All oils showed repellent activity at 800μg/cm2. OECR exhibited greater residual efficacy. Each EO demonstrated superior insecticidal activity against specific C. felis felis stages.

Isolation and characterization of Thymus serpyllum L. essential oil and mass fragmentation analysis of major constituents

ABSTRACT The essential oils were isolated from Thymus serpyllum L. leaves, stem, flowers and whole plant using hydrodistillation technique and % yield was determined. The chemical constituents were studied using Gas Chromatography-Mass Spectrometry and Gas Chromatography-Flame Ionisation Detection. The analysis revealed the presence of 38 compounds in the essential oils obtained from different plant parts. Identification of compounds was achieved by detailed analysis of mass spectrum and retention indices. The major constituents of essential oil from the whole plant were thymol (35.25%), p-cymene (27.57%), thymol acetate (8.03%) and γ-terpinene (6.92%). In leaves they were thymol (45.59%), p-cymene (24.26%), thymol acetate (6.41%), and β-bisabolene (5.91%); whereas in flowers these were thymol (68.74%) and thymol acetate (7.40%) and in the stem, these were thymol (55.15%) and thymol acetate (8.01%). Specifically, it is the first report wherein essential oil constituents of T. serpyllum L. whole plant, leaves, flowers, and stems have been analyzed separately. Further, fundamental analysis of complex mass fragmentation patterns of terpenes and terpenoids using EI-MS has been achieved and the logical reason for the fragmentation pattern has been elaborated. Detailed elaboration of the mass fragmentation pattern may strengthen the EI-MS-based compound identification of terpenes and terpenoids from essential oils.

The First Study on Cultivating Roman Chamomile (Chamaemelum nobile (L.) All.) for Its Flower and Essential Oil in Southeast Serbia

Roman chamomile (Chamaemelum nobile (L.) All.) is a perennial herbaceous medicinal plant species that has not yet been thoroughly researched in terms of the influence of growing conditions on its morphological characteristics, flower yield, and the content and quality of its essential oil (EO). The plant material was harvested in the subsequent two production years at three localities in Southeast Serbia, differing in soil type (Alluvial soil, Rendzina, and Calcomelanosol). Based on two-year average values, the best results were obtained from plants grown on Rendzina, including the yield of fresh flowers (1850.2 g/m2), the highest plant height (49.3 cm), the number of branches (4.1), leaves (11.6), and flower heads (3.6), the flower diameter (1.6 cm), and the essential oil content (1.6%). The major EO constituent obtained from the plants growing on Rendzina and Calcomelanosol was 3-methyl pentyl angelate (20.8% and 15.2%, respectively). In the EO obtained from the plants growing on Alluvial soil, the major EO constituent was isobutyl angelate (13.0%), while the content of 3-methyl pentyl angelate was close to it (12.2%). The outcomes of this study provide guidelines for further research related to the cultivation of a Roman chamomile genotype on various soil types in a hilly region of Southeast Serbia, where most cultivated plants cannot be grown.

Antifungal efficacy and phytochemical characterization of citronella (Cymbopogon winterianus Jowitt ex Bor) essential oil against fungal pathogens causing severe diseases in Mentha arvensis L.

Mentha arvensis L. (family Lamiaceae) is one of the important medicinal plants and India is the largest producer of Mentha oil in the world, contributing about 80% of the total global production followed by China (9%), Brazil (7%) and the USA (4%). However, this crop suffers quantitative and qualitative losses due to the wilt and leaf spot diseases caused by the fungi Fusarium oxysporum and Alternaria alternata, respectively; therefore, an attempt has been made for the management of these fungal pathogens. The citronella essential oil was extracted by hydro-distillation method (Clevenger, 1928). The oil thus extracted was used for in vitro antifungal efficacy against the both fungi F. oxysporum and A. alternata, using poison food technique. The results showed that the minimum inhibitory concentration (MIC) of the citronella oil against F. oxysporum and A. alternata was 1.0 μL/mL; however, it was cidal in nature at 1.2 μL /mL and 1.5 μL/mL against both fungi, respectively. Further, phytochemical characterization of citronella oil was done using GC/GC-MS. Gas chromatographic analysis of the citronella oil revealed 18 phytoconstituents which were identified by retention indices aided with NIST-MS database. The major constituents of essential oil were citronellal (28.78%), geraniol (26.31%), citronellol (12.90%), geranial (9.85%), and neral (7.9%). The findings of the current study show that citronella oil could be an alternative to synthetic fungicides, after detailed investigations.

