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Rajesh Luthra - One of the best experts on this subject based on the ideXlab platform.

  • Geranyl Acetate esterase controls and regulates the level of geraniol in lemongrass (Cymbopogon flexuosus Nees ex Steud.) mutant cv. GRL-1 leaves.
    Zeitschrift fur Naturforschung. C Journal of biosciences, 2009
    Co-Authors: Deepak Ganjewala, Rajesh Luthra
    Abstract:

    Essential oil isolated from lemongrass (Cymbopogon flexuosus) mutant cv. GRL-1 leaves is mainly composed of geraniol (G) and Geranyl Acetate (GA). The proportion of G and GA markedly fluctuates during leaf development. The proportions of GA and G in the essential oil recorded at day 10 after leaf emergence were approximately 59% and approximately 33% respectively. However, the level of GA went down from approximately 59 to approximately 3% whereas the level of G rose from approximately 33 to approximately 91% during the leaf growth period from day 10 to day 50. However, the decline in the level of GA was most pronounced in the early (day 10 to day 30) stage of leaf growth. The trend of changes in the proportion of GA and G has clearly indicated the role of an esterase that must be involved in the conversion of GA to G during leaf development. We isolated an esterase from leaves of different ages that converts GA into G and has been given the name Geranyl Acetate esterase (GAE). The GAE activity markedly varied during the leaf development cycle; it was closely correlated with the monoterpene (GA and G) composition throughout leaf development. GAE appeared as several isoenzymes but only three (GAE-I, GAE-II, and GAE-III) of them had significant GA cleaving activity. The GAE isoenzymes pattern was greatly influenced by the leaf developmental stages and so their GA cleaving activities. Like the GAE activity, GAE isoenzyme patterns were also found to be consistent with the monoterpene (GA and G) composition. GAE had an optimum pH at 8.5 and temperature at 30 degrees C. Besides GAE, a compound with phosphatase activity capable of hydrolyzing Geranyl diphosphate (GPP) to produce geraniol has also been isolated.

  • An esterase is involved in geraniol production during palmarosa inflorescence development.
    Phytochemistry, 2003
    Co-Authors: Vinod Shanker Dubey, Ritu Bhalla, Rajesh Luthra
    Abstract:

    Total incorporation of exogenously administered [2-14C]Acetate into essential oil of palmarosa (Cymbopogon martinii) was found to be relatively higher than that of either [U-14C]sucrose or [U-14C]glucose during inflorescence development. Among the major essential oil constituents, biogenesis of Geranyl Acetate was much higher than that of geraniol. Alkaline hydrolysis of [14C]labeled Geranyl Acetate revealed that the majority of the label incorporated into Geranyl Acetate was present in the geraniol moiety, indicating that only newly synthesized geraniol gets acetylated to form Geranyl Acetate. Geranyl Acetate cleaving esterase (GAE) activity followed a similar pattern during both in vivo and in vitro inflorescence development, with maximum activity at immature inflorescence stages, suggesting the involvement of GAE in geraniol production during inflorescence development. Five esterase isozymes (Est-A to E) were detected in the enzymic fraction of palmarosa inflorescence and all showed GAE activity, with Est-B being significantly increased during inflorescence development. The role of GAE in geraniol production and improving the palmarosa oil quality is discussed.

  • Sucrose mobilization in relation to essential oil biogenesis during palmarosa (Cymbopogon martinii Roxb. Wats. var.motia) inflorescence development
    Journal of biosciences, 2003
    Co-Authors: Vinod S. Dubey, Ritu Bhalla, Rajesh Luthra
    Abstract:

    Palmarosa inflorescence with partially opened spikelets is biogenetically active to incorporate [U-14C]sucrose into essential oil. The percent distribution of14C-radioactivity incorporated into Geranyl Acetate was relatively higher as compared to that in geraniol, the major essential oil constituent of palmarosa. At the partially opened spikelet stage, more of the geraniol synthesized was acetylated to form Geranyl Acetate, suggesting that majority of the newly synthesized geraniol undergoes acetylation, thus producing more Geranyl Acetate.In vitro development of palmarosa inflorescence, fed with [U-14C]sucrose, resulted in a substantial reduction in percent label from Geranyl Acetate with a corresponding increase in free geraniol, thereby suggesting the role of an esterase in the production of geraniol from Geranyl Acetate. At time course measurement of14CO2 incorporation into geraniol and Geranyl Acetate substantiated this observation. Soluble acid invertase was the major enzyme involved in the sucrose breakdown throughout the inflorescence development. The activities of cell wall bound acid invertase, alkaline invertase and sucrose synthase were relatively lower as compared to the soluble acid invertase. Sucrose to reducing sugars ratio decreased till fully opened spikelets stage, concomitant with increased acid invertase activity and higher metabolic activity. The phenomenon of essential oil biosynthesis has been discussed in relation to changes in these physiological parameters.

