The biosynthesis of thymol, carvacrol, and thymohydroquinone in Lamiaceae proceeds via cytochrome P450s and a short-chain dehydrogenase

Whole-cell bioconversion for producing thymoquinone by engineered Saccharomyces cerevisiae

Thymoquinone, extracted from the black seeds of Nigella sativa, is a natural substance with highly beneficial effects against various human diseases. In this study, we aimed to construct a Saccharomyces cerevisiae strain that, produce thymoquinone from thymol, a relatively inexpensive substrate. To achieve this, cytochrome P450 from Origanum vulgare was expressed in S. cerevisiae for the bioconversion of thymol to thymoquinone, with the co-expression of cytochrome P450 reductase (CPR) from Arabidopsis thaliana, ATR1. Additionally, flexible linkers were used to connect these two enzymes. Furthermore, modifications were performed to expand the endoplasmic reticulum (ER) space, leading to increased thymoquinone production. After integrating the genes into the chromosome and optimizing the media components, a significant improvement in the thymol-to-thymoquinone conversion rate and yield were achieved. This study represents a possibility of the production of thymoquinone, a bioactive ingredient of a plant, using an engineered microbial cell.

Assessment of Antimicrobial and Cytotoxic Activities of Liposomes Loaded with Curcumin and Lippia origanoides Essential Oil

(1) Introduction: Curcumin and Lippia origanoides essential oils have a broad spectrum of biological activities; however, their physicochemical instability, low solubility, and high volatility limit their therapeutic use. Encapsulation in liposomes has been reported as a feasible approach to increase the physicochemical stability of active substances, protect them from interactions with the environment, modulate their release, reduce their volatility, improve their bioactivity, and reduce their toxicity. To date, there are no reports on the co-encapsulation of curcumin and Lippia origanoides essential oils in liposomes. Therefore, the objective of this work is to prepare and physiochemical characterize liposomes loaded with the mixture of these compounds and to evaluate different in vitro biological activities. (2) Methods: Liposomes were produced using the thin-layer method and physiochemical characteristics were calculated. The antimicrobial and cytotoxic activities of both encapsulated and non-encapsulated compounds were evaluated. (3) Results: Empty and loaded nanometric-sized liposomes were obtained that are monodisperse and have a negative zeta potential. They inhibited the growth of Staphylococcus aureus and did not exhibit cytotoxic activity against mammalian cells. (4) Conclusions: Encapsulation in liposomes was demonstrated to be a promising strategy for natural compounds possessing antimicrobial activity.

Phytochemical Composition, Antioxidant and Antimicrobial Activity of Three Monarda Species: M. bradburiana L. C. Beck, M. × media Willd., and M. punctata L

Plants of the genus Monarda receive growing interest as the sources of herbal raw materials with wide range of potential applications in food, cosmetics, and phytopharmaceutical industry. This study aimed to evaluate the differences in chemical characteristics and biological activity among different organs of plants representing three underinvestigated species of this genus: Monarda bradburiana L. C. Beck, Monarda × media Willd., and Monarda punctata L. The content of phenolic compounds and the antioxidant activity of leaves, stems, and inflorescences were determined. Essential oil (EO) content, composition, and antimicrobial activity were also examined. M. punctata leaves and inflorescences had the highest EO content (4.43 % and 5.59 %, respectively), with carvacrol as a dominant constituent. Leaf EO was also rich in thymoquinone (17.48 %). In EOs of M. bradburiana and M. × media, thymol dominated. EOs inhibited the growth of all tested strains of microorganisms at a concentration of 0.625 μL×mL-1. The studied plant organs were rich in phenolic compounds, especially rosmarinic acid. M. bradburiana inflorescences were distinguished by high linarin content. Differences in flavonoid distribution seem to have special chemotaxonomic importance. Further research is needed to facilitate standardisation of the investigated plant organs as potential new herbal raw materials.

