Vapor and Liquid Phase Profiles of Essential Oils from Abies, Picea and Pinus Species and Their Phytotoxic Interactions with Weed Growth in Pre- and Post-Emergence Conditions

The chemical content of essential oils (EO) obtained from the leaves of four Pinaceae (Abies alba, Picea abies, Pinus cembra and Pinus mugo) was investigated by SPME-GC-MS technique. The vapor phase was characterized by the monoterpenes with values higher than 95.0%. Among them, a-pinene (24.7–48.5%), limonene (17.2–33.1%) and b-myrcene (9.2–27.8%) were the most abundant. The monoterpenic fraction prevailed over the sesquiterpenic one ( 74.7%) in the EO liquid phase. Limonene was the major compound in A. alba (30.4%), P. abies (20.3%) and P. mugo (78.5%), while a-pinene in P. cembra (36.2%). Regarding the phytotoxic properties, EOs were studied at different doses (2–100 L) and concentrations (2–20/100 L/mL). All EOs were found to be significantly active (p-value < 0.05) against the two recipient species in a dose-dependent way. In pre-emergence tests, germination of Lolium multiflorum and Sinapis alba was reduced by up to 62–66% and 65–82%, respectively, as well as their growth by up to 60–74% and 65–67%, due to the effects of compounds in both the vapor and liquid phases. In post-emergence cconditions, at the highest concentration, the phytotoxicity of EOs caused heavy symptoms and, in the case of S. alba, A. alba EO completely destroyed (100%) the treated seedlings

Impact of Achillea moschata Wulfen on germination and growth of weed species Echinochloa oryzoides (Ard.) Fritsch and Lolium multiflorum Lam

Weeding is a practice of primary importance both in conventional agriculture where the intensive use of herbicides can represent a significant environmental risk and in organic farming where this practice is prohibited. Therefore, the need to identify alternative means of controlling weeds is evident. In this respect, allelopathy proves to be a useful tool to be integrated with conventional agronomic techniques for the management of infesting flora. In this work, we investigated the phytotoxic potential of Achillea moschata Wulfen (Asteraceae) against Echinochloa oryzoides (Ard.) Fritsch and Lolium multiflorum Lam., two noxious plants for crops such as rice and wheat. Preliminary anti-germination assays were carried out in controlled conditions by testing both the powder (0.25 g) and the aqueous extract (1%, 10% and 20%) from the A. moschata aerial parts. The obtained results showed that the powder was more effective than the extract in inhibiting seed germination (up to –81.6% vs –48.8% at 20% concentration) and seedling development (up to –99.4% vs –75.9% at 20% concentration) of both target species, although L. multiflorum was more susceptible than E. oryzoides to treatments. Furthermore, the chemical composition of the two used matrices was characterized by Solid-Phase Microextraction (SPME) sampling technique and Gas Chromatograph/Mass spectrometer (GC/MS) analyses. Camphor (25.8% and 49.9%) and 1,8 cineole (25.9% and 20.7%) were the main constituents in the samples, followed by bornyl acetate (6.7%) in the powder and fragranol (10.5%) in the aqueous extract

In-vitro evaluation of different antimicrobial combinations with and without colistin against carbapenem-resistant acinetobacter baumannii

