Chemical composition,cytotoxicity, antimicrobial and antifungal activity of several essential oils

Essential oils (EOs) are known and used for their biological, antibacterial, antifungal and antioxidant properties. Numerous studies have shown that EOs exhibit a large spectrum of biological activities in vitro. The incidence of drug-resistant pathogens and the toxicity of antibiotics have drawn attention to the antimicrobial activity of natural products, encouraging the development of alternative treatments. The aim of this study was to analyse the phytochemical and the cytotoxic characteristic of 36 EOs; we then evaluated the antimicrobial activity of the less-toxic EOs on Gram-positive, Gram-negative and fungi strains. The results showed low cytotoxicity in seven EOs and good activity against Gram-negative and Candida spp. strains. Based on our results, EOs could be proposed as a novel group of therapeutic agents. Further experiments are necessary to confirm their pharmacological effectiveness, and to determine potential toxic effects and the mechanism of their activity in in vivo models.     

Radical scavenging and antimicrobial activities of Croton zehntneri,Pterodon emarginatus and Schinopsis brasiliensis essential oils and their major constituents: estragole,trans-anethole, β-caryophyllene and myrcene

The essential oils (EOs) from the Brazilian species Croton zehntneri, Pterodon emarginatus and Schinopsis brasiliensis were examined for their chemical constituents, and antioxidant and antimicrobial activities. The composition of EOs was determined by using gas chromatography coupled with mass spectrometry analysis, while the antioxidant activity was evaluated through the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC) assays. Furthermore, the antimicrobial activity was investigated against Escherichia coli and Pseudomonas aeruginosa (both Gram-negative), Staphylococcus aureus (Gram-positive) and Candida parapsilosis (fungus). The main components of C. zehntneri, P. emarginatus and S. brasiliensis were identified as estragole, trans-anethole, β-caryophyllene and myrcene. Among the EOs, P. emarginatus showed the highest antioxidant activity, with an IC₅₀ of 7.36 mg/mL and a Trolox equivalent antioxidant capacity of 3748 μmol/g determined by DPPH and ORAC assays, respectively. All EOs showed low activities against the bacterial strains tested, whereas the C. zehntneri oil and its main constituent estragole exhibited an appreciable antifungal activity against C. parapsilosis.     

Comparative study of the chemical profiling,antioxidant and antimicrobial activities of essential oils of different parts of Thymus willdenowii Boiss & Reut

The analysis of Thymus willdenowii Boiss &; Reut essential oils (TW EOs) shows 33 components accounting for (96.3–97.7%) of all identified. The main constituents of TW EOs were thymol (35.5–47.3%), p-cymene (13.9–23.8%), γ-terpinene (8.9–20.3%). The antioxidant assays revealed that all TW EOs tested showed strong activities, the antimicrobial effect of TW EOs has been tested against isolated clinical strains of Proteus mirabilis (ATCC 35659), Escherichia coli (ATCC 25922), Candida albicans (ATCC 10231), Bacillus cereus (ATCC 10876), and Aspergillus brasilliensis (ATCC 16404). The antimicrobial test indicates that TW EOs show an inhibition effect against all the tested bacteria with a MIC of 6.9 to 27.6 μg/mL^?1. These results proving that the essential oils extracted from Thymus willdenowii Boiss &; Reut may be a new potential source of natural antimicrobial applied in pharmaceutical and food industries.     

GC–MS characterisation and biological activity of essential oils from different vegetative organs of Plectranthus barbatus and Plectranthus caninus cultivated in north Italy

Essential oils (EOs) from the roots, stems and leaves of Plectranthus barbatus (A) and Plectranthuscaninus (B), cultivated in north Italy, were obtained by steam distillation and chemically characterised by gas chromatography–mass spectrometry. The highest yields were obtained from roots (268.15 and 673.60 mg/kg from A and B), followed by leaves (64.34 and 26.65 mg/kg) and stems (19.76 and 18.63 mg/kg). A total of 128 structures were identified in A and 121 in B. Fe⁺⁺ chelating and antiradical activities (DPPH and ABTS) were evaluated: root and stem EOs showed the strongest activities, while EOs from leaves did not show relevant activities. All EOs were tested for their in vitro antimicrobial activity, showing optimal growth-inhibition in antibiogram (?>35 mm) and MIC tests (32–64 μg/mL) against Candida albicans, while EOs from leaves of both species showed a good activity (25 < ? < 34 mm, MIC 64–128 μg/mL) against Escherichia coli.     

