Methyl Epijasmonate Research Articles

Formation and isomerization of (Z)-methyl epijasmonate, the key contributor of the orchid-like aroma, during tea processing

The elegant orchid-like fragrance of tea has always been tea processors and consumers' top priority. Controlling the production process is very important for tea aroma formation. This study aims to investigate the synthesis of (Z)-methyl epijasmonate (epi-MeJA), a key contributor to orchid-like aroma properties in tea, during tea processing. The changes in content of epi-MeJA were analysed during the processing of two tea varieties (Anxi Tieguanyin and Taiping Houkui) with typical orchid-like fragrance. It was found to be mainly synthesized and accumulated during tea processing, as fresh tea leaves contained little or even no epi-MeJA. Its content was positively correlated with the processing time in the enzyme active stages (before fixation). During the fixation stages, isomerization occurred due to high temperatures, with a degree of epimerization to the much less odor active isomer (Z)-methyl jasmonate. Isomerization could also occurred during the drying process, which is dominated by the drying temperature.

Sensomics-Assisted Characterization of Key Flowery Aroma Compounds in Lu’an Guapian Green Tea Infusion (Camellia sinensis)

The volatile fraction was isolated from the premium and common grade of Lu'an Guapian green tea infusion by solvent-assisted flavor evaporation distillation. With the application of aroma extract dilution analysis, a total of 52 aroma-active compounds were revealed in the flavor dilution (FD) factor area of 32-8192. Besides, five additional odorants with higher volatility were identified using solid-phase microextraction. The aroma profiles, FD factors, and quantitative data of premium Guapian (PGP) and common Guapian (CGP) showed apparent differences. The intensity of the flowery attribute was significantly higher in PGP than in CGP, while cooked vegetable-like was the most outstanding odor note in CGP. The recombination experiment and the omission test of PGP clarified that dimethyl sulfide, (E,E)-2,4-heptadienal, (E)-β-ionone, (E,Z)-2,6-nonadienal, 2-methylbutanal, indole, 6-methyl-5-hepten-2-one, hexanal, 3-methylbutanal, γ-hexalactone, methyl epijasmonate, linalool, geraniol, and (Z)-3-hexen-1-ol were the key odorants of PGP tea infusion. The omission and addition tests of flowery odorants manifested that (E)-β-ionone, geraniol, and (E,E)-2,4-heptadienal, with higher odor activity values in PGP than in CGP, contributed to the flowery attribute most. The difference in the concentration of the abovementioned odorants with flowery odor notes could be one of the main factors which led to the difference in aroma quality between the two grades of Lu'an Guapian.

Comprehensive profiling of volatile components in Taiping Houkui green tea

Taiping Houkui green tea is well-known in China for its noble aroma. Six tea strains from the Shidacha population (the predominant raw materials for Taiping Houkui green tea) and three other varieties were used to prepare green teas via the conventional techniques of Taiping Houkui green tea manufacture. Aroma evaluation confirmed that green teas produced from Shidacha strains possessed good aroma qualities. A total of ninety-six volatile compounds were identified and quantified. Hierarchical cluster analysis separated the nine green teas into three groups, and principal component analysis identified 16 volatiles (with variance importance values greater than one) that contributed to the separation. Thirty-three volatiles with odor activity values above one were identified, the highest twenty being methyl epi-jasmonate, octanal, (Z)-jasmone, β-ionone, geraniol, indole, methyl jasmonate, nonanal, decanal, linalool, benzeneacetaldehyde, phenylethyl alcohol, α-ionone, 1-octen-3-ol, cedrol, benzaldehyde, dimethyl sulfide, hexanal, 3-methylbutanal, and β-cyclocitral. All of these may be key odorants in Taiping Houkui green tea. This study suggests that the unique aroma of Taiping Houkui green tea depends both on a premium tea plant and the manufacturing process.

Characterization and Quantitative Comparison of Key Aroma Volatiles in Fresh and 1-Year-Stored Keemun Black Tea Infusions: Insights to Aroma Transformation during Storage.

The aroma of Keemun black tea (KBT) changes during storage. We investigated key aroma volatiles of fresh KBT (FKBT) and KBT stored for 1 year. Through gas chromatography–olfactometry–mass spectrometry/aroma extract dilution analysis (GC-O-MS/AEDA), 27 aroma volatiles with a flavor dilution (FD) value ≥16 were quantitated. In odor activity value (OAV) analysis, the two samples had nearly the same key aroma volatiles; (Z)-methyl epijasmonate was the exception. Dimethyl sulfide, 3-methylbutanal, 2-methylpropanal, and linalool had especially high OAVs. Except for β-damascenone, volatiles with OAVs > 1 had higher concentrations in FKBT, which revealed that most key aroma compounds were lost during storage. Sweet, malty, floral, and green/grassy aromas corresponded directly to certain compounds. Lastly, the addition test indicated that the addition of several key aroma volatiles decreasing during storage could enhance the freshness of KBT aroma, which may be a potential to control the aroma style of KBT or other teas in industry.