Comparison of data processing strategies using commercial vs. open-source software in GC-Orbitrap-HRMS untargeted metabolomics analysis for food authentication: thyme geographical differentiation and marker identification as a case study

Untargeted analysis of gas chromatography-high-resolution mass spectrometry (GC-HRMS) data is a key and time-consuming challenge for identifying metabolite markers in food authentication applications. Few studies have been performed to evaluate the capability of untargeted data processing tools for feature extraction, metabolite annotation, and marker selection from untargeted GC-HRMS data since most of them are focused on liquid chromatography (LC) analysis. In this framework, this study provides a comprehensive evaluation of data analysis tools for GC-Orbitrap-HRMS plant metabolomics data, including the open-source MS-DIAL software and commercial Compound Discoverer™ software (designed for Orbitrap data processing), applied for the geographical discrimination and search for thyme markers (Spanish vs. Polish differentiation) as the case study. Both approaches showed that the feature detection process is highly affected by unknown metabolites (Levels 4-5 of identification confidence), background signals, and duplicate features that must be carefully assessed before further multivariate data analysis for reliable putative identification of markers. As a result, Compound Discoverer™ and MS-DIAL putatively annotated 52 and 115 compounds at Level 2, respectively. Further multivariate data analysis allowed the identification of differential compounds, showing that the putative identification of markers, especially in challenging untargeted analysis, heavily depends on the data processing parameters, including available databases used during compound annotation. Overall, this method comparison pointed out both approaches as good options for untargeted analysis of GC-Orbitrap-HRMS data, and it is presented as a useful guide for users to implement these data processing approaches in food authenticity applications depending on their availability.

Metabolism of phenolic compounds catalyzed by Tomato CYP736A61

Cytochrome P450s (CYPs) regulate plant growth and stress responses by producing diverse primary and secondary metabolites. However, the function of many plant CYPs remains unknown because, despite their structural similarity, predicting the enzymatic activity of CYPs is difficult. In this study, one member of the CYP736A subfamily (CYP736A61) from tomatoes was isolated and characterized its enzymatic functions. CYP736A61 was successfully expressed in Escherichia coli through co-expression with molecular chaperones. The purified CYP736A61 showed hydroxylation activity toward 7-ethoxycoumarin, producing 7-hydroxycoumarin or 3-hydroxy 7-ethoxycoumarin. Further substrate screening revealed that dihydrochalcone and stilbene derivates (resveratrol and polydatin) are the substrates of CYP736A61. CYP736A61 also mediated the hydroxylation of resveratrol and polydatin, albeit with low activity. Importantly, CYP736A61 mediated the cleavage of resveratrol and polydatin as well as pinostilbene and pterostilbene. Interestingly, CY736A61 also converted phloretin to naringenin chalcone. These results suggest that CYP736A61 is a novel CYP enzyme with stilbene cleavage activity.

Subcellular compartmentalization in the biosynthesis and engineering of plant natural products

Plant natural products (PNPs) are specialized metabolites with diverse bioactivities. They are extensively used in the pharmaceutical, cosmeceutical and food industries. PNPs are synthesized in plant cells by enzymes that are distributed in different subcellular compartments with unique microenvironments, such as ions, co-factors and substrates. Plant metabolic engineering is an emerging and promising approach for the sustainable production of PNPs, for which the knowledge of the subcellular compartmentalization of their biosynthesis is instrumental. In this review we describe the state of the art on the role of subcellular compartments in the biosynthesis of major types of PNPs, including terpenoids, phenylpropanoids, alkaloids and glucosinolates, and highlight the efforts to target biosynthetic pathways to subcellular compartments in plants. In addition, we will discuss the challenges and strategies in the field of plant synthetic biology and subcellular engineering. We expect that newly developed methods and tools, together with the knowledge gained from the microbial chassis, will greatly advance plant metabolic engineering.

Carvacrol is potential molecule for diabetes treatment

Diabetes is an important chronic disease that can lead to various negative consequences and complications. In recent years, several new alternative treatments have been developed to improve diabetes. Carvacrol found in essential oils of numerous plant species and has crucial potential effects on diabetes. The anti-diabetic effects of carvacrol have also been comprehensively studied in diabetic animal and cell models. In addition, carvacrol could improve diabetes through affecting diabetes-related enzymes, insulin resistance, insulin sensitivity, glucose uptake, anti-oxidant, and anti-inflammatory mechanisms. The use of carvacrol alone or in combination with anti-diabetic therapies could show a significant potential effect in the treatment of diabetes. This review contributes an overview of the effect of carvacrol in diabetes and anti-diabetic mechanisms.