Comprehensive analyses of inhibition of the Chinese traditional food-packaging materials, Indocalamus latifolius leaves (Zongye) on Aspergillus flavus

Abstract Objectives The contamination of Aspergillus flavus and aflatoxins (AFs) is one of the most serious safety problems in food and feed. The discovery and application of plant-sourced antifungal agents are hot topics in mycotoxin control. In this study, we aim to develop efficient strategies to control A. flavus and subsequent contamination by AFs. Materials and Methods We focused on Zongye essential oil, which was extracted from Indocalamus latifolius leaves (Zongye, the traditional food-packaging materials). Its antifungal and antitoxin activities were observed by volatile test, and the significant morphological and ultrastructural variations were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. The main components of Zongye essential oil were analyzed by gas chromatography-mass spectrometry (GC-MS). RNA sequencing (RNA-Seq) and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) analyses were used to reveal the inhibitory mechanism. Results Among them, No. 2 Zongye essential oil completely inhibited the growth and toxin production of A. flavus after 10 µL treatment. Under Zongye essential oil treatment, evidently morphological and ultrastructural variations were observed, such as hyphae shrinkage, partial distortion, and a decrease in conidia number. Longifolene and linalool were the major constituents of Zongye essential oil, accounting for 9.55% and 7.95%, respectively, and linalool had stronger inhibitory effects on fungal growth and mycotoxin biosynthesis than longifolene. Based on the experimental results, the antifungal mechanism was proposed: down-regulations of membrane proteins (AFLA_005560, AFLA_019420, and AFLA_084310, etc.) and conidial genes (fblC, steA, and abaA, etc.) inhibited fungal development, and anti-aflatoxigenic activity might be due to significant down-regulation of AF cluster genes and global regulators (AtfA and AtfB). Conclusion A novel antifungal agent, Zongye essential oil, was identified, and its inhibitory mechanism was comprehensively clarified, which is helpful to control AF contamination in an environmentally friendly way.

Phytochemical and biological investigations on Centranthus kellereri (Stoj., Stef. & T. Georgiev) Stoj. & Stef. and C. ruber (L.) DC. and their potential as new medicinal and ornamental plants.

Centranthus kellereri is a Bulgarian endemic plant species, found only in two locations in the world: The Balkans Mountains (Stara Planina), above the town of Vratsa, and The Pirin Mountains, above the town of Bansko, Bulgaria. Being endemic and endangered species precluded any significant research on it. The hypothesis of this study was that the populations of C. kellereri may represent genetically, phytochemically, and morphologically distinct forms and these will differentiate from C. ruber. Furthermore, C. kellereri possibly imperfect embryology may preclude its more widespread distribution under natural conditions. This study revealed the phytochemical profile, antioxidant activity, embryology, surface microstructural morphological traits, and genetic differences between the C. kellereri plants from the only two natural populations and compares them to the ones of the related and better-known plant C. ruber. The essential oil (EO) content in aboveground plant parts and in roots was generally low and the EO composition varied significantly as a function of plant part, year of sampling, location, and species. Methylvaleric acid was a major EO constituent in the C. kellereri EO, ranging between 60.2% and 71.7% of the total EO. The EO included monoterpenes, sequiterpenes, long-chain alkanes and fatty acids. Phytochemical analyses of plant tissue revealed the occurrence of 32 compounds that were tentatively identified as 6 simple phenolics, 18 flavonoids, 1 quinone, 1 lipid, 1 alkaloid, 2 diterpenes, and 3 triterpenes. There were differences in detected compounds between the C. kellereri plants at the two locations and between the roots and shoots in both species. The total phenols and flavonoids varied between the two species but were also dissimilar between the plants from the two populations of C. kelleri. Free radical scavenging activity, measured with ABTS and DPPH in aqueous and methanol extracts, had similar values; however, overall, C. kellereri from Vratsa showed the highest antioxidant activity while C. ruber had the lowest activity. Genetic analyses showed a clear differentiation between C. kellereri and C. ruber, and between the two populations of C. kellereri. Embryological studies revealed the peculiarities of the male and female generative spheres of the two species that were defined as being sexually reproducing. The pollen had high viability; however, the low viability of seeds demonstrated possible high sensitivity of C. kellereri to the environmental conditions, perhaps the main factor modifying and restricting the population sizes. The SEM analyses exposed differences in surface microstructural traits between the species (C. kellereri and C. ruber) but also between the two populations of C. kellereri. The observed dissimilarities in genetic makeup, micromorphological characteristics, and phytochemical composition strongly indicate that the two populations can be classified as distinct subspecies or varieties of C. kellereri; var. pirinensis and var. balkanensis. Further research is needed to introduce C. kellereri into culture and develop it as a high-value specialty crop or ornamental in order to conserve C. kellereri natural populations. C. kellereri may be utilized as a source for phytochemicals of interest and as an ornamental plant like C. ruber; however, it may have a greater environmental plasticity and adaptation as evidenced by its current locations.

