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PubMed2004

Water-soluble ruthenium(II) catalysts [RuCl2(eta6-arene)[P(CH2OH)3]] for isomerization of allylic alcohols and alkyne hydration.

The novel water-soluble ruthenium(II) complexes [RuCl(2)(eta(6)-arene)[P(CH(2)OH)(3)]]2a-c and [RuCl(eta(6)-arene)[P(CH(2)OH)(3)](2)][Cl]3a-c have been prepared in high yields by reaction of dimers [[Ru(eta(6)-arene)(micro-Cl)Cl](2)](arene = C(6)H(6)1a, p-cymene 1b, C(6)Me(6)1c) with two or four equivalents of P(CH(2)OH)(3), respectively. Complexes 2/3a-c are active catalysts in the redox isomerization of several allylic alcohols into the corresponding saturated carbonyl compounds under water/n-heptane biphasic conditions. Among them, the neutral derivatives [RuCl(2)(eta(6)-C(6)H(6))[P(CH(2)OH)(3)]]2a and [RuCl(2)(eta(6)-p-cymene)[P(CH(2)OH)(3)]]2b show the highest activities (TOF values up to 600 h(-1); TON values up to 782). Complexes 2/3a-c also catalyze the hydration of terminal alkynes.

Journal Article↗
PubMed2006

Transition metal complexes with wide-angle dithio-, diseleno- and ditelluroethers: properties and structural systematics.

The ligands o-C(6)H(4)(CH(2)EMe)(2) (E = S or Se) have been prepared and characterised spectroscopically. A systematic study of the coordination chemistry of these, together with the telluroether analogue, o-C(6)H(4)(CH(2)TeMe)(2), with late transition metal centers has been undertaken. The planar complexes [MCl(2){o-C(6)H(4)(CH(2)SMe)(2)}] and [M{o-C(6)H(4)(CH(2)EMe)(2)}(2)](PF(6))(2) (M = Pd or Pt; E = S or Se), the distorted octahedral [RhCl(2){o-C(6)H(4)(CH(2)EMe)(2)}(2)]Y (E = S or Se: Y = PF(6); E = Te: Y = Cl) and [RuCl(2){o-C(6)H(4)(CH(2)EMe)(2)}(2)] (E = S, Se or Te), the dithioether-bridged binuclear [{RuCl(2)(p-cymene)}(2){micro-o-C(6)H(4)(CH(2)SMe)(2)}] and the tetrahedral [M'{o-C(6)H(4)(CH(2)EMe)(2)}(2)]BF(4) (M' = Cu or Ag; E = S, Se or Te) have been obtained and characterised by IR and multinuclear NMR spectroscopy ((1)H, (63)Cu, (77)Se{(1)H}, (125)Te{(1)H} and (195)Pt), electrospray MS and microanalyses. Crystal structures of the parent o-C(6)H(4)(CH(2)SMe)(2) and seven complexes are described, which show three different stereoisomeric forms for the chelated ligands, as well as the first example of a bridging coordination mode in [{RuCl(2)(p-cymene)}(2){micro-o-C(6)H(4)(CH(2)SMe)(2)}]. These studies reveal the consequences of the sterically demanding o-xylyl backbone, which typically leads to unusually obtuse E-M-E chelate angles of approximately 100 degrees .

Journal Article↗
PubMed2000

Quantitative high performance liquid chromatographic analysis of diterpenoids in agni-casti fructus.