Aroma characterization and their changes during the processing of black teas from the cultivar, Camellia sinensis (L.) O. Kuntze cv. Jinmudan

Jinmudan (JMD) black tea is processed from the JMD cultivar (Camellia sinensis (L.) O. Kuntze cv. Jinmudan). Dried JMD black tea (JMD-D) received a score of 7.43 in the quantitative descriptive analysis, indicating that it had the strongest fruity flavor. Many volatile compounds (129) were identified by solvent assisted flavor evaporation and gas chromatograph mass spectrometry. In total, 26 aroma active compounds, including (Z)-methyl epi-jasmonate (flavour dilution factor (FD): 128–1024), benzeneacetaldehyde (FD: 512–1024), linalool (FD: 256–1024), geraniol (FD: 256–512), jasmine lactone (FD: 64–1024), were identified in JMD-D and controls through an aroma extract dilution analysis and gas chromatography-mass spectrometry olfactometry. On the basis of the FD values, odor activity values, and relative quantification results, the volatiles of fruit flavor derived from lipids, such as jasmine lactone, were prominent in JMD-D compared to the controls. During the processing of the four types of black tea, the volatile fraction concentration increased mainly from the fresh leaf to the fermentation stage and decreased in the drying stage.

Enantiomeric distributions of volatile lactones and terpenoids in white teas stored for different durations

Precise identification of the compounds characteristic to stored white teas is urgently needed as these products have unique flavors and health benefits that improve with storage duration. Owing to the potential applications in food quality discrimination, specific regularities between the enantiomeric distributions of 23 volatile lactones and terpenoids and storage durations of white teas were expected and investigated by enantioselective gas chromatography-mass spectrometry (Es-GC-MS) combined with multivariate statistical analysis. High correlation coefficients (−0.853 to 0.695) and significant differences (P < 0.001) between the enantiomeric ratios (ERs) of (2S, 5S)-linalool oxide A, (2S, 5R)-linalool oxide B, (2R, 5S)-theaspirane B, S-linalool, and (1R, 2S)-methyl epijasmonate and the storage durations (0–7 years) were obtained, and the contents of S-linalool and S/R-dihydroactinidiolide significantly decreased and increased, respectively, with the increasing of storage duration. Therefore, the aforementioned lactone and terpenoid enantiomers are potential markers for the reliable differentiation of white teas stored for different time periods.

Characterization of the orchid-like aroma contributors in selected premium tea leaves

The orchid-like odor of a tea infusion is regarded as a noble aroma and an essential sensory attribute for certain premium teas. Such tea leaves are difficult to make and the quality is not always reproducible. This study is focused on the molecular sensory basis of the orchid-like attribute in tea brews. The aroma is defined as jasmine- and magnolia-like floral notes with a fruity undertone and found to be closely related to the flower scent of the orchid Cymbidium faberi Rolfe (hui lan) by a sensory panel. Gas chromatography mass spectrometry (GC-MS) and aroma extract dilution analysis revealed that the key contributor was (Z)-methyl epijasmonate (epi-MeJA), which was also one of the main odor compounds in the flower scent of C. faberi and in the infusions of selected high-quality teas. Concentration of epi-MeJA was ranging from 0.09 to 2.2µg/g in the oolong and green tea leaves.

Characterisation of odorant compounds and their biochemical formation in green tea with a low temperature storage process

We produced low temperature (15°C) processed green tea (LTPGT) with higher aroma contents than normal green tea (Sencha). Normal temperature processed green tea (NTPGT), involved storing at 25°C, and Sencha had no storing process. Sensory evaluation showed LTPGT had higher levels of floral and sweet odorants than NTPGT and Sencha. Aroma extract dilution analysis and gas chromatography–mass spectrometry–olfactometry indicated LTPGT had 12 aroma compounds with high factor dilution values (FD). Amongst LTPGT’s 12 compounds, indole, jasmine lactone, cis-jasmone, coumarin, and methyl epijasmonate contributed to floral, fruity and sweet characters. In particular, indole increased initially, peaking at 16h, then gradually decreased. Feeding experiments suggested [15N]indole and [15N]oxygenated indoles (OX-indoles) were produced from [15N]anthranilic acid. We proposed the increase in indole was due to transformation of anthranilic acid during the 16h storage and the subsequent decline in indole level was due to its conversion to OX-indoles.

ChemInform Abstract: Synthesis of 12-Oxophytodienoic Acid (12-OxoPDA) and the Compounds of Its Enzymic Degradation Cascade in Plants, OPC-8:0, -6:0, -4:0 and -2: 0 (epi-Jasmonic Acid), as Their Methyl Esters.

