Chemical composition and antimicrobial activity of essential oils of Thymus algeriensis,Eucalyptus globulus and Rosmarinus officinalis from Morocco

BACKGROUND: The present study reports on the antimicrobial activity and chemical composition of the essential oils (EOs) of Thymus algeriensis, Eucalyptus globulus and Rosmarinus officinalis from Morocco. RESULTS: The composition of these species was analysed by GC‐MS, and 65 components were identified. Eucalyptus globulus EO showed a great similarity with EOs from other regions, with 1,8‐cineole (79.85%) the major component. Also rich in this constituent was Rosmarinus officinalis (43.99%). However, the chemical profile of Thymus algeriensis was rather different, and for the first time such a high content of borneol (23.48%) has been described in this EO. The antimicrobial activity of these species has also been studied against seven pathogenic and spoiling bacteria of significant importance. According to the results, Thymus algeriensis showed the best bacteriostatic and bactericidal effect, followed by Eucalyptus globulus and Rosmarinus officinalis. CONCLUSIONS: As far as we know this is the first time that minimum inhibitory and bactericidal concentration values have been reported for Eucalyptus globulus EO. Our data support the possible use of this EO as well as Thymus algeriensis EO, as potential natural agents in preservatives for food and pharmaceutical products. Copyright © 2011 Society of Chemical Industry     

Antioxidant and anticholinesterase activity of essential oils and ethanol extracts of <Emphasis Type="Italic">Thymus algeriensis</Emphasis> and <Emphasis Type="Italic">Teucrium polium</Emphasis> from Algeria

This study aimed to investigate the cholinesterase (ChE) inhibitory and antioxidant activities of essential oil (EO) and ethanolic extract (EE) of two Lamiaceae medicinal plants from Algeria: Thymus algeriensis Boiss. & Reut. and Teucrieum polium subsp capitatum. The chemical composition of EOs analyzed by GC and GC–MS revealed the presence of carvacrol (43.2%), p-cymene (18.7%) and γ-terpinene (14.8%) as major compounds in T. algeriensis, while germacrene D (25.0%), bicyclogermacrene (10.4%), β-pinene (11.3%) and spathulenol (5.8%) were the most important components in T. polium oil. The best inhibitory activity on acetylcholinesterase (AChE) was exhibited by the EO of T. algeriensis. On the other hand, T. polium oil was more efficient against butyrylcholinesterase (BChE) than against AChE, whereas EEs showed weak or no inhibitory effect, particularly against AChE. Antioxidant activity was evaluated by β-carotene bleaching, ferric and cupric reducing powers and inhibition of ABTS^?+, DPPH^? and superoxide radicals. EOs showed different antioxidant trends depending on the assay used while ethanol extracts had high activity with all tests.     

Satureja horvatii essential oil: In vitro antimicrobial and antiradical properties and in situ control of Listeria monocytogenes in pork meat

The dominant compounds in Satureja horvatii oil were p-cymene (33.14%), thymol (26.11%) and thymol methyl ether (15.08%). The minimum inhibitory concentration (MIC) varied from 0.03 to 0.57 mg/mL for bacteria, and from 0.56 to 2.23 mg/mL for yeast strains, while minimum bactericidal/yeast-cidal concentration (MBC/MYC) varied from 0.07 to 1.15 mg/mL and 1.11 to 5.57 mg/mL for bacteria and yeasts, respectively. The antiradical potential of the essential oil was evaluated using hydroxyl radical (•OH) generated in Fenton reaction. The meat preserving potential of essential oil from Satureja horvatii was investigated against L. monocytogenes. Essential oil successfully inhibited development of L. monocytogenes in pork meat. Sensorial evaluation on flavor and color of meat was performed. The color and flavor of meat treated with essential oil improved after 4 days of storage. S. horvatii essential oil can act as a potent inhibitor of food spoiling microorganisms, in meat products and also can be a useful source of natural antioxidants.     