Carbapenem-resistant Acinetobacter baumannii (CR-Ab) infections are associated with high morbidity and mortality. The aim of the study was to evaluate the in-vitro activity of different antimicrobial combinations (with and without colistin, COL) against clinical isolates of CR-Ab collected from patients with CR-Ab infection, including unconventional combinations such as COL + VANcomycin (VAN) and COL + rifampin (RIF). CR-Ab strains were collected from hospitalized patients at Sapienza University of Rome. Antimicrobial susceptibility patterns were determined throughout MIC50/90s whereas the synergistic activity was evaluated by qualitative (i.e., checkerboard) and quantitative (i.e., killing studies) methods. All the strains were found oxacillinase (OXA) producers and tigecycline (TIG) sensitive whereas 2 strains were resistant to COL. Application of the checkerboard method indicated complete synergism in COL combinations at different extension: 21.4%, 57.1%, 42.8%, 35.7% for COL + meropenem (MEM), COL + RIF, COL + VAN and COL + TIG, respectively, with the non-conventional combinations COL + VAN and COL + RIF exhibiting the highest rate of synergism. Regarding COL-free combination, complete synergism was observed in 35.7% of the strains for MEM + TIG. Killing studies showed that the combinations COL + MEM, COL + TIG and MEM + TIG were bactericidal and synergistic against both colistin-sensitive and low colistin-resistant strains whereas only the combinations COL + VAN and COL + RIF showed an early and durable bactericidal activity against all the tested strains, with absence of growth at 24 h. This study demonstrated that COL-based combinations lead to a high level of synergic and bactericidal activity, especially COL + VAN and COL + RIF, even in the presence of high level of COL resistance

Chemical and antimicrobial analyses of Sideritis romana L. subsp. purpurea (Tal. ex Benth.) Heywood, an endemic of the Western Balkan

A comprehensive study on essential oil and different solvent extracts of Sideritis romana L. subsp. purpurea (Tal. ex Benth.) Heywood (Lamiaceae) from Montenegro is reported. The gas chromatography-mass spectrometry analysis of the essential oil revealed a total of 43 components with bicyclogermacrene (23.8%), germacrene D (8%), (E)-caryophyllene (7.9%) and spathulenol (5.5%) as the major ones. Sesquiterpenoid group was found to be the most dominant one (64.8%), with 19.9% of the oxygenated forms. In the crude methanol extract of the investigated plant, obtained by Sohhlet exraction, the total phenol content was 14.7 ± 0.4 mg of GA/g, the total flavonoids were 0.29 ± 0.03% expressed as hyperoside percentage, whereas the total tannins content was 0.22 ± 0.04% expressed as pyrogallol percentage. For the antimicrobial activity determination, the following microorganisms have been used: methicillin-susceptible Staphylococcus aureus (MSSA (American Type Culture Collection (ATCC) 29213)) and methicillin-resistant S. aureus (MRSA (clinical strain)), Escherichia coli (ATCC 25922), carbapenem-susceptible Klebsiella pneumoniae (clinical strain), carbapenem-resistant K. pneumoniae (clinical strain) and Candida albicans (ATCC 14053). The essential oil showed high potency against MSSA and MRSA, both at high (~5 × 10 5 CFU/mL) and low (~5 × 10 3 CFU/mL) inoculum. With respect to MSSA, the minimal inhibitory concentration (MIC) value was 0.307 mg/mL, with bactericidal activity obtained at 0.615 mg/mL, while, in the case of MRSA, the MIC and minimal bactericidal concentration (MBC) values were 0.076 and 0.153 mg/mL, respectively. Regarding anti-Candida albicans activity, the MIC value was 2.46 mg/mL without reaching fungicidal activity. In addition to the observed essential oil efficacy, different solvent extracts were analyzed for their antimicrobial activity. Similarly to the essential oil, thehighest efficacy was observed against both MSSA and MRSA strains, at high and low inoculums, in the case of the 1,2-dichloroethane and methanol extracts. A potent fungicidal activity has been also found for the n-hexane and 1,2-dichloroethane extracts. It can be concluded that Sideritis romana L. subsp. purpurea (Tal. ex Benth.) Heywood provides a wide range of application in different fields such as phytochemistry, pharmacology, toxicology or pharmacognosy

High potency of melaleuca alternifolia essential oil against multi-drug resistant gram-negative bacteria and methicillin-resistant staphylococcus aureus