  • Biotransformation of Geranyl Acetate to geraniol during palmarosa (Cymbopogon martinii, Roxb. wats. var. motia) inflorescence development.
    Phytochemistry, 2001
    Co-Authors: Vinod Shanker Dubey, Rajesh Luthra
    Abstract:

    Only immature palmarosa (Cymbopogon martinii, Roxb. wats. var. motia) inflorescence with unopened spikelets accumulated essential oil substantially. Geraniol and Geranyl Acetate together constituted about 90% of the palmarosa oil. The proportion of Geranyl Acetate in the oil decreased significantly with a corresponding increase of geraniol, during inflorescence development. An esterase enzyme activity, involved in the transformation of Geranyl Acetate to geraniol, was detected from the immature inflorescence using a gas chromatographic procedure. The enzyme, termed as Geranyl Acetate cleaving esterase (GAE), was found to be active in the alkaline pH range with the optimum at pH 8.5. The catalysis of Geranyl Acetate was linear up to 6 h, and after 24 h of incubation, 75% of the Geranyl Acetate incubated was hydrolyzed. The GAE enzymic preparation, when stored at 4 degrees C for a week, was quite stable with only 40% loss of activity. The physiological role of GAE in the production of geraniol during palmarosa inflorescence development has been discussed.

  • Changes in Monoterpene Content Accompanying Development of Cymbopogon winterianus Jowitt Leaves
    Journal of Essential Oil Research, 1991
    Co-Authors: Rajesh Luthra, Neelam Singh, Srikant Sharma
    Abstract:

    ABSTRACT At different developmental stages, citronella Java (Cymbopogon winterianus Jowitt) leaves were analyzed for essential oil content and composition. Only immature leaves (up to 75% leaf expansion) were biogenetically active to synthesize and accumulate essential oil substantially. The relative percentage of geraniol and citronellol in the oil from immature leaf increased with increase in tissue age along the leaf blade, and was accompanied by a corresponding decrease in Geranyl Acetate and citronellyl Acetate. During leaf ontogeny, the amount of citronellal, geraniol and citronellol in the essential oil increased with leaf expansion; whereas, the amount of Geranyl Acetate and citronellyl Acetate decreased. As the leaf matured, a significant decrease in the essential oil, citronellal and geraniol contents was observed. The essential oil level showed a highly significant linear association with the citronellal and geraniol content; whereas, the geraniol content was positively correlated with citronel...

Vinod Shanker Dubey - One of the best experts on this subject based on the ideXlab platform.

  • An esterase is involved in geraniol production during palmarosa inflorescence development.
    Phytochemistry, 2003
    Co-Authors: Vinod Shanker Dubey, Ritu Bhalla, Rajesh Luthra
    Abstract:

    Total incorporation of exogenously administered [2-14C]Acetate into essential oil of palmarosa (Cymbopogon martinii) was found to be relatively higher than that of either [U-14C]sucrose or [U-14C]glucose during inflorescence development. Among the major essential oil constituents, biogenesis of Geranyl Acetate was much higher than that of geraniol. Alkaline hydrolysis of [14C]labeled Geranyl Acetate revealed that the majority of the label incorporated into Geranyl Acetate was present in the geraniol moiety, indicating that only newly synthesized geraniol gets acetylated to form Geranyl Acetate. Geranyl Acetate cleaving esterase (GAE) activity followed a similar pattern during both in vivo and in vitro inflorescence development, with maximum activity at immature inflorescence stages, suggesting the involvement of GAE in geraniol production during inflorescence development. Five esterase isozymes (Est-A to E) were detected in the enzymic fraction of palmarosa inflorescence and all showed GAE activity, with Est-B being significantly increased during inflorescence development. The role of GAE in geraniol production and improving the palmarosa oil quality is discussed.

