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Evaluation of antibacterial properties and biochemical effects of monoterpenes on plant pathogenic bacteria

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Abstract

The antibacterial activity of twelve monoterpenes, namely camphene, (R)-camphor, (R)-carvone, 1,8-cineole, cuminaldehyde, (S)-fenchone, geraniol, (S)-limonene, (R)-linalool, (1R,2S,5R)-menthol, myrcene and thymol was tested against two plant pathogenic bacteria Agrobacterium tumefaciens and Erwinia carotovora var. carotovora using agar dilution method. For a better understanding of monoterpenes mechanisms of action, the inhibitory effect of three monoterpenes (R)-linalool, myrcene and thymol was assessed on dehydrogenases and polyglacturonase activities. Among the tested monoterpenes, thymol, (S)-limonene and myrcene were the most potent antibacterial compounds against A. tumefaciens with minimum inhibitory concentration (MIC) of 1000 mg/L. Thymol was also the most effective compounds against E. carotovora var. carotovora, while camphene, cunimaldhyde and 1,8-cineole were the less effective compounds against both bacteria. In biochemical studies, myrcene caused the highest inhibitory effect on dehydrogenases activity of the two tested bacteria, followed by thymol. However, thymol showed the highest inhibitory effect on polygalacturonase activity of both tested bacteria, followed by (R)-linalool. In general, there was a positive correlation between the antibacterial activity of monoterpenes and their inhibitory effects on both enzymes. This is the first report for the determination of MIC and enzymes inhibitory effects of tested monoterpenes on plant pathogenic bacteria.

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... A number of environmental variables including certain xenobiotics (e.g. pesticides) influence these functions [11,12] . In fact, oxygen free radicals are reportedly involved in toxicity of numerous chemicals including pesticides and in pathogenesis of many diseases [13][14][15] . ...
... The use of natural antioxidants for curing pesticide induced kidney toxicity or injury is being studied extensively [12] . Also, there are several reports on oils indicating that it results in alterations of pharmacologic responses to drugs [17] . ...
... Pesticides induce oxidative stress as well as alter the defense mechanisms of detoxification and scavenging enzymes [12,15,[40][41][42] . These toxic compounds impair the cellular function, enzymes activity and produce cytotoxic changes through generation of ROS [12,15,34] . ...
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Objective: To investigate the effects of prallethrin on renal dysfunction biomarkers, antioxidant enzyme activities and lipid peroxidation (LPO) in rats and the protective effect of Origanum majorana essential oil. Methods: Rats were divided into four groups of seven rats in each group: (I) received only olive oil, (II) treated with 64.0 mg/kg body weight prallethrin (1/10 LD50) in olive oil via oral route daily for 28 d, (III) treated with 64.0 mg/kg body weight prallethrin (1/10 LD50) and essential oil (160 μL/kg body weight) in olive oil and (IV) received essential oil (160 μL/kg body weight) in olive oil via oral route twice daily for 28 d. Results: Prallethrin caused significant increase in LPO and decrease in superoxide dismutase, glutathione peroxidase and glutathione reduced. Consistent histological changes were found in the kidney of prallethrin treatment. Co-administration of essential oil attenuated the prallethrin induced renal toxicity and oxidative stress by decreasing LPO in kidney, creatinine, urea and uric acid levels in serum. In addition, superoxide dismutase, glutathione peroxidase activity and glutathione reduced level were increased in kidney in prallethrin-essential oil groups. Conclusions: We can conclude that prallethrin induced oxidative damage and renal toxicity in male rat. The administration of essential oil provided significant protection against prallethrin-induced oxidative stress, biochemical changes and histopathological damage.
... Crude extracts and constituents from about thirty species of Cinnamomum displayed significant activities, namely antibacterial, anticancer, antifungal, antiseptic, antiviral, anti-inflammatory, antipyretic, antioxidant, chemopreservative, cytotoxic, anti-diabetic, antiulcer, immune stimulant, etc. Compounds such as Camphene, Cuminaldehyde, Eugenol, Proanthocyanidins etc., have been reported to be responsible for these activities [11,12,13]. The compounds Camphene and Cuminaldehyde exhibit antibacterial and antifungal properties [14]. Treatment with Camphene exhibited no toxicity in human hepatic cells; also, it has been reported to have antitumor activities [15]. ...
... Crude extracts and constituents from about thirty species of Cinnamomum displayed significant activities, namely antibacterial, anticancer, antifungal, antiseptic, antiviral, anti-inflammatory, antipyretic, antioxidant, chemopreservative, cytotoxic, anti-diabetic, antiulcer, immune stimulant, etc. Compounds such as Camphene, Cuminaldehyde, Eugenol, Proanthocyanidins etc., have been reported to be responsible for these activities [11][12][13]. The compounds Camphene and Cuminaldehyde exhibit antibacterial and antifungal properties [14]. Treatment with Camphene exhibited no toxicity in human hepatic cells; also, it has been reported to have antitumor activities [15]. ...
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Urease is an enzyme that plays a significant role in the hydrolysis of urea into carbonic acid and ammonia via the carbamic acid formation. The resultant increase in pH leads to the onset of various pathologies such as gastric cancer, urolithiasis, hepatic coma, hepatic encephalopathy, duodenal ulcers and peptic ulcers. Urease inhibitors can reduce the urea hydrolysis rate and development of various diseases. The Cinnamomum genus is used in a large number of traditional medicines. It is well established that stem bark of Cinnamomum cassia exhibits antiulcerogenic potential. The present study evaluated the inhibitory effect of seven extracts of Cinnamomum camphora, Cinnamomum verum and two pure compounds Camphene and Cuminaldehyde on urease enzyme. Kinetic studies of potential inhibitors were carried out. Methanol extract (IC50 980 µg/mL) of C. camphora and a monoterpene Camphene (IC50 0.147 µg/mL) possess significant inhibitory activity. The Lineweaver Burk plot analysis suggested the competitive inhibition by methanol extract, hexane fraction and Camphene. The Gas Chromatography-Mass Spectroscopy (GC–MS) analysis of hexane fraction revealed the contribution of various terpenes. The present study targets terpenes as a new class of inhibitors that have potential therapeutic value for further development as novel drugs.
... Monoterpenes and phenylpropenes have been reported to possess inhibitory effect on the growth of A. tumefaciens and E. carotovora var. carotovora (El-Zemity et al., 2008;Abdel Rasoul et al., 2012), E. amylovora (Sato et al., 2007;Scortichini and Rossi 2008) and Xanthomonas campestris pv. phaseoli var. ...
... Similarly, (El-Zemity and Ahmed, 2005) noticed that the essential oils with high content of phenolic monoterpenes, such as carvacrol, eugenol and thymol showed strong antifungal activity. Also, (Abdel Rasoul et al.,2012) reported the effect of inhibiton 12 monoterpenes on the growth of E. carotovora var. carotovora and A. tumefaciens. ...
... Flavonoids on the other hand are involved in inhibition of nucleic acid synthesis, cytoplasmic membrane function, and energy metabolism (Cushnie and Lamb 2005). Rasoul et al. (2012), terpenoids show inhibitory effects on pathogens through interaction with membrane structure and function. The interactions result in membrane expansion, increased membrane fluidity and permeability, disturbance of membrane-embedded proteins and alteration of ion transport processes (Rasoul et al. 2012). ...
... Rasoul et al. (2012), terpenoids show inhibitory effects on pathogens through interaction with membrane structure and function. The interactions result in membrane expansion, increased membrane fluidity and permeability, disturbance of membrane-embedded proteins and alteration of ion transport processes (Rasoul et al. 2012). Similarly, the antibacterial activity of alkaloids is related to the presence of OH group in the structure that reacts and changes the nature of bacterial cell, consequently increasing the permeability of the cell membrane (Straus and Hancock 2006). ...
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Yemata G, Desta B, Fetene M. 2019. In vitro antibacterial activity of traditionally used medicinal plants against Xanthomonas campestris pv. musacearum in Ethiopia. Biodiversitas 20: 555-561. In Ethiopia, traditional medicinal plants have long been used to treat human and livestock ailments. Nevertheless, studies about the use of these plant extracts to control crop diseases are scarce. Therefore, the aim of the present study was to evaluate the antibacterial activity of traditionally used medicinal plants against Xanthomonas campestris pv. musacearum (Xcm). The bioactive chemicals from leaf samples were drawn using methanol by maceration method. Total phenolic content of the extracts was determined by Folin Ciocalteau reagent. The antibacterial activity of leaf extracts was evaluated by disc diffusion method. The phytochemical analysis revealed the presence of alkaloids, flavonoids, phenolic compounds, terpenoids, tannins and saponins. Extracts with higher total phenolic content had greater antibacterial activity. The extract of each species showed antibacterial activity against Xcm on a dose dependent manner. Significant differences were recorded between species and test concentrations. The extract of Bersama abyssinica exhibited the strongest antibacterial activity at 200 mg/mL followed by Ricinus communis, Eucalyptus citriodora and Acokanthera schimperi. At lower test concentrations, extracts of E. citriodora and R. communis revealed higher antibacterial activity. Moreover, these species had lower bacteriostatic and bactericidal concentrations. The results showed the potential potency of E. citriodora and R. communis leaf extracts in controlling enset bacterial wilt. However, further studies on the identification of chemical compounds and in vivo evaluation of the extracts are recommended.