Pharmacological data have indicated that part of the dopaminergic activity of Vitex agnus-castus is attributed to the labdan diterpenoids found in the fruits. Therefore an analytical method for the standardization of rotundifuran (1), vitexilactone (2) and 6 beta,7 beta-diacetoxy-13-hydroxy-labda-8,14-diene (3) was developed. Because of the time-consuming and expensive isolation of the diterpenoids, p-cymene was chosen as an internal standard. The concentration of rotundifuran in different extracts and trade samples of the drug varies between 0.04 and 0.30% in the drug and between 1.04 and 2.23% in the extract. The concentration of vitexilactone was generally lower between 0.016 and 0.167% for the drug and between 0.34 and 1.01% for the extract. The determined concentration of 6 beta,7 beta-diacetoxy-13-hydroxy-labda-8,14-diene in the drug was in the range of 0.02 and 0.10% and in the extract in the range of 0.18 and 0.80%. Determination of the factors of correction of p-cymene gave 5.63 for rotundifuran, 2.73 for vitexilactone and 3.74 for 6 beta,7 beta-diacetoxy-13-hydroxy-labda-8,14-diene.

Chromatography, High Pressure Liquid↗
PubMed2003

Chemical composition and in vitro evaluation of antioxidant effect of free volatile compounds from Satureja montana L.

As a part of an investigation of natural antioxidants from Dalmatian aromatic plants, in this paper we report a study of the antioxidant activity related to the chemical composition of savory free volatile compounds. Twenty-one compounds were identified in the essential oil without fractionation, representing 97.4% of the total oil. The major compound was phenolic monoterpene thymol (45.2%). Other important compounds were monoterpenic hydrocarbons p-cymene (6.4%) a nd gamma-terpinene (5.9%)and oxygen-containing compounds carvacrol methyl ether (5.8%), thymol methyl ether (5.1%), carvacrol (5.3%), geraniol (5.0%) and borneol (3.9%). The evaluation of antioxidant power was performed in vitro by the beta-carotene bleaching and thiobarbituric acid (TBA) methods. As determined with both methods, the total savory essential oil as well as different fractions or pure constituents containing hydroxyl group exhibited relatively strong antioxidant effect. The hydrocarbons, when isolated as CH fraction, showed the poorest effectiveness in spite the fact that this fraction contained gamma-terpinene, alpha-terpinene, p-cymene and terpinolene which previously were identified as potential antioxidants.

Antioxidants↗
PubMed2003

Aromatic monoterpenoid glycosides from Cruciata taurica.

Two new aromatic monoterpenoid glycosides, cruciaside A (2,5-O-beta-D-diglucopyranosyl-3-hydroxy-p-cymene) (1) and cruciaside B (5-O-beta-D-glucopyranosyl-2,3-dihydroxy-p-cymene) (2), were isolated from aerial parts of Cruciata taurica. The structures of the new compounds were determined by spectral and chemical methods. The new compounds seem to be promising as taxonomic markers for C. taurica.

Glycosides↗
PubMed2003

Expansion of growth substrate range in Pseudomonas putida F1 by mutations in both cymR and todS, which recruit a ring-fission hydrolase CmtE and induce the tod catabolic operon, respectively.

Pseudomonas putida F1 can assimilate benzene, toluene and ethylbenzene using the toluene degradation pathway, and can also utilize p-cymene via p-cumate using the p-cymene and p-cumate catabolic pathways. In the present study, P. putida F1 strains were isolated that were adapted to assimilate new substrates such as n-propylbenzene, n-butylbenzene, cumene and biphenyl, and the molecular mechanisms of genetic adaptation to an expanded range of aromatic hydrocarbons were determined. Nucleotide sequence analyses showed that the selected strains have mutations in the cymR gene but not in todF gene. The impairment of the repressor CymR by mutation led to the constitutive expression of CmtE, a meta-cleavage product hydrolase from the cmt operon. This study also showed that CmtE has a broad range of substrates and can hydrolyse meta-cleavage products formed from biphenyl and other new growth substrates via the toluene degradation pathway. However, the artificially constructed strain P. putida F1(cymR : : Tc(r)) and a recombinant P. putida F1, which expressed CmtE constitutively, could not grow on the new substrates. The adapted strains possess the tod operon, which is induced by new growth substrates that are poor inducers of wild-type P. putida F1. When the todS gene from the adapted strains was introduced in a trans manner to P. putida F1(cymR : : Tc(r)), the resulting recombinant strains were able to grow on biphenyl and other new substrates. This finding indicates that the TodS sensor was altered to recognize these substrates and this conclusion was confirmed by nucleotide sequence analyses. Amino acid substitutions were found in the regions corresponding to the receiver domain and the second PAS domain and their boundaries in the TodS protein. These results showed that P. putida F1 adapted strains capable of growth on n-propylbenzene, n-butylbenzene, cumene and biphenyl possess mutations to employ CmtE and to induce the tod catabolic operon by the new growth substrates.

