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Several species of Lavandula produce essential oils (EOs) consisting mainly of monoterpenes including linalool, one of the most abundant and scent-determining oil constituents. Although R-linalool dominates the EOs of lavenders, varying amounts (depending on the species) of the S-linalool enantiomer can also be found in these plants. Despite its relatively low abundance, S-linalool contributes a sweet, pleasant scent and is an important constituent of lavender EOs. While several terpene synthase genes including R-linalool synthase have been cloned from lavenders many important terpene synthases including S-linalool synthase have not been described from these plants. In this study, we employed RNA-Seq and other complementary sequencing data to clone and functionally characterize the sparsely expressed S-linalool synthase cDNA (LiS-LINS) from Lavandula × intermedia. Recombinant LiS-LINS catalyzed the conversion of the universal monoterpene precursor geranyl diphosphate to S-linalool as the sole product. Intriguingly, LiS-LINS exhibited very low (~ 30%) sequence similarity to other Lavandula terpene synthases, including R-linalool synthase. However, the predicted 3D structure of this protein, including the composition and arrangement of amino acids at the active site, is highly homologous to known terpene synthase proteins. LiS-LINS transcripts were detected in flowers, but were much less abundant than those corresponding to LiR-LINS, paralleling enantiomeric composition of linalool in L. × intermedia oils. These data indicate that production of S-linalool is at least partially controlled at the level of transcription from LiS-LINS. The cloned LiS-LINS cDNA may be used to enhance oil composition in lavenders and other plants through metabolic engineering.

Numerous studies have indicated the pharmacological properties of linalool, a volatile terpene alcohol found in many flowers and spice plants, including anti‐nociceptive, anti‐inflammatory, and neuroprotective activities. The aim of this study was to explore the mechanisms of neuroprotection provided by (±) linalool and its enantiomer, (R)‐(−) linalool against oxygen, and glucose deprivation/reoxygenation (OGD/R) in PC12 cells. PC12 cells were treated with (±) linalool and (R)‐(−) linalool before exposure to OGD/R condition. Cell viability, reactive oxygen species (ROS) production, malondialdehyde (MDA) level, DNA damage, and the levels of proteins related to apoptosis were evaluated using MTT, comet assay, and western blot analysis, respectively. IC50 values for the PC12 cells incubated with (±) linalool and (R)‐(−) linalool were 2700 and 2600 μM after 14 h, as well as 5440 and 3040 μM after 18 h, respectively. Survival of the ischemic cells pre‐incubated with (±) linalool and (R)‐(−) linalool (100 μM of both) increased compared to the cells subjected to the OGD/R alone (p < .001). ROS and MDA formation were also decreased following incubation with (±) linalool and (R)‐(−) linalool compared to the OGD/R group (p < .01). In the same way, pre‐treatment with (±) linalool and (R)‐(−) linalool significantly reduced OGD/R‐induced DNA injury compared to that seen in OGD/R group (p < .001). (±) Linalool and (R)‐(−) linalool also restored Bax/Bcl‐2 ratio and cleaved caspase‐3 and caspase‐9 (p < .001, p < .01) following ischemic injury. The neuroprotective effect of linalool against ischemic insult might be mediated by alleviation of oxidative stress and apoptosis. This study indicated, for the first time, that (±) linalool and its enantiomer, (R)‐(‐) linalool protected PC12 cells against injury induced by oxygen and glucose deprivation/reoxygenation (OGD/R) via the mitigation of oxidative stress and the downregulation of Bax/Bcl‐2, caspase‐3 and caspase‐9, resulting in decreased apoptotic cell death.

Boswellia tree bark exudes oleo-gum resin in response to wounding, which is rich in terpene volatiles. But, the molecular and biochemical basis of wound-induced formation of resin volatiles remains poorly understood. Here, we combined RNA-sequencing (RNA-seq) and metabolite analysis to unravel the terpene synthase (TPS) family contributing to wound-induced biosynthesis of resin volatiles in B. serrata, an economically-important Boswellia species. The analysis of large-scale RNA-seq data of bark and leaf samples representing more than 600 million sequencing reads led to the identification of 32 TPSs, which were classified based on phylogenetic relationship into various TPSs families found in angiosperm species such as TPS-a, b, c, e/f, and g. Moreover, RNA-seq analysis of bark samples collected at 0–24 h post-wounding shortlisted 14 BsTPSs that showed wound-induced transcriptional upregulation in bark, suggesting their important role in wound-induced biosynthesis of resin volatiles. Biochemical characterization of a bark preferentially-expressed and wound-inducible TPS (BsTPS2) in vitro and in planta assays revealed its involvement in resin terpene biosynthesis. Bacterially-expressed recombinant BsTPS2 catalyzed the conversion of GPP and FPP into (S)-( +)-linalool and (E)-(−)-nerolidol, respectively, in vitro assays. However, BsTPS2 expression in Nicotiana benthamiana found that BsTPS2 is a plastidial linalool synthase. In contrast, cytosolic expression of BsTPS2 did not form any product. Overall, the present work unraveled a suite of TPSs that potentially contributed to the biosynthesis of resin volatiles in Boswellia and biochemically characterized BsTPS2, which is involved in wound-induced biosynthesis of (S)-( +)-linalool, a monoterpene resin volatile with a known role in plant defense.