Mentha pulegium L.: A Plant Underestimated for Its Toxicity to Be Recovered from the Perspective of the Circular Economy

The aim of the study was to investigate the micromorphology of Mentha pulegium leaves and flowers harvested in three different Sicilian (Italy) areas with peculiar pedo-climatic conditions, and to characterize the phytochemical profile, the phytotoxic activity, and the eco-compatibility of their essential oils (EOs) for potential use as safe bioherbicides. Light microscopy (LM) and scanning electron microscopy (SEM) highlighted that M. pulegium indumentum consists of non-glandular and glandular trichomes of different types. Peltate trichomes of plants from the different sites showed few significant differences in dimension and abundance, but they were characterized by a surprisingly high number of secretory cells both in leaves and flowers. Phytochemical analyses showed that oxygenated monoterpenes were the most abundant class in all the EOs investigated (92.2–97.7%), but two different chemotypes, pulegone/isomenthone and piperitone/isomenthone, were found. The complex of morphological and phytochemical data indicates that soil salinity strongly affects the expression of the toxic metabolite pulegone, rather than the EO yield. Phytotoxicity tests showed a moderate activity of EOs against the selected species as confirmed by α-amylase assay. Moreover, the low toxicity on brine shrimp provided a rationale for the possible use of investigated EOs as eco-friendly herbicides.     

Antimicrobial activity and phytochemical analysis of crude extracts and essential oils from medicinal plants

We aimed to establish a phytochemical analysis of the crude extracts and performed GC-MS of the essential oils (EOs) of Eugenia uniflora L. (Myrtaceae) and Asteraceae species Baccharis dracunculifolia DC, Matricaria chamomilla L. and Vernonia polyanthes Less, as well as determining their antimicrobial activity. Establishment of the minimal inhibitory concentrations of the crude extracts and EOs against 16 Staphylococcus aureus and 16 Escherichia coli strains from human specimens was carried out using the dilution method in Mueller-Hinton agar. Some phenolic compounds with antimicrobial properties were established, and all EOs had a higher antimicrobial activity than the extracts. Matricaria chamomilla extract and E. uniflora EO were efficient against S. aureus strains, while E. uniflora and V. polyanthes extracts and V. polyanthes EO showed the best antimicrobial activity against E. coli strains. Staphylococcus aureus strains were more susceptible to the tested plant products than E. coli, but all natural products promoted antimicrobial growth inhibition.     

Phytochemical compounds and antiradical,antimicrobial, and cytotoxic activities of the extracts from Hypericum scabrum L. Flowers

Abstract

Hypericum scabrum L. has been widely used in traditional medicine for the treatment of many diseases just as the other Hypericum species. In the present study, the antiradical, antimicrobial and cytotoxic activities of water and ethanol extracts of H. scabrum flowers were investigated. Their phytochemical contents and composition were also determined. The water and ethanol extracts are better scavenged ABTS (97.89 and 98.99%) and OH radicals (96.36 and 97.33%); the water extract is better scavenged DPPH radicals (91.66%) than the standard antioxidant BHA (94.33, 85.19, 90.16%, respectively). Flowers of H. scabrum contain flavonoids, phenolic acids, vitamins and phytosterols, dominated by catechin, vanillic acid, vitamin K and ergosterol. The extracts exhibit a strong cytotoxic activity against MCF-7, HCT-116, and LNCaP cancer cell lines. It is found that their antimicrobial activities are higher than the standard antibiotics. These results indicate that H. scabrum flowers have potent antiradical, antimicrobial and cytotoxic activities.     