... Pesticides induce oxidative stress as well as alter the defense mechanisms of detoxification and scavenging enzymes (Rasoul et al., 2012;Mossa et al., 2012;Mansour & Mossa, 2010;Marzouk et al., 2011). These toxic compounds impair the cellular function, enzymes activity and produce cytotoxic changes through generation of ROS (Rasoul et al., 2012;Mossa et al., 2012;Abbassy & Mossa, 2012). ...
... Pesticides induce oxidative stress as well as alter the defense mechanisms of detoxification and scavenging enzymes (Rasoul et al., 2012;Mossa et al., 2012;Mansour & Mossa, 2010;Marzouk et al., 2011). These toxic compounds impair the cellular function, enzymes activity and produce cytotoxic changes through generation of ROS (Rasoul et al., 2012;Mossa et al., 2012;Abbassy & Mossa, 2012). These free radicals also damage the cell components including proteins, lipids and DNA (Persson et al., 2014). ...
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We evaluated the brain, lung, and heart oxidative stress in rats exposed to aerosol of an over-the-counter pyrethroid insecticide product in Nigeria. The experimental animals were randomly divided into four groups: group I (control) was not exposed to the insecticide aerosol, while groups II, III, and IV were exposed to 6.0 mL m-3, 12.0 mL m-3, and 18 mL m-3 of insecticide aerosol respectively. Exposures were carried out in wooden-glass chambers one hour daily for six weeks. Malondialdehyde (MDA) and reduced glutathione (GSH) concentrations, as well as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione S-transferase (GST) activities were determined. The brain, lung, and heart showed no significant difference in their weights and relative weights compared with the control. A significant increase in brain lipid peroxidation (LPO) was seen in groups III and IV, while there was no significant increase in lung and heart LPO compared with control. Significant decrease in the brain and lung GSH were observed in all the treatment groups when compared with the control, but only group IV showed significant reduction in heart GSH. Also, activities of lung GST and SOD were decreased compared with control, while the activity of GPx in the lung was significantly increased in group III. Lastly, non-significant increase in lung CAT activity was recorded in groups II and III, but decreased in group IV compared with control. Prolonged and incessant exposure to the insecticide aerosol over a long period of time may lead to tissue oxidative stress. These findings suggest that the use of insecticide aerosol for domestic purposes should be regulated.
... Several researchers have described the antibacterial activity of citral, linalool, α-terpineol, citronellal, geraniol, and linalyl acetate against different pathogens [25,[27][28][29][30][31]. The antibacterial effect of citral against E. coli K12, Listeria innocua, and L. monocytogenes have been reported by Belda-Galbis et al. [32] and Silva-Angulo et al. [33]. ...
... The bacterial suspensions were centrifuged at 6000 rpm for 7 min and cell pellets were pre-fixed on glutaraldehyde solution 2.5% (with cacodylate buffer 0.1 mol/L) for 24 h at −4 • C. Then samples were washed three times for 10 min with cacodylate buffer and post-fixed on 1.0% osmium tetroxide. The samples, which were washed on cacodylate buffer for 15, 30, and 60 min, were dehydrated in a graded ethanol series (30,50,70,80, and 100%). Later, samples were embedded in propylene oxide and resin in ratios of 1:3, 1:1, 3:1, and pure resin for 12, 4, 12 and 24 h, the sample blocks were polymerized in an oven at 60 • C, for 48 h. ...
Article
Citrus bacterial canker (CBC) caused by Xanthomonas citri subsp. citri (Xcc), is the most devastating of the citrus diseases worldwide. During our study, we found that Essential oils (EOs) of some citrus cultivars are effective on Xcc. Therefore, it prompted us to determine the plant metabolites responsible for the antibacterial properties. We obtained EOs from some locally cultivated citrus by using a Clevenger apparatus and their major constituents were identified by gas chromatography/mass spectrometry (GC-MS). The effect of Citrus aurantium, C. aurantifolia, Fortunella sp. EOs and their major constituents were evaluated against Xcc-KVXCC1 using a disk diffusion assay. Minimal inhibitory and bactericidal concentration of the EOs and their constituents were determined using the broth microdilution method. C. aurantium, C. aurantifolia Eos, and their major constituents including citral, linalool, citronellal, geraniol, �-terpineol, and linalyl acetate indicated antibacterial effects against Xcc. The C. aurantifolia EO and citral showed the highest antibacterial activity among the tested EOs and constituents with inhibition zones of 15 � 0.33 mm and 16.67 � 0.88 mm, respectively. Synergistic effects of the constituents were observed between �-terpineol-citral, citral-citronellal, citral-geraniol, and citronellal-geraniol by using a microdilution checkerboard assay. Transmission electron microscopy revealed that exposure of Xcc cells to citral caused cell wall damage and altered cytoplasmic density. We introduced C. aurantifolia and C. aurantium EOs, and their constituents citral, �-terpineol, citronellal, geraniol, and linalool as possible control agents for CBC.
... Alpha and β -pinene have antimicrobial activities 18,19 . Myrcene is known for its antifungal 20 and antibacterial properties 21 . Limonene presents a strong antifungal activity 20,22-24 and it has been proven that antifungal activity of citrus essential oils on Aspergillus flavus, Penicillium chrysogenum and Penicillium verrucosum was explained by its prevalence 25 . ...
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Banana (Musa sp.) ranks fourth in term of worldwide fruit production, and has economical and nutritional key values. The Cavendish cultivars correspond to more than 90% of the production of dessert banana while cooking cultivars are widely consumed locally around the banana belt production area. Many plants, if not all, produce Volatile Organic Compounds (VOCs) as a means of communication with their environment. Although flower and fruit VOCs have been studied for banana, the VOCs produced by the plant have never been identified despite their importance in plant health and development. A volatile collection methodology was optimized to improve the sensitivity and reproducibility of VOCs analysis from banana plants. We have identified 11 VOCs for the Cavendish, mainly (E,E)-α-farnesene (87.90 ± 11.28 ng/μl), methyl salicylate (33.82 ± 14.29) and 6-methyl-5-hepten-2-one (29.60 ± 11.66), and 14 VOCs for the Pacific Plantain cultivar, mainly (Z,E)-α-farnesene (799.64 ± 503.15), (E,E)-α-farnesene (571.24 ± 381.70) and (E) β ocimene (241.76 ± 158.49). This exploratory study paves the way for an in-depth characterisation of VOCs emitted by Musa plants.
... The present findings and published data led to the speculation that the antibacterial effect of geraniol may result through interaction with the membrane structure and the function of the bacteria. Furthermore, geraniol might cross the cell membranes penetrating into the interior of the cell and interacting with intracellular sites critical for antibacterial activity [27]. ...
Article
The chemical composition and antibacterial activity of Thymus glabrescens Willd. (Lamiaceae) essential oil were examined, as well as the association between it and chloramphenicol. The antibacterial activities of geraniol and thymol, the main constituents of T. glabrescens oil, individually and in combination with chloramphenicol, were also determined. The interactions of the essential oil, geraniol, and thymol with chloramphenicol toward five selected strains were evaluated using the microdilution checkerboard assay in combination with chemometric methods. Oxygenated monoterpenes were the most abundant compound class in the oil, with geraniol (22.33%) as the major compound. The essential oil exhibited in vitro antibacterial activity against all tested bacterial strains, but the activities were lower than those of the standard antibiotic and thymol. A combination of T. glabrescens oil and chloramphenicol produced a strong synergistic interaction (FIC indices in the range 0.21–0.87) and a substantial reduction of the MIC value of chloramphenicol, thus minimizing its adverse side effects. The combinations geraniol-chloramphenicol and thymol-chloramphenicol produced synergistic interaction to a greater extent, compared with essential oil-chloramphenicol association, which may indicate that the activity of the thyme oil could be attributed to the presence of significant concentrations of geraniol and thymol.
... The present findings and published data led to the speculation that the antibacterial effect of geraniol may result through interaction with the membrane structure and the function of the bacteria. Furthermore, geraniol might cross the cell membranes penetrating into the interior of the cell and interacting with intracellular sites critical for antibacterial activity [10]. The results of antibacterial activity of the combination of geraniol-tetracycline are different compared with the results of S. kitaibelii oiltetracycline combination. ...
