Cyclization mechanism of monoterpenes catalyzed by monoterpene synthases in dipterocarpaceae

Monoterpenoids are typically present in the secretory tissues of higher plants,and their biosynthesis is catalyzed by the action of monoterpene synthases(MTSs).However,the knowledge about these enzymes is restricted in a few plant species.MTSs are responsible for the complex cyclization of monoterpene precursors,resulting in the production of diverse monoterpene products.These enzymatic reactions are considered exceptionally complex in nature.Therefore,it is crucial to understand the catalytic mechanism of MTSs to elucidate their ability to produce diverse or specific monoterpenoid products.In our study,we analyzed thirteen genomes of Dipterocarpaceae and identified 38 MTSs that generate a variety of monoterpene products.By focusing on four MTSs with different product spectra and analyzing the formation mechanism of acyclic,monocyclic and bicyclic products in MTSs,we observed that even a single amino acid mutation can change the specificity and diversity of MTS products,which is due to the synergistic effect between the shape of the active cavity and the stabilization of carbon-positive intermediates that the mutation changing.Notably,residues N340,I448,and phosphoric acid groups were found to be significant contributors to the stabilization of intermediate terpinyl and pinene cations.Alterations in these residues,either directly or indirectly,can impact the synthesis of single monoterpenes or their mixtures.By revealing the role of key residues in the catalytic process and establishing the interaction model between specific residues and complex monoterpenes in MTSs,it will be possible to reasonably design and engineer different catalytic activities into existing MTSs,laying a foundation for the artificial design and industrial application of MTSs.

Identification of key gene networks controlling monoterpene biosynthesis during grape ripening by integrating transcriptome and metabolite profiling

Monoterpenes are typical aroma components of muscat grape cultivars,providing pleasant floral and fruity aromas to grapes and wines.However,the molecular mechanism of monoterpene biosynthesis between muscat and non-muscat grape remains unclear.Here,the muscat grape cultivar‘Jumeigui’and the non-muscat grape cultivar‘Kyoho’were chosen as plant materials for a comprehensive transcriptome and metabolite analysis.The gas chromatography-mass spectrometry(GC-MS)analysis demonstrated that a total of 27 and 23 monoterpene compounds were identified and quantified in the‘Jumeigui’and‘Kyoho’grape,respectively.‘Jumeigui’grape accumulated significantly higher concentrations of monoterpenes than‘Kyoho’grape.Furthermore,geraniol,linalool,geranic acid,and β-citronellol might be important odorants contributing to the floral character of the‘Jumeigui’grape due to the high levels odor activity values(OAVs).Transcriptome analysis demonstrated that the expression profiles of VvDXS,VvGGPPS.SSU1,Vv TPS-b/g showed a positive correlation with monoterpene accumulation in grapes.In addition,the expression patterns of the genes involved in jasmonic acid(JA)synthesis and signal were also positively correlated with monoterpene accumulation.All these results will help guide the functional verification of candidate genes related to monoterpene biosynthesis,as well as identify the master transcriptional and hormonal regulators of this pathway in grapes.

Itoside O,a new linear monoterpene glycoside from the bark and twigs of Itoa orientalis

To investigate the chemical components of the barks and twigs ofltoa orientalis. A new linear monoterpene glycoside named itoside O was isolated from the crude extract of Itoa orientalis together with 11 known compounds. The new compound was identified to be 3,7-dimethyl-1, 6-octadien-3, 10-dihydroxyl-10-O-α-L-arabinopyranosyl （1 -→6）-O-β-D-glucopyranoside by 1D and 2D NMR analysis, and all known compounds were isolated from this plant for the first time.

Structural characterization of monoterpene indole alkaloids in ethanolic extracts of Rauwolfia species by liquid chromatography with quadrupole time-of-flight mass spectrometry

Rauwolfia species(Apocynaceae) are medicinal plants well known worldwide due to its potent bioactive monoterpene indole alkaloids(MIAs) such as reserpine,ajmalicine,ajmaline,serpentine and yohimbine.Reserpine,ajmalicine and ajmaline are powerful antihypertensive,tranquilizing agents used in hypertension.Yohimbine is an aphrodisiac used in dietary supplements.As there is no report on the comparative and comprehensive phytochemical investigation of the roots of Rauwolfia species,we have developed an efficient and reliable liquid chromatography-tandem mass spectrometry(LC–MS/MS) method for ethanolic root extract of Rauwolfia species to elucidate the fragmentation pathways for dereplication of bioactive MIAs using highperformance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry(HPLC–ESI–QTOF–MS/MS) in positive ion mode.We identified and established diagnostic fragment ions and fragmentation pathways using reserpine,ajmalicine,ajmaline,serpentine and yohimbine.The MS/MS spectra of reserpine,ajmalicine,and ajmaline showed C-ring-cleavage whereas E-ring cleavage was observed in serpentine via Retro Diels Alder(RDA).A total of 47 bioactive MIAs were identified and characterized on the basis of their molecular formula,exact mass measurements and MS/MS analysis.Reserpine,ajmalicine,ajmaline,serpentine and yohimbine were unambiguously identified by comparison with their authentic standards and other 42 MIAs were tentatively identified and characterized from the roots of Rauwolfia hookeri,Rauwolfia micrantha,Rauwolfia serpentina,Rauwolfia verticillata,Rauwolfia tetraphylla and Rauwolfia vomitoria.Application of LC–MS followed by principal component analysis(PCA) has been successfully used to discriminate among six Rauwolfia species.

