Chemotypes, extraction, chemical composition and use of lippia alba essential oil. Lippia alba is a plant widely distributed in tropical, subtropical and temperate zones of the Americas, Africa and Asia. The essential oil of L. Therefore, this study is aimed at conducting a review of the main chemotypes, extraction methods, composition and application of the essential oil of L. In this study, the main chemotypes and its relation to genetic and morphological characteristics are discussed.
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Phytochemistry 67 — Dynamic pathway allocation in early terpenoid biosynthesis of stress-induced lima bean leaves. Received 7 November ; received in revised form 6 December Available online 31 March Dedicated to Professor Rod Croteau on the occasion of his 60th birthday.
Two independent pathways contribute in higher plants to the formation of isopenteny1 diphosphate IDP , the central building block of isoprenoids. In general, the cytosolic mevalonate pathway MVA provides the precursors for sesquiterpenes and sterols, whereas the plastidial methylerythritol pathway MEP furnishes the monoterpene-, diterpene- and carotenoids. Administration of deuterium labeled 1-deoxy- D -xylulose and mevalolactone to lima beans Phaseolus lunatus , followed by gas chromatographic separation and mass spectro- metric analysis of de novo produced volatiles revealed that the strict separation of both pathways does not exist.
Isotopic ratio mass spectrom- etry IRMS at natural abundance levels demonstrated independently and without the need for labeled precursors a dynamic allocation of the MVA- or the MEP-pathway in the biosynthesis of the nerolidol-derived homoterpene 4,8-dimethy1-nona-1,3,7-triene DMNT.
All rights reserved. Terpenes are frequently used by the producing organism in interactions with its environment, as protection against enemies, parasites and pathogens as well as attractants for pollinators and seed-dispersing animals Harborne, With more than 25, known compounds terpenes and terpenoids form one of the largest and perhaps most structurally diverse groups of secondary metabolites Con- nolly and Hill, E-mail address: Boland ice.
The synthesis of the terpenoid natural products is contin- ued by terpene synthases and terpene cyclases. All of these later enzymatic reactions proceed through allylcation inter- mediates followed by isomerizations, cyclizations, and hydride- or methyl shifts. The reactivity of the cations along with their tendency to rearrange is one of driving forces gen- erating the enormous structural diversity of terpenoids. Bartram et al. Finally, the skeleton can be substituted, oxidized, reduced or conjugated e.
The origin of IDP The two pathways. The MVA pathway. The HMG-CoA reductase plays a key role in the regulation of the isopren- oid biosynthesis in plants and animals Bach et al. The MEP pathway. Administration experiments with 1 3 C-acetate and bacte- ria Flesch and Rohmer, or 1 3 C-glucose and gingko leaves Gingko biloba Schwarz, exhibited in the iso- lated terpenoids labeling patterns that were not consistent with an MVA-origin.
This led to the discovery of a meva- lonate-independent pathway starting by condensation of. The latter is rearranged and reduced to the key intermediate 2- C -methyl- D -erythritol 4-phosphate MEP Takahashi et al. Eisenreich et al. Whereas mono- and diterpenes are synthesized in the plastids, the production of sesquiterpenes and sterols is located in the cytosol McGarvey and Croteau, Enzymes of the MVA-pathway have been isolated from the cytosol, whereas genes coding for enzymes of the MEP-pathway possess typical plastid-targeting sequences Lange et al.
For example, in leaves of the lima bean, adminis- tration of deuterium labeled mevalonic acid resulted in a. Scheme 1. On the other hand, monoterpenes and ses- quiterpenes, especially DMNT, also showed a high degree of labeling after administration of deuterium labeled deoxy- D -xylulose DOX.
This observation suggests that the plant may be able to use both pathways in a dynamic fash- ion to overcome limiting conditions Piel et al. Other exceptions from the classical assignment of the dif- ferent terpenoid classes to the MVA- and MEP-pathway have been reported for chamomile Adam and Zapp, , Catharanthus roseus Arigoni et al. The use of 1 3 C-labeled glucose in combination with 1 3 C NMR spectroscopy has provided in recent years a very detailed view into the metabolic networks funneled by glu- cose-derived building blocks Eisenreich et al.