Article
The chemical composition and antibacterial activity of Satureja kitaibelii Wierzb. ex Heuff. (savory) essential oil were examined, as well as the association between it and standard antimicrobials: tetracycline and chloramphenicol. The antibacterial activities of geraniol, the main constituent of S. kitaibelii oil, individually and in combination with standard antimicrobials were also determined. The interactions of the essential oil and geraniol with antimicrobials toward five selected strains were evaluated using the microdilution checkerboard assay in combination with chemometric methods. Oxygenated monoterpenes were the most abundant compound class in the oil (59.7%), with geraniol (50.4%) as the major compound. The essential oil exhibited in vitro antibacterial activity against all tested bacterial strains, but the activities were lower than those of the standard antimicrobials. The combinations savory oil-chloramphenicol, savory oil-tetracycline and geraniol-chloramphenicol produced predominantly synergistic interactions (FIC indices in the range 0.21-0.87) and substantial reductions in the MIC values of antimicrobials against Gram-negative bacteria, the pharmacological treatment of which is very difficult nowadays. In the PCA and HCA analyses these combinations form a separate group.
... Pesticides induce oxidative stress as well as alter the defense mechanisms of detoxification and scavenging enzymes (Rasoul et al., 2012;Mossa et al., 2012;Mossa, 2010a, 2011;Marzouk et al., 2011). Overproduction of ROS can exacerbate oxidative stress and ROS generation has been linked to a number of disease processes, such as heart disease (Giordano, 2005), diabetes (Rolo and Palmeira, 2006), liver injury Mossa, 2010a, 2011;Mossa, 2004;Jaeschke, 2000), cancer (Klaunig and Kamendulis, 2004) and aging (Bokov et al., 2004). ...
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Extra-pulmonary oxidative stress investigations of exposure to aerosol, of an over-the-counter pyrethroid insecticide product in Nigeria in Wistar rats were carried out. Four groups of five animals each were used in this study, and were exposed to different concentrations of the insecticide aerosol. Malondialdehyde (MDA) and reduced glutathione (GSH) concentrations were determined in the liver, kidney and testes, while the activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione S-transferase (GST) were determined in liver only. Liver, kidney and testes showed no significant difference in their weights and relative weights when compared with control, except Groups II and III where significant increase in liver weight was recorded. There was no significant increase in liver, kidney and testis MDA concentration when compared with the control. There was significant decrease in testis GSH for all groups, while significant increase was seen in Groups III and IV for kidney GSH, and Group II only for liver GSH. The activities of liver CAT, SOD, GST and GPx were reduced, but showed no significant difference when compared with the control. Our investigations therefore revealed that the compositions of the pyrethroid insecticide product may not play any role in extra-pulmonary tissue oxidative damage.
... Friedman et al. (2002) also reported that geraniol was the most bactericidal active against E. coli (with a bactericidal activity value of BA 50 0.15), L. monocytogenes and S. enterica. As a monoterpene member, geraniol had antimicrobial inhibitory effects through the interaction with membrane structure and function due to their lipophilic and solubility properties (Rasoul et al., 2012). ...
Conference Paper
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The effect of antimicrobial activity of antiseptic hand gel containing propolis and geraniol was evaluated. Log reduction of microorganisms (the initial number was about 5 log CFU/ml) of hand gels containing ethanolic extract of propolis and geraniol compared with ethanol hand gel as the active ingredient was done in phosphate buffer saline (in vitro). The hand gel with EEP and geraniol (EEPGer) showed the strongest antimicrobial activity against S. aureus and E. coli. Those cell counts reduced by 90% within 15 and 30 sec, respectively. For the in vivo, the swab test from 110 volunteer' hands before and after using different hand gels including EEPGer, ethanol or triclosan (commercial) showed that the antibacterial activity against total plate count after using three hand gels were not significant difference (p ≤ 0.05). Therefore, the application of propolis and geraniol in antiseptic hand gel can be used as natural alternative to replace chemical substances.
... This could lead to: membrane expansion, increase in membrane fluidity and permeability, disruption of membrane-embedded proteins, inhibition of respiration, alteration of ion transport and other enzymatic reactions. [17] The anti-MRSA activity of C. odorata leaves in this study could have been due to the contribution of the membrane disruption activities of the monoterpenes on the cells of MRSA. ...
Article
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Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a strain of the bacterium Staphylococcus aureus characterized by its multi-drug resistance to penicillins, clindamycin, tetracyclines, macrolides, aminoglycosides, fluoroquinolones, etc. Chromolaena odorata R.M. King & H. Rob is a potential and promising plant that should be explored for the management of diseases caused by MRSA because its fractions have anti-MRSA activities. Objective: The aim To screen and identify the chemical constituents of the anti-MRSA fractions of C. odorata leaves. Materials and Methods: Seven isolates of MRSA and methicillin-susceptible S. aureus (MSSA) and a control strain S. aureus NCIBB 8588 were used for this study. Fresh leaves of C. odorata were collected from Igbinedion University, Okada environs, Edo State, Nigeria. The fractions obtained were analyzed with a Gas Chromatography-Mass Spectrometry (GC-MS) analyzer to identify their chemical constituents. Results: A total of eight fractions (F1, F2, F3, F4, F5, F7, F8, F9) obtained from the leaves of C. odorata were analyzed for their chemical constituents. They contain essential oils which were: α-pinene, β-pinene, 1,8-cineole, σ-elemene, terpineol, camphene, cymene, linalool, terpinolene and α-phallandrene. Free fatty acids were also identified: namely, hexanoic acid (caproic acid), dodecanoic acid (lauric acid), decanoic acid (capric acid) and octanoic acid (caprylic acid). Constituents common in fractions F2 and F3 with the highest anti-MRSA activities were: α-pinene, camphene, octanoic acid and decanoic acid. Conclusion: C. odorata is a promising anti-MRSA agent that can be explored for the synthesis of novel drugs for use in the treatment of MRSA infections. Key words: Chromolaena odorata, Free fatty acids, Gas Chromatography-Mass Spectrometry, Methicillin-resistant, Monoterpenes, Staphylococcus aureus
... On the other hand, the composition of curcumene was increasing along with the increasing of steam flow rate. Curcumene is known for its fine antioxidant ability and has a good comparison with butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) as the standard antioxidant while camphene has an antibacterial capability (Mark E. et al. 2010;Rasoul et al. 2012). ...
Conference Paper
In Indonesia ginger was usually used as a seasoning for dishes, an ingredient for beverage and a source of herbal medicines. Beside raw usage, ginger can be processed to obtain the essential oil which has many advantages such as proven to be an active antimicrobial and having an antioxidant ability. There are a lot of methods to extract essential oil from ginger, one of which is steam distillation. The aim of the current study was to investigate the effect of variation of time process and steam flow rate in the yield on ginger essential oil steam distillation extraction process. It was found that the best operation condition was 0.35 ml/s as the steam flow rate which yields 2.43% oil. The optimum time process was predicted at 7.5 hours. The composition of the oil was varied depend on the flow rate and every flow rate has its own major component contained in the oil. Curcumene composition in the oil was increased as increased steam flow rate applied, but the composition of camphene was decreased along with...
... For their part, essential oils and their ingredients alone induce both stimulatory and inhibitory effects on plants, herbivores, microorganisms [14,15] and soil enzymes [16]. They may increase or decrease the size of bacterial populations, change the microbial community profiles and influence the activity of various microbial taxa [17,18,19]. Hassiotis [20], Hassiotis and Dina [21] found depressing effects of essential oils on AM fungi. ...
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The arbuscular mycorrhizal fungi (AMF) and the essential oils are both agents of sustainable agriculture, and their independent effects on the community of free-living soil microbes have been explored. In a tomato pot experiment, conducted in a sandy loam mixture, we examined the independent and joint effects of inoculation with the fungus Rhizophagous irregularis and the addition of Mentha spicata essential oil on the structure of the soil microbial community and the activity of soil enzymes involved in the N-cycle, during the pre-symbiosis phase. Plants were grown for 60 days and were inoculated with R. irregularis. Then pots were treated with essential oil (OIL) weekly for a period of a month. Two experimental series were run. The first targeted to examine the effect of inoculation on the microbial community structure by the phospholipid fatty acids analysis (PLFAs), and enzyme activity, and the second to examine the effects of inoculation and 939 AIMS Microbiology Volume 3, Issue 4, 938-959. essential oil addition on the same variables, under the hypothesis that the joint effect of the two agents would be synergistic, resulting in higher microbial biomass compared to values recorded in singly treated pots. In the AMF pots, N-degrading enzyme activity was dominated by the activity of urease while in the non-inoculated ones by the activities of arylamidase and glutaminase. Higher microbial biomass was found in singly-treated pots (137 and 174% higher in AMF and OIL pots, respectively) compared with pots subjected to both treatments. In these latter pots, higher activity of asparaginase (202 and 162% higher compared to AMF and OIL pots, respectively) and glutaminase (288 and 233% higher compared to AMF and OIL pots, respectively) was found compared to singly-treated ones. Soil microbial biomasses and enzyme activity were negatively associated across all treatments. Moreover, different community composition was detected in pots only inoculated and pots treated only with oil. We concluded that the two treatments produced diverging than synergistic effects on the microbial community composition whereas their joint effect on the activity of asparaginase and glutaminase were synergistic.