Exogenous melatonin differentially affects biomass, total carbohydrates, and essential oil production in peppermint upon simultaneous exposure to chitosan-coated Fe3O4 NPs

Melatonin and iron play important roles in the growth processes and production of secondary metabolites in medicinal plants. To evaluate the effects of melatonin and Chitosan-Coated Iron Oxide Nanoparticles (Fe-CTs NPs) on peppermint growth, essential oil content and constituents, total carbohydrates and antioxidant enzyme activities, a factorial experiment was conducted based on randomized complete block design (CRBD) with three replications (n = 3). Treatments consisted of different concentrations of melatonin (0, 100, and 200 mg L−1) and Fe-CTs NPs (0, 7.5, and 15 mg L−1). During the experiment, foliar applications of melatonin and Fe-CTs NPs were performed three times with 20 days’ interval. Treatments with melatonin, and Fe-CTs NPs had significant effects on the studied traits. The results showed that with increasing melatonin and Fe-CTs NPs concentrations, fresh and dry weights, total carbohydrates, and leaf area index were significantly (P < 0.05) increased in treated plants. The highest CAT and APX activities were observed in plants treated with melatonin at 100 mg L−1 and Fe-CTs NPs at 15 mg L−1. Eucalyptol, Menthyl acetate, Thiophene, 2-ethyl-5-(2-methylpropyl), Mint furanone, and Viridiflorol were found as the major essential oil constituents in peppermint plants under experimental treatments. Moreover, analytical results showed that the highest amount of Menthol (38.48 %) was obtained in plants exposed to Fe-CTs NPs at 7.5 mg L−1, however, the highest L-Menthone (30.53 %) was observed in plants treated with melatonin at 200 mg L−1 and Fe-CTs NPs at 15 mg L−1. The findings provide insights into the regulatory mechanisms of melatonin and Fe-CTs NPs on peppermint growth, physiology and biosynthesis of volatile compounds.

Electrochemical sensing of monoterpene phenols in plant essential oils using a molecularly imprinted polymer dual-template sensor

Monoterpene phenols are naturally occurring aromatic compounds found in plant essential oils, contributing to their distinct flavors, fragrances, and medicinal properties. Thymol and carvacrol, major constituents of thyme and oregano essential oils, have garnered significant attention due to their diverse biological activities. Here, we propose the development of a novel double template molecular imprinted electrochemical sensor (DT-MIP sensor) for the selective and simultaneous detection of thymol and carvacrol. The sensor's performance was optimized by varying the quantity of functional monomer, cross-linker, and template molecules during MIP synthesis. The DT-MIP sensor demonstrated superior recognition properties and high sensitivity, with detection limits of 0.11 μM for carvacrol and 0.24 μM for thymol. Selectivity tests confirmed minimal interference from potential interfering agents. GC-MS analysis validated the sensor's accuracy in detecting thymol and carvacrol concentrations in thyme and oregano essential oils. The simplicity, cost-effectiveness, and portability of the DT-MIP sensor offer promising applications in food quality control, environmental monitoring, and medical diagnostics.