Physicochemical Characteristics, Antioxidant Properties, Aroma Profile, and Sensory Qualities of Value-Added Wheat Breads Fortified with Post-Distillation Solid Wastes of Aromatic Plants

The influence of incorporation of post-distillation solid wastes of the aromatic plants (SWAP), oregano, rosemary, lemon balm, and spearmint into wheat breads at 1% and 2% levels on their physicochemical and sensorial properties, and antioxidant and volatile profiles were investigated. SWAP breads had darker crumbs and crust and greener crumbs compared to the control, but rather similar loaf specific volume and textural attributes (crust puncture test and crumb Texture Profile Analysis). Although the mold growth on bread crumb surface was not inhibited by SWAP presence, LC-DAD-MS revealed a large increase in terpenoids, like carnosic acid (all SWAP), carnosol (rosemary) and carvacrol (oregano), phenolic (rosmarinic and salvianolic) acids and flavonoids in bread with SWAP inclusion, leading to enhanced antioxidant capacity (ABST, DPPH and FRAP assays). The distinct aromatic plant flavors were detected in the fortified breads by trained assessors and confirmed by SPME-GC/MS volatile analysis, showing high levels of terpenoids in SWAP breads, like carvacrol (oregano), caryophyllene (rosemary and lemon balm), and carvone (spearmint), and rendering the 2% fortification unacceptable by consumers. Nevertheless, breads with 1% oregano or rosemary waste had similar control overall acceptability scores, indicating that SWAP can be a promising ingredient for developing antioxidant-enriched wheat breads.

Essential Oils of Artemisia frigida Plants (Asteraceae): Conservatism and Lability of the Composition

Plants of arid regions have adapted to harsh environments during the long span of their evolution and have developed a set of features necessary for their survival in water-limited conditions. Artemisia frigida Willd. (Asteraceae) is a widely distributed species possessing significant cenotic value in steppe ecosystems due to its high frequency and abundance. This study examines different patterns of formation of essential oil composition in A. frigida plants under the influence of heterogeneous factors, including climate and its integral characteristics (HTC, Cextr, SPEI and others). The work is based on the results of our research conducted in Russia (Republic of Buryatia, Irkutsk region), Mongolia, and China, from 1998 to 2021. A total of 32 constant compounds have been identified in the essential oil of A. frigida throughout its habitat range in Eurasia, from Kazakhstan to Qinghai Province, China. Among them, camphor, 1,8-cineol and bornyl acetate are the dominant components, contained in 93-95% of the samples. Among the sesquiterpenoids, germacrene D is the dominant component in 67% of the samples. The largest variability within the composition of the essential oils of A. frigida is associated with significant differences in the climatic parameters when plants grow in high-altitude and extrazonal conditions.

The effect of induced polyploidy on phytochemistry, cellular organelles and the expression of genes involved in thymol and carvacrol biosynthetic pathway in thyme (Thymus vulgaris)

Induced polyploidy usually results in larger vegetative and reproductive plant organs. In order to study the effect of chromosome doubling on Thymus vulgaris, three levels of colchicine concentration including 0.1, 0.3 and 0.5% (w/v) were applied for 6, 12 and 24 hours on apical meristem of 2- and 4-leaf seedlings. Ploidy level was evaluated by flow cytometry and microscopic chromosome counting. Chemical composition of essential oils extracted by hydro-distillation was analyzed by gas Chromatography/mass spectrometry (GC/MS) and gas Chromatography (GC). The application of 0.3% colchicine at 4-leaf seedling for 6 hours resulted in the highest survival rate and the highest number of tetraploid plants. Cytogenetic and flow cytometry analyses confirmed the increase of chromosome number from 2n=2x=30 in diploids to 2n=4x=60 in induced tetraploids. Tetraploid plants had larger leaves, taller and thicker stems, dense branching, longer trichome, larger stomata, larger guard cells, and decreased number of stomata. The number of chloroplasts and mitochondria increased significantly in tetraploid plants by 1.66 and 1.63 times, respectively. The expression of CYP71D178, CYP71D180 and CYP71D181 increased in tetraploids by 3.27, 7.39 and 2.15 times, respectively, probably resulting in higher essential oil compounds, as tetraploids outyielded the diploid plants by 64.7% in essential oil, 40.9% in thymol and 18.6% in carvacrol content.

