New Iridoids and Acyclic Monoterpenoids from the Roots and Rhizomes of Valeriana officinalis var. latifolia.

Five new iridoids, valeralides A-E (1-5), two new acyclic monoterpenoids, valeralides F (6) and G (7), together with two known iridoids (8 and 9), were isolated from the roots and rhizomes of Valeriana officinalis var. latifolia. Their structures were elucidated based on 1D and 2D NMR, as well as HR-ESI-MS spectroscopic data. The absolute configuration of compounds 1-4 were elucidated based on electronic circular dichroism (ECD) calculation. In addition, all the isolates were evaluated for their inhibition on nitric oxide production, cytotoxicity and anti-influenza A virus activity.

Design, synthesis and antiviral evaluation of novel conjugates of the 1,7,7-trimethylbicyclo[2.2.1]heptane scaffold and saturated N-heterocycles via 1,2,3-triazole linker.

A new series of heterocyclic derivatives with a 1,7,7-trimethylbicyclo[2.2.1]heptane fragment was designed, synthesised and biologically evaluated. Synthesis of the target compounds was performed using the Cu(I) catalysed cycloaddition reaction. The key starting substances in the click reaction were an alkyne containing a 1,7,7-trimethylbicyclo[2.2.1]heptane fragment and a series of azides with saturated nitrogen-containing heterocycles. Some of the derivatives were found to exhibit strong antiviral activity against Marburg and Ebola pseudotype viruses. Lysosomal trapping assays revealed the derivatives to possess lysosomotropic properties. The molecular modelling study demonstrated the binding affinity between the compounds investigated and the possible active site to be mainly due to hydrophobic interactions. Thus, combining a natural hydrophobic structural fragment and a lysosome-targetable heterocycle may be an effective strategy for designing antiviral agents.

Transcriptomics Reveals the Molecular Basis for Methyl Jasmonate to Promote the Synthesis of Monoterpenoids in Schizonepeta tenuifolia Briq.

BACKGROUND: Methyl jasmonate has an important effect on the synthesis of plant secondary metabolites. Schizonepeta tenuifolia Briq. has a wide range of pharmacological effects and the secondary metabolites are dominated by monoterpenes (pulegone, menthone). OBJECTIVE: It is essential to determine the changes in secondary metabolites in S. tenuifolia under methyl jasmonate treatment and to probe the molecular mechanism. This can improve the accumulation of secondary metabolites in the medicinal plant S. tenuifolia and enrich the information gene expression at different MeJA levels, which can help to elucidate the molecular mechanism of monoterpenoid synthesis in S. tenuifolia. METHODS: In this study, we determined the changes in the content of monoterpenoids in S. tenuifolia under methyl jasmonate treatment. Meanwhile, we established a transcriptome database of S. tenuifolia under methyl jasmonate level using high-throughput sequencing. RESULTS: A certain concentration of MeJA promoted the accumulation of monoterpenoids in S. tenuifolia. The transcriptome database of S. tenuifolia leaves under 0, 50, 100 and 250 µM MeJA treatment was established. We generated 88,373 unigenes with an N50 length of 2678 bp, of which 50,843 (57.53%) can be annotated in at least one database. Compared with the CK (0 µM) group, 12,557 (50 µM), 15,409 (100 µM) and 13,286 (250 µM) differentially expressed genes were identified. GO and KEGG enrichment analysis revealed that JA signal transduction and monoterpenoid synthesis were the two most significant enrichment pathways. The expression levels of related DEGs involved in JA signaling and monoterpenoid synthesis were significantly up-regulated by MeJA. In addition, our phenotypic and differentially expressed gene association analysis revealed that monoterpenoid biosynthesis in S. tenuifolia was more associated with genes involved in plant trichome branching, phytohormone signaling and transcriptional regulation. CONCLUSIONS: This study confirmed that methyl jasmonate significantly promoted monoterpenoid biosynthesis in S. tenuifolia. A large number of genes responding to methyl jasmonate were associated with JA signaling and monoterpenoid biosynthesis.

Role of CYP6MS subfamily enzymes in detoxification of Sitophilus zeamais after exposure to terpinen-4-ol and limonene.