Floral biology insights into essential oil yield and chemical composition in davana (Artemisia pallens Bess), a high-value aromatic plant of India

Floral organs are identified as the major source of essential oil production in some prime aromatic plants. The quality and quantity of the essential oil are also influenced by the floral developmental stages. The present study was undertaken in A. pallens Bess (davana) with respect to its floral biology and floral sequence in relation to the essential oil yield and its chemical constituents for industrial extraction. The findings revealed that floral (inflorescence) biomass is the primary source of essential oil yield in davana, with the highest oil yield (0.90 ml/100 g) recovered during the blooming stage, followed by herbage (stems and leaves) biomass. Furthermore, cis-davanone, the major chemical constituent of davana essential oil, was recorded at a higher percentage in the bud stage (66.36±0.60%) followed by the blooming stage (60.56±0.20%) and the seed setting stage (40.54±0.80%). These findings can be used to optimize harvest timing in order to obtain higher quality and quantity of davana essential oil.

Chemical characterization of mint (Mentha spp.) germplasm from Central Java, Indonesia

Abstract. Lianah L, Kusumarini N, Hafshah M, Krisantini K, Kurniawati A, Ahmad MA. 2023. Chemical characterization of mint (Mentha spp.) germplasm from Central Java, Indonesia. Biodiversitas 24: 4307-4313. The main objective of this work was to evaluate and compare the leaf production and oil content of the four mint genotypes (Mentha spp.) from Central Java, Indonesia. Four genotypes were collected from Rejosari Village, Kudus District, Central Java, Indonesia, namely spearmint (Mentha spicata), peppermint (Mentha x piperita), orange mint (Mentha x piperita ‘Orange’) and chocolate mint (Mentha x piperita ‘Chocolate’). Essential oil extraction was carried out by steam distillation. Identification of the chemical compounds of the oil and their relative percentage were analyzed using GC-MS. Leaves productivity ranged between 500-1000 kg/ha, and essential oil content from 0.4 to 1.36%. The major essential oil constituents detected were 1,8-cineole, carvone, limonene, linalool, linalyl acetate, menthol, menthone, menthyl acetate, and piperitenone oxide. Chocolate mint had the highest leaf production and the highest content of essential oil (4.17%) and menthone yield (28%) compared to the other genotypes.

In Vitro and In Vivo Antimelanogenesis Effects of Leaf Essential Oil from Agathis dammara.

Agathis species are widely distributed around Southeast Asia, Australasia, South Pacific islands, and etc. Traditionally, Agathis species have been used as the folk medicines, the common ethnopharmacological uses of Agathis genus are the treatments of headache and myalgia. This study aims to investigate the chemical composition of Agathis dammara (Lamb.) Rich. leaf essential oil and to explore its antimelanogenesis effect. The chemical constituents of leaf essential oil are analyzed using gas chromatography-mass spectrometry (GC-MS), the major constituents of leaf essential oil are sesquiterpenoids. The major constituents are δ-cadinene (16.12%), followed by γ-gurjunene (15.57%), 16-kaurene (12.43%), β-caryophyllene (8.58%), germacrene D (8.53%), and γ-cadinene (5.33%). As for the in vitro antityrosinase activity, leaf essential oil inhibit the tyrosinase activity of mushroom when the substrate is 3,4-dihydroxyphenylalanine (L-DOPA). Leaf essential oil prevents tyrosinase from acting as diphenolase and catalyzing L-DOPA to dopaquinone, and converting into dark melanin pigments. A. dammara leaf essential oil also exhibits the in vivo antimelanogenesis effect, leaf essential oil reduces 43.48% of melanin formation in zebrafish embryos at the concentration of 50 μg/mL. Results reveal A. dammara leaf essential oil has the potential for developing the skin whitening drug and depigmentation ingredient for hyperpigmentary disorders.