Purpose: Herein, an extended investigation of Tea tree oil (TTO) against a number of multi-drug resistant (MDR) microorganisms in liquid and vapor phases is reported. Methods: The activity of TTO was tested against methicillin-sensitive Staphylococcus aureus (MSSA), Escherichia coli, and clinical strains of methicillin-resistant S. aureus (MRSA), extended-spectrum beta lactamases producer carbapenem-sensitive Klebsiella pneumoniae (ESBL-CS-Kp), carbapenem-resistant K. pneumoniae (CR-Kp), Acinetobacter baumannii (CR-Ab), and Pseudomonas aeruginosa (CR-Pa). Minimal inhibitory/bactericidal concentrations (MIC/MBCs) and synergistic activity between TTO and different antimicrobials were determined. In the vapor assay (VP), TTO-impregnated discs were placed on the lid of a petri dish and incubated for 24 h at 37°C. Results: TTO showed a potent bactericidal activity against all the tested microorganisms. TTO in combination with each reference antimicrobial showed a high level of synergism at sub-inhibitory concentrations, particularly with oxacillin (OXA) against MRSA. The VP assay showed high activity of TTO against CR-Ab. Conclusion: Evaluation of in-vitro activity clearly indicated TTO as a potential effective antimicrobial treatment either alone or in association with known drugs against MDR. Therefore, TTO could represent the basis for a possible role in non-conventional regimens against S. aureus and Gram-negative MDR. TTO in VP might represent a promising option for local therapy of pneumonia caused by CR-Ab

Antimicrobial and antibiofilm activity and machine learning classification analysis of essential oils from different mediterranean plants against pseudomonas aeruginosa

Pseudomonas aeruginosa is a ubiquitous organism and opportunistic pathogen that can cause persistent infections due to its peculiar antibiotic resistance mechanisms and to its ability to adhere and form biofilm. The interest in the development of new approaches for the prevention and treatment of biofilm formation has recently increased. The aim of this study was to seek new non-biocidal agents able to inhibit biofilm formation, in order to counteract virulence rather than bacterial growth and avoid the selection of escape mutants. Herein, different essential oils extracted from Mediterranean plants were analyzed for their activity againstP. aeruginosa. Results show that they were able to destabilize biofilm at very low concentration without impairing bacterial viability. Since the action is not related to a bacteriostatic/bactericidal activity onP. aeruginosa, the biofilm change of growth in presence of the essential oils was possibly due to a modulation of the phenotype. To this aim, application of machine learning algorithms led to the development of quantitative activity-composition relationships classification models that allowed to direct point out those essential oil chemical components more involved in the inhibition of biofilm production. The action of selected essential oils on sessile phenotype make them particularly interesting for possible applications such as prevention of bacterial contamination in the community and in healthcare environments in order to prevent human infections. We assayed 89 samples of different essential oils asP. aeruginosaanti-biofilm. Many samples inhibitedP. aeruginosabiofilm at concentrations as low as 48.8 µg/mL. Classification of the models was developed through machine learning algorithms

Properties and limits of some essential oils: chemical characterisation, antimicrobial activity, interaction with antibiotics and cytotoxicity

Because of the emergence of multi-drug resistance bacteria and fungi, alternatives to conventional antimicrobial therapy are needed. This study aims to evaluate in vitro the antimicrobial activity of: Mirtus communis, Coriandrum sativum, Pelargonium capitatum, Cuminum cyminum, Ocimum basilicum, Citrus aurantium amara, Cymbopogon. winterianus, Cymbopogon martini, Salvia sclarea, Melaleuca alternifolia and Mentha suaveolens essential oils on bacteria and fungi, in relation to their chemical composition. The potential interaction of M. alternifolia (TTO), C. sativum (CDO) and M. suaveolens (EOMS) essential oils when used in combination with gentamicin and fluconazole has been evaluated. The results obtained showed a synergic effect on some bacteria and fungi, with FICI values ≤5. The cytotoxicity of TTO, CDO and EOMS was investigated towards HeLa cells. Only EOMS did not result cytotoxic at the active concentrations on micro-organisms. Further studies are necessary to obtain optimal ratios and dosing regimens for higher therapeutic efficacy and to decrease toxicological profiles