Food security is an important basis and guarantee to national safety, the loss caused by storage pests was a serious problem which affects the food security widely. Frequent application of chemical pesticides caused several critical crises including the development of resistance, pesticide residues, environmental pollution, and exposure risk to human or non-target organisms. The utilization of volatile components acts as a natural alternative for controlling storage pests has aroused extensive interest in recent years. It has been reported that terpinene-4-ol and limonene showed significant insecticidal activity against Sitophilus zeamais in our previous studies, which was evaluated to have strong influences to CYP450 genes. To determine the links and roles of related genes, we identified the SzCYP6MS subfamily genes which encoded a putative protein of 493 or 494 amino acids. Then, the expression of four CYP6MS subfamily genes were increased significantly under the fumigation stress by terpinen-4-ol and limonene, which was determined by the RT-qPCR analysis compared with non-fumigated colonies. In addition, we determined that RNAi-mediated CYP6MS genes knockdown significantly increased the sensitivity of S. zeamais to terpinen-4-ol and limonene, the mortality rates of insects with knocked down CYP6MS1, CYP6MS5, CYP6MS6, CYP6MS8, and CYP6MS9 genes increased by 25%, 25%, 16%, 17%, and 4% in terpinen-4-ol treatment groups and by 29%, 25%, 15%, 22%, and 3% in limonene treatment groups compared with that in the control groups, respectively. Finally, it was validated that CYP6MS5 exhibited the most stable binding with terpinen-4-ol that was similar to the result between CYP6MS8 and limonene which were verified by molecular docking analysis. In together, this study demonstrates the potential of terpinen-4-ol and limonene used as novel botanical pesticides to control storage pests, thereby reducing application of chemical pesticides and postponing resistance development.

Monoterpene Thiols: Synthesis and Modifications for Obtaining Biologically Active Substances.

Monoterpene thiols are one of the classes of natural flavors that impart the smell of citrus fruits, grape must and wine, black currants, and guava and are used as flavoring agents in the food and perfume industries. Synthetic monoterpene thiols have found an application in asymmetric synthesis as chiral auxiliaries, derivatizing agents, and ligands for metal complex catalysis and organocatalysts. Since monoterpenes and monoterpenoids are a renewable source, there are emerging trends to use monoterpene thiols as monomers for producing new types of green polymers. Monoterpene thioderivatives are also known to possess antioxidant, anticoagulant, antifungal, and antibacterial activity. The current review covers methods for the synthesis of acyclic, mono-, and bicyclic monoterpene thiols, as well as some investigations related to their usage for the preparation of the compounds with antimicrobial properties.

[Monoterpenoids from Paeoniae Radix Rubra based on UPLC-Q-TOF-MS].

The ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry(UPLC-Q-TOF-MS) was used to conduct the qualitative analysis of the monoterpene chemical components from Paeoniae Radix Rubra. Gradient elution was performed on C_(18) HD(2.1 mm×100 mm, 2.5 µm) column with a mobile phase of 0.1% formic acid(A) and acetonitrile(B). The flow rate was 0.4 mL·min~(-1) and the column temperature was 30 ℃. MS analysis was conducted in both positive and negative ionization modes using electrospray ionization(ESI) source. Qualitative Analysis 10.0 was used for data processing. The identification of chemical components was realized by the combination of standard compounds, fragmentation patterns, and mass spectra data reported in the literature. Forty-one monoterpenoids in Paeoniae Radix Rubra extract were identified. Among them, 8 compounds were reported in Paeoniae Radix Rubra for the first time and 1 was presumed to be the new compound 5″-O-methyl-galloylpaeoniflorin or its positional isomer. The method in this study realizes the rapid identification of monoterpenoids from Paeoniae Radix Rubra and provides a material and scientific basis for quality control and further study on the pharmaceutical effect of Paeoniae Radix Rubra.

Density-functional theory of the catnip molecule, nepetalactone.

Nepetalactones belongs to the group of iridoid monoterpenoids, which are present in the aerial parts of nepeta plants. Nepetalactone is an attractant to feline animals causing euphoric effects, while it is a repellent to mosquitoes and cockroaches. It is also a pheromone for several insect aphid species. The main objective of this research was to study the electronic and spectral properties of nepetalactones. We investigated its structural properties using hybrid density-functional theory of B3LYP and WB97XD functional with the 6-311++G(d,p) basis set to optimize the geometry, and then computed the electronic structure, HOMO-LUMO, natural bond orbitals, molecular electronic potential and its contour map. We also obtained spectral signatures of NMR, IR and UV-Vis, and compared them with experimental data from the literature. The DFT study provided different electronic and spectral information that will be of value for further research on making new derivatives of nepetalactones for commercial purposes. Nepetalactones have a promising future in the development of novel mosquito repellents for the control of malaria and arboviral diseases.