  • Biotransformation of Geranyl Acetate to geraniol during palmarosa (Cymbopogon martinii, Roxb. wats. var. motia) inflorescence development.
    Phytochemistry, 2001
    Co-Authors: Vinod Shanker Dubey, Rajesh Luthra
    Abstract:

    Only immature palmarosa (Cymbopogon martinii, Roxb. wats. var. motia) inflorescence with unopened spikelets accumulated essential oil substantially. Geraniol and Geranyl Acetate together constituted about 90% of the palmarosa oil. The proportion of Geranyl Acetate in the oil decreased significantly with a corresponding increase of geraniol, during inflorescence development. An esterase enzyme activity, involved in the transformation of Geranyl Acetate to geraniol, was detected from the immature inflorescence using a gas chromatographic procedure. The enzyme, termed as Geranyl Acetate cleaving esterase (GAE), was found to be active in the alkaline pH range with the optimum at pH 8.5. The catalysis of Geranyl Acetate was linear up to 6 h, and after 24 h of incubation, 75% of the Geranyl Acetate incubated was hydrolyzed. The GAE enzymic preparation, when stored at 4 degrees C for a week, was quite stable with only 40% loss of activity. The physiological role of GAE in the production of geraniol during palmarosa inflorescence development has been discussed.

Lígia Salgueiro - One of the best experts on this subject based on the ideXlab platform.

  • Antifungal activity of the essential oil of Thymus villosus subsp. lusitanicus against Candida, Cryptococcus, Aspergillus and dermatophyte species
    Industrial Crops and Products, 2013
    Co-Authors: Eugénia Pinto, Maria José Gonçalves, Carlos Cavaleiro, Karnjana Hrimpeng, Jéssica Pinto, Sara Vaz, Luís A. Vale-silva, Lígia Salgueiro
    Abstract:

    Abstract Composition and antifungal activity of the essential oil (EO) of Thymus villosus subsp. lusitanicus and its main components Geranyl Acetate, terpinen-4-ol, linalool and geraniol against clinically relevant yeasts and moulds were studied. EO from the plant's aerial parts was obtained by hydrodistillation and analyzed by GC and GC–MS. The oil showed high contents of Geranyl Acetate and terpinen-4-ol and, in lower percentage, linalool and geraniol. Minimum inhibitory concentrations (MICs) were measured according to the reference Clinical and Laboratory Standards Institute (CLSI) broth macrodilution protocols. Minimum fungicidal concentrations (MFCs) were determined by subsequent subculturing of the same cell suspensions in solid medium. The inhibition of germ tube formation and the influence of the EO on cytoplasmic membrane integrity, analyzed by flow cytometry, were also investigated in Candida albicans . In addition, the effect of the EO on mitochondrial function was studied. The EO, Geranyl Acetate and geraniol displayed low MIC and similar MFC values against dermatophytes and Cryptococcus neoformans (0.04–0.64 μL/mL), while terpinen-4-ol showed a weaker activity (1.25–2.5 μL/mL). However, Aspergillus species are likely to be more resistant than other studied fungi and the fungicidal activity of the EO against these moulds could be due to terpinen-4-ol and geraniol rather than Geranyl Acetate. Linalool showed week activity against all the tested strains. Regarding Candida species, the EO susceptibility profiles seem to be diverse and were not directly correlated with fluconazole susceptibility patterns. Moreover, the inhibition of yeast-mycelium transition was demonstrated at sub-inhibitory concentrations of the EO in C. albicans ATCC 10231. Our findings revealed that the fungicidal activity of the EO is probably due, at least in part, to its ability to cause rapid metabolic arrest and plasma membrane disruption. The yield of T. villosus ’ essential oil and its broad fungicidal activity are compatible with an industrial use, particularly for pharmaceutical, therapeutic and food preservation purposes.