Effect of the Distillation Time on the Chemical Composition,Antioxidant Potential and Antimicrobial Activity of Essential Oils from Different Cannabis sativa L. Cultivars

Within the unavoidable variability of various origins in the characteristics of essential oils, the aim of this study was to evaluate the effect of the distillation time on the chemical composition and biological activity of Cannabis sativa essential oils (EOs). The dry inflorescences came from Carmagnola, Kompolti, Futura 75, Gran Sasso Kush and Carmagnola Lemon varieties from Abruzzo region (Central Italy), the last two being new cultivar here described for the first time. EOs were collected at 2 h and 4 h of distillation; GC/MS technique was applied to characterize their volatile fraction. The EOs were evaluated for total polyphenol content (TPC), antioxidant capacity (AOC) and antimicrobial activity against food-borne pathogens and spoilage bacteria. The time of distillation particularly influenced EOs chemical composition, extracting more or less terpenic components, but generally enriching with minor sesquiterpenes and cannabidiol. A logical response in ratio of time was observed for antioxidant potential, being the essential oils at 4 h of distillation more active than those distilled for 2 h, and particularly Futura 75. Conversely, except for Futura 75, the effect of time on the antimicrobial activity was variable and requires further investigations; nevertheless, the inhibitory activity of all EOs against Pseudomonas fluorescens P34 was an interesting result.     

Chemical composition and antimicrobial activity of the essential oils from flowers and leaves of Grindelia integrifolia DC

Essential oils from flowers and leaves of Grindelia integrifolia DC. were investigated for the first time in terms of chemical composition and antimicrobial activity. The GC-FID/MS analysis allowed for the identification of 58 and 72 volatiles, comprising 92.4 and 90.1% of the oils, respectively. The major components of the flower oil were α-pinene (34.9%) and limonene (13.1%), while myrcene (16.9%), spathulenol (12.3%), β-eudesmol (11.9%) and limonene (10.1%) dominated among the leaf volatiles. The antimicrobial activity, evaluated against 12 selected bacteria and fungus, was found moderate, with the strongest effect of both oils observed against C. albicans (MIC = MBC: 0.63 and 0.31 mg/mL for flower and leaf oil, respectively).     

Phytochemical profiling and antimicrobial activity of ginger (Zingiber officinale) essential oils against important phytopathogens

The objectives of this study were to profile ginger essential oils (EOs) phytochemical constituents and antimicrobial activity against important phytopathogens. Ginger EOs was extracted using a modified Clevenger-type apparatus by hydro-distillation then followed by GCMS and headspace analysis of its phytochemical constituents. The phytoconstituents identified were monoterpenes and sesquiterpene hydrocarbons. Food poisoned and disc diffusion techniques were applied to determine the percentage inhibition of fungal mycelial and bacterial growth respectively. The EOs produced mycelial growth inhibition in all the test fungal pathogens after five days of incubation. The MIC and MFC of the EOs on the tested fungi were in the range of 1 μl/ml and 5–6 μl/ml, respectively. The bacterial growth of all the tested isolates was also affected by EOs at 100–500 µl/ml, from weak to strong antibacterial activity. The EOs affected the Xanthomonas oryzae pv. oryzae-strain A isolate most at a higher concentration of 400–500 μl/ml with mean inhibition of 20.66 mm and 22.66 mm respectively, which are found to be effective. The MIC values on the bacterial pathogens were at100 μl/ml. The inhibition zone of positive control (streptomycin) at 15 µg/disc was 25.00 mm and appeared to be efficient. Metabolomics analysis to concurrently quantify variability among multiple compounds in the data sets and identify such compounds responsible for the X. oryzae pv. oryzae-strain-A inhibition were determined. The cross-validated PLS model has shown a strong correlation between ginger EOs and bioactivity. The action of ginger EOs on the cell structure was fully identified using SEM by observing the changes in morphology and integrity of X. oryzae pv. oryzae-strain-A cells. The DMSO treatment (control) showed a normal rod shape cell, while treatment with the ginger EOs showed irregular shape with sunken surfaces, and treatment with antibiotics display abnormal growth of the cells. These findings can, therefore, propose that the ginger EOs could be used as a new antimicrobial agent in suppressing the growth of phytopathogens and as possible new alternatives to synthetic fungicides and bactericides.     