Synthesis and Antiviral Properties of Camphor-Derived Iminothiazolidine-4-Ones and 2,3-Dihydrothiazoles.

A set of heterocyclic products was synthesized from natural (+)-camphor and semi-synthetic (-)-camphor. Then, 2-Imino-4-thiazolidinones and 2,3-dihydrothiazoles were obtained using a three-step procedure. For the synthesized compounds, their antiviral activity against the vaccinia virus and Marburg virus was studied. New promising agents active against both viruses were found among the tested compounds.

Essential Oil Compositions of Pinus Species (P. contorta Subsp. contorta, P. ponderosa var. ponderosa, and P. flexilis); Enantiomeric Distribution of Terpenoids in Pinus Species.

Pinus species are important in traditional medicine throughout their ranges, and pine essential oils are of interest in aromatherapy and as topical treatments. In this work, the leaf (needle) essential oils of Pinus ponderosa var. ponderosa and Pinus contorta subsp. contorta from Oregon and Pinus flexilis growing in Idaho, have been obtained by hydrodistillation and analyzed by gas chromatographic techniques. The leaf essential oil of P. ponderosa was dominated by ß-pinene (21.5-55.3%), methyl chavicol (8.5-41.5%), α-pinene (3.6-9.6%), δ-3-carene (3.6-6.2%), and α-terpineol (1.4-5.3%). The major components of P. contorta essential oil were ß-phellandrene (23.8%), terpinen-4-ol (11.0%). The essential oil of P. flexilis was dominated by α-pinene (37.1%), ß-pinene (21.9%), bornyl acetate (12.8%), and camphene (8.5%). Chiral gas chromatography revealed the enantiomeric ratios of α-pinene and limonene to be variable, but (-)-ß-pinene predominated in Pinus essential oils.

Synthesis of Trifluoromethylated Monoterpene Amino Alcohols.

For the first time, monoterpene trifluoromethylated ß-hydroxy-benzyl-O-oximes were synthesized in 81-95% yields by nucleophilic addition of the Ruppert-Prakash reagent (TMSCF3) to the corresponding ß-keto-benzyl-O-oximes based on (+)-nopinone, (-)-verbanone and (+)-camphoroquinone. Trifluoromethylation has been determined to entirely proceed chemo- and stereoselective at the C=O rather than C=N bond. Trifluoromethylated benzyl-O-oximes were reduced to the corresponding α-trifluoromethyl-ß-amino alcohols in 82-88% yields. The structure and configuration of the compounds obtained have been established.

Monoterpenoid biosynthesis by engineered microbes.

Monoterpenoids are C10 isoprenoids and constitute a large family of natural products. They have been used as ingredients in food, cosmetics, and therapeutic products. Many monoterpenoids such as linalool, geraniol, limonene, and pinene are volatile and can be found in plant essential oils. Conventionally, these bioactive compounds are obtained from plant extracts by using organic solvents or by distillation method, which are costly and laborious if high-purity product is desired. In recent years, microbial biosynthesis has emerged as alternative source of monoterpenoids with great promise for meeting the increasing global demand for these compounds. However, current methods of production are not yet at levels required for commercialization. Production efficiency of monoterpenoids in microbial hosts is often restricted by high volatility of the monoterpenoids, a lack of enzymatic activity and selectivity, and/or product cytotoxicity to the microbial hosts. In this review, we summarize advances in microbial production of monoterpenoids over the past 3 years with particular focus on the key metabolic engineering strategies for different monoterpenoid products. We also provide our perspective on the promise of future endeavors to improve monoterpenoid productivity.

Synthesis and Oxidative Transformations of New Chiral Pinane-Type γ-Ketothiols: Stereochemical Features of Reactions.

Chiral γ-ketothiols, thioacetates, thiobenzoate, disulfides, sulfones, thiosulfonates, and sulfonic acids were obtained from ß-pinene for the first time. New compounds open up prospects for the synthesis of other polyfunctional compounds combining a biologically active pinane fragment with various pharmacophore groups. It was shown that the syntheses of sulfanyl and sulfonyl derivatives based on 2-norpinanone are characterized by high stereoselectivity in comparison with similar reactions of pinocarvone. The conditions for the preparation of diastereomerically pure thioacetyl and thiobenzoyl derivatives based on pinocarvone, as well as for the chemoselective oxidation of γ-ketothiols with chlorine dioxide to the corresponding thiolsulfonates and sulfonic acids, were selected. The effect of the VO(acac)2 catalyst on the increase in the yields of thiosulfonates was shown. A new direction of the transformation of thiosulfonates with the formation of sulfones was revealed. In the case of pinocarvone-based sulfones, the configuration is inversed at the C2 atom. An epimerization scheme is proposed.