This technique also allowed to quantify the contribution of the MVA- and MEP-pathway to the biosynthesis of individual terpenoids Eisenreich et al. Studies on the cross-talk between the pathways showed in Arabidopsis thaliana no altered expression of the relevant genes suggesting that posttranscriptional factors control the early terpenoid biosynthesis Laule et al.
More- over, isolated chloroplasts and proteoliposomes from solu- bilized proteins of the plastidial envelope membranes were recently shown to be capable of an unidirectional export of IDP and GDP. The process was found to be controlled by.
The biosynthesis of DMNT in lima bean leaves provides unique advantages as a model, to study a dynamic pathway allocation in response to stress factors and elicitors. The plant does not store terpenoids, but synthesizes DMNT and other volatile terpenoids de novo after elicitation. Moreover, as outlined in Scheme 2 , DMNT 1 results from the sesquiterpene alcohol, nerolidol 2 , by oxidative degradation.
Here we report on the dynamic pathway allocation in the lima bean Phaseolus lunatus during early terpenoid bio- synthesis focusing on the biosynthesis of DMNT as a model system. Results and discussion. Labeling studies. After insect wounding or induction by jasmonic acid JA , lima bean leaves start to emit a blend of volatiles. Scheme 2. Spider mite Tetranychus urticae induced volatiles from the lima bean P. IS: internal standard n -bromodecane.
Scheme 3. Major compounds are terpenoids such as E - b -ocimene 3 , linalool 4 , b -caryophyllene 5 , and DMNT 1 , together with compounds from fatty acid metabolism and the shikimate pathway see Fig. To investigate the pathway allocation in the induced terpenoids, labeled precursors for the MVA- or MEP-pathway, namely d 2 - DOX 6 and ds-MVA 7 were administered to freshly detached lima bean leaves and the incorporation of the deuterium atoms into the terpenoids was determined by gas chromatography mass spectroscopy GC—MS.
Then, the emitted vola- tiles were collected and analyzed by GC-MS. Monoterpenes Depending on the labeled precursor, the molecular masses of the terpenes could shift by two or four mass units per isoprene unit after administration of d 2 -DOX 6 or d 5 - MVA 7 , respectively see Scheme 3. In the case of the monoterpenes E - b -ocimene 3 and linalool 4 , the molecular masses shifted by 2 or 4 units depending on incorporation of one or two molecules of d 2 -DOX 6.
The same terpenoids displayed a shift of 4 or 8 mass units after administration of d 5 -MVA 7. The number of deuterium isotopes per molecule was determined by integration of the corresponding ion traces and the degree of labeling was calculated as follows:.
As shown in Fig. Concentration-dependent degree of labeling of the monoterpenes ocimene 3 and linalool 4. The degree of labeling of the collected volatiles was calculated according to Eq. The concentration of 7 corresponds to the R -enantiomer in the administered racemate. Average values and standard deviations from three independent feeding experiments are given.
The conjugated diene 1 is formed by an elimination of the C 5 -H S i along with a formal C 4 -segment from the polar head Schemes 2 and 4 of 3 S -nerolidol 2 Degenhardt and Gershenzon, ; Donath and Boland, As demonstrated in Scheme 4 , this fragmentation not only removes four carbons of the terminal isoprene unit but also one deuterium atom from the central C 5 - block d 2 -DOX as precursor of d 6 - 2.
Accordingly, the molecular mass of DMNT 1 can increase only by 3 mass units. In this case, the position of a single labeled C 5 -unit within the DMNT molecule 1 can be deduced from the characteristic fragmentation pattern of the mass spectrum see Fig. Cyclization of farnesyl diphosphate to caryophyllene 5 proceeds with loss of a hydrogen atom after the cyclization. Scheme 4. Concentration-dependent degree of labeling of the sesquiterpenes DMNT 1 and caryophyllene 5. The degree of labeling was calculated according to Eq.