Chemical composition and biological activities of Algerian Thymus oils

The compositions of essential oils isolated from nine samples of three Thymus species (Thymus algeriensis, Thymus pallescens and Thymus dréatensis) were analysed by GC and GC–MS, and a total of 114 components were identified. T. pallescens collected from various regions showed a great similarity in their compositions and were characterised by carvacrol (44.4–57.7%), p-cymene (10.3–17.3%) and γ-terpinene (10.8–14.2%) as the major components for four samples; only one sample was thymol-rich (49.3%) with a small amount of carvacrol (9.0%). On the other hand, T. algeriensis showed a chemical polymorphism, even for samples from the same location, and two new chemotypes for this species were proposed. Oxygen-containing monoterpenes were the predominant class (76.3%) in T. dreatensis oil, with linalool (30.4%), thymol (20.2%) and geraniol (19.6%) as the principal constituents. The oils were screened for their possible antioxidant activities by four complementary assays, namely DPPH free radical scavenging, hydroxyl radical scavenging, inhibition of lipid peroxidation and reducing power. The two new chemotypes of T. algeriensis exhibited strong hydroxyl radical scavenging (IC₅₀ = 2.2–3.3 μg/ml), but were not or only slightly active against the other radicals and exhibited a weak reducing power. Despite their chemical similarity, T. pallescens oils sometimes produced significant differences in their antioxidant activities. The essential oils were also screened for their antimicrobial activity against five bacteria (three Gram-positive and two Gram-negative) and one yeast (Candida albicans). The tested essential oils showed antimicrobial activity against the microorganisms used, in particular against two important pathogens, C. albicans and Helicobacter pylori.     

Essential oil composition,antimicrobial and antioxidant activities of Satureja cuneifolia Ten.

Satureja cuneifolia Ten. is a well-known aromatic plant which is frequently used as a spice and herbal tea in Anatolia. S. cuneifolia oil was analyzed by gas chromatography/mass spectrometry (GC/MS). The major components of S. cuneifolia oil were carvacrol (44.99%) and p-cymene (21.61%). The essential oil of S. cuneifolia exhibited antimicrobial activity against all of the tested foodborne and spoilage bacteria. The minimum inhibitory concentration (MIC) values for test bacteria which were sensitive to the essential oil of S. cuneifolia were in the range of 600–1400 μg/ml. Antioxidant activities of the essential oil and the methanolic extract from S. cuneifolia were evaluated by using DPPH radical scavenging, β-carotene–linoleic acid bleaching and metal chelating activity assays. In addition, the amounts of total phenol components in the plant methanolic extract (222.5 ± 0.5 μg/mg) and the oil (185.5 ± 0.5 μg/mg) were determined.     

Antimicrobial effects of selected plant essential oils on the growth of a Pseudomonas putida strain isolated from meat

The inhibitory effect of 60 different essential oils was evaluated on a Pseudomonas putida strain of meat origin, associated with meat spoilage. Essential oils were tested at concentrations from 0.003 to 0.8% (wt/vol) to determine minimum inhibitory and maximal tolerated concentrations (MIC and MTC, respectively) using an agar medium culture. Of the 60 samples tested, Corydothymus capitatus essential oil was the most active showing a MIC of 0.025% and a MTC of 0.06%. Seven essential oils (Cinnamomum cassia, Origanum compactum, Origanum heracleoticum, Satureja hortensis, Satureja montana, Thymus vulgaris carvacroliferum, Thymus vulgaris thymoliferum) have shown a strong antimicrobial activity against P. putida with a MIC of 0.05% and a MTC ranging from 0.013% to 0.025%. Ten other oils (Cinnamomum verum (leaf and bark), Eugenia caryophyllus, Cymbopogon martinii var. motia, Cymbopogon nardus, Melaleuca linariifolia, Origanum majorana, Pimenta dioica, Thymus satureoides, Thymus serpyllum) showed a high antimicrobial activity showing a MIC ranging from 0.1% to 0.4%, while the remaining were less active showing a MIC ? 0.8%.     