Novel Bispidine-Monoterpene Conjugates-Synthesis and Application as Ligands for the Catalytic Ethylation of Chalcones.

A number of new chiral bispidines containing monoterpenoid fragments have been obtained. The bispidines were studied as ligands for Ni-catalyzed addition of diethylzinc to chalcones. The conditions for chromatographic analysis by HPLC-UV were developed, in which the peaks of the enantiomers of all synthesized chiral products were separated, which made it possible to determine the enantiomeric excess of the resulting mixture. It was demonstrated that bispidine-monoterpenoid conjugates can be used as the ligands for diethylzinc addition to chalcone C=C double bond but not as inducers of chirality. Besides products of ethylation, formation of products of formal hydrogenation of the chalcone C=C double bond was observed in all cases. Note, that this formation of hydrogenation products in significant amounts in the presence of such catalytic systems was found for the first time. A tentative scheme explaining the formation of all products was proposed.

Composition of Essential Oils from Roots and Aerial Parts of Carpesium cernuum and Their Antibacterial and Cytotoxic Activities.

Carpesium cernuum L., one of the two Carpesium species occurring in Europe, in the Far East and India, found use as a vegetable and a traditional medicinal remedy for several ailments. In the present study, compositions of essential oils distilled from roots and shoots of C. cernuum plants, cultivated in the open field, have been studied by GC-MS-FID supported by NMR spectroscopy. The analyses led to the identification of 120 compounds in total, of which 115 were found in aerial parts and 37 in roots of the plants. The major constituents found in the oil from shoots were: α-pinene (35%) and 2,5-dimethoxy-p-cymene (thymohydroquinone dimethyl ether, 12%), whereas 2,5-dimethoxy-p-cymene (55%), thymyl isobutyrate (9%) and thymol methyl ether (8%) predominated in the essential oil obtained from the roots. Antibacterial and cytotoxic activities of the essential oils distilled from C. cernuum were also tested. The essential oil from aerial parts of the plant demonstrated good inhibitory activity against Staphylococcus aureus ATCC 29213 and Escherichia coli ATCC 25922 (MIC: 15.6 µL/mL).

Citral and geraniol induce necrotic and apoptotic cell death on Saccharomyces cerevisiae.

Essential oils and their main components, monoterpenes, have been proven to be important alternatives for the control of pathogenic and spoiling microorganisms, but the mode of action of these compounds is poorly understood. This work aimed to determine the mode of action of citral and geraniol on the model yeast Saccharomyces cerevisiae using a flow cytometry approach. Exponentially growing yeast cells were treated with different concentrations of citral and geraniol for 3 h, and evaluated for cell wall susceptibility to glucanase, membrane integrity, reactive oxygen species (ROS) accumulation, mitochondrial membrane potential, and metacaspase activity. Results provide strong evidence that citral and geraniol acute fungicidal activity against Saccharomyces cells involves the loss of membrane and cell wall integrity resulting in a dose-dependent apoptotic/necrotic cell death. However, yeast cells that escape this first cell membrane disruption, particularly evident on sub-lethal concentration, die by metacaspase-mediated apoptosis induced by the accumulation of intracellular ROS. The deleted mutant on the yca1 gene showed high tolerance to citral and geraniol.

Investigation of monoterpenoid resistance mechanisms in Pseudomonas putida and their consequences for biotransformations.

Monoterpenoids are widely used in industrial applications, e.g. as active ingredients in pharmaceuticals, in flavor and fragrance compositions, and in agriculture. Severe toxic effects are known for some monoterpenoids making them challenging compounds for biotechnological production processes. Some strains of the bacterium Pseudomonas putida show an inherent extraordinarily high tolerance towards solvents including monoterpenoids. An understanding of the underlying factors can help to create suitable strains for monoterpenoids de novo production or conversion. In addition, knowledge about tolerance mechanisms could allow a deeper insight into how bacteria can oppose monoterpenoid containing drugs, like tea tree oil. Within this work, the resistance mechanisms of P. putida GS1 were investigated using selected monoterpenoid-hypertolerant mutants. Most of the mutations were found in efflux pump promoter regions or associated transcription factors. Surprisingly, while for the tested monoterpenoid alcohols, ketone, and ether high efflux pump expression increased monoterpenoid tolerance, it reduced the tolerance against geranic acid. However, an increase of geranic acid tolerance could be gained by a mutation in an efflux pump component. It was also found that increased monoterpenoid tolerance can counteract efficient biotransformation ability, indicating the need for a fine-tuned and knowledge-based tolerance improvement for production strain development.Key points• Altered monoterpenoid tolerance mainly related to altered activity of efflux pumps.• Increased tolerance to geranic acid surprisingly caused by decreased export activity. • Reduction of export activity can be beneficial for biotechnological conversions.