... (Wang et al. 2019) as well as on plant pathogenic bacteria Agrobacterium tumefaciens and Erwinia carotovora var. carotovora (AbdelRasoul et al. 2012). On the other hand, several studies on essential oils containing high amounts of p-cymene and thymol(Bukvi cki et al. 2014;Yang et al. 2014) have shown excellent antimicrobial activities against some Gram-positive (Listeria monocytogenes) and Gram-negative (Salmonella typhimurium and Escherichia coli) bacteria and yeast strains (Pichia membranaefaciens, Zygosacharomyce bailii and Aureobasidium pullulans). ...
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Essential oils have been used for a long time in several fields of interest. Recently, they have also been applied in the conservation of Cultural Heritage to contrast biodeterioration replacing the most current biocides toxic for humans and environment. Inula crithmoides L. (syn. Limbarda crithmoides (L.) Dumort) is a halophyte species distributed along the Mediterranean coasts and it is used as an edible vegetable since the young leaves or shoots are eaten raw or cooked. Several biological properties have been determined for this plant including antimicrobial activities. In this study the volatile composition of the aerial part of an accession from the Aeolian Islands, Sicily (Italy) is described. Furthermore, the in vitro antibacterial assay against four species of bacteria isolated from a XX century Tholu Bhommalu, a leather painted puppet from Andhra Pradesh (India), was showed by the Agar disc diffusion method.
... Geraniol significantly increased the efficacy of ampicillin against S. aureus, but the mechanism behind this synergistic effect is still unclear. There are reports suggesting geraniol's ability to penetrate into the interior of the bacterial cell and subsequently interacting with intracellular sites [12] and this may be the reason for its antibacterial potential against multiple bacteria. Further studies have reported that geraniol potentiated the effect of chloramphenicol by sixteen-fold against Gram-negative bacteria by inhibiting the efflux mechanism [13]. ...
Article
The antibacterial activity of geraniol and its effect in combination with ampicillin, amoxicillin and clarithromycin against Staphylococcus aureus, Escherichia coli and Helicobacter pylori was tested. The minimum inhibitory concentrations (MICs) and combinatory effects of geraniol against the bacteria were assessed by using the modified broth microdilution and checkerboard assay, respectively. The combinatory effect is expressed as fractional inhibitory concentration index (FICI). The MIC of geraniol against S. aureus, E. coli and H. pylori was found to be 11200, 5600, and 7325 μg/mL, respectively. A significant synergistic effect was observed with geraniol and ampicillin against S. aureus with FICI in the range 0.19 to 0.32. Geraniol and ampicillin exhibited a partial synergistic effect against E. coli. A similar effect was observed with geraniol and clarithromycin against S. aureus. A partial synergistic effect was observed with clarithromycin and geraniol against H. pylori with the FICI value in the range 0.86 to 0.89. An additive effect was observed with geraniol and amoxicillin combination against H. pylori. However, the amoxicillin and clarithromycin dose was reduced by thirty-two fold when combined with geraniol against H. pylori. The anti-H. pylori effect of geraniol with clarithromycin and amoxicillin could be of potential interest in the treatment of H. pylori infection and associated ulcers in humans. Further, geraniol, in combination with other antibiotics, has substantial therapeutic potential against S. aureus and E.coli infection.
... Although we did not measure such responses, legume crop compensation may have been facilitated through the frequent application of pesticidal plant extracts. This could involve other forms of plant protection by direct control of bacterial or fungal pathogens ( Soylu et al., 2010;Marei et al., 2012;Rasoul et al., 2012), or indirect physiological assistance by acting as a topical green fertilizer ( Jama et al., 2000), bio- stimulant ( Pretali et al., 2016), or foliar feed (Shaaban, 2001). We are undertaking further field trials to assess the multiple benefits of using pesticidal plants for smallholder crop production, which should provide more evidence for their integration in to agro- ecologically sustainable crop production systems. ...
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In the fight against arthropod crop pests using plant secondary metabolites, most research has focussed on the identification of bioactive molecules. Several hundred candidate plant species and compounds are now known to have pesticidal properties against a range of arthropod pest species. Despite this growing body of research, few natural products are commercialized for pest management whilst on-farm use of existing botanically-based pesticides remains a small, but growing, component of crop protection practice. Uptake of natural pesticides is at least partly constrained by limited data on the trade-offs of their use on farm. The research presented here assessed the potential trade-offs of using pesticidal plant extracts on legume crop yields and the regulating ecosystem services of natural pests enemies. The application of six established pesticidal plants (Bidens pilosa, Lantana camara, Lippia javanica, Tephrosia vogelii, Tithonia diversifolia, and Vernonia amygdalina) were compared to positive and negative controls for their impact on yields of bean (Phaseolus vulgaris), cowpea (Vigna unguiculata), and pigeon pea (Cajanus cajan) crops and the abundance of key indicator pest and predatory arthropod species. Analysis of field trials showed that pesticidal plant treatments often resulted in crop yields that were comparable to the use of a synthetic pesticide (lambda-cyhalothrin). The best-performing plant species were T. vogelii, T. diversifolia, and L. javanica. The abundance of pests was very low when using the synthetic pesticide, whilst the plant extracts generally had a higher number of pests than the synthetic but lower numbers than observed on the negative controls. Beneficial arthropod numbers were low with synthetic treated crops, whereas the pesticidal plant treatments appeared to have little effect on beneficials when compared to the negative controls. The outcomes of this research suggest that using extracts of pesticidal plants to control pests can be as effective as synthetic insecticides in terms of crop yields while tritrophic effects were reduced, conserving the non-target arthropods that provide important ecosystem services such as pollination and pest regulation. Thus managing crop pests using plant secondary metabolites can be more easily integrated in to agro-ecologically sustainable crop production systems.
... Although we did not measure such responses, legume crop compensation may have been facilitated through the frequent application of pesticidal plant extracts. This could involve other forms of plant protection by direct control of bacterial or fungal pathogens (Soylu et al., 2010;Marei et al., 2012;Rasoul et al., 2012), or indirect physiological assistance by acting as a topical green fertilizer (Jama et al., 2000), biostimulant (Pretali et al., 2016), or foliar feed (Shaaban, 2001). We are undertaking further field trials to assess the multiple benefits of using pesticidal plants for smallholder crop production, which should provide more evidence for their integration in to agroecologically sustainable crop production systems. ...
... Monoterpene ketones chosen as the starting compounds in the presented study have already been described with negligible antibacterial activity (Gallucci et al. 2009;Rasoul et al. 2012;Kozioł et al. 2014). This characteristics was confirmed in our research group (Kozioł et al. 2018), we observed that nearly all monoterpene ketones had no bacteriostatic activity up to 250 mg/mL under standard, CLSI (2012) approved conditions. ...
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Incorporation of the Beckmann rearrangement into the presented research resulted in the formation of nitrogen-containing terpenoid derivatives originating from naturally occurring compounds. Both starting monoterpenes and obtained derivatives were subjected to estimation of their antibacterial potential. In the presented study, Staphylococcus aureus was the most sensitive to examined compounds. The Minimal Inhibitory Concentration (MIC) experiments performed on S. aureus demonstrated that the (−)-menthone oxime (−)-8 and (+)-pulegone oxime (+)-13 had the best antibacterial activity among the tested derivatives and starting compounds. Their MIC90 value was 100 µg/mL. The obtained derivatives were also evaluated for their inhibitory activity against bacterial urease. Among the tested compounds, three active inhibitors were found – oxime 14 and lactams (−)-15 and 16 limited the activity of Sporosarcina pasteurii urease with Ki values of 174.3 µM, 43.0 µM and 4.6 µM, respectively. To our knowledge, derivative 16 is the most active antiureolytic lactam described to date.
... They may be safe because they were used originally as food flavors, perfumes, decongestants, external analgesics, and antiseptics (Templeton, 1969). Monoterpenes exhibited pesticidal activity to a wide spectrum of agricultural pests such bacteria, fungi, insects, weeds, and mites, which make these compounds useful as potential alternatives to harmful synthetic pesticides (Grodnitzky and Coats, 2002;Abdelgaleil et al., 2009;Badawy et al., 2010;Garcia et al., 2008;Kordali et al., 2007;Rabea and Badawy, 2014;Herrera et al., 2015;Abdel Rasoul et al., 2012). Preliminary studies have suggested that specific compounds such as linalool and substances with free alcoholic phenolic groups (Perrucci et al., 1995) such as the oxygenated terpenoids (terpinen-4-ol) (Walton et al., 2004) exhibited greatest acaricidal activity. ...