Essential oils of Lavandula bipinnata and their antimicrobial activities

The essential oils from dried leaves of Lavandula bipinnata (Roth) Kuntze (Lamiaceae), obtained by soxhlet extraction was analysed by gas chromatography–mass spectrometry (GC–MS) and was evaluated for in vitro antimicrobial activity. The most common components usually found in lavender essential oils were present in the oil samples analysed, out of 43 peaks, 29 components, which constitute 72.38%, were identified in the essential oil. The major constituents were transcarveol (18.93%), pulegone (8.45%), camphor (7.09%) and menthol (5.89%). Other constituents present in fairly good amounts are pipertone (4.65%), caryophyllene oxide (3.68%), linalyl acetate (3.37%) and bicyclogermacrene (3.09%). The essential oil was screened for antimicrobial activity by disc diffusion assay and minimum inhibitory concentration (MIC) against bacteria and fungus. Results reveal that L. bipinnata essential oils are inhibitory against the tested bacteria and fungal strains.     

Use of surface-smear bacteria for inhibition ofListeria monocytogeneson the rind of smear cheese

Surface-smear micro-organisms isolated from Taleggio cheese were screened for their ability to inhibitListeria monocytogenes. Most of the isolates showing antilisterial activity (19% of the total) consisted of coryneform bacteria, mainly belonging to theMicrobacterium lacticumspecies. The inhibitory activity was observed also after growth at 5°C and pH 6·0. After cross-inhibition tests among inhibitory strains and between these and other pigmented, non-inhibitory strains, two bacterial mixtures were assayed as surface-smear starter of Taleggio cheese. At different ripening stages (1, 20 and 40 days), the cheese surface was contaminated with 2·5×10²cfu cm⁻²L. monocytogenes(Ohio strain) and the growth evaluated over 15 days of incubation at 5°C. Contrary to the laboratory experiments,Listeriacould not be completely inhibited on the cheese surface. With 5·5–6·0 pH range of the cheese rind, (lower than usual values), the growth of surface-smear bacteria was delayed, or even stopped. Nevertheless, a listeriostatic effect was achieved on the surface of cheese samples contaminated at the end of ripening. This seemed to confirm the essential role played by surface-smear bacteria, within the rind microflora, in controlling the development of contaminant micro-organisms, and by competitive bacteria in reducing the overall risks associated with soft cheese. The mechanisms involved in the selection and the growth of competing bacteria on the cheese surface are also discussed.     

Chemical composition and in vitro antimicrobial activity of the essential oil of Origanum minutiflorum O Schwarz & PH Davis

The essential oil obtained by hydrodistillation from the aerial parts of Origanum minutiflorum O Schwarz & PH Davis, an endemic species in Turkey, was analysed for its antimicrobial activity in vitro. Gas chromatography/mass spectrometry analysis of the essential oil resulted in the identification of 34 constituents accounting for 961.5 mL L^?1 of the oil, the major compounds present being carvacrol (793.4 mL L^?1), p‐cymene (32.6 mL L^?1) and γ‐terpinene (21.4 mL L^?1). The in vitro antimicrobial activity of the essential oil was investigated in order to evaluate its efficacy against 16 bacteria and two yeasts, using disc diffusion and minimum inhibitory concentration methods. The essential oil showed strong antimicrobial activity against all test micro‐organisms except Pseudomonas aeruginosa. Its main components carvacrol and p‐cymene were also assayed for their antimicrobial activities. Carvacrol exhibited comparable activity to the crude oil, proving it to be the main component responsible for the biological activity observed. This study demonstrates the in vitro antimicrobial activity of the essential oil of this endemic remedy against a wide spectrum of clinically important micro‐organisms, including pathogenic yeasts, being the first report on the anticandidal properties of the essential oil of O. minutiflorum. Copyright © 2006 Society of Chemical Industry     

罗文莎叶挥发油的化学成分及抑菌与酶抑制作用

利用气相色谱—质谱(GC-MS)联用仪测定罗文莎叶挥发油的化学组成;采用纸片扩散法和微量肉汤稀释法进行体外抑菌试验,并测定罗文莎叶挥发油对胰脂肪酶和a-葡萄糖苷酶活性的抑制效果.结果表明,罗文莎叶挥发油中共检出17种化学成分,占挥发油总量的98.5％,主要组分为桉叶油醇(30.89％)、樟脑(21.67％)、香树烯(1...     