Spice-Derived Phenolic Compounds: Potential for Skin Cancer Prevention and Therapy

Skin cancer is a condition characterized by the abnormal growth of skin cells, primarily caused by exposure to ultraviolet (UV) radiation from the sun or artificial sources like tanning beds. Different types of skin cancer include melanoma, basal cell carcinoma, and squamous cell carcinoma. Despite the advancements in targeted therapies, there is still a need for a safer, highly efficient approach to preventing and treating cutaneous malignancies. Spices have a rich history dating back thousands of years and are renowned for their ability to enhance the flavor, taste, and color of food. Derived from various plant parts like seeds, fruits, bark, roots, or flowers, spices are important culinary ingredients. However, their value extends beyond the culinary realm. Some spices contain bioactive compounds, including phenolic compounds, which are known for their significant biological effects. These compounds have attracted attention in scientific research due to their potential health benefits, including their possible role in disease prevention and treatment, such as cancer. This review focuses on examining the potential of spice-derived phenolic compounds as preventive or therapeutic agents for managing skin cancers. By compiling and analyzing the available knowledge, this review aims to provide insights that can guide future research in identifying new anticancer phytochemicals and uncovering additional mechanisms for combating skin cancer.

Intraspecific divergence in essential oil content, composition and genes expression patterns of monoterpene synthesis in Origanum vulgare subsp. vulgare and subsp. gracile under salinity stress

BACKGROUND

Oregano (Origanum vulgare L.), one of the important medicinal plants in the world, has valuable pharmacological compounds with antimicrobial, antiviral, antioxidant, anti-inflammatory, antispasmodic, antiurolithic, antiproliferative and neuroprotective activities. Phenolic monoterpenes such as thymol and carvacrol with many medical importance are found in Oregano essential oil. The biosynthesis of these compounds is carried out through the methyl erythritol-4 phosphate (MEP) pathway. Environmental stresses such as salinity might improve the secondary metabolites in medicinal plants. The influence of salinity stress (0 (control), 25, 50 and 100 mM NaCl) on the essential oil content, composition and expression of 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), γ-terpinene synthase (Ovtps2) and cytochrome P450 monooxygenases (CYP71D180) genes involved in thymol and carvacrol biosynthesis, was investigated in two oregano subspecies (vulgare and gracile).

RESULTS

Essential oil content was increased at low NaCl concentration (25 mM) compared with non-stress conditions, whereas it was decreased as salinity stress intensified (50 and 100 mM). Essential oil content was significantly higher in subsp. gracile than subsp. vulgare. The highest (0.20 mL pot-1) and lowest (0.06 mL pot-1) amount of essential oil yield was obtained in subsp. gracile at 25 and 100 mM NaCl, respectively. The content of carvacrol, as the main component of essential oil, decreased with increasing salinity level in subsp. gracile, but increased in subsp. vulgare. The highest expression of DXR, Ovtps2 and CYP71D180 genes was observed at 50 mM NaCl in subsp. vulgare. While, in subsp. gracile, the expression of the mentioned genes decreased with increasing salinity levels. A positive correlation was obtained between the expression of DXR, Ovtps2 and CYP71D180 genes with carvacrol content in both subspecies. On the other hand, a negative correlation was found between the expression of CYP71D180 and carvacrol content in subsp. gracile.

CONCLUSIONS

The findings of this study demonstrated that both oregano subspecies can tolerate NaCl salinity up to 50 mM without significant reduction in essential oil yield. Also, moderate salinity stress (50 mM NaCl) in subsp. vulgare might increase the carvacrol content partly via increment the expression levels of DXR, Ovtps2 and CYP71D180 genes.