Adaptation, Physiological↗
PubMed1995

Antimicrobial activity of the major components of the essential oil of Melaleuca alternifolia.

Tea tree oil, or the essential oil of Melaleuca alternifolia, is becoming increasingly popular as a naturally occurring antimicrobial agent. The antimicrobial activity of eight components of tea tree oil was evaluated using disc diffusion and broth microdilution methods. Attempts were also made to overcome methodological problems encountered with testing compounds which have limited solubility in aqueous media. After assessing media with and without solubilizing agents, the disc diffusion method was used to determine the susceptibility of a range of micro-organisms to 1,8-cineole, 1-terpinen-4-ol, rho-cymene, linalool, alpha-terpinene, gamma-terpinene, alpha-terpineol and terpinolene. While the disc diffusion method lacked reproducibility, it was considered useful as a procedure for screening for antimicrobial activity. Terpinen-4-ol was active against all the test organisms while rho-cymene demonstrated no antimicrobial activity. Linalool and alpha-terpineol were active against all organisms with the exception of Pseudomonas aeruginosa. Minimum inhibitory and minimum cidal concentrations of each component against Candida albicans, Escherichia coli and Staphylococcus aureus were determined using a broth microdilution method. Modifications to this method overcame solubility and turbidity problems associated with the oil components and allowed the antimicrobial activity of each of the components to be quantified reproducibly. There was reasonable agreement between minimum inhibitory concentrations and zones of inhibition. These results may have significant implications for the future development of tea tree oil as an antimicrobial agent.

Anti-Infective Agents, Local↗
PubMed2002

Effects of storage conditions on the composition of Citrus tamurana Hort. ex Tanaka (hyuganatsu) essential oil.

Compositional changes of Citrus tamurana Hort. ex Tanaka (hyuganatsu) essential oil were analyzed after storage for 1, 3, 6, and 9 weeks at -21, 5, 20, and 30 degrees C. The total amount of oxides increased greatly. The contents of monoterpene alcohols and ketones also increased. The total amount of monoterpene hydrocarbons was unchanged up to 30 degrees C. However, the contents of myrcene, gamma-terpinene, and terpinolene decreased, while there was a considerable increase in p-cymene. Among the sesquiterpene hydrocarbons, considerable increases in the (-)-cedrene, gamma-elemene, and alpha-humullene contents were noted in samples stored at 30 degrees C, and the trans-beta-farnesene content decreased during storage. The total content of monoterpene alcohols was increased slightly. The content of trans-carveol increased during storage. p-Cymene, trans-carveol, isopiperitone, and limonene oxide contents increased, while gamma-terpinene, terpinolene, and citronellal contents decreased significantly during storage. The changes of these compounds during storage can serve as a quality index for hyuganatsu essential oil.

Citrus↗
PubMedDate not supplied

Analysis of essential oil of Coridothymus capitatus (L.) and its antibacterial and antifungal activity.

The water-distilled essential oil the leaves of Coridothymus capitatus were analyzed by GC/MS and also analyzed by direct thermal desorption GC/MS. Comparison was made between two analyses techniques. The essential oil consisted mainly of monoterpenes 98.9%, while oxygenated hydrocarbons were identified as 55.6 % and non-oxygenated hydrocarbons as 43.6%. As major components were found carvacrol (35.6%), p-cymene (21.0%), thymol (18.6%), gamma-terpinene (12.3%), alpha-terpinene (3.2%), beta-myrcene (3.0%) and alpha-thujene (1.3%) by hydrodistillation and by the GC/MS method. The direct thermal desorption GC/MS analysis also showed the same major components, namely carvacrol (51.6%), thymol (21.7%), p-cymene (9.7%) gamma-terpinene (8.2%), alpha-terpinene (1.64%). The essential oil of C. capitatus showed strong activity against S. aureus, P. vulgaris, P. aeruginosa, E. coli, K. pneumonia, B.