Phytochemical profile and biological activities of Deverra tortuosa (Desf.)DC.: a desert aromatic shrub widespread in Northern Region of Saudi Arabia

The present study describes the chemical composition of the essential oil of different plant parts of Devrra tortuosa; in vivo and in vitro biological activities of plant extract and essential oils. Apiol was found to be the major component of the oil (between 65.73% and 74.41%). The best antioxidant activities were observed for the oil of flowers (IC50 = 175 μg/ml). The samples of stems and roots exhibit lower antioxidant activity (IC50 = 201 μg/ml and 182 μg/ml, respectively). The values of IC50 showed that the extracts of methanol exhibit the highest antioxidants activities (IC50 = 64.8 102 μg/ml). EOs showed excellent antifungal activity against yeasts with low azole susceptibilities (i.e. Malassezia spp. and Candida krusei). The MIC values of oils varied between 2.85 mg/mL and 27 mg/mL. The obtained results also showed that the plant extracts inhibited the germination and the shoot and root growth of Triticum æstivum seedlings.     

Phytochemical composition and in vitro screening of the antimicrobial activity of essential oils on oral pathogenic bacteria

In this study, the activity of essential oils (EOs) against microorganisms involved in oral diseases was evaluated. Fourteen EOs were selected and subjected to gas chromatographic analysis, including Illicium verum, Eucaliptus globulus, Eugenia caryophyllata, Leptospermum scoparium, Mentha arvensis, Mentha piperita, Myrtus communis, Salvia officinalis, Melaleuca alternifolia, Rosmarinus officinalis, Lavandula x intermedia, Thymus capitatus and Thymus vulgaris. These EOs were tested for their antimicrobial activity on Streptococcus mutans and Lactobacillus species clinically isolated from dental surgery patients. The antibacterial activity was evaluated by means of the disc diffusion and the minimum inhibitory concentration (MIC). Five EOs, having shown an interesting antimicrobial activity, were selected for a second screening in combination between them and with chlorhexidine. From the second assays, two EO–EO and three EO-chlorhexidine associations gave interesting results as potential constituents of mouthwashes, especially for the contribution of oxygenated monoterpenes, including menthol, thymol and carvacrol.     

Chemical Composition and Antimicrobial Activity of the Essential Oils Extracted by Microwave-Assisted Hydrodistillation from the Flowers of Two Plumeria Species

Microwave-assisted hydrodistillation (MAHD) was applied to obtain essential oils from the fresh flowers of Plumeria rubra Linn (PRL) and Plumeria rubra Linn var. acutifolia (PRLA) cultivated in China, which were subsequently analyzed via gas chromatography with flame ionization detection and gas chromatography with mass spectrometry. The essential oils were assessed for their antimicrobial activity. A variation of the chemical composition attributed to varieties was revealed. The essential oil of PRLA was found to have a high content of carboxylic acids (59.7%) with n-hexadecanoic acid (35.8%) and n-tetradecanoic acid (11.2%) as main components. Whereas, the PRL oil was characterized by high hydrocarbon content (38.6%), in which 9-hexacosene (14.6%) was found to be the major constituent. All essential oils possessed antimicrobial activity especially against five bacteria with diameter of inhibition zone (DD) and minimum inhibitory concentrations (MIC) values in the range of 6.8 to 21.3 mm and 2.8 to 46.5 mg/mL, respectively.     

Antibacterial activity of essential oils mixture against PSA

Pseudomonas syringae pv. actinidiae (PSA) is the causal agent of bacterial canker of kiwifruit. It is very difficult to treat pandemic disease. The prolonged treatment with antibiotics, has resulted in failure and resistance and alternatives to conventional antimicrobial therapy are needed. The aim of our study was to analyse the phenotypic characteristics of PSA, identify new substances from natural source i.e. essential oils (EOs) able to contain the kiwifruit canker and investigate their potential use when utilised in combination. Specially, we investigated the morphological differences of PSA isolates by scanning electron microscope, and the synergic action of different EOs by time-kill and checkerboard methods. Our results demonstrated that PSA was able to produce extracellular polysaccharides when it was isolated from trunk, and, for the first time, that it was possible to kill PSA with a mixture of EOs after 1 h of exposition. We hypothesise on its potential use in agriculture.     