Cuticular property affects the insecticidal synergy of major constituents in thyme oil against houseflies, Musca domestica

Plant essential oils are intricate blends comprising predominantly of monoterpenes and some sesquiterpenes. These oils display diverse bioactivities against targeted organisms, often arising from complex interactions among their constituents, which may demonstrate synergistic or antagonistic effects. Despite their wide use as botanical insecticides, the mechanisms behind these interactions and their effects on bioactivity are poorly understood. This study investigated the synergistic interaction of thymol and p-cymene, two major constituents of Thymus vulgaris essential oil, on the larvae and adults of the housefly, Musca domestica. The results showed that p-cymene synergized the insecticidal activity of thymol in adult houseflies, but not in larvae. GC–MS analyses and bioassays indicated the increased cuticular penetration of thymol by p-cymene was the mechanism of synergy, which was observed only in the adults. Two potential routes were proposed: the expansion of the wetting area, or the disruption of cuticular integrity through dissolving the wax layer. The sequential application and large-volume treatment bioassay results suggested that the former was the more likely mechanism. Also, the hydrophobicity of the cuticle seemed critical for this stage-specific synergy. Wax-devoid adults failed to show synergistic toxicity, whereas artificially wax-coated larvae gained a synergistic effect. Overall, the findings provide insights into the synergistic mechanism of insecticidal activity of plant essential oils and suggest potential applications in developing effective strategies using penetration-enhancing synergists.

Antifungal Properties of Pinus eldarica and Pinus longifolia Fruit Extracts against Candida Species Isolated from Vulvovaginal Candidiasis Patients

Introduction:Candidiasis is a disease with serious problems in women. With the increasing drug resistance and risks of the drugs, we investigated the effect of different cone extracts of Pinus eldarica and Pinus longifolia against Candida species isolated from vulvovaginal candidiasis patients.Materials and Methods::Candida species isolated from 50 patients were identified by routine mycological methods, including morphology of corn mil agar, chromium agar, germination, and biochemical methods. The anti-candida properties of the extracts and essential oils of Pinus eldarica and Pinus longifolia were investigated using agar diffusion and microdilution test. The essential oil was then analyzed by Gas chromatography-mass spectrometry (GC-MS).Results:The major constituents of Pinus longifolia essential oil included 23.16% alpha-pinene, 2.59% beta-caryophyllene, 23.61% delta-3-carene, 0.24% carcin-4-hydroxy, 13.56% m-cymene, 0.45% alpha-humulene, and 2.12% junipene. The major constituents of Pinus eldarica essential oil included 29.13% alpha-pinene, 14.22% beta-caryophyllene, 11.70% delta-3-carene, -14.22% carcin-4-hydroxy, 4.29% beta-pinene, 3.59%, alpha humulene, and 8.86% junipene. The results of antifungal tests showed that aqueous, ethanolic, and methanolic extracts had a weak anti-candida effect. By changing the solvent and using petroleum ether solvent, it was found that petroleum ether extract and cone essential oil of Pinus longifolia and Pinus eldarica exhibited a relatively strong anti-candida effect.Discussion and Conclusion:Comparison of Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC) of four extracts of Pinus longifolia and Pinus eldarica against different Candida showed that the lowest MIC and MFC were related to essential oil, petroleum ether extract, methanolic extract, ethanolic extract, and aqueous extract, respectively.