  • Composition and biological activity of the essential oil from Thapsia minor, a new source of Geranyl Acetate
    Industrial Crops and Products, 2012
    Co-Authors: Maria José Gonçalves, Maria Teresa Cruz, Ana Cristina Tavares, Carlos Cavaleiro, Maria Celeste Lopes, Jorge M. Canhoto, Lígia Salgueiro
    Abstract:

    Abstract The essential oils from aerial parts of Thapsia minor Hoffmanns. & Link (Apiaceae), obtained by hydrodistillation, were analyzed by gas-chromatography and gas-chromatography–mass spectrometry. Oxygenated monoterpenes represented the main fraction with Geranyl Acetate (82.3–83.0%) as the major constituent, making this plant a good source of this compound. Biological activity of the essential oil was evaluated against several fungal strains. The highest activity was found against dermatophyte strains, Crytococcus neoformans and Candida guillermondii with minimal inhibitory concentrations values from 0.32 μl/ml to 1.25 μl/ml. The antifungal activity could be associated with the significant contribution of the oxygenated monoterpene Geranyl Acetate. Furthermore, this essential oil demonstrated to have potent anti-inflammatory in vitro activity, at concentrations that did not affect macrophages and keratinocytes viability, being the anti-inflammatory properties of the oil mainly due to Geranyl Acetate. These favorable results emphasize the antifungal and anti-inflammatory abilities of the molecule Geranyl Acetate and further support the exploitation of T. minor oil for pharmaceutical industry, in order to find new phytopharmaceuticals.

  • Chemotaxonomic study on Thymus villosus from Portugal.
    Biochemical systematics and ecology, 2000
    Co-Authors: Lígia Salgueiro, Roser Vila, Xavier Tomas, Salvador Cañigueral, Jorge Paiva, António Proença Da Cunha, Tomás Adzet
    Abstract:

    The composition of the essential oils of four populations of Thymus villosus subsp. lusitanicus (Boiss.) Coutinho from Portugal was investigated by GC and GC-MS. To study the chemical polymorphism the results obtained from GC analyses of the volatile oils from individual plants from four populations were submited to Principal Component and Cluster analyses. A comparision with the essential oil of T. villosus subsp. villosus, previously studied by us was done. Important di!erences with regard to the major constituents in these two taxa were found. Linalool, Geranyl Acetate, geraniol and terpinen-4-ol were the main components of the essential oils of T. villosus subsp. lusitanicus, whereas in the oil of T. villosus subsp. villosus p-cymene, myrcene and a-terpineol were the major ones. Although, both taxa showed chemical polymorphism, di!erent types of essential oils were characterized in each one: linalool; linalool/ terpinen-4-ol/trans-sabinene hydrate; linalool/1,8-cineole; Geranyl Acetate/geraniol; Geranyl Acetate/geraniol/1,8-cineole in T. villosus subsp. lusitanicus and p-cymene/camphor/linalool; p-cymene/borneol; linalool/geraniol/Geranyl Acetate; a-terpineol/camphor/myrcene in T. villosus subsp. villosus. Thus, the two subspecies of T. villosus can be easely di!erenciated by the composition of their essential oils. ( 2000 Elsevier Science Ltd. All rights reserved.

Didier Combes - One of the best experts on this subject based on the ideXlab platform.

  • Geranyl Acetate synthesis by lipase-catalyzed transesterification in supercritical carbon dioxide
    Enzyme and Microbial Technology, 1993
    Co-Authors: Warawut Chulalaksananukul, Jean-stéphane Condoret, Didier Combes
    Abstract:

    Abstract The synthesis of Geranyl Acetate by transesterification catalyzed by immobilized lipase from Mucor miehei was studied in supercritical carbon dioxide (SCCO2) and compared with n-hexane. The influence of water content on the thermostability of the enzyme was investigated in SCCO2. The increase of water content and increase of temperature diminished enzyme stability. The half-life of the dry enzyme in SCCO2 at 100°C was about 24 h. The effect of ester chain length on the rate of reaction was investigated. Propyl Acetate was found to be the best substrate for Geranyl Acetate synthesis in both media. In order to define the optimal conditions of the reaction, optimization of water content was carried out. The water content of the solid phase seemed to be the most important factor for the activity of the enzyme. The same optimum, 8–10% (w/w) water content, was determined in both media. The kinetics of the reaction are suggested to fit a Ping-Pong Bi Bi mechanism in which inhibition by excess of geraniol has been identified. The values of all apparent kinetic parameters which were not affected by the external diffusional limitations were calculated. The differences between the kinetic constants in both media were discussed. Considering the reaction rates and the maximum velocity of the reaction, the SCCO2 is not better than the conventional organic solvents, such as hexane, for the reaction of transesterification between geraniol and propyl Acetate.