Monoterpene Glycosides from the Roots of Paeonia lactiflora

A new monoterpene glycoside, together with nine known ones, 3-O-methylpaeoniflorin, mudanpioside J, paeoniflorin, benzoylpaeoniflorin, oxypaeoniflorin, benzoyloxypaeoniflorin, oxybenzoylpaeoniflorin, albiflorin and lactiflorin, was isolated from the roots of Paeonia lactiflora Pall.. The structure of the new compound was elucidated as galloylalbiflorin by the spectro- scopic evidence including ESI-MS, 1D- and 2D-NMR spectra.

Paeonivayin, A New Monoterpene Glycoside from Paeonia delavayi

A new monoterpene glycoside named paeonivayin with other seven known compounds were isolated from the roots of Paeonia delavayi Franch. and their structures were determined by means of spectroscopic studies.

Two New Monoterpene Diglycosides from Winchia calophylla A.DC

Two new monoterpene diglycosides, wincaloside A (1) and wincaloside B (2), along with loganin (3) were isolated from the stem barks of Winchia calophylla A. DC. The structures of 1 and 2 were established by spectroscopic and chemical methods.

A New Monoterpene Glycoside from Swertia punicea

A new monoterpene glycoside, 2,6-dimethyl-2E,6E-octadienoic acid 1,6'-lactone 8-beta-D-glucopyranoside, was isolated from Swertia punicea, accompanying with six known compounds 1-O-primeverosyl-3,7-dimethoxy-8-hydroxyxanthone, 1-O-primeverosyl-3,7,8-tri-methoxyxan-thone, epi-eustomoside, 1-hydroxy-3,7,8-trimethoxyxanthone, 1,8-dihydroxy-3,7-dimethoxy xanthone and isovitexine. Their structures were elucidated based on spectral evidence.

A New Monoterpene Glycoside from Paeonia veitchii

A new monoterpene glycoside, acetoxypaeoniflorin, was isolated from the root cortex of Paeonia veitchii Lynch.. The structure was elucidated by spectral methods.

A New Monoterpene Glucoside from the Leaves of Betula platyphylla Suk.

A new monoterpene glucoside. (2E,67.)-2.6-dimethyl-8-beta -D-glucosyloxy-2,6-octadienoic acid, was isolated from the leaves of Betula platyphylla Suk. The structure was established by spectroscopic data.

A Novel Monoterpene Glycoside from Swertia mileensis

A novel monoterpene glycoside, mileenside, was isolated from Swertia mileensis by repeated normal and reverse phase silica gel chromatography and its structure was elucidated mainly based on spectral evidence.

Two new monoterpene glycosides from Doellingeria scaber

Two new methane-type monoterpene glycosides were isolated from the roots of Doellingeria scaber. Their structures were identified as trans-p-menthane-1α,2β,8-triol 8-O-β-D-（3′,6′-diangeloyloxy）-glucopyranoside and trans-p-menthane-1α,2β,8-triol 8-O-β-D-（3′-angeloyloxy,6′-isobutyloxy）-glucopyranoside based on 1D and 2D NMR spectroscopy.

New monoterpene phenyl ethers from Illicium micranthum

Seven new monoterpene phenyl ethers,namely micranthumnins A-G(1-7),were isolated from the stem bark of Illicium micranthum(Illiciaceae).Their structures were elucidated by comprehensive spectroscopic analyses including MS,IR,1D and 2D NMR.All compounds were evaluated for their anti-AChE activities.

A Monoterpene Glycoside from Ehinacea purpurea

Aim To separate and identify chemical constituents of Ehinacea purpurea . Methods Five compounds were isolated from the plant using chromatography. Their structures were elucidated by spectroscopy. Results Five compounds were isolated and their structures were identified as 2, 6 dimethyl 7 octene 2, 3, 6 triol 2 O β D glucopyranoside (1), 7, 8 furocoumarin (2), 6 methoxy 7 hydroxycoumarin (3), caffeic acid (4), methyl caffeate (5), and ethyl caffeate (6). Conclusion All these compounds were obtained from the plant for the first time.