Anti-Bacterial Agents↗
PubMed2000

Diastereoselectivity an chiral ruthenium complexes of chiraphos monoxide ligands: epimerization, quasiracemates, and Lewis acid catalysis.

Heterobidentate chelating ligands comprising P,O-donor sets produce chiral metal centers when bound to arene-ruthenium complexes. The cymene complex [CyRu(eta2-chelate-P,O)Cl]+ cations are precursors to 16-electron dicationic strong Lewis acids which have potential use in asymmetric catalysis. Sixteen-electron complexes of this type, however, also provide a pathway with a low energy barrier to epimerization of the metal center in intermediates. With the chiral ligand (R,R)-chiraphos monoxide, the metal center in [CyRu(eta2)-(R,R)-Ph2PCHMeCHMe Ph2PO-P,O)Cl]+ epimerizes to minimize steric interactions in the two diastereomers yielding a 8. 2:1 dr in solution. Nevertheless, upon crystallization a new equilibrium is obtained in the solid and the crystals obtained have a 1:1 dr. These crystals are quasiracemates, which contain equal amounts of the (RRu) and (SRu)-CyRu-P-O-Cl stereocenters within the same crystal. The doubly charged Lewis acid, [CyRu(eta2-(R, R)-Ph2PCHMeCHMe Ph2PO-P,O)(solvate)]2+ derived from the chloro complex by chloride abstraction with AgSbF6 gave modest ee's (30%) in the Diels-Alder reaction of methacrolein with cyclopentadiene.

Acetonitriles↗
PubMed2005

New insight into solvent effects on the formal HOO. + HOO. reaction.

The 2,2'-azobis(isobutyronitrile)(AIBN)-induced autoxidation of gamma-terpinene (TH) at 50 degrees C produces p-cymene and hydrogen peroxide in a radical-chain reaction having HOO* as one of the chain-carrying radicals. The kinetics of this reaction in cyclohexane and tert-butyl alcohol show that chain termination involves the formal HOO. + HOO. self-reaction over a wide range of gamma-terpinene, AIBN, and O2 concentrations. However, in acetonitrile this termination process is accompanied by termination via the cross-reaction of the terpinenyl radical, T., with the HOO. radical under conditions of relatively high [TH] (140-1000 mM) and low [O2] (2.0-5.5 mM). This is because the formal HOO. + HOO. reaction is comparatively slow in acetonitrile (2k approximately 8 x 10(7) M(-1) s(-1)), whereas, this reaction is almost diffusion-controlled in tert-butyl alcohol and cyclohexane, 2k approximately 6.5 x 10(8) and 1.3 x 10(9) M(-1) s(-1), respectively. Three mechanisms for the bimolecular self-reaction of HOO. radicals are considered: 1) a head-to-tail hydrogen-atom transfer from one radical to the other, 2) a head-to-head reaction to form an intermediate tetroxide, and 3) an electron-transfer between HOO. and its conjugate base, the superoxide radical anion, O2-.. The rate constant for reaction by mechanism (1) is shown to be dependent on the hydrogen bond (HB) accepting ability of the solvent; that by mechanism (2) is shown to be too slow for this process to be of any importance; and that by mechanism (3) is dependent on the pH of the solvent and its ability to support ionization. Mechanism (3) was found to be the main termination process in tert-butyl alcohol and acetonitrile. In the gas phase, the rate constant for the HOO. + HOO. reaction (mechanism (1)) is about 1.8 x 10(9) M(-1) s(-1) but in water at pH< or =2 where the ionization of HOO. is completely suppressed, this rate constant is only 8.6 x 10(5) M(-1) s(-1). The very large retarding effect of water on this reaction has not previously been explained. We find that it can be quantitatively accounted for by using Abraham's HB acceptor parameter, beta(2)(H), for water of 0.38 and an estimated HB donor parameter, alpha(2)(H), for HOO. of about 0.87. These Abraham parameters allow us to predict a rate constant for the HOO. + HOO. reaction in water at 25 degrees C of 1.2 x 10(6) M(-1) s(-1) in excellent agreement with experiment.