Morphological, phytochemical, and transcriptome analyses provide insights into the biosynthesis of monoterpenes in Monarda citriodora

MAIN CONCLUSION

Morphological, phytochemical, and transcriptome analyses revealed candidate genes involved in the biosynthesis of volatile monoterpenes and development of glandular trichomes in Monarda citriodora. Monarda citriodora Cerv. ex Lag. is a valuable aromatic plant due to the presence of monoterpenes as major constituents in its essential oil (EO). Thus, it is of sheer importance to gain knowledge about the site of the biosynthesis of these terpenoid compounds in M. citriodora, as well as the genes involved in their biosynthesis. In this study, we studied different types of trichomes and their relative densities in three different developmental stages of leaves, early stage of leaf development (L1), mid-stage of leaf development (L2), and later stage of leaf development (L3) and the histochemistry of trichomes for the presence of lipid and terpenoid compounds. Further, the phytochemical analysis of this plant through GC-MS indicated a higher content of monoterpenes (thymol, thymoquinone, γ-terpinene, p-cymene, and carvacrol) in the L1 stage with a substantial decrease in the L3 stage of leaf development. This considerable decrease in the content of monoterpenes was attributed to the decrease in the trichome density from L1 to L3. Further, we developed a de novo transcriptome assembly by carrying out RNA sequencing of different plant parts of M. citriodora. The transcriptome data revealed several putative unigenes involved in the biosynthesis of specialized terpenoid compounds, as well as regulatory genes involved in glandular trichome development. The data generated in the present study build a strong foundation for further improvement of M. citriodora, in terms of quantity and quality of its essential oil, through genetic engineering.

Comparative transcriptome analysis to identify putative genes involved in carvacrol biosynthesis pathway in two species of Satureja, endemic medicinal herbs of Iran

Satureja is rich in phenolic monoterpenoids, mainly carvacrol, that is of interest due to diverse biological activities including antifungal and antibacterial. However, limited information is available regarding the molecular mechanisms underlying carvacrol biosynthesis and its regulation for this wonderful medicinal herb. To identify the putative genes involved in carvacrol and other monoterpene biosynthesis pathway, we generated a reference transcriptome in two endemic Satureja species of Iran, containing different yields (Satureja khuzistanica and Satureja rechingeri). Cross-species differential expression analysis was conducted between two species of Satureja. 210 and 186 transcripts related to terpenoid backbone biosynthesis were identified for S. khuzistanica and S. rechingeri, respectively. 29 differentially expressed genes (DEGs) involved in terpenoid biosynthesis were identified, and these DEGs were significantly enriched in monoterpenoid biosynthesis, diterpenoid biosynthesis, sesquiterpenoid and triterpenoid biosynthesis, carotenoid biosynthesis and ubiquinone and other terpenoid-quinone biosynthesis pathways. Expression patterns of S. khuzistanica and S. rechingeri transcripts involved in the terpenoid biosynthetic pathway were evaluated. In addition, we identified 19 differentially expressed transcription factors (such as MYC4, bHLH, and ARF18) that may control terpenoid biosynthesis. We confirmed the altered expression levels of DEGs that encode carvacrol biosynthetic enzymes using quantitative real-time PCR (qRT-PCR). This study is the first report on de novo assembly and transcriptome data analysis in Satureja which could be useful for an understanding of the main constituents of Satureja essential oil and future research in this genus.

Differential RNA-Seq Analysis Predicts Genes Related to Terpene Tailoring in Caryopteris × clandonensis

Enzymatic terpene functionalization is an essential part of plant secondary metabolite diversity. Within this, multiple terpene-modifying enzymes are required to enable the chemical diversity of volatile compounds essential in plant communication and defense. This work sheds light on the differentially transcribed genes within Caryopteris × clandonensis that are capable of functionalizing cyclic terpene scaffolds, which are the product of terpene cyclase action. The available genomic reference was subjected to further improvements to provide a comprehensive basis, where the number of contigs was minimized. RNA-Seq data of six cultivars, Dark Knight, Grand Bleu, Good as Gold, Hint of Gold, Pink Perfection, and Sunny Blue, were mapped on the reference, and their distinct transcription profile investigated. Within this data resource, we detected interesting variations and additionally genes with high and low transcript abundancies in leaves of Caryopteris × clandonensis related to terpene functionalization. As previously described, different cultivars vary in their modification of monoterpenes, especially limonene, resulting in different limonene-derived molecules. This study focuses on predicting the cytochrome p450 enzymes underlying this varied transcription pattern between investigated samples. Thus, making them a reasonable explanation for terpenoid differences between these plants. Furthermore, these data provide the basis for functional assays and the verification of putative enzyme activities.