  • Kinetics of Geranyl Acetate synthesis by lipase-catalysed transesterification in n-hexane
    Enzyme and Microbial Technology, 1992
    Co-Authors: Warawut Chulalaksananukul, Jean-stéphane Condoret, Didier Combes
    Abstract:

    The synthesis of Geranyl Acetate by transesterification catalysed by immobilized lipase of Mucor miehei was studied. To obtain the highest yield for Geranyl Acetate synthesis, the effect of ester chain length on the rate of reaction was investigated. Propyl Acetate was found to be the best substrate for Geranyl Acetate synthesis. The kinetics of reaction are suggested to agree with a ping-pong Bi Bi mechanism in which inhibition by excess of geraniol has been identified. The values of all apparent kinetic parameters were computed. No evidence of any significant external diffusional limitation that could account for these values has been detected. In order to define the optimal conditions of the reaction, optimization of water content through the distribution ratio of water between solvent and support was examined.

Vinod S. Dubey - One of the best experts on this subject based on the ideXlab platform.

  • Sucrose mobilization in relation to essential oil biogenesis during palmarosa (Cymbopogon martinii Roxb. Wats. var.motia) inflorescence development
    Journal of biosciences, 2003
    Co-Authors: Vinod S. Dubey, Ritu Bhalla, Rajesh Luthra
    Abstract:

    Palmarosa inflorescence with partially opened spikelets is biogenetically active to incorporate [U-14C]sucrose into essential oil. The percent distribution of14C-radioactivity incorporated into Geranyl Acetate was relatively higher as compared to that in geraniol, the major essential oil constituent of palmarosa. At the partially opened spikelet stage, more of the geraniol synthesized was acetylated to form Geranyl Acetate, suggesting that majority of the newly synthesized geraniol undergoes acetylation, thus producing more Geranyl Acetate.In vitro development of palmarosa inflorescence, fed with [U-14C]sucrose, resulted in a substantial reduction in percent label from Geranyl Acetate with a corresponding increase in free geraniol, thereby suggesting the role of an esterase in the production of geraniol from Geranyl Acetate. At time course measurement of14CO2 incorporation into geraniol and Geranyl Acetate substantiated this observation. Soluble acid invertase was the major enzyme involved in the sucrose breakdown throughout the inflorescence development. The activities of cell wall bound acid invertase, alkaline invertase and sucrose synthase were relatively lower as compared to the soluble acid invertase. Sucrose to reducing sugars ratio decreased till fully opened spikelets stage, concomitant with increased acid invertase activity and higher metabolic activity. The phenomenon of essential oil biosynthesis has been discussed in relation to changes in these physiological parameters.

  • Changes in the essential oil content and its composition during palmarosa (Cymbopogon martinii (Roxb.) Wats. var. motia) inflorescence development
    Flavour and Fragrance Journal, 2000
    Co-Authors: Vinod S. Dubey, Gopal R. Mallavarapu, R Luthra
    Abstract:

    The ~owering tops of palmarosa "Cymbopo'on martinii# consist of spikelets and each spikelet is further composed of racemes and a leaf!like structure called a spathe( Both racemes and spathe contain essential oil( Changes in fresh weight\ dry weight\ chlorophyll and essential oil content and its major constituents\ viz( geraniol and Geranyl Acetate\ were examined for both racemes and spathe at various stages of spikelet devel! opment( The essential oil content was maximal at the unopened spikelets stage and decreased signi_cantly thereafter( At unopened spikelets stage\ the proportion of Geranyl Acetate "47(5)# in the raceme oil was relatively greater compared with geraniol "26(1)#\ whereas the spathe oil contained more geraniol "50(8)# compared with Geranyl Acetate "22(3)#( The relative percentage of Geranyl Acetate in both the oils\ however\ decreased sig! ni_cantly with development and this is accompanied by a corresponding increase in the percentage of geraniol( Analysis of the volatile constituents from racemes and spathes "from mature spikelets# and seeds by capillary GC indicated 17 minor constituents besides the major constituent geraniol( "E#!Nerolidol was detected for the _rst time in an essential oil from this species( The geraniol content predominated in the seed oil\ whereas the Geranyl Acetate content was higher in the raceme oil( Copyright 1999 John Wiley + Sons\ Ltd(