Organ dependency variation of the chemical composition of Ziziphus lotus volatile fractions

The extended application fields of the essential oils keep them a subject of interest. In this study, we investigated the aerial part essential oil and the fruit essential oil of the wild plant Ziziphus lotus, collected from the southern region of Tunisia. These essential oils obtained by hydrodistillation using a Clevenger-type apparatus showed an extraction yield of 0.013% and 0.0046% respectively. The qualitative and quantitative analysis of the samples using GC-MS/GC-FID revealed two distinct compositions. Apocarotenoid derivatives characterized the essential oil of the aerial part; the major compound was hexahydrofarnesyl acetone (23.2%) followed by geranylacetone (12.5%) and cis-hexenyl-3-benzoate (11.1%). While the abundance of fatty acid marked the fruit essential oil. The noticed major compounds were 2-pentadecanone (16.9%), dodecanoic acid ethyl ester (14.5%) and n-hexadecanoic acid (13.0%). Such chemical composition may explain the traditional use of Ziziphus lotus as a drug to treat various pathologies. DOI: http://dx.doi.org/10.5281/zenodo.555296

Unraveling the Antimicrobial Effectiveness of Coridothymus capitatus Hydrolate against Listeria monocytogenes in Environmental Conditions Encountered in Foods: An In Vitro Study

The increased resistance of bacteria to antimicrobials, as well as the growing interest in innovative and sustainable alternatives to traditional food additives, are driving research towards the use of natural food preservatives. Among these, hydrolates (HYs) have gained attention as "mild" alternatives to conventional antimicrobial compounds. In this study, the response of L. monocytogenes ATCC 7644 exposed to increasing concentrations of Coridothymus capitatus HY (CHY) for 1 h at 37 °C was evaluated by means of Phenotype Microarray, modelling the kinetic data obtained by inoculating control and treated cells into GEN III microplates, after CHY removal. The results revealed differences concerning the growth dynamics in environmental conditions commonly encountered in food processing environments (different carbon sources, pH 6.0, pH 5.0, 1-8% NaCl). More specifically, for treated cells, the lag phase was extended, the growth rate was slowed down and, in most cases, the maximum concentration was diminished, suggesting the persistence of stress even after CHY removal. Confocal Laser Scanner Microscopy evidenced a diffuse aggregation and suffering of the treated cells, as a response to the stress encountered. In conclusion, the treatment with HY caused a stressing effect that persisted after its removal. The results suggest the potential of CHY application to control L. monocytogenes in food environments

Essential oils against bacterial isolates from cystic fibrosis patients by means of antimicrobial and unsupervised machine learning approaches

Recurrent and chronic respiratory tract infections in cystic fibrosis (CF) patients result in progressive lung damage and represent the primary cause of morbidity and mortality. Staphylococcus aureus (S. aureus) is one of the earliest bacteria in CF infants and children. Starting from early adolescence, patients become chronically infected with Gram-negative non-fermenting bacteria, and Pseudomonas aeruginosa (P. aeruginosa) is the most relevant and recurring. Intensive use of antimicrobial drugs to fight lung infections inevitably leads to the onset of antibiotic resistant bacterial strains. New antimicrobial compounds should be identified to overcome antibiotic resistance in these patients. Recently interesting data were reported in literature on the use of natural derived compounds that inhibited in vitro S. aureus and P. aeruginosa bacterial growth. Essential oils, among these, seemed to be the most promising. In this work is reported an extensive study on 61 essential oils (EOs) against a panel of 40 clinical strains isolated from CF patients. To reduce the in vitro procedure and render the investigation as convergent as possible, machine learning clusterization algorithms were firstly applied to pick-up a fewer number of representative strains among the panel of 40. This approach allowed us to easily identify three EOs able to strongly inhibit bacterial growth of all bacterial strains. Interestingly, the EOs antibacterial activity is completely unrelated to the antibiotic resistance profile of each strain. Taking into account the results obtained, a clinical use of EOs could be suggested