Cyclohexane Monoterpenes↗
PubMed2003

Antibacterial and antifungal activity of juniper berry oil and its selected components.

Juniper berry oil is stated to possess a wide spectrum of pharmacological activities and its monographs are included in some National Pharmacopoeias. The antibacterial and antifungal activity of the oil was reported by some authors. In our study we estimated the antibacterial and antifungal activity of three different juniper berry oils and their main components. All the micro-organisms used in this experiment were isolated from patients of Regional Hospital of Gdańsk and some of them showed resistance against commonly used antibiotics. Only one of the oils (labelled A) revealed good antimicrobial properties. None of the single oil components was a stronger antibacterial and antifungal inhibitor than the oil A itself. Our data suggest that the antimicrobial activity of juniper oil A is the result of either the specific composition of the oil A (highest concentration of (-)-alpha-pinene, p-cymene and beta-pinene) or activity of a single non-identified compound. The presence of an adulterant in the oil was excluded.

Anti-Bacterial Agents↗
PubMed2002

Modeling the partition of volatile aroma compounds from a cloud emulsion.

Parameters determining the partitioning behavior of volatile compounds between a cloud emulsion and the gas phase were measured under static equilibrium headspace conditions, using volatiles (e.g., ethyl hexanoate, cymene, and octanol) representing different volatilities and different degrees of hydrophobicity. The significant factors were the molecular characteristics of the volatile and the concentration of the oil phase. The nature of the lipid (C8 and C12 triglycerides), particle size, and emulsifier type (modified starch and gum arabic) did not significantly alter volatile partitioning. An empirical model based on the partition behavior and physicochemical parameters of 67 volatile compounds was produced. This predicted the partition of volatiles (R(2) = 0.83) in cloud emulsions as a function of lipid content. The significant terms (P < 0.05) in the empirical model were Log P, Log solubility, the dipole vector, and the oil fraction.

Beverages↗
PubMed2003

Seasonal and phenological variations of the essential oil from the narrow endemic species Artemisia molinieri and its biological activities.

The volatile components of the aerial parts of Artemisia molinieri, an endemic wormwood of southern France, were analyzed by GC and GC-MS. Among the 69 compounds identified, major components were ascaridole (19-76%), alpha-terpinene (traces-36%), p-cymene (1-17%), 1,8-cineole (0.3-8%), and germacrene D (0.6-15%). Quantitative variations have been characterized following the season, the phenological cycle, and the aging of the plants. Bioassays have been performed on a sample of essential oil, which has shown a strong inhibition of the growth of both tested yeasts (Candida albicans and Saccharomyces cerevisiae var. chevalieri) and minor activity on both tested Gram-negative bacteria (Escherichia coli and Enterococcus hirae). The oils have shown interesting antioxidant activities on the basis of alpha-tocopherol as reference compound, up to 400-1200%.

Antioxidants↗
PubMed2004

Investigation of the Origanum onites L. essential oil using the chorioallantoic membrane (CAM) assay.