Incorporation of only one or two d 4 -IDP units leads to mass shifts of 3 and 4, or 7 and 8 mass units. However, administra- tion of d 2 -DOX 6 also led to a concentration-dependent high degree of labeling in DMNT 1 and caryophyllene 5 ca.
The enzymes of the MEP-pathway are located in the chloroplast, whereas the biosynthesis of the sesquiterpenes takes place in the cytosol. Since the MEP-pathway contrib- utes much more to the sesquiterpene biosynthesis Fig. The initial linear increase of the extent of labeling of the monoterpenes indicates that the export of the interme- diates from the chloroplast to the cytosol depends on the concentration of plastidial d 2 -DOX 6 and the according concentration of d 2 -IDP.
This is further supported by. The analysis of the mass spectra in the peak areas A — D Fig. The labeling of the third isoprene unit is lost Scheme 4 during the oxidative degradation of 3 S -nerolidol 2 Donath and Boland, The ioniza- tion of the terminal dimethyl allyl group leads to a loss of a methyl group see inset in spectrum D , Fig.
In a similar manner the structures, i. However, the probability was not identical for all possible combinations. As to be taken from Fig. However, this sequence is not strict since also other positional combina- tions were observed albeit at lower abundance. Interestingly, and in contrast to the linear correlation of the labeling rate of DMNT 1 with the concentration of d 2 -DOX 6 in the medium, the simultaneous administra- tion of d 2 -DOX 6 and d 5 -MVA 7 shows only an initial correlation ca.
Higher concentrations of d 2 -DOX 6 even led to a reduction of the degree of label- ing ca. Since a charged molecule like IDP cannot pass membranes, the recently described transporters balance the gradient between the compartments Bick and Lange, Thus, increasing concentrations of d 4 -IDP in the cytosol prevent the import of d 2 -IDP from the cytosol, consistent with the data of Fig.
Similar observations were made for the biosynthesis of b -caryophyllene 5. To block the MEP-pathway, fosmidomycin Okuhara et al. In cells Mu and Md mass is overlapped by the fragmentation of isotopomer Um. For each isotopomer the average value of three administration experi- ments is given.
For abbreviations of the isotopomers, see Table 1. Administration of both labeled precursors at concentration of about 5 mg ml 1 led to severe necrosis of the leaves; no volatile production was observed.
The chromatograms Fig. Pre- treatment of the lima bean leaves with fosmidomycin com-. Gas chromatographic separation of JA-induced volatiles from Phaseolus lunatus. A without inhibitor pre-treatment, B after inhibition of the MVA-pathway by cerivastatin , C after inhibition of the MEP-pathway by fosmidomycin, D after simultaneous inhibition of both pathways by cerivastatin and fosmidomycin.
Compounds: 1 : 3 Z -hexenyl acetate, 2 : ocimene, 3 : linalool, 4 : 4,8-dimethylnona-1,3,7-triene DMNT , 5 :. A pre-treatment of the leaves with cerivastatin did not com- pletely block the biosynthesis of DMNT 1 , but reduced its production by ca. Simultaneous addition of both inhibitors fully suppressed the de novo biosynthesis of all terpenoids. IRMS studies Isotopic ratio mass spectroscopy IRMS of stable iso- topes at natural abundance is an excellent tool for the reli- able investigation of the dynamic pathway allocation in the biosynthesis of terpenoids Jux et al.
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Phytochemistry 67 — Dynamic pathway allocation in early terpenoid biosynthesis of stress-induced lima bean leaves. Received 7 November ; received in revised form 6 December Available online 31 March Dedicated to Professor Rod Croteau on the occasion of his 60th birthday. Two independent pathways contribute in higher plants to the formation of isopenteny1 diphosphate IDP , the central building block of isoprenoids. In general, the cytosolic mevalonate pathway MVA provides the precursors for sesquiterpenes and sterols, whereas the plastidial methylerythritol pathway MEP furnishes the monoterpene-, diterpene- and carotenoids. Administration of deuterium labeled 1-deoxy- D -xylulose and mevalolactone to lima beans Phaseolus lunatus , followed by gas chromatographic separation and mass spectro- metric analysis of de novo produced volatiles revealed that the strict separation of both pathways does not exist.