Chemical Composition and Antimicrobial Activity of Essential Oil of Matricaria recutita

Matricaria recutita is a herbaceous plant belonging to the Asteraceae family. The present study reports the chemical composition and antimicrobial activity of M. recutita essential oil and its main compounds. The essential oil was obtained from the aerial parts of the M. recutita by hydrodistillation and analyzed by gas chromatography-mass spectrometry. The major components were α-bisabolol oxide (38%), followed by camphene (9.11%), sabinene (4.87%), limonene (6%),1,8-cineole (7.12%), camphor (6.54%), and α-pinene (6%). Essential oil of chamomile was evaluated for its antibacterial activities against three gram-positive and four gram-negative pathogenic bacteria. The essential oil and its main compounds were particularly active against Bacillus cereus, with the lowest minimum inhibitory concentration and minimum bactericidal concentration value (0.022 and 1.5 μg /mL). In conclusion, these results support the use of the essential oil and its main compounds for their antimicrobial properties.     

Bactericidal and antibiofilm properties of Rumex japonicus Houtt. on multidrug-resistant Staphylococcus aureus isolated from milk

Multidrug-resistant (MDR) Staphylococcus aureus and its biofilm formation have been challenging to control in milk and dairy industries. Biofilms formed by Staph. aureus may result in the failure of antibacterial agents and disinfectants to penetrate the biofilm in an attempt to control contamination. Novel natural antibacterial agents are required to combat MDR bacteria and biofilms. In this study, we evaluated the bactericidal, antibiofilm, and antimotility effects of Rumex japonicus Houtt. (RJH) extract on MDR Staph. aureus isolated from milk. The RJH extract exhibited good antibacterial activity against MDR strains with minimum inhibitory concentrations (MIC) ranging from 0.78 to 6.25 mg/mL and minimum bactericidal concentrations ranging from 3.125 to 12.5 mg/mL. The extract showed strong inhibition of biofilm formation (81.9%) at sub-MIC value and eradication of biofilm at higher concentrations. The motility of Staph. aureus was effectively blocked by the extract. Major compounds emodin, chrysophanol, and physcion were identified in RJH extract using HPLC-linear trap quadrupole (LTQ)/Orbitrap-mass spectrometry. The extract was nontoxic to human epithelial cell lines such as Caco-2 and HT-29 cell lines at concentrations ranging from 0.1 to 0.5 mg/mL, and from 0.1 to 0.75 mg/mL, respectively. These findings suggest that RJH extract could be an alternative to synthetic preservatives in milk and dairy products.     

竹叶精油组分构成及其抑菌活性的研究

目的研究竹叶精油的化学组分构成,并考察其体外抑菌活性。方法以食品常见腐败菌(枯草芽孢杆菌、金黄色葡萄球菌、大肠杆菌和酿酒酵母)作为供试菌,采用平板打孔法对竹叶精油的抑菌活性进行研究;并通过气相色谱-质谱联用技术对竹叶精油的组分构成进行分析鉴定。结果竹叶精油共鉴定出41个化合物,含量占挥发性成分总量的97.36%,主要成分为棕榈酸(19.35%)、植物醇(10.54%)和二十五烷(9.89%)等。竹叶精油对4种供试菌株均有抑制作用,研究发现大肠杆菌是最敏感的,其最小抑菌浓度为0.56 mg/mL。结论本研究可为竹叶精油在食品工业中的深入利用提供一定的理论技术支持。     

Chemical Composition and Antimicrobial Activity of the Essential Oil from the Peel of Shatian Pummelo (Citrus Grandis Osbeck)