In this study, cetylpyridinium peroxyphosphotungstate was synthesized as an environmentally benign phase transfer catalyst with high catalytic activity from cetylpyridinium chloride, phosphotungstic acid, and hydrogen peroxide. The chemical structure of the catalyst was identified by SEM, XRD, FT-IR, ICP, elemental analysis, XPS, and TGA/DTG, revealing its catalytic activity to be related to the regular and dense distribution of pores on its surface. High catalytic activity was demonstrated in the oxidation of linalool to furanoid and pyranoid linalool oxides using hydrogen peroxide in low toxicity organic solvents such as ethanol and ethyl acetate. The total yield and total selectivity of furanoid and pyranoid linalool oxides were optimized by varying parameters including the catalyst loading, hydrogen peroxide amount, reaction temperature, and reaction time. Optimized conditions providing furanoid and pyranoid linalool oxides with 80.1% total yield were 10 wt% catalyst and 1.16 mL/g 30% H 2 O 2 (vs. linalool) at 30 °C for 1.5 h. This procedure has the advantages of high yield, employing a green oxidant, and non-toxic reagents.

Thyme oil (TO) is derived from the flowers of various plants belonging to the genus Thymus. It has been used as a therapeutic agent since ancient times. Thymus comprises numerous molecular species exhibiting diverse therapeutic properties that are dependent on their biologically active concentrations in the extracted oil. It is therefore not surprising that oils extracted from different thyme plants present different therapeutic properties. Furthermore, the phenophase of the same plant species has been shown to yield different anti-inflammatory properties. Given the proven efficacy of TO and the diversity of its constituents, a better understanding of the interactions of the various components is warranted. The aim of this review is to gather the latest research findings regarding TO and its components with respect to their immunomodulatory properties. An optimization of the various components has the potential to yield more effective thyme formulations with increased potency.

Plant volatile organic compounds (VOCs) mediate many interactions, and the function of common VOCs is especially likely to depend on ecological context. We used a genetic mapping population of wild tobacco, Nicotiana attenuata, originating from a cross of 2 natural accessions from Arizona and Utah, separated by the Grand Canyon, to dissect genetic variation controlling VOCs. Herbivory-induced leaf terpenoid emissions varied substantially, while green leaf volatile emissions were similar. In a field experiment, only emissions of linalool, a common VOC, correlated significantly with predation of the herbivore Manduca sexta by native predators. Using quantitative trait locus mapping and genome mining, we identified an (S)-(+)-linalool synthase (NaLIS). Genome resequencing, gene cloning, and activity assays revealed that the presence/absence of a 766-bp sequence in NaLIS underlies the variation of linalool emissions in 26 natural accessions. We manipulated linalool emissions and composition by ectopically expressing linalool synthases for both enantiomers, (S)-(+)- and (R)-(−)-linalool, reported to oppositely affect M. sexta oviposition, in the Arizona and Utah accessions. We used these lines to test ovipositing moths in increasingly complex environments. The enantiomers had opposite effects on oviposition preference, but the magnitude of the effect depended strongly both on plant genetic background, and complexity of the bioassay environment. Our study reveals that the emission of linalool, a common VOC, differs by orders-of-magnitude among geographically interspersed conspecific plants due to allelic variation in a linalool synthase, and that the response of a specialist herbivore to linalool depends on enantiomer, plant genotype, and environmental complexity.