Plant terpene specialized metabolism: complex networks or simple linear pathways?

From the perspectives of pathway evolution, discovery and engineering of plant specialized metabolism, the nature of the biosynthetic routes represents a critical aspect. Classical models depict biosynthesis typically from an end-point angle and as linear, for example, connecting central and specialized metabolism. As the number of functionally elucidated routes increased, the enzymatic foundation of complex plant chemistries became increasingly well understood. The perception of linear pathway models has been severely challenged. With a focus on plant terpenoid specialized metabolism, we review here illustrative examples supporting that plants have evolved complex networks driving chemical diversification. The completion of several diterpene, sesquiterpene and monoterpene routes shows complex formation of scaffolds and their subsequent functionalization. These networks show that branch points, including multiple sub-routes, mean that metabolic grids are the rule rather than the exception. This concept presents significant implications for biotechnological production.

Carvacrol-A Natural Phenolic Compound with Antimicrobial Properties

The main purpose of this article is to present the latest research related to selected biological properties of carvacrol, such as antimicrobial, anti-inflammatory, and antioxidant activity. As a monoterpenoid phenol, carvacrol is a component of many essential oils and is usually found in plants together with its isomer, thymol. Carvacrol, either alone or in combination with other compounds, has a strong antimicrobial effect on many different strains of bacteria and fungi that are dangerous to humans or can cause significant losses in the economy. Carvacrol also exerts strong anti-inflammatory properties by preventing the peroxidation of polyunsaturated fatty acids by inducing SOD, GPx, GR, and CAT, as well as reducing the level of pro-inflammatory cytokines in the body. It also affects the body's immune response generated by LPS. Carvacrol is considered a safe compound despite the limited amount of data on its metabolism in humans. This review also discusses the biotransformations of carvacrol, because the knowledge of the possible degradation pathways of this compound may help to minimize the risk of environmental contamination with phenolic compounds.

A GC-MS and LC-HRMS perspective on the chemotaxonomic investigation of the natural hybrid Origanum × lirium and its parents, O. vulgare subsp. hirtum and O. scabrum

INTRODUCTION

The genus Origanum L. (Lamiaceae) is widespread in the Mediterranean region. However, approximately 75% of the species are only encountered in the eastern part. Out of these, a total of nine species (11 taxa) and three natural hybrids occur in Greece. Nevertheless, so far, there is no consensus regarding their precise botanical classification in the literature. In fact, the taxon Origanum × lirium has been proposed both as a separate species as well as natural hybrid between Origanum vulgare subsp. hirtum and Origanum scabrum.

OBJECTIVES

In this scope, the aim of the current study is to shed light on the matter through the investigation of the chemical composition of both the essential oils and the polar extracts of the mentioned taxa, collected from different geographical regions of Greece.

RESULTS

As it was demonstrated by both gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-high-resolution mass spectrometry (LC-HRMS) data, and highlighted by our comparative analysis, it can be stipulated that Origanum × lirium shares its chemotype to a large extent with its parent species concerning both volatile and polar constituents. Additionally, geographical origin conditions stood out as a key factor influencing their chemical composition.

CONCLUSION

Altogether, the present work provides useful information on the chemical composition of the taxa under investigation, while our findings support the opinion that Origanum × lirium should be considered not as a separate species, but rather as a hybrid on the way to becoming a species.