Chemical Composition and In Vitro Antimicrobial, Antioxidant, and Tyrosinase-Inhibiting Activity of Essential Oils Extracted From the Leaves and Twigs of Calocedrus macrolepis var. formosana

In this study, we focused on evaluating the antimicrobial, antioxidant, and tyrosinase-inhibiting properties of leaf and twig essential oils from Calocedrus macrolepis var. formosana. Additionally, we determined the major components associated with these effects. The findings revealed that α-pinene (36.4%) and limonene (23.6%) were the dominant components in the leaf essential oil, while α-pinene (36.2%), ferruginol (22.5%), and limonene (13.1%) were the major constituents in the twig essential oil. However, when comparing the biological activities of the 2 essential oils, the twig essential oil demonstrated excellent inhibitory effects against skin pathogens, as well as strong antioxidant and tyrosinase-inhibiting activities, in contrast to the leaf essential oil. The twig essential oil also exhibited excellent antimicrobial activity against 5 skin pathogenic strains, with the strongest inhibitory effect being that against Staphylococcus aureus, S epidermidis, and Candida albicans, which was accompanied by an inhibition zone of 46 to 48 mm, a minimum inhibitory concentration (MIC) of 125 μg/mL, and a minimum bactericidal concentration (MBC) of 250 μg/mL. The inhibitory activity of the twig essential oil against lipid peroxidation was found to be potent, as evidenced by an IC50 value of 216 ± 1.9 μg/mL. It also exhibited strong scavenging activity against free radicals, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) (IC50 = 121.6 ± 0.5 μg/mL) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (IC50 = 136.8 ± 1.6 μg/mL) cation radicals. In addition, it exhibited a high cupric ion reducing–antioxidant capacity (CUPRAC), with the A0.50 value determined to be 186.28 ± 0.5 μg/mL. It also exhibited adequate activity in terms of inhibiting in vitro tyrosinase activity, as evidenced by an IC50 value of 168.5 ± 0.6 μg/mL. Further analysis revealed that ferruginol was the active component responsible for the antimicrobial, antioxidative, and tyrosinase-inhibiting activities observed in twig oil. These findings suggest that the twig oil is a promising candidate for further research because of its favorable antimicrobial, antioxidative, and tyrosinase-inhibiting activity.

Chemical composition and antimicrobial activity of essential oil obtained from the rhizomes of Kaempferia champasakensis: in vitro and molecular docking studies

Kaempferia champasakensis Picheans. & Koonterm (Zingiberaceae) is locally known as “Dia Lien hoa trang” in Vietnam. Despite a previous study on the essential oils (EO) of K. champasakensis leaves, no other studies have reported the chemical components and biological activities of K. champasakensis. Therefore, this study aims to identify the chemical constituents of the EO from the rhizomes of K. champasakensis and evaluate their antimicrobial activity, which has been re-confirmed through molecular docking studies. The gas chromatography-mass spectrometry (GC/MS) analysis revealed sixty-one constituents (95.4%) present in the EO of K. champasakensis rhizomes. Among them, camphene (40.7%), α-pinene (10.2%), and β-pinene (7.6%) were identified as the main compounds in the EO. Bioassays indicated its antimicrobial activity in the order of inhibitory effectiveness: Staphylococcus aureus > Enterococcus faecalis ≈ Candida albicans > Bacillus cereus ≈ Escherichia coli > Salmonella enterica > Pseudomonas aeruginosa. The molecular docking study of ligand-protein interactions involving the major constituents of EO was conducted against target proteins related to Staphylococcus aureus, Enterococcus faecalis, Candida albicans, Bacillus cereus, and Escherichia coli main activities. The results revealed that α-pinene exhibited strong binding affinity against E. coli, β-pinene demonstrated more effective inhibition against E. faecalis and B. cereus, and camphene primarily exhibited activity against C. albicans and S. aureus. Furthermore, the analysis of interactions between the main compounds and the selected proteins was elucidated in the current study. This is the first time that chemical components of the EO of K. champasakensis rhizomes and their antimicrobial activity have been reported. These findings contributed to the basis for further studies on the chemical compositions and biological effects of K. champasakensis.