This study examines the chemical constituents, antioxidant potential, antibacterial mechanism, and antiproliferative activity of Cinnamomum zeylanicum bark essential oil. The compositions of the oil were analyzed by GC-MS, and the major constituents were found to be (E)-cinnamaldehyde (71.50%), linalool (7.00%), β-caryophyllene (6.40%), eucalyptol (5.40%), and eugenol (4.60%). C. zeylanicum essential oil contained remarkable levels of phenolic and bioactive compounds with outstanding ability to scavenge free radicals and inhibit β-carotene oxidation. The growth of pathogenic and spoilage bacteria, especially Gram-positive ones (i.e. Listeria innocua, Staphylococcus aureus, and Bacillus cereus), was highly inhibited by the oil, compared to the Gram-negative pairs (i.e. Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhi). The cells of L. innocua and E. coli (as the most sensitive and resistant strains to the oil, respectively) treated with C. zeylanicum essential oil were observed by scanning electron microscopy to unravel structural changes. It was observed that the essential oil quickly exerted its antibacterial activity through disrupting cell envelope and facilitating the leakage of intracellular compounds. The essential oil had also a dose-dependent antiproliferative effect on adipose-derived mesenchymal stem cells (AT-MSCs), and the cell proliferation could be induced by low concentrations of the oil. The present study indicated that C. zeylanicum essential oil with remarkable antioxidant and antimicrobial properties could be applied to develop novel natural preservatives for food and medicinal purposes.

The purpose of this article is to present recent studies on the antimicrobial properties of linalool, the mechanism of action on cells and detoxification processes. The current trend of employing compounds present in essential oils to support antibiotic therapy is becoming increasingly popular. Naturally occurring monoterpene constituents of essential oils are undergoing detailed studies to understand their detailed effects on the human body, both independently and in doses correlated with currently used pharmaceuticals. One such compound is linalool, which is commonly found in many herbs and is used to flavor black tea. This compound is an excellent fragrance additive for cosmetics, enhancing the preservative effect of the formulations used in them or acting as an anti-inflammatory on mild skin lesions. Previous studies have shown that it is extremely important due to its broad spectrum of biological activities, i.e., antioxidant, anti-inflammatory, anticancer, cardioprotective and antimicrobial. Among opportunistic hospital strains, it is most active against Gram-negative bacteria. The mechanism of action of linalool against microorganisms is still under intensive investigation. One of the key aspects of linalool research is biotransformation, through which its susceptibility to detoxification processes is determined.

Limited evidence has suggested that terpenes found in Cannabis sativa are analgesic, and could produce an “entourage effect” whereby they modulate cannabinoids to result in improved outcomes. However this hypothesis is controversial, with limited evidence. We thus investigated Cannabis sativa terpenes alone and with the cannabinoid agonist WIN55,212 using in vitro and in vivo approaches. We found that the terpenes α-humulene, geraniol, linalool, and β-pinene produced cannabinoid tetrad behaviors in mice, suggesting cannabimimetic activity. Some behaviors could be blocked by cannabinoid or adenosine receptor antagonists, suggesting a mixed mechanism of action. These behavioral effects were selectively additive with WIN55,212, suggesting terpenes can boost cannabinoid activity. In vitro experiments showed that all terpenes activated the CB1R, while some activated other targets. Our findings suggest that these Cannabis terpenes are multifunctional cannabimimetic ligands that provide conceptual support for the entourage effect hypothesis and could be used to enhance the therapeutic properties of cannabinoids.

(S)-(+)-linalool, a valuable acyclic monoterpenol secondary metabolite of plants, finds extensive applications in the food, flavor and fragrance, pharmaceutical, and daily chemical industries. Microbial synthesis offers two pathways for its production, among which the mevalonate (MVA) pathway derived from halophilic archaea is more widely employed. However, the traditional Haloarchaea-type MVA pathway relies on bifunctional enzyme catalysis, consuming 3 molecules of ATP. Moreover, the catalytic activity of natural linalool synthase (LIS) is generally low, failing to meet industrial requirements. Additionally, linalool exhibits significant toxicity to microbial hosts, thereby limiting the production capacity of conventional chassis microorganisms. To address these bottlenecks, this study implemented systematic optimizations: Firstly, the Archaeal mevalonate pathway was reconstructed by replacing the original bifunctional enzyme with two monofunctional enzymes, successfully reducing ATP consumption to 2 molecules. Secondly, through directed screening and rational design, a high-activity linalool synthase mutant, CsMLISI331V/I444L, derived from Coriandrum sativum, was obtained. Furthermore, an enzyme fusion strategy was adopted, involving the introduction of a long flexible linker between key genes, which significantly enhanced catalytic efficiency. Finally, S. marcescens HBQA7ΔsIaAB-pyc, a strain previously screened in our laboratory with broad-spectrum tolerance to terpenoids, was selected as the novel chassis cell. Collectively, these efforts resulted in the construction of a microbial cell factory for the efficient synthesis of (S)-(+)-linalool, laying a solid foundation for industrial-scale production.