Antioxidant Properties of Thymoquinone, Thymohydroquinone and Black Cumin (Nigella sativa L.) Seed Oil: Scavenging of Superoxide Radical Studied Using Cyclic Voltammetry, DFT and Single Crystal X-ray Diffraction

Black cumin seeds and seed oil have long been used in traditional foods and medicine in South Asian, Middle Eastern and Mediterranean countries and are valuable flavor ingredients. An important ingredient of black cumin is the small molecule thymoquinone (TQ), which manifests low toxicity and potential therapeutic activity against a wide number of diseases including diabetes, cancer and neurodegenerative disorders. In this study, the antioxidant activities of black seed oil, TQ and a related molecule found in black cumin, thymohydroquinone (THQ), were measured using a direct electrochemical method to experimentally evaluate their superoxide scavenging action. TQ and the black seed oil showed good superoxide scavenging ability, while THQ did not. Density Functional Theory (DFT) computational methods were applied to arrive at a chemical mechanism describing these results, and confirmed the experimental Rotating Ring Disk Electrode (RRDE) findings that superoxide oxidation to O2 by TQ is feasible, in contrast with THQ, which does not scavenge superoxide. Additionally, a thorough inquiry into the unusual cyclic voltammetry pattern exhibited by TQ was studied and was associated with formation of a 1:1 TQ-superoxide radical species, [TQ-O2]−•. DFT calculations reveal this radical species to be involved in the π-π mechanism describing TQ reactivity with superoxide. The crystal structures of TQ and THQ were analyzed, and the experimental data reveal the presence of stacking intermolecular interactions that can be associated with formation of the radical species, [TQ-O2]−•. All three of these methods were essential for us to arrive at a chemical mechanism that explains TQ antioxidant activity, that incorporates intermolecular features found in the crystal structure and which correlates with the measured superoxide scavenging activity.

Specialized metabolism by trichome-enriched Rubisco and fatty acid synthase components

Acylsugars, specialized metabolites with defense activities, are secreted by trichomes of many solanaceous plants. Several acylsugar metabolic genes (AMGs) remain unknown. We previously reported multiple candidate AMGs. Here, using multiple approaches, we characterized additional AMGs. First, we identified differentially expressed genes between high- and low-acylsugar-producing F2 plants derived from a cross between cultivated tomato (Solanum lycopersicum) and a wild relative (Solanum pennellii), which produce acylsugars that are ∼1% and ∼20% of leaf dry weight, respectively. Expression levels of many known and candidate AMGs positively correlated with acylsugar amounts in F2 individuals. Next, we identified lycopersicum-pennellii putative orthologs with higher nonsynonymous to synonymous substitutions. These analyses identified four candidate genes, three of which showed enriched expression in stem trichomes compared to underlying tissues (shaved stems). Virus-induced gene silencing confirmed two candidates, Sopen05g009610 [beta-ketoacyl-(acyl-carrier-protein) reductase; fatty acid synthase component] and Sopen07g006810 (Rubisco small subunit), as AMGs. Phylogenetic analysis indicated that Sopen05g009610 is distinct from specialized metabolic cytosolic reductases but closely related to two capsaicinoid biosynthetic reductases, suggesting evolutionary relationship between acylsugar and capsaicinoid biosynthesis. Analysis of publicly available datasets revealed enriched expression of Sopen05g009610 orthologs in trichomes of several acylsugar-producing species. Similarly, orthologs of Sopen07g006810 were identified as solanaceous trichome-enriched members, which form a phylogenetic clade distinct from those of mesophyll-expressed "regular" Rubisco small subunits. Furthermore, δ13C analyses indicated recycling of metabolic CO2 into acylsugars by Sopen07g006810 and showed how trichomes support high levels of specialized metabolite production. These findings have implications for genetic manipulation of trichome-specialized metabolism in solanaceous crops.

Gagones A-F: Six prenylated chalcones from the heartwood of Mansonia gagei

Six undescribed prenylated chalcones gagones A-F were isolated from the acetone fraction of Mansonia gagei heartwood. Their structures were unambiguously established based on spectroscopic analysis (HRESIMS, 1D and 2D NMR), as well as comparison to literature data. Their absolute configurations were elucidated using DP4 and electronic circular dichroism calculations. Isolated compounds were evaluated for their inhibitory activity against α-glucosidase and DPPH assay. All of the tested compounds exhibited better activity than that of acarbose (IC₅₀ 93.6 ± 0.5 μM). Among them, gagone D exhibited the highest α-glucosidase inhibitory with the IC₅₀ value of 3.6 ± 0.4 μM. For antioxidant activity, gagones A-C, and E showed more active than that of ascorbic acid (IC₅₀ 30.2 ± 0.5 μM) with the IC₅₀ values of 13.2 ± 0.7, 20.1 ± 0.4, 19.3 ± 0.5 and 12.8 ± 0.2 μM, respectively.