New Monoterpenoids and Polyketides from the Deep-Sea Sediment-Derived Fungus Aspergillus sydowii MCCC 3A00324.

Chemical study of the secondary metabolites of a deep-sea-derived fungus Aspergillus sydowii MCCC 3A00324 led to the isolation of eleven compounds (1-11), including one novel (1) and one new (2) osmane-related monoterpenoids and two undescribed polyketides (3 and 4). The structures of the metabolites were determined by comprehensive analyses of the NMR and HRESIMS spectra, in association with quantum chemical calculations of the 13C NMR, ECD, and specific rotation data for the configurational assignment. Compound 1 possessed a novel monoterpenoid skeleton, biogenetically probably derived from the osmane-type monoperpenoid after the cyclopentane ring cleavage and oxidation reactions. Additionally, compound 3 was the first example of the α-pyrone derivatives bearing two phenyl units at C-3 and C-5, respectively. The anti-inflammatory activities of 1-11 were tested. As a result, compound 6 showed potent inhibitory nitric oxide production in lipopolysaccharide (LPS)-activated BV-2 microglia cells with an inhibition rate of 94.4% at the concentration of 10 µM. In addition, a plausible biosynthetic pathway for 1 and 2 was also proposed.

Essential Oils Extracted from Different Species of the Lamiaceae Plant Family as Prospective Bioagents against Several Detrimental Pests.

On the basis of the side effects of detrimental synthetic chemicals, introducing healthy, available, and effective bioagents for pest management is critical. Due to this circumstance, several studies have been conducted that evaluate the pesticidal potency of plant-derived essential oils. This review presents the pesticidal efficiency of essential oils isolated from different genera of the Lamiaceae family including Agastache Gronovius, Hyptis Jacquin, Lavandula L., Lepechinia Willdenow, Mentha L., Melissa L., Ocimum L., Origanum L., Perilla L., Perovskia Kar., Phlomis L., Rosmarinus L., Salvia L., Satureja L., Teucrium L., Thymus L., Zataria Boissier, and Zhumeria Rech. Along with acute toxicity, the sublethal effects were illustrated such as repellency, antifeedant activity, and adverse effects on the protein, lipid, and carbohydrate contents, and on the esterase and glutathione S-transferase enzymes. Chemical profiles of the introduced essential oils and the pesticidal effects of their main components have also been documented including terpenes (hydrocarbon monoterpene, monoterpenoid, hydrocarbon sesquiterpene, and sesquiterpenoid) and aliphatic phenylpropanoid. Consequently, the essential oils of the Lamiaceae plant family and their main components, especially monoterpenoid ones with several bioeffects and multiple modes of action against different groups of damaging insects and mites, are considered to be safe, available, and efficient alternatives to the harmful synthetic pesticides.

Cordatols A-D, four new anti-inflammatory bis-monoterpenoids from Illigera cordata.

Cordatols A-D (1-4), four new limonene-derived bis-monoterpenoids plausibly biosynthesized via hetero-Diels-Alder cyclization and sequential hydrolyses of their monoterpene precursors, were isolated from the aerial parts of Illigera cordata. The structures, including absolute configuration, were established by spectroscopic analysis and further confirmed by a two-steps bioinspired chemical transformation. Moreover, compounds 1-4 exhibited moderate in vitro anti-inflammatory activity with IC50 values ranging from 17.5 to 24.6 µM. This study may provide a novel structural template for potential anti-inflammatory agent discovery.

Practical method for increasing optical purity of cis-verbenol.

R/S mixture of monoterpene alcohol cis-verbenol can be separated in preparative scale by its conversion into phthalic mono-ester and subsequent crystallization of its diastereomeric salts with (R)-α-methylbenzylamine and (S)-α-methylbenzylamine. Finally, basic methanolysis of the resolved phthalic mono-esters results (S)-cis-verbenol and (R)-cis-verbenol in high enantiomeric and diastereomeric purity.