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Six natural monoterpenes (1,8-cineole, (-)-citronellal, limonene, α-pinene, pulegone and 4-terpineol) showed high acaricidal activity by fumigant and contact actions against adult females of the two-spotted spider mite, Tetranychus urticae Koch. The monoterpenes exhibited varying degrees of acaricidal potency using contact toxicity test after 24 and 48 h of treatment, where the LC 50 values were <160 and 45 mg/L, respectively. In fumigation test, of these six monoterpenes, pulegone exhibited the highest toxicity (LC 50 = 3.81 mg/L air), while (-)-citronellal had the lowest fumigant toxicity (LC 50 = 15.20 mg/L air). All compounds had high inhibitory effect on acetylcholinesterase (AChE) and gama amino butyric acid transaminase (GABA-T) activities. Pulegone was the most AChE inhibitor (IC 50 = 8.79 mg/L), while 4-terpineol revealed the lowest inhibitory effect (IC 50 = 32.82 mg/L). However, limonene caused the highest inhibition of GABA-T (IC 50 = 11.37 mg/L). The molecular docking studies revealed that the compounds displayed different binding interactions with the amino acid residues at the catalytic sites of AChE and GABA-T enzymes. Noncovalent interactions especially van der Waals, hydrogen bonding as well as hydrophobic was found between the compounds and the enzymes. A significant relationship was found between the docking score and the biological activity of monoterpenes compared to the standard acaricide pyridaben. In silico ADMET properties were also performed and displayed potential for the development of good acaricidal candidates.
... They are naturally formed from the condensation of two isoprene units. They have shown in a broad extent of pests such as bacteria, fungi, and insects, which make these compounds useful as potential alternatives to harmful synthetic pesticides (Garcia et al. 2008;Abdelgaleil et al. 2009;Badawy et al. 2010;Abdel Rasoul et al. 2012;Rabea and Badawy 2014;Herrera et al. 2015;Marchese et al. 2017;Ieri et al. 2019;Saad et al. 2019). ...
... Their medicinal value is due to their richness with secondary metabolites such as polyphenols, flavonoids, alkaloids, essential oils, and tannins which are known by their important biological activities. Furthermore, many scientific researches demonstrated plant compounds showing target sites other than those currently used by antibiotics; they are active against resistant microbial pathogens (Abdel Rasoul et al. 2012;Martinez 2018). ...
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The aim of this study is to evaluate the polyphenolic and flavonoid contents in the leaves extracts of Ruscus hypophyllum. Antioxidant activity was estimated by α,α-diphenyl-β-picrylhydrazyl (DPPH) and 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) assays. The anticoagulant activity of Ruscus extracts was evaluated in vitro, using the prothrombin time (PT) and a PTT-activated partial thromboplastin time tests. The antibacterial activity was tested against large number of important medically and resistant bacteria by the broth dilution method. In this study, ethyl acetate and chloroform extracts displayed the highest total phenols contents (74.76 mg EAG/g and 73.89 mg EAG/g, respectively) and flavonoid content 40 and 32.43 mg EC/g, respectively. The GC-MS analysis of ethyl acetate extract confirmed the presence of oxygenated sesquiterpenes and hydrocarbon diterpenes with percentages of 16.41% and 10.72%, respectively, but chloroform extract was rich with, oxygenated monoterpenes, and oxygenated diterpenes, with percentages of 6.19 and 3.27%, respectively. Among tested extracts, ethyl acetate exhibited the best antioxidant and anticoagulant activities. Furthermore, ethyl acetate and chloroform extracts showed important antibacterial activity against resistant bacteria methicillin-resistant Staphylococcus aureus (SARM), Acinetobacter imipenem-resistant (IMP/R), P. aeruginosa imipenem-resistant (IMP/R) and extended-spectrum beta-lactamase producing E. cloacae (BLSE) with minimal inhibitory concentration (MIC) values varying between 0.125 and 0.5 mg/mL.
... Microbiological studies evidenced the antibacterial properties of myrcene on Staphylococcus aureus, Escherichia coli, Salmonella enterica [17] as well as on plant pathogenic bacteria Agrobacterium tumefaciens and Erwinia carotovora var. carotovora [18]. Moreover, the ability of myrcene to locate in the cellular membranes was reported [19,20]. ...
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β-myrcene (myrcene) is the main component of the hop essential oil, the latter being a plant derived extract of a wide range of antimicrobial properties. To get a deeper insight in the role of myrcene in the membrane-related activity of the total extract, in this work the effect of this terpene on the lipid monolayers was investigated. The aim of the studies was to analyze and to compare the influence of myrcene on the one component films formed by the lipids typical of plant and fungi membranes and differing in the structure of both polar and non-polar part of the molecule. The experiments involved the surface pressure-area measurements, the penetration and the relaxation studies, Brewster angle microcopy and Grazing incidence X-ray diffraction (GIXD) studies. It was found that myrcene causes the decrease of the condensation and/or stability and morphology of the lipid monolayers, however its exact effect is determined by the concentration and by the lipid type. Moreover, the mechanisms leading to the alterations within the organization of the film are different depending on the monolayer material and they may involve the extraction of the molecules from the interface and/or accommodation of terpene in the lipid environment. It was also summarized that although myrcene and the hop essential oil affect the properties of the lipid films they act on the studied membranes according to different mechanisms.
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Terpenes are a multifarious group of secondary compounds present throughout the living world that function primarily in defence, or otherwise in regulating interactions between an organism and its environment. Terpene synthases (TPS) are a mid-sized gene family whose diversity and make-up reflects a plant’s ecological requirements and unique adaptive history. Here we catalogue TPS in Melaleuca alternifolia and examine lineage-specific expansion in TPS relative to other sequenced Myrtaceae. Overall, far fewer (37) putative TPS genes were identified in M. alternifolia compared with Eucalyptus grandis (113) and E. globulus (106). The number of genes in clade TPS-b1 (12), which encode enzymes that produce cyclic monoterpenes, was proportionally larger in M. alternifolia than in any other well-characterised plant. Relative to E. grandis, the isoprene-/ocimene-producing TPS-b2 clade in M. alternifolia tended to be proportionally smaller. This suggested there may be lineage-specific subfamily change in Melaleuca relative to other sequenced Myrtaceae, perhaps as a consequence of its semi-aquatic evolutionary history.
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Citrullus colocynthis (CCT) is a non-hardy, herbaceous perennial vine, branched from the base. Originally from Tropical Asia and Africa, it is now widely distributed in the Sistan phytogeographic region of Iran. In a search of alternative ways to control plant disease, essential oil from seeds of CCT was examined for antibacterial properties. The seeds are edible and have a high oil content with a large proportion of linoleic acid (C18:2) which is important for human nutrition and an essential fatty acid also contains only traces of linolenic acid (C18:3). Antibacterial activity of oil separated from the seeds was tested against Xanthomonas campestris, Burkholderia cenocepacia, Pseudomonas syringae and Agrobacterium tumefaciens. The agar disc diffusion method was used to assess inhibitory effect by measuring the inhibition zone against the test microorganisms. Antibacterial activity of the seeds oil was confirmed for all bacterial, but with different ranges. This activity was observed to be dose-independent. X. campestris was the most sensitive bacterium tested. A weak inhibitory effect was found against Pseudomonas syringae. These results offer a scientific basis for the use of C. colocynthis seed oil to prevent diseases caused by these bacteria.
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Many cyclic hydrocarbons, e.g. aromatics, cycloalkanes, and terpenes, are toxic to microorganisms. The primary site of the toxic action is probably the cytoplasmic membrane, but the mechanism of the toxicity is still poorly understood. The effects of cyclic hydrocarbons were studied in liposomes prepared from Escherichia coli phospholipids. The membrane-buffer partition coefficients of the cyclic hydrocarbons revealed that these lipophilic compounds preferentially reside in the membrane. The partition coefficients closely correlated with the partition coefficients of these compounds in a standard octanol-water system. The accumulation of hydro carbon molecules resulted in swelling of the membrane bilayer, as assessed by the release of fluorescence self-quenching of fluorescent fatty acid and phospholipid analogs. Parallel to the expansion of the membrane, an increase in membrane fluidity was observed. These effects on the integrity of the membrane caused an increased passive flux of protons and carboxyfluorescein. In cytochrome c oxidase containing proteoliposomes, both components of the proton motive force, the pH gradient and the electrical potential, were dissipated with increasing concentrations of cyclic hydrocarbons. The dissipating effect was primarily the result of an increased permeability of the membrane for protons (ions). At higher concentrations, cytochrome c oxidase was also inactivated. The effective concentrations of the different cyclic hydrocarbons correlated with their partition coefficients between the membrane and aqueous phase. The impairment of microbial activity by the cyclic hydrocarbons most likely results from hydrophobic interaction with the membrane, which affects the functioning of the membrane and membrane-embedded proteins.