The in vivo test on the chorioallantoic membrane of the fertilized hen's egg (CAM assay) is a current method to determine antiangiogenic, antiinflammatory activity and toxic effects of individual compounds or complex plant extracts. The method is used for testing natural compounds in small amounts for revealing various modes of action and the complex mechanisms related to angiogenesis and inflammation. Furthermore, possible side effects such as membrane irritation, toxic, and anticoagulant properties of the investigated material in question can be detected. For the evaluation, the essential oil obtained by hydrodistillation of the aerial parts of Origanum onites L., a common spice and medicinal plant, was tested for its effect in the chorioallantoic membrane (CAM) assay. The essential oil composition was revealed by means of gas chromatography-mass spectrometry (GC-MS). Eighty three components were identified, representing 99.1% of the total oil. Carvacrol, thymol, p-cymene, and gamma-terpinene were found as major components and were also individually tested in the CAM assay. Along with the monoterpenes carvacrol and thymol, their methyl ether derivatives were also examined for comparison of their physiological action. Neither the essential oil nor its components showed any pronounced antiinflammatory or antiangiogenic property in the CAM assay, at 10-250 microg/pellet. However, the irritant effect of the essential oil was linked to thymol in a dose-response fashion, up to 10 microg/pellet, where it was still showing irritation.

Allantois↗
PubMed2004

In vitro antimicrobial and antioxidant activities of the essential oils and various extracts of Thymus eigii M. Zohary et P.H. Davis.

This study was designed to examine the in vitro antimicrobial and antioxidant activities of the essential oil and various extracts obtained from aerial parts of Thymus eigii. The essential oil was particularly found to possess stronger antimicrobial activity, whereas other nonpolar extracts and subfractions showed moderate activity and polar extracts remained almost inactive. GC-MS analysis of the oil resulted in the identification of 39 compounds, representing 93.7% of the oil; thymol (30.6%), carvacrol (26.1%), and p-cymene (13.0%) were the main components. The samples were also subjected to a screening for their possible antioxidant activity by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and beta-carotene-linoleic acid assays. In the former case, the polar subfraction of the methanol extract was found to be superior to all extracts tested, only 16.8 microg/mL of which provided 50% inhibition, whereas all extracts, particularly the polar ones, seem to inhibit the oxidation of linoleic acid in the latter case. These data were further supported by total phenolics analysis, indicating that the antioxidative potential of the extracts was closely related to their phenolic constituents.

Anti-Bacterial Agents↗
PubMed2005

Effect of solution conductivity on the volatile constituents of Origanum dictamnus L. in nutrient film culture.

The chemical composition of the essential oils obtained from leaves and bracts of hydroponically cultivated Origanum dictamnus L. (Cretan dittany), growing under various electrical conductivity (EC) levels (2.0, 4.0, and 6.0 mS/cm), was studied, using the nutrient film technique (NFT). The analysis of the essential oil content was achieved by GC-MS technique, and totals of 41 and 38 different compounds were identified in both cases of large-leaved and narrow-leaved samples of leaves and bracts, respectively. Differences in the composition content and of the percentage of each of the constituents in the two studied samples (i.e., large-leaved and narrow-leaved) and within the essential oils of leaves and bracts in both samples were observed. Carvacrol and p-cymene were identified as the main constituents in all essential oils, whereas thymoquinone was found in higher percentage in the essential oils of large-leaved than in narrow-leaved plants. The results obtained from GC-MS analysis were submitted to chemometric analysis, and a phenotypic similarity of the essential oils of narrow-leaved O. dictamnus was observed, whereas the essential oils of large-leaved O. dictamnus showed two separate subgroups.

Benzoquinones↗
PubMed2006

Composition of the essential oils of Thymus and Origanum species from Algeria and their antioxidant and antimicrobial activities.

The composition of the essential oils of Origanum and Thymus species restricted to Algeria and the North Africa region was determined. Antioxidant and antibacterial activities of the isolated essential oils were also determined. The oils of oregano plants were strongly characterized by p-cymene (16.8-24.9%), gamma-terpinene (16.8-24.9%), thymol (8.4-36.0%), and carvacrol (1.1-29.7%), a thymol chemotype for Origanum floribundum and a alpha-terpineol chemotype for Thymus numidicus being described for the first time. The strains of Listeria monocytogenes tested were relatively resistant to the action of essential oils of either Origanum or Thymus species. All essential oils possessed antioxidant activity, but this was dependent on the specific chemical composition and the method employed to determine such activity.

Algeria↗