Oviposition deterrent activity of hydrolate, aqueous extract and major constituents of essential oil from the leaves of Eugenia uniflora (Myrtaceae) for the control of Aedes aegypti

Aedes aegypti is the main vector of arboviral diseases, such as dengue, Zika and chikungunya. The emergence of resistance to synthetic insecticides constitutes an important obstacle to combating the mosquito. Thus, studies have investigated the potential of natural products as an alternative to synthetic chemicals. The aim of the present study was to evaluate the oviposition deterrent activity of different products extracted from the leaves of Eugenia uniflora, which is a native species of Brazil with known bioactive properties but explored little for the control of A. aegypti. The major constituents identified in the essential oil from E. uniflora by gas chromatography coupled to mass spectrometry were selina-1,3,7(11)-trien-8-one (65.83%) and selina-1,3,7(11)-trien-8-one epoxide (13.53%). These major constituents were also identified in the dynamic headspace of the hydrolate and aqueous extract and in the ether fraction of the aqueous extract together with pyrogallol. Other classes of secondary metabolites were also identified in the aqueous extract using high-performance liquid chromatography, such as gallic acid, myricetrin and ellagic acid. The results of the bioassays suggest significant oviposition deterrent activity for the essential oil at concentrations of 9–36 ppm, the isolated substance selina-1,3,7(11)-trien-8-one epoxide at 3.6 ppm, the aqueous extract at 51% (v/v) and hydrolate at 53% (v/v). The magnitude of oviposition deterrent activity for the products extracted from the leaves of E. uniflora, especially the hydrolate and aqueous extract, was one of the most notable ever reported for the inhibition of oviposition by gravid females of A. aegypti. The aqueous extract and hydrolate achieved greater than 90% inhibition. Moreover, the minimum concentration (3.6 ppm) with deterrent activity found for the substance isolated from the essential oil: selina-1,3,7(11)-trien-8-one epoxide - is one of the lowest ever described in the literature.

Thymol-Nanoparticles as Effective Biocides against the Quarantine Pathogen Xylella fastidiosa.

Quarantine pathogens require the investigation of new tools for effective plant protection. In particular, research on sustainable agrochemicals is the actual challenge. Plant extracts, essential oils, and gels are natural sources of efficient biocides, such as aromatic secondary metabolites. Thymol is the major phenolic constituent of thyme and oregano essential oils, and it can inhibit many pathogenic microbes. Thymol nanoparticles were obtained through adsorption on CaCO3 nanocrystals, exploiting their carrier action. High loading efficiency and capability were reached as verified through UV and TGA measurements. We report the first study of thymol effect on Xylella fastidiosa, conducing both fluorometric assay and in vitro inhibition assay. The first test confirmed the great antibacterial effect of this compound. Finally, an in vitro test revealed an interesting synergistic action of thymol and nanocarriers, suggesting the potential application of thymol-nanoparticles as effective biocides to control Xylella fastidiosa infection.

Essential oil composition and antimicrobial potential of aromatic plants grown in the mid-hill conditions of the Western Himalayas

Essential oils are highly concentrated natural extracts obtained from plants, rich in bioactive constituents with antimicrobial properties, but the distinctive climate of the Western Himalayan region influences the same. Aromatic and medicinal plants, viz., Origanum majorana, Origanum vulgare, Cymbopogon winterianus, Pelargonium graveolens, and Nepeta cataria were grown in the foothills of the Western Himalayan condition and evaluated for essential oil content, composition, and their effect on some of the most common pathogenic microorganisms. The essential oil content (%) was 0.77, 0.45, 1.37, 0.15 and 0.17% in O. majorana, O. vulgare, C. winterianus, P. graveolens, and N. cataria, respectively. The major essential oil constituents of the isolated oils were terpinen-4-ol, thymol, citronellal, citronellol, and nepetalactone, contributing 41.24%, 31.81%, 43.13%, 43.35% and 91.43% in O. majorana, O. vulgare, C. winterianus, P. graveolens, and N. cataria, respectively. Well-diffusion assay revealed that the essential oil of O. majorana and O. vulgare was active against both the tested Gram-positive, viz., Bacillus subtilis MTCC 121, Micrococcus luteus MTCC 2470, and Staphylococcus aureus MTCC 96; and Gram-negative, viz., Escherichia coli MTCC 43, Klebsiella pneumoniae MTCC 109, and Pseudomonas aeruginosa MTCC 2453 bacteria, while the essential oil of C. winterianus, P. graveolens, and N. cataria showed activity against only some Gram-positive bacteria. Minimum inhibitory concentration (v/v) values indicated the highest efficacy of O. majorana essential oil against B. subtilis (0.5%), M. luteus (1%), and S. aureus (1%), while O. vulgare was most efficient to E. coli (2%) and K. pneumoniae (2%). C. winterianus essential oil did not inhibit any bacterial strains. M. luteus was susceptible to the essential oil of P. graveolens (1%) and N. cataria (0.5%) at low concentrations. Present findings showed the association between the chemical constituents’ profile of isolated essential oils from the Himalayan region and their antimicrobial activity, indicating their perspective to be utilized as antibacterial means.