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The effects of beta-pinene on yeast cells were studied. This terpene inhibited respiration with glucose or ethanol as the substrate. The inhibition depended on the ratio of the terpene to the amount of yeast cells; for a fixed concentration of pinene, inhibition decreased as the amount of yeast cells increased. Pinene also inhibited the pumping of protons and K+ transport, but this inhibition was more marked with with ethanol than with glucose as the substrate, indicating the mitochondrial localization of the inhibition. The studies on isolated mitochondria showed a series of effects, starting with the disappearance of the respiratory control and deenergization of the organelles and followed by an inhibition of respiration at higher concentrations of the terpene. The effect on respiration could be localized to the cytochrome b region of the electron transport chain. No effect could be detected on the activity of ATPase. The effects can be ascribed to a localization of pinene on membranes which was also accompanied by a decrease in the fluorescence polarization of diphenyl hexatriene, probably meaning an increase in the fluidity of the membrane, localized preferentially to the mitochondria.
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Strains of Pseudomonas syringae pv. syringae resistant to copper, streptomycin, or both compounds were recovered from symptomless and diseased tissue of four woody hosts in three nurseries in Oklahoma. In strains resistant to copper and streptomycin (Cur Smr), resistance to both compounds was cotransferred with a single plasmid which was either 68, 190, or 220 kilobase pairs (kb). All Cus Smr strains contained a 68-kb conjugative plasmid. Cur Sms strains contained one plasmid which varied in size from 60 to 73 kb. All conjugative plasmids which transferred streptomycin resistance contained sequences homologous to the strA and strB Smr genes from the broad-host-range plasmid RSF1010. The Smr determinant was subsequently cloned from a 68-kb Cur Smr plasmid designated pPSR1. A restriction map detailing the organization of the homologous Smr genes from pPSR1 and RSF1010 and cloned Smr genes from P. syringae pv. papulans and Xanthomonas campestris pv. vesicatoria revealed the conservation of all sites studied. The Cur genes cloned from P. syringae pv. tomato PT23 and X. campestris pv. vesicatoria XV10 did not hybridize to the Cur plasmids identified in the present study, indicating that copper resistance in these P. syringae pv. syringae strains may be conferred by a distinct genetic determinant.
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The essential oil of Melaleuca alternifolia (tea tree) exhibits broad-spectrum antimicrobial activity. Its mode of action against the Gram-negative bacterium Escherichia coli AG100, the Gram-positive bacterium Staphylococcus aureus NCTC 8325, and the yeast Candida albicans has been investigated using a range of methods. We report that exposing these organisms to minimum inhibitory and minimum bactericidal/fungicidal concentrations of tea tree oil inhibited respiration and increased the permeability of bacterial cytoplasmic and yeast plasma membranes as indicated by uptake of propidium iodide. In the case of E. coli and Staph. aureus, tea tree oil also caused potassium ion leakage. Differences in the susceptibility of the test organisms to tea tree oil were also observed and these are interpreted in terms of variations in the rate of monoterpene penetration through cell wall and cell membrane structures. The ability of tea tree oil to disrupt the permeability barrier of cell membrane structures and the accompanying loss of chemiosmotic control is the most likely source of its lethal action at minimum inhibitory levels.
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Plant essential oils are widely used as fragrances and flavours in the cosmetic, perfume, drug and food industries. Oxygenated monoterpenes are widespread components of the essential oils, usually occurring in high amount. In this paper, the antibacterial activities of twenty-one oxygenated monoterpenes (borneol, borneol acetate, camphor, carvone, 1,8-cineole, citronellal, beta-citronellol, dihydrocarvone, fenchol, fenchone, geraniol acetate, isomenthol, limonene oxide, linalool, linalool acetate, nerol, nerol acetate, terpinen-4-ol, alpha-terpineol, menthol and menthone) and penicillin (standard antibiotic) were determined using a disc diffusion method (in vitro) against 63 bacterial strains, belonging to 37 different genera and 54 species (plant, food and clinic origins). The results showed that the oxygenated monoterpenes exhibited a variable degree of antibacterial activities. These compounds also inhibited the growth of bacterial strains by producing a weak zone of inhibition from 7 to 11 mm in diameter, depending on the susceptibility of the tested bacteria. Among the tested compounds, nerol, linalool alpha-terpineol, fenchol and terpinen-4-ol showed antibacterial activity at a broad spectrum. However, their antibacterial activities were lower than those of penicillin. In contrast to these compounds, camphor and 1,8-cineole exhibited no inhibition effects on the growth of all tested bacteria.
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Certain plant essential oils show a broad spectrum of activity against pest insects and plant pathogenic fungi, and some oils have a long tradition of use in the protection of stored products. Recent investigations indicate that some chemical constituents of these oils interfere with the octopaminergic nervous system in insects. As this target site is not shared with mammals, most essential oil chemicals are relatively non-toxic to laboratory animals and fish in toxicological tests, and meet the criteria for "reduced risk" pesticides. Some of these oils and their constituent chemicals are widely used as flavoring agents in foods and beverages and are even exempt from pesticide registration in the United States. This special regulatory status combined with the wide availability of essential oils from the flavor and fragrance industries, has made it possible to fast-track commercialization of essential oil-based pesticides in the U.S.A. Though well received by consumers for use against home and garden pests, these "green pesticides" can also prove effective in agricultural situations, particularly for organic food production.
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Twenty two naturally occurring monoterpenoid compounds were selected for antifungal evaluation against two of the most common postharvest pathogens on temperate fruits, Botrytis cinerea and Monilinia fructicola. Experiments were carried out in order to examine the separate effects of these compounds on spore germination and mycelial growth. The growth inhibition test was conducted by incorporating the compounds into the medium, or by exposing the fungi to the vapor of the monoterpenoids. The results showed that carvacrol and thymol, the only two phenolic monoterpenoids, were the most potent inhibitors to the two pathogens in the germination and growth inhibition tests. Both of the compounds completely prevented the spore germination and mycelial growth of B. cinerea and M. fructicola at 100 μg/mL. Even at 10 μg/mL medium (0.25 mg/petri dish) in the volatility test, carvacrol and thymol had 85% and 82% inhibition at 48 h against B. cinerea, and 38% and 57% against M. fructicola, respectively. Other monoterpenoids such as eugenol, citronellol, geraniol, citral, (—)-perillaldehyde, citronellal, (—)-perillyl alcohol and (—)-menthol were good growth inhibitors (by contact) although their activities toward the two pathogens were slightly different, with higher inhibition found against the M. fructicola.
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A bacterium, isolated from infected tubers of calla (Zantedeschia spp.), was confirmed as a soft rot pathogen by completion of Koch's postulates and was identified as Erwinia carotovora subsp. carotovora (Jones 1901) Bergey et al. 1923. This paper confirms the identity of E. carotovora subsp. carotovora as the cause of bacterial soft rot of this important ornamental plant in New Zealand.
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Essential oils of Thymbra spicata, Satureja thymbra, Salvia fruticosa, Laurus nobilis, Mentha pulegium, Inula viscosa, Pimpinella anisum, Eucalyptus camaldulensis, and Origanum minitiflorum plants growing wild in southern Turkey were investigated by means of GC-FID, and 20 components were identified. The main ones were gamma-terpinene, p-cymene, thymol, and carvacrol as well as 1,8-cineole, pulegone, and anethole. Biological assays showed that fungitoxicity against the soil-borne plant disease-causing fungi Fusarium moniliforme, Rhizoctonia solani, Sclerotinia sclerotiorum, and Phytophthora capsici was due to different concentrations of the phenolic fraction (especially thymol and/or carvacrol) in the essential oils.
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Five selected compounds, geraniol, (R)-(–)-linalool, terpineol, γ-terpinene and 1,8-cineole, were tested for their influence on airborne microbes when vaporized with an air washer. Terpineol and 1,8-cineole showed the highest antimicrobial activities. The average reduction of germ count was 68% and 64%, respectively. Although γ-terpinene gave the lowest result among the compounds investigated, the average reduction of germ count was still 40%. When water without volatile compounds was sprayed, the colony forming units increased. These results show the positive effect of selected aroma compounds on the reduction of microbes in the room. Copyright © 2007 John Wiley & Sons, Ltd.
Article
The in vitro antimicrobial activity of geraniol and citronellol towards seven strains of Erwinia amylovora, the causal agent of ‘fire blight’of Rosaceous plants, was assessed in tube cultures. All of the strains tested at 1 × 105 cfu/ml were inhibited for 24 h by geraniol in the range 600–1500 mg/1, whereas its minimum bactericidal concentration was 800–1700 mg/1. Citronellol was less effective, being bactericidal for only two of seven strains. RIF-NY, isolated from apple orchards, was relatively resistant to geraniol; 1700 mg/1 of the chemical only reduced the growth of an inoculum of 1 × 107 cfu/ml. In general, such terpenoids commenced exerting a bactericidal effect 6 h after addition to the suspensions, even if geraniol added at 1700 mg/1 to 1 × 103 cfu/ml of five strains, commenced its bactericidal activity earlier than 6 h.