The synthesis of 12-Oxophytodienoic acid, and the compounds of its enzymic degradation sequence, OPC-8:0, -6:0, -4:0 and -2:0, important plant metabolites derived from linolenic acid, is reported. The syntheses use the known cyclopent-3-ene-1,2-diacetic acid as an early intermediate, and this is derived from the Cope rearrangement of 5-vinyltrinorborn-2-ene via bicyclo[4.3.0]nona-3,7-diene. lodolactonisation and tributyltin hydride reduction provides the key intermediate (3-oxo-2-oxabicyclo[3.3.0]octan-6-yl)acetic acid for the OPC series, whilst phenylselenolactonisation and elimination provides the necessary unsaturated lactone (7-oxo-8-oxabicyclo[3.3.0]oct-2-en-4-yl)acetic acid for 12-oxoPDA. Members of the OPC-series were made by chain extending the saturated oxabicyclooctane acid: that for the OPC-4:0 involved double Arndt–Eistert reaction, whilst the intermediates for OPC-6:0 and -8:0 were made by Kolbe anodic crossed coupling. The lactones were then converted via their lactols, Wittig reaction, esterification and oxidation, into the compounds of the OPC ester series, including OPC-2:0 (methyl epi-jasmonate).The unsaturated lactone 8-(7-oxo-8-oxabicyclo[3.3.0]oct-2-en-4-yl)octanoic acid required for 12-oxoPDA synthesis could also be prepared by anodic synthesis either from (7-oxo-8-oxabicyclo[3.3.0]oct-2-en-4-yl)acetic acid, or from its 2-phenylseleno-2, 3-dihydro precursor as elimination occurred concomitantly during the reaction. Since yields were low, the unsaturated acid lactone was converted into its lactol and the (Z)-pent-2-enyl side-chain was inserted first. After TBDMS blocking of the cyclopentene hydroxy group, the side-chain was elaborated to give 5-(pent-2-enyl)cyclopent-2-enylacetaldehyde and chain extension carried out by a Grignard-demesylation procedure. Sequential desilylation and depyranylation, followed by oxidation of the diol, gave 12-oxoPDA, isolated as its methyl ester.

ChemInform Abstract: Synthesis of Both the Enantiomers of Methyl Epijasmonate.

Abstract Both the pure enantiomers of methyl epijasmonate 1 with potato-tuber inducing activity were synthesized stereoselectively starting from 2-oxabicyclo[3.3.0]-oct-6-en-3-one 6 in 20% yield through 11 steps.

Online RPLC-GC via TOTAD Method To Isolate (+)-Methyl Epijasmonate from Lemon (Citrus limon Burm.)

Pure (+)-methyl epijasmonate was isolated from lemon ( Citrus limon Burm.) for the first time. To that aim, two commercial essential oils and one homemade extract were included in the present paper. First, a study on the appropriate chromatographic conditions to avoid the epimerization from methyl epijasmonate to the more stable methyl jasmonate was accomplished. The results obtained are discussed. The presence of (+)-methyl epijasmonate in the three samples studied was initially established through the direct injection into GC-MS. However, the overlapping of (+)-methyl epijasmonate with other matrix components made it necessary to employ a multidimensional technique. RPLC-GC analysis via through-oven transfer adsorption-desorption (TOTAD) provided the selectivity and sensitivity required, reflecting that the homemade lemon extract was an adequate natural source to obtain pure (+)-methyl epijasmonate by means of the collection of the corresponding RPLC fraction.

Syntheses and Odor Descriptions of Cyclopropanated Compounds. Part 5

AbstractAnalogs of methyl jasmonate (=methyl (1R*,2R*)‐3‐oxo‐2‐[(Z)‐pent‐2‐enyl]cyclopentaneacetate; MJA) bearing a cyclopropane ring, double bond, or a F‐substituent were synthesized, and their odor characteristics were examined. Most of the analogs with the same stereochemical properties as methyl epijasmonate showed odor properties superior to MJA. Interestingly, the enol acetate of MJA had a diffusive orchid‐like note.

Synthesis of methyl epijasmonate and cis-3-(2-oxopropyl)-2-(pent-2Z-enyl)-cyclopentan-1-one

A novel and efficient synthesis of both (±)-methyl epijasmonate and (±)-cis-3-(2-oxopropyl)-2-(pent-2Z-enyl)-cyclopentan-1-one is described. The key step to establish the cis-stereochemistry on the 5-membered ring is an ionic Diels–Alder reaction, which is high yielding and highly regioselective. Subsequent key steps include oxidative cleavage of the six-membered ring, Wittig coupling and for the synthesis of epijasmonate, the haloform reaction.