Highly Oxygenated Monoterpenes from Eupatorium fortunei

A pair of epimers of highly-oxygenated monoterpenes were isolated from the traditional Chinese medicine Eupatorium fortunei. Their structures were elucidated on the basis of the spectral analysis as （1R＊, 2S＊, 3R＊, 4R＊, 6S＊）-1, 2, 3, 6-tetrehydroxy-p-menthane （1） and （1S＊, 2S＊, 3S＊, 4R＊, 6R＊）-1, 2, 3, 6-tetrehydroxy-p-menthane （2）.

Dissectol A, A Novel Monoterpene Glycoside from Incarvillea dissectifoliola

Dissectol A, a novel monoterpene glycoside was isolated from the methanol part of the 95% EtOH extract of Incarvillea dissecfoliola and its structure was determined by 1D and 2D NMR data.

Larvicidal efficacy of monoterpenes against the larvae of Anopheles gambiae

Objective:To evaluate the larvicidal efficacy of eight volatile components of essential oils against 3rd instar larvae of Anopheles gambiae s.s.Methods:Larvicidal effects of each compound were evaluated in both laboratory and semi-field trials.Stock solution was prepared and serial dilutions were made in six concentrations for each compound.A total of 20 larvae were exposed to larvicides for each replicate and monitored at intervals of 12,24,48 and 72 h.Larvae monitoring was done on basis of dead and live larvae in all intervals.Results:All assayed compounds were larvicides and presented varying degrees of larval toxicity,with LC50 values ranging from 1.28 to 1 938.92 mg/L depending on the treatment time(12,24,48 or 72 h).(-)-Perillyl alcohol presented the strongest larvicidal activity towards Anopheles gambiae larvae,with LC_(50) values of 73.60,18.36,1.72 and1.28 mg/L after 12,24,48 and 72 h of exposure,respectively.The next strongest were(-)-isopulegol(LC_(50)= 135.10,49.39,34.39 and 20.22 mg/L) and(-)-carvone epoxide(LC_(50)= 168.86,124.74,80.84 and 23.46 mg/L).After 12,24 and 48 h of treatment,hydroxydihydrocarvone was the least toxic compound,with LC_(50) values of 1 938.92,1 172.18 and 401.03 mg/L,respectively.Conclusions:The data obtained in this study suggest that all evaluated monoterpenes,especially(-)-perillyl alcohol,have remarkable larvicidal effects and may be considered as potential sources for the development of suitable natural larvicides for mosquito management programs.Further small-scale field trials should be conducted.

Eucaglobulin, A New Complex of Gallotannin and Monoterpene from Eucalyptus globulus

Eucaglobulin 1, a new complex of gallotannin and monoterpene, was isolated from the leaves of Eucalyptus globulus. Its structure was determined by spectral methods.

Monoterpene hydrocarbons,major components of the dried leaves essential oils of five species of the genus Eucalyptus from Cote d’Ivoire

The chemical composition of the essential oils obtained from the dried leaves of five species of the genus Eucalyptus (E. camaldulensis, E. de-glupta, E. grandis, E. torelliana, E. urophylla) growing in C?te d’Ivoire, was analyzed by means of GC and GC/MS. The density and the refractive index were measured. The major components of all these oils are: α-pinene, β-pinene, α-phellandrene, limonene, γ-terpinene, p-cymene and β-caryo-phyllene. The particularity of these oils is their monoterpene hydrocarbons major components.

Serum monoterpene levels, glucose homeostasis, lipid profiles, and metabolic syndrome in adults: NHANES, 2013–2014

Monoterpenes are organic compounds which have been studied for their medicinal benefits.However,the association between monoterpene exposure and metabolic parameters in humans is unknown.We investigated the connection between three specific monoterpenes(α-pinene,β-pinene,and limonene),glucose homeostasis biomarkers,lipid profiles,and metabolic syndrome(MS)in 1627 adults from the National Health and Nutrition Examination Survey(NHANES)2013–2014.We found serum levels ofα-pinene andβ-pinene were positively associated with fasting glucose,total cholesterol,triglyceride,and apolipoprotein B.In addition,increased levels of limonene andΣmonoterpene(sum of three monoterpene chemicals)were linked to higher insulin,β-cell function,total cholesterol,low density lipoprotein cholesterol(LDL-C),triglycerides,and apolipoprotein B.Participants with all three monoterpenes above the 50th percentile had notably higher values for total cholesterol and triglycerides compared to those with all three monoterpenes below the 50th percentile(P for trend<0.001).Regarding MS,higher serum concentrations ofα-pinene were linked to an increased risk of high-density lipoprotein cholesterol(HDL-C)insufficiency and hypertriglyceridemia.Elevated concentrations ofβ-pinene were associated with a higher prevalence of hypertriglyceridemia.Moreover,increased levels of limonene andΣmonoterpene were connected to a higher risk of MS,larger waist circumference,low HDL-C,hypertriglyceridemia,and higher blood pressure according to MS criteria.In conclusion,serum monoterpenes levels were linked to glucose regulation,lipid profiles,and indicators of MS.Further studies are necessary to clarify the potential causal relationships.