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Six strains of crown gall bacteria were isolated from flowering cherry. It was revealed by Otten paper electrophoresis that of the six strains, only BYH18-4 possessed the octopine type Ti plasmid, the remainder having nopaline type Ti plasmid. BYH5-1 was identified by physiological and biochemical tests to be Agrobacterium tumefaciens (originally biovar 1). The other five were A. rhizogenes (originally biovar 2). It was demonstrated with Stonier''s method of double layer medium that flowering cherry crown gall bacteria exhibited different sensitivities to agrocin produced by biocontrol strain K1026. Strain K1026 on greenhouse-grown sunflower seedlings exerted a relatively potent inhibitory action on flowering cherry crown gall bacteria. Artificial inoculation showed that K1026 produced 67–99% inhibition of flowering cherry crown gall disease, compared with the treatment of inoculation with crown gall bacteria only.
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New mechanisms of action for herbicides are highly desirable to fight evolution of resistance in weeds, to create or exploit unique market niches, and to cope with new regulatory legislation. Comparison of the known molecular target sites of synthetic herbicides and natural phytotoxins reveals that there is little redundancy. Comparatively little effort has been expended on determination of the sites of action of phytotoxins from natural sources, suggesting that intensive study of these molecules will reveal many more novel mechanisms of action. Examples of natural products that inhibit unexploited steps in the amino acid, nucleic acid, and other biosynthetic pathways are given. AAL-toxin, hydantocidin, and various plant-derived terpenoids are discussed. Strategies and potential pitfalls of using natural products as leads for new herbicide classes are summarized.
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Certain essential plant oils, widely used as fragrances and flavors in the perfume and food industries, have long been reputed to repel insects. Recent investigations in several countries confirm that some plant essential oils not only repel insects, but have contact and fumigant insecticidal actions against specific pests, and fungicidal actions against some important plant pathogens. As part of an effort aimed at the development of reduced-risk pesticides based on plant essential oils, toxic and sublethal effects of some essential oil terpenes and phenols have been investigated using the tobacco cutworm (Spodoptera litura) and the green peach aphid (Myzus persicae) as model pest species. In this paper I review (i) the range of biological activities of essential oils and their constituents; (ii) their toxicity and proposed mode-of-action in insects; (iii) their potential health and environmental impacts as crop protectants; and (iv) commercialization of pesticides based on plant essential oils.
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A study was conducted to assess the allelopathic effect of two volatile monoterpenes viz. cineole and citronellol on Ageratum conyzoides with a view to explore the possibility of their exploitation for future weed management. Both the monoterpenes severely affected the germination, speed of germination, seedling growth, chlorophyll content and respiratory activity. After two weeks of exposure, the weed plants wilted. Out of the two monoterpenes, cineole was more toxic in causing injury to the weed.
Article
The bactericidal effect of 3 natural agents (carvacrol, thymol, and eugenol) was evaluated as well as their binary and ternary mixtures on Listeria innocua inactivation in liquid model systems. Minimal bactericidal concentrations (MBC) of these agents were determined, and then binary and ternary mixtures were evaluated. Culture media were inoculated with L. innocua and incubated for 72 h at 35 °C. Turbidity of studied systems were determined every 24 h. The most effective individual antimicrobial agent was carvacrol, followed by thymol and then eugenol with MBCs of 150, 250, and 450 mg kg(-1), respectively. It was observed that the most effective binary mixture was 75 mg kg(-1) carvacrol and 62.5 mg kg(-1) thymol. Furthermore, the ternary mixture carvacrol-thymol-eugenol in concentrations of 75, 31.25, and 56.25 mg kg(-1), correspondingly, was the most effective for L. innocua inactivation. Several binary and ternary mixtures of these 3 natural antimicrobial agents worked adequately to inactivate L. innocua.
Article
The antibacterial activity of thymol has been well established and reported in the scientific literature. Continued suppression of bacterial growth following limited exposure to antimicrobial compounds at different concentrations greater than or equal to the minimum inhibitory concentration level (MIC) and at concentrations less than the MIC can be used as an indicator of biological activity, and are respectively referred to as a post-antibacterial effect (PAE) and a post-antibiotic sub-MIC effect (PA-SME). In this study, the PAE and the PA-SME of thymol against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus cereus were investigated. A spectrophotometric method was used to determine the PAE and the PA-SME of thymol against the selected test strains. Thymol exhibited a considerable PAE and PA-SME at MIC and sub-MIC concentrations against test strains. The greatest duration of both the PAE and the PA-SME was observed for thymol against E. coli and P. aeruginosa. The PAE and PA-SME times for E. coli were 12 and 8 h, respectively, and for P. aeruginosa were 11 and 7.5 h, respectively. The duration of the PAE and PA-SME observed for S. aureus and B. cereus was shorter than for Gram-negative strains.
Article
Among the main (> or = 0.7%) components of some essential oils, considerable antibacterial activity was shown by terpenoid and phenylpropanoid derivatives containing phenol and alcohol functionalities. A reduced or no activity was shown by those derivatives containing ketones, aldehydes, ethers, and ester functionalities as well as the remaining terpenoids. Eugenol emulsion treatments (1-8 mg/mL) of bean seeds bearing about 2.6 x 10(6) cfu/seed of strain ICMP239 of Xanthomonas campestris pv. phaseoli var. fuscans determined a highly significant reduction of the bacteria on seeds. In particular, eugenol at 4 mg/mL disinfect seeds bearing about 7.0 x 10(2) cfu/seed and lower densities. However, after 72 h, incubation treatments with 2, 4, and 8 mg/mL of eugenol caused germination reduction of 3%, 7%, and 16%, respectively, which was significantly different from the controls. No effect on germination was observed with 1 mg/mL eugenol emulsion treatment. These data indicate eugenol as potentially useful for bean seed disinfection from X. campestris pv. phaseoli var. fuscans. Further studies on the effects on seed vitality and on formulation of essential oils are needed.
Article
Microbial transformations of cyclic hydrocarbons have received much attention during the past three decades. Interest in the degradation of environmental pollutants as well as in applications of microorganisms in the catalysis of chemical reactions has stimulated research in this area. The metabolic pathways of various aromatics, cycloalkanes, and terpenes in different microorganisms have been elucidated, and the genetics of several of these routes have been clarified. The toxicity of these compounds to microorganisms is very important in the microbial degradation of hydrocarbons, but not many researchers have studied the mechanism of this toxic action. In this review, we present general ideas derived from the various reports mentioning toxic effects. Most importantly, lipophilic hydrocarbons accumulate in the membrane lipid bilayer, affecting the structural and functional properties of these membranes. As a result of accumulated hydrocarbon molecules, the membrane loses its integrity, and an increase in permeability to protons and ions has been observed in several instances. Consequently, dissipation of the proton motive force and impairment of intracellular pH homeostasis occur. In addition to the effects of lipophilic compounds on the lipid part of the membrane, proteins embedded in the membrane are affected. The effects on the membrane-embedded proteins probably result to a large extent from changes in the lipid environment; however, direct effects of lipophilic compounds on membrane proteins have also been observed. Finally, the effectiveness of changes in membrane lipid composition, modification of outer membrane lipopolysaccharide, altered cell wall constituents, and active excretion systems in reducing the membrane concentrations of lipophilic compounds is discussed. Also, the adaptations (e.g., increase in lipid ordering, change in lipid/protein ratio) that compensate for the changes in membrane structure are treated.
Article
Many cyclic hydrocarbons, e.g. aromatics, cycloalkanes, and terpenes, are toxic to microorganisms. The primary site of the toxic action is probably the cytoplasmic membrane, but the mechanism of the toxicity is still poorly understood. The effects of cyclic hydrocarbons were studied in liposomes prepared from Escherichia coli phospholipids. The membrane-buffer partition coefficients of the cyclic hydrocarbons revealed that these lipophilic compounds preferentially reside in the membrane. The partition coefficients closely correlated with the partition coefficients of these compounds in a standard octanol-water system. The accumulation of hydrocarbon molecules resulted in swelling of the membrane bilayer, as assessed by the release of fluorescence self-quenching of fluorescent fatty acid and phospholipid analogs. Parallel to the expansion of the membrane, an increase in membrane fluidity was observed. These effects on the integrity of the membrane caused an increased passive flux of protons and carboxyfluorescein. In cytochrome c oxidase containing proteoliposomes, both components of the proton motive force, the pH gradient and the electrical potential, were dissipated with increasing concentrations of cyclic hydrocarbons. The dissipating effect was primarily the result of an increased permeability of the membrane for protons (ions). At higher concentrations, cytochrome c oxidase was also inactivated. The effective concentrations of the different cyclic hydrocarbons correlated with their partition coefficients between the membrane and aqueous phase. The impairment of microbial activity by the cyclic hydrocarbons most likely results from hydrophobic interaction with the membrane, which affects the functioning of the membrane and membrane-embedded proteins.