Nanovesicles Loaded with Origanum onites and Satureja thymbra Essential Oils and Their Activity against Food-Borne Pathogens and Spoilage Microorganisms

Food poisoning is a common cause of illness and death in developing countries. Essential oils (EOs) could be effective and safe natural preservatives to prevent and control bacterial contamination of foods. However, their high sensitivity and strong flavor limit their application and biological effectiveness. The aim of this study was firstly the chemical analysis and the antimicrobial evaluation of the EOs of Origanum onites L. and Satureja thymbra L. obtained from Symi island (Greece), and, secondly, the formulation of propylene glycol-nanovesicles loaded with these EOs to improve their antimicrobial properties. The EOs were analyzed by GC-MS and their chemical contents are presented herein. Different nanovesicles were formulated with small average sizes, high homogeneity, and optimal ζ-potential. Microscopic observation confirmed their small and spherical shape. Antibacterial and antifungal activities of the formulated EOs were evaluated against food-borne pathogens and spoilage microorganisms compared to pure EOs. Propylene glycol-nanovesicles loaded with O. onites EO were found to be the most active formulation against all tested strains. Additionally, in vitro studies on the HaCaT cell line showed that nanovesicles encapsulated with EOs had no toxic effect. The present study revealed that both EOs can be used as alternative sanitizers and preservatives in the food industry, and that their formulation in nanovesicles can provide a suitable approach as food-grade delivery system.     

Chemical Composition Analysis and Antimicrobial Screening of the Essential Oil of a Rare Plant from Jordan: Ducrosia flabellifolia

The composition of the essential oil isolated from the fresh and dry leaves of Ducrosia flabellifolia Boiss. (Apiaceae) was determined by gas chromatography and gas chromatography–mass spectrometry using hydrodistillation and solid phase microextraction (SPME). The hydrodistilled oil of the fresh leaves yielded 38 components, accounting for 98.67% of the total oil content, while thirty components were detected from the fresh leaves by solid phase microextraction (94.85%). Fifty-one and 36 components were identified in the hydrodistilled and SPME oils of the dried leaves amounting to 98.78% and 94.52%, respectively. A total of 25 components accounting for 97.24% of the total composition were characterized in the SPME oil of the fresh flowers. Aliphatic compounds predominated in the volatile fractions of the leaves and flowers of both methods with n-decanol, n-decanal, and dodecanal as the main constituents. The α- and ß-pinene were the major monoterpenoids in the oils. The hydrodistilled oil was screened for its antimicrobial and antioxidant activities. The minimal inhibitory concentration of the volatile oil was determined using a microdilution method in 96 well plates against a panel of gram (+), gram (?) bacteria, and fungi. Overnight cultures of reference strains of Candida albicans, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were used as test microorganisms. The oil exhibited the best activity against C. albicans (MIC 234 µg/mL) and S. aureus (MIC 234 µg/mL) whereas weak activity was detected against E. coli and P. aeruginosa. No antioxidant activity could be detected.     

Antibacterial Effects of Essential Oils of Seven Medicinal-Aromatic Plants Against the Fish Pathogen Aeromonas veronii bv. sobria: To Blend or Not to Blend?

Despite progress achieved, there is limited available information about the antibacterial activity of constituents of essential oils (EOs) from different medicinal-aromatic plants (MAPs) against fish pathogens and the complex interactions of blended EOs thereof. The present study aimed to investigate possible synergistic antimicrobial effects of EOs from seven Greek MAPs with strong potential against Aeromonas veronii bv. sobria, a fish pathogen associated with aquaculture disease outbreaks. The main objective was to evaluate whether blending of these EOs can lead to increased antimicrobial activity against the specific microorganism. A total of 127 combinations of EOs were prepared and their effect on A. veronii bv. sobria growth was tested in vitro. We examined both the inhibitory and bactericidal activities of the individual EOs and compared them to those of the blended EOs. The vast majority of the investigated combinations exhibited significant synergistic and additive effects, while antagonistic effects were evident only in a few cases, such as the mixtures containing EOs from rosemary, lemon balm and pennyroyal. The combination of EOs from Greek oregano and wild carrot, as well as the combinations of those two with Spanish oregano or savoury were the most promising ones. Overall, Greek oregano, savoury and Spanish oregano EOs were the most effective ones when applied either in pure form or blended with other EOs.     