The chemical composition of the essential oil obtained from the peel of Shatian pummelo was analyzed by gas chromatography/mass spectrometry. Twenty-one components were identified. The monoterpenes and sesquiterpene hydrocarbons were the principal compound groups with 96.64% (w/w) of the total oil, among which, limonene was observed dominant (89.96 ± 1.64%), followed by β-myrcene (4.49 ± 0.38%), α-pinene (0.63 ± 0.05%), 3-carene (0.48 ± 0.04%), caryophyllene (0.47 ± 0.04%), and other minor constitutes. Esters, alcohols, ketones, aldehydes, and ether represented 3.15% of the total oil. Results by the disc diffusion method and minimum inhibitory concentration determination method showed that the essential oil contained a wide-spectrum antimicrobial activity against Penicillium chrysogenum ATCC 10106, Bacillus subtilis ATCC 21616, Staphylococcus aureus ATCC 25923, and Escherichia coli ATCC 25922, with their inhibition zones ranging from 8.27 ± 1.07 mm to 20.71 ± 1.50 mm. The MIC values were ranging from 4.69 to 37.50 μL/mL. However, no inhibition effect was observed on the Aspergillus niger ATCC 16888.     

Phytochemicals of ethanolic extract and essential oil of Persicaria hydropiper and their potential as antibacterial agents for food packaging polylactic acid film

This study aims to determine phytochemicals and antibacterial activity of ethanolic extract and essential oil of Persicaria hydropiper, and their potential as antibacterial agents in polylactic acid (PLA) film. The yield of ethanolic extract and essential oil were 11.02 and 0.70%, respectively. Chlorogenic acid, ferulic acid, rutin, myricetin and quercetin were detected as major components in the P. hydropiper ethanolic extract, while dodecanal, caryophyllene, caryophyllene oxide, decanal, α‐caryophyllene, citronellol, heptadecanal, linalool and phytol were detected in the P. hydropiper essential oil. Based on the disc diffusion assay, both ethanolic extract and essential oil of P. hydropiper possessed antibacterial activity against bacteria Staphylococcus aureus only at different concentrations, with minimum inhibitory concentration values: 0.625 and 5 mg/ml, respectively; and minimum bactericidal concentration values: 5 and 40 mg/ml, respectively. However, they found to show antibacterial activity against three bacteria S. aureus, Escherichia coli and Salmonella Typhimurium at different concentrations and time using time‐kill kinetics assay. Incorporation of ethanolic extract and essential oil in PLA film also exhibited an antibacterial effect against S. aureus. Our findings confirmed the potential use of both P. hydropiper ethanolic extract and essential oil as antibacterial agents in biodegradable PLA film.     

Angiotensin-converting enzyme inhibitory activity in Mexican Fresco cheese

The objective of this study was to evaluate if Mexican Fresco cheese manufactured with specific lactic acid bacteria (LAB) presented angiotensin I-converting enzyme inhibitory (ACEI) activity. Water-soluble extracts (3 kDa) obtained from Mexican Fresco cheese prepared with specific LAB (Lactococcus, Lactobacillus, Enterococcus, and mixtures: Lactococcus-Lactobacillus and Lactococcus-Enterococcus) were evaluated for ACEI activity. Specific peptide fractions with high ACEI were analyzed using reverse phase-HPLC coupled to mass spectrometry for determination of amino acid sequence. Cheese containing Enterococcus faecium or a Lactococcus lactis ssp. lactis-Enterococcus faecium mixture showed the largest number of fractions with ACEI activity and the lowest half-maximal inhibitory concentration (IC₅₀; <10 μg/mL). Various ACEI peptides derived from β-casein [(f(193-205), f(193-207), and f(193-209)] and α_S1-casein [f(1-15), f(1-22), f(14-23), and f(24-34)] were found. The Mexican Fresco cheese manufactured with specific LAB strains produced peptides with potential antihypertensive activity.     