Synthesis of (±)-Methyl Epijasmonate and (±)-Methyl Dihydroepijasmonate by Diastereoselective Protonation

The synthesis of (±)-methyl epijasmonate (1) was carried out by Michael addition of lithium diallylcuprate to enone 3 and diastereoselective enolate protonation with the chelating proton source 2-(methyliminomethyl)phenol (4; 85% ds), followed by ozonolysis, oxidation, esterification, and Lindlar hydrogenation. During the ozonisation, epimerization to the thermodynamically more stable trans-isomer takes place to some extent, so that 1 was isolated with a cis:trans ratio of 72:28. The analogous transformation of enone 7 with lithium diallylcuprate and 2-(methyliminomethyl)phenol (4) furnished ketone 8 with 94% ds; this was then transformed into (±)-methyl dihydroepijasmonate (2) with a cis:trans ratio of 91:9. The olfactory properties of this product are superior to those available from commercial sources

An enantiospecific synthesis of (+)-methyl epijasmonate and (−)-methyl cucurbate from L-glutamic acid

An enantiospecific route to jasmonoid natural products, (+) - methyl epijasmonate and (−)-methyl cucurbate from L-glutamic acid is reported. The key step is a 5-(3,4) ene cyclization of a functionalized 1,6-diene as chiron, which sets up three chiral centres with a high degree of diastereoselectivity.

Diastereoselective Protonation of Chiral Enolates with Chelating Proton Donors under Reagent Control: Scope, Mechanism, and Applications

AbstractEndocyclic keto‐enolates of type 2 can be protonated under reagent control with high diastereoselectivities when chelating proton donors with a salicylate structure are used. The stereochemical course of these protonations is hardly affected by the ring size, the substitution pattern, and the presence of additional stereogenic centers in the enolate. The substrates can be prepared by conjugate cuprate addition as well as deprotonation; in the latter case, good diastereoselectivities are obtained by removal of competing proton sources and the inclusion of transmetalation steps. The chelate complex A serves as a mechanistic model that makes the usual trial and error search for stereoselective protonating agents unnecessary. The method is applied to stereoselective syntheses of a precursor for methyl epijasmonate and of the insect pheromone (2S,3S)‐diprionyl acetate.

Synthesis and biological activities of methyl 3,7- and 4,5-didehydrojasmonates

Methyl 3,7-didehydrojasmonate was synthesized as an analogue of methyl epijasmonate. This analogue inhibited the germination of lettuce seed more strongly than methyl jasmonate. Methyl 4,5-didehydrojasmonate was also synthesized and its biological activities were comparable to those of methyl jasmonate.

A Convenient Synthesis of (-)-Methyl Epijasmonate

A short, enantioselective synthesis of (-)-methyl epi-jasmonate, ent-1, has been achieved starting from readily available Corey lactone aldehyde 9. The key features include the stereoselective installation of 2,3-cis-disubstituted side-chains by hydrogenation of dienoate 8 and subsequent one-carbon degradation.

Stereochemical Control over Three Contiguous Stereogenic Centers in the Intramolecular Ene Reaction of Activated 1,6-Dienes. Application to the Synthesis of (±)-Methyl Cucurbate and (±)-Methyl Epijasmonate

The influence of a protected alcohol group adjacent to the ene or enophile component on diastereoselectivity in both thermal and Lewis acid-catalyzed 5-(3,4) ene reactions of a series of 1,6-dienes 1−7 has been studied. The results indicate that its effect can be considerable, and in one example, with a gem-dimethyl group on the connecting chain and a large silyl protecting group on the hydroxyl, the diastereocontrol was almost perfect, with three stereogenic centers and one double bond geometry set up in one step, e.g., 4 → 10. This new finding was exploited in a synthesis of epijasmonoid natural products, (±)-methyl cucurbate (19) and (±)-methyl epijasmonate (18) starting from aldehyde 24, where the key step was a highly diastereocontrolled 5-(3,4) ene cyclization 23 → 22.

Methyl Jasmonates in Developing Strawberry Fruit (Fragaria ananassa Duch. Cv. Kent)

Two isomeric methyl jasmonates were isolated from extracts of strawberry fruit (Fragaria ananassa Duch. cv. Kent) by means of micropreparative gas chromatography. Enantiomeric separation and comparison with reference compounds allowed the determination of their absolute configuration as (3R,7S)-(+)-methyl epi-jasmonate and (3R,7R)-(−)-methyl jasmonate, respectively. Their genuine content in fruit was monitored throughout the ripening period from 7 days after anthesis (DAA) to the overripe stage (36 DAA). On a per weight basis, the sum of both isomers had a maximum concentration of 277.5 μg kg-1 in immature fruits and then steadily decreased. The levels of methyl jasmonates in strawberry may affect aroma formation and further events during fruit development. Keywords: Strawberry; Fragaria ananassa; methyl jasmonates; multidimensional preparative GC; enantiomeric separation; flavor; plant growth regulator