Antimicrobial properties and chemical composition of liquid and gaseous phases of essential oils

The antimicrobial properties of fifteen essential oils (EOs) tested on seventeen microorganisms were determined using the vapour-agar contact method. The most effective EOs (i.e. Lavandula angustifolia, Cymbopogon nardus, Citrus aurantifolia, Juniperus communis, Myrtus communis and Cinnamomum zeylanicum), whose volatile components afforded the best antimicrobial properties, were selected for a detailed study of chemical composition. All these six EOs contained one to three main components that presented 67–91 mass % of total mass of a corresponding essential oil. The amount of other components was much lower (less than 5 mass %). The volatile components of Lavandula angustifolia exhibited the most effective antimicrobial properties because they completely inhibited the tested bacteria and fungi within 3 days and 1 week, respectively. The components of Lavandula angustifolia with the highest concentration in the gaseous phase were linalool (99.0 ppmv), eucalyptol (44.9 ppmv), linalyl acetate (25.9 ppmv), myrcene (22.2 ppmv), β-trans-ocimene (19.7 ppmv), camphor (16.7 ppmv) and limonene (14.9 ppmv).     

Lavandin (Lavandula × intermedia Emeric ex Loiseleur) essential oil from Spain: determination of aromatic profile by gas chromatography–mass spectrometry,antioxidant and lipoxygenase inhibitory bioactivities

Lavandin (Lavandula × intermedia Emeric ex Loiseleur) essential oils (EOs), from Abrial, Super and Grosso cultivars, cultivated and extracted in the South East of Spain, were analysed by using GC/MS to determine their composition, in both relative (peak area) and absolute (using standard curves) concentrations. Linalool (34–47%), linalyl acetate (17–34%), camphor (4–9%) and eucalyptol (3–7%) were determined as the main molecules. This characterisation was completed with the enantioselective gas chromatography, where ( ? )-linalool, (+)-camphor and ( ? )-linalyl acetate were determined as the main components. Antioxidant activity was evaluated positively by several methods: activity against free radicals, chelating and reducing power, probably due to linalool and linalyl acetate. Mild inhibitory activity on lipoxygenase was observed supporting potential anti-inflammatory activity, mainly due to linalool and camphor. These properties support the potential use of L. × intermedia essential oils as natural cosmetic and natural pharmaceutical ingredient to fight several skin diseases.     

Combination of analytical and microbiological techniques to study the antimicrobial activity of a new active food packaging containing cinnamon or oregano against E. coli and S. aureus

The aim of this work is the optimization and application of a group of analytical and microbiological techniques in the study of the activity of essential oils (EOs) incorporated in a new antimicrobial packaging material and the research in depth of the interaction between the microbial cells and the individual compounds present in the active material. For this purpose the antimicrobial activity of the active packaging containing cinnamon or oregano was evaluated against E. coli and S. aureus. The vapour phase activity and the direct contact between the antimicrobial agents themselves, or once incorporated in the packaging material, and the microbial cells have been studied. The direct contact was studied using a broth dilution method. The vapour phase was evaluated by using a new method which involves the use of a filter disk containing the EOs. Furthermore, the kill time assay was used to determine the exposure time for the maximum efficiency in packaging, and transmission electron microscopy was used to investigate the antimicrobial activity and the possible mechanism of action against E. coli and S. aureus. Finally, the compounds absorbed by cells were identified. The results showed that the techniques used provide relevant information about the antibacterial activity of cinnamon and oregano in direct contact as well as in the vapour phase. The antimicrobial packaging showed a fast efficiency which supports its likely application as a food packaging material. Bacteria treated with EOs exhibit a wide range of significant abnormalities; these include formation of blebs, coagulation of cytoplasmatic constituents, collapse of the cell structure and lack of cytoplasmatic material. Some of these observations are correlated to the ability of some of these substances to disrupt envelop structure, especially the inner membrane. After an extraction from dead cells, cinnamaldehyde was detected by GC-MS in E. coli exposed to the active packaging containing cinnamon.