Article
Some monoterpenes and their carbonylated products were evaluated for their antibacterial and antifungal properties. The carbonylation of tested monoterpenes was shown to increase the bacteriostatic and fungistatic activities specifically by the contact method. Concerning the killing effects, only (1R,2S,5R)-isopulegol, its carbonylated products, and (R)-carvone showed significant bactericidal activities, particularly against Enterococcus faecium and Escherichia coli above a concentration of 10 microliters/ml. A fungicidal efficiency of (1R,2S,5R)-isopulegol and (R)-carvone against Aspergillus niger was also noted. It seems that the presence of an oxygenated function in the framework increases the antimicrobial properties. However, monoterpenes were more active using a micro-atmosphere method.
Article
The volatile oils of black pepper [Piper nigrum L. (Piperaceae)], clove [Syzygium aromaticum (L.) Merr. & Perry (Myrtaceae)], geranium [Pelargonium graveolens L'Herit (Geraniaceae)], nutmeg [Myristica fragrans Houtt. (Myristicaceae), oregano [Origanum vulgare ssp. hirtum (Link) Letsw. (Lamiaceae)] and thyme [Thymus vulgaris L. (Lamiaceae)] were assessed for antibacterial activity against 25 different genera of bacteria. These included animal and plant pathogens, food poisoning and spoilage bacteria. The volatile oils exhibited considerable inhibitory effects against all the organisms under test while their major components demonstrated various degrees of growth inhibition.
Article
The antibacterial activity of 14 essential oils and their major constituents in the gaseous state was evaluated against Haemophilus influenzae, Streptococcus pneumoniae, Streptococcus pyogenes and Staphylococcus aureus. For most essential oils examined, H. influenzae was most susceptible, followed by S. pneumoniae and S. pyogenes, and then S. aureus. Penicillin-susceptible and -resistant S. pneumoniae were comparable in susceptibility. Escherichia coli, which was used as a control, showed least susceptibility. A minimal inhibitory dose (MID) was introduced as a measure of the vapour activity. Among 14 essential oils, cinnamon bark, lemongrass and thyme oils showed the lowest MID, followed by essential oils containing terpene alcohols as major constituents. The essential oils containing terpene ketone, ether and, in particular, hydrocarbon had high MIDs. The vapour activity on short exposure was comparable to that following overnight exposure, and rapid evaporation was more effective than slow evaporation of essential oils. The vapour concentration and absorption into agar of essential oils reached a maximum 1 or 2 h after rapid evaporation. These results indicate that the antibacterial action of essential oils was most effective when at high vapour concentration for a short time.
Article
Essential oils of Origanum onites, Satureja thymbra, Salvia fruticosa (Greek sage), and Salvia pomifera subsp. calycina plants growing wild in Greece and their components carvacrol, camphor, and 1,8-cineole, were assayed for antifungal activity against 13 fungal species. Among the fungi tested were food poisoning, plant, animals and human pathogenic species. The oils presented various degrees of inhibition against all the fungi investigated. The highest and broadest activity was shown by the carvacrol content oils (O. onites and S. thymbra), while the oil of sage was the least effective. Carvacrol exhibited the highest and 1,8-cineole the lowest level of antifungal activity among the components tested.
Article
The vapors of citral, its isomers geranial and neral, and its related compounds were examined for their effect on Penicillium digitatum, Penicillium italicum, and Geotrichum candidum, the major fungi responsible for postharvest spoilage of citrus. Vapor of citral and its two isomers generated from 15 microL L(-1) aqueous solutions in Petri dishes inhibited development of the three pathogens, with concentrations of 2-6 microL L(-1) also being effective against P. italicum. Vapors of citral and geranial from 15 microL L(-1) solutions were fungicidal to P. digitatum and G. candidum, while neral was fungicidal to G. candidum. Citral-related compounds were much less effective, with effectiveness decreasing from citronellal to citronellol and citronellic acid. R and S isomers of these three citral-related compounds generally had similar effects on the fungi tested.
Article
The essential oil extracted from palmarosa (Cymbopogon martinii) has proven anti-microbial properties against cells of Saccharomyces cerevisiae. Low concentrations of the oil (0.1%) inhibited the growth of S. cerevisiae cells completely. The composition of the sample of palmarosa oil was determined as 65% geraniol and 20% geranyl acetate as confirmed by GC-FTIR. The effect of palmarosa oil in causing K(+) leakage from yeast cells was attributed mainly to geraniol. Some leakage of magnesium ions was also observed. Blocking potassium membrane channels with caesium ions before addition of palmarosa oil did not change the extent of K(+) ion leakage, which was equal to the total sequestered K(+) in the cells. Palmarosa oil led to changes in the composition of the yeast cell membrane, with more saturated and less unsaturated fatty acids in the membrane after exposure of S. cerevisiae cells to the oil. Some of the palmarosa oil was lost by volatilization during incubation of the oil with the yeast cells. The actual concentration of the oil components affecting the yeast cells could not therefore be accurately determined.
Article
The chemical composition of the essential oil of Chysactinia mexicana was analyzed by gas chromatography-mass spectrometry. Seventeen compounds were characterized; eucalyptol (41.3%), piperitone (37.7%), and linalyl acetate (9.1%) were found as the major components. The essential oil of leaves and piperitone completely inhibited Aspergillus flavus growth at relatively low concentrations (1.25 and 0.6 mg/mL, respectively).
Article
To assess the potential of essential oils and structurally related synthetic food additives in reducing bacterial pathogens in swine intestinal tract. The antimicrobial activity of essential oils/compounds was measured by determining the inhibition of bacterial growth. Among 66 essential oils/compounds that exhibited > or =80% inhibition towards Salmonellatyphimurium DT104 and Escherichia coli O157:H7, nine were further studied. Most of the oils/compounds demonstrated high efficacy against S. typhimurium DT104, E. coli O157:H7, and E. coli with K88 pili with little inhibition towards lactobacilli and bifidobacteria. They were also tolerant to the low pH. When mixed with pig cecal digesta, these oils/compounds retained their efficacy against E. coli O157:H7. In addition, they significantly inhibited E. coli and coliform bacteria in the digesta, but had little effect on the total number of lactobacilli and anaerobic bacteria. Some essential oils/compounds demonstrated good potential, including efficacy, tolerance to low pH, and selectivity towards bacterial pathogens, in reducing human and animal bacterial pathogens in swine intestinal tract. This study has identified candidates of essential oils/compounds for in vivo studies to develop antibiotic substitutes for the reduction of human and animal bacterial pathogens in swine intestinal tract.
Article
The present article reports the antimicrobial efficacy of four monoterpenes (thymol, carvacrol, p-cymene, and gamma-terpinene) against the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Escherichia coli. For a better understanding of their mechanism of action, the damage caused by these four monoterpenes on biomembranes was evaluated by monitoring the release, following exposure to the compounds under study, of the water-soluble fluorescent marker carboxyfluorescein (CF) from large unilamellar vesicles (LUVs) with different lipidic composition (phosphatidylcholine, PC, phosphatidylcholine/phosphatidylserine, PC/PS, 9:1; phosphatidylcholine/stearylamine, PC/SA, 9:1). Furthermore, the interaction of these terpenes with dimyristoylphosphatidylcholine multilamellar vesicles as model membranes was monitored by means of differential scanning calorimetry (DSC) technique. Finally, the results were related also with the relative lipophilicity and water solubility of the compounds examined. We observed that thymol is considerably more toxic against S. aureus than the other three terpenes, while carvacrol and p-cymene are the most inhibitory against E. coli. Thymol and carvacrol, but not gamma-terpinene and p-cymene, caused a concentration-dependent CF leakage from all kinds of LUVs employed; in particular, thymol was more effective on PC and PC/SA LUVS than on PC/PS vesicles, while carvacrol challenge evoked a CF leakage from PC/PS LUVs similar to that induced from PC/SA LUVs, and lower than that measured with PC vesicles. Concerning DSC experiments, these four terpenes caused a decrease in Tm and (especially carvacrol and p-cymene) DeltaH values, very likely acting as substitutional impurities. Taken together, our findings lead us to speculate that the antimicrobial effect of thymol, carvacrol, p-cymene, and gamma-terpinene may result, partially at least, from a gross perturbation of the lipidic fraction of the plasmic membrane of the microorganism. In addition to being related to the physicochemical characteristics of the compounds (such as lipophilicity and water solubility), this effect seems to be dependent on the lipidic composition and net surface charge of the microbic membranes. Furthermore, the compounds might cross the cell membranes, thus penetrating into the interior of the cell and interacting with intracellular sites critical for antibacterial activity.
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