ANALYSIS OF THE ESSENTIAL OIL OF ARTEMISIA ABSINTHIUM IN TWO HARVEST TIMES

Artemisia absinthium, also known as wormwood, is used in traditional medicine as anti-parasitic and analgesic. The aim of the present study was to evaluate the effect of four doses of mineral fertilization in two harvest times on the content and composition of the essential oils produced by A. absinthium. The tested doses of mineral fertilization were the following: without fertilization (D0); 50% of the recommended dose (D1); recommended dose (D2); and 150% of the recommended dose (D3). The plants were cultivated in 10 L pots kept in greenhouse. The samples for extracting the essential oils were collected at 60 and 125 days after transplantation (DAT). The essential oils were obtained by hydrodistillation using a Clevenger-type apparatus. Identification and relative percentage of the compounds in the essential oils were performed by GC-MS. The essential oils content varied from 0.04% to 0.41% w/w. The highest essential oil content obtained was 0.41% using the dose D3 at 120 DAT. Myrcene and Z-isocitral were the major constituents of essential oils. According to the results obtained, A. absinthium can be used as a source of myrcene, depending on the dosage of mineral fertilization used and the time of harvest.

Essential Oil Composition of Seven Bulgarian Hypericum Species and Its Potential as a Biopesticide.

Hypericum species and especially H. perforatum L. are well known for their therapeutic applications. The present study assessed the essential oil (EO) composition, and antifungal and aphid suppression activity of seven Bulgarian Hypericum species. The EOs were analyzed by GC-MS-FID. Two experiments were conducted. In the first experiment, H. perforatum, H. maculatum, and H. hirsutum were used. Additionally, the EO composition of H. perforatum extracted via hydrodistillation (ClevA) and via commercial steam distillation (Com) were compared. The second experiment compared the EOs of H. perforatum, H. cerastoides, H. rumeliacum, H. montbretii, and H. calycinum (flowers and leaves) extracted via hydrodistillation and collected with n-hexane. Overall, the EO constituents belonged to four classes, namely alkanes, monoterpenes, sesquiterpenes, and fatty acids. The main class for compounds in H. maculatum and H. perforatum (section Hypericum) were sesquiterpenes for both experiments except for H. perforatum (Com). Hypericum montbretii (section Drosocarpium) EO had monoterpenes (38.09%) and sesquiterpenes (37.09%) as major groups, while H. hirsutum EO (section Taeniocarpium) contained predominately alkanes (67.19%). Hypericum hirsutum EO contained cedrol (5.04%), found for the first time in Hypericum species. Fatty acids were the main compounds in H. cerastoides (section Campylopus), while monoterpenes were the most abundant class in H. rumeliacum and H. calycinum EOs. α-Pinene and germacrene D were the major EO constituents of all analyzed Hypericum species except for H. hirsutum and H. cerastoides. Hypericum perforatum EO (Com) had significant repellent and insecticidal activity against two aphid species, Rhopalosiphum padi (Bird Cherry-oat aphid) and Sitobion avenae (English grain aphid) at concentrations of 0%, 1%, 2.5%, 3.5%, 4.5%, and 5%. The tested EOs did not show significant activity against selected economically important agricultural fungal pathogens Fusarium spp., Botrytis cinerea, Colletotrichum spp., Rhizoctonia solani, and Aspergillus sp. The EO of the Hypericum species found in the Bulgarian flora could be utilized for the development of new biopesticides for aphid control.