斜叶黄檀精油功能活性

本文主要测定斜叶黄檀精油中的挥发性成分、多酚和黄酮含量,采用体外抗氧化评价斜叶黄檀精油的清除DPPH和ABTS自由基能力、总还原力和总抗氧化能力,以金黄色葡萄球菌(G+)、化脓性链球菌(G+)、大肠杆菌(G-)、铜绿假单胞菌(G-)、鼠伤寒沙门氏菌(G-)以及白色念珠菌(真菌)为待测菌,评价精油的抑菌效果,通过对酪氨酸酶的抑制活性评价精油抑制黑色素的形成能力。结果表明斜叶黄檀精油在浓度为0.18 mg/mL时,对DPPH和ABTS自由基的清除能力均达到70%左右,在浓度分别为0.18 mg/mL和1 mg/mL时,总还原力和总抗氧化能力的吸光度值均达到0.4以上。对金黄色葡萄球菌、化脓性链球菌以及白色念珠菌的抑菌圈直径分别为:12.83、11.50和10.25 mm,呈现中敏程度的抑制性,但对三种革兰氏阴性菌无明显的抑制效果。精油对酪氨酸酶的抑制活性要强于阳性对照熊果苷,在浓度为0.1 mg/mL抑制率将近90%。本文得出斜叶黄檀精油有较好的抗氧化活性、抑制革兰氏阳性菌和真菌以及抑制酪氨酸酶活性,比较完善的介绍了斜叶黄檀精油的功能活性。     

Olive oil polyphenol extract inhibits vegetative cells of Bacillus cereus isolated from raw milk

This study was conducted to analyze the antibacterial effect of olive oil polyphenol extract (OOPE) against vegetative cells of Bacillus cereus isolated from raw milk and reveal the possible antibacterial mechanism. The diameter of inhibition zone, minimum inhibitory concentration, minimum bactericidal concentration, and survival counts of bacterial cells in sterile normal saline and pasteurized milk were used to evaluate the antibacterial activity of OOPE against B. cereus vegetative cells. The changes in intracellular ATP concentration, cell membrane potential, content of bacterial protein, and cell morphology were analyzed to reveal possible mechanisms of action. Our results showed the diameter of inhibition zone, minimum inhibitory concentration, and minimum bactericidal concentration of OOPE against B. cereus vegetative cells were 18.44 ± 0.55 mm, 0.625 mg/mL, and 1.25 mg/mL, respectively. Bacillus cereus GF-1 vegetative cells were decreased to undetectable levels from about 8 log cfu/mL after treatments with 0.625 mg/mL of OOPE in normal saline at 30°C for 3 h and in pasteurized milk at 30°C for 10 h. The antibacterial mechanisms of OOPE against B. cereus GF-1 vegetative cells may be due to the reduction of intracellular ATP concentrations, cell membrane depolarization, decrease of bacterial protein content, and leakage from cytoplasm. These findings illustrated that OOPE could be used to prevent the growth of contaminating B. cereus cells in dairy products.     

Antibacterial activity of Thymus capitatus and Thymus algeriensis essential oils against four food‐borne pathogens inoculated in minced beef meat

The antibacterial activity of the essential oils extracted from Thymus capitatus and Thymus algeriensis was studied against Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Pseudomonas aeruginosa. In this study, the disk method showed that T. capitatus EO has a strong antibacterial effect, whereas T. algeriensis EO showed a moderate activity. In addition, the inhibitory effect of both EOs was evaluated against four pathogenic strains inoculated experimentally (10⁸ CFU/g) in the minced beef meat, mixed with different concentrations of EOs, and stored for 15 days. Both EOs at low concentrations (0.01 and 0.05% [vol/wt]) exerted a bacteriostatic effect (p < .001), only against E. coli and S. typhimurium. However, at higher concentrations (1 and 3% [vol/wt]), the bactericidal activity was pronounced (p < .0001), in particular in the case of T. capitatus EO against all strains, except P. aeruginosa. The latter was still present after 15 days of storage, which explains its resistance.

Practical applications

Results from this study were confirmed that both thyme EOs could be considered as a very promising natural preservatives for foods from microbial spoilage in the food industries, also they can serve to inhibit or prevent the growth of food‐borne pathogens.