Optimizing the Distillation of Greek Oregano-Do Process Parameters Affect Bioactive Aroma Constituents and In Vitro Antioxidant Activity?

The aim of the present work was to optimize the conditions of the distillation process at a pilot scale to maximize the yield of specific bioactive compounds of the essential oil of oregano cultivated in Greece, and subsequently to study the in vitro antioxidant activity of these oils. Steam distillation was conducted at an industrial distillery and a Face-Centered Composite (FCC) experimental design was applied by utilizing three distillation factors: time, steam pressure and temperature. Essential oil composition was determined by static headspace gas chromatography-mass spectrometry (HS-GC/MS). To obtain a comprehensive profile of the essential oils, instrumental parameters were optimized, including sample preparation, incubation conditions, sampling process, injection parameters, column thermal gradient and MS conditions. With the applied GC-MS method, more than 20 volatile compounds were identified in the headspace of the oregano essential oils and their relative percentages were recorded. Carvacrol was the most prominent constituent under all distillation conditions applied. Data processing revealed time as the main factor which most affected the yield. The Desired Space (DSc) was determined by conducting a three-dimensional response surface analysis of the independent and dependent variables, choosing yields of thymol and carvacrol as optimization criteria. The in vitro antioxidant activity of the essential oils of all samples was measured in terms of the interaction with the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) after 20 and 60 min. The most prominent essential oils at different distillation conditions were also tested as inhibitors of lipid peroxidation. Higher % values of carvacrol and thymol were correlated to higher antioxidant activity. Evaluating the impact of the distillation conditions on the in vitro results, it seems that lower pressure, less time and higher temperature are crucial for enhanced antioxidant activities.

Creation of new germplasm resources, development of SSR markers, and screening of monoterpene synthases in thyme

BACKGROUND

Thyme derived essential oil and its components have numerous applications in pharmaceutical, food, and cosmetic industries, owing to their antibacterial, antifungal, and antiviral properties. To obtain thyme essential oil with different terpene composition, we developed new germplasm resources using the conventional hybridization approach.

RESULTS

Phenotypic characteristics, including essential oil yield and composition, glandular trichome density, plant type, and fertility, of three wild Chinese and seven European thyme species were evaluated. Male-sterile and male-fertile thyme species were crossed in different combinations, and two F₁ populations derived from Thymus longicaulis (Tl) × T. vulgaris 'Fragrantissimus' (Tvf) and T. vulgaris 'Elsbeth' (Tve) × T. quinquecostatus (Tq) crosses were selected, with essential oil yield and terpene content as the main breeding goals. Simultaneously, simple sequence repeat (SSR) primers were developed based on the whole-genome sequence of T. quinquecostatus to authenticate the F₁ hybrids. A total of 300 primer pairs were selected, and polymerase chain reaction (PCR) was carried out on the parents of the two hybrid populations (Tl, Tvf, Tve, and Tq). Based on the chemotype of the parents and their F₁ progenies, we examined the expression of genes encoding two γ-terpinene synthases, one α-terpineol synthase, and maybe one geraniol synthase in all genotypes by quantitative real-time PCR (qRT-PCR).

CONCLUSION

We used hybridization to create new germplasm resources of thyme, developed SSR markers based on the whole-genome sequence of T. quinquecostatus, and screened the expression of monoterpene synthase genes in thyme. The results of this study provide a strong foundation for the creation of new germplasm resources, construction of the genetic linkage maps, and identification of quantitative trait loci (QTLs), and help gain insight into the mechanism of monoterpenoids biosynthesis in thyme.

Comprehensive identification of terpene synthase genes and organ-dependent accumulation of terpenoid volatiles in a traditional medicinal plant Angelica archangelica L

Angelica archangelica L. is a traditional medicinal plant of Nordic origin that produces an unusual amount and variety of terpenoids. The unique terpenoid composition of A. archangelica likely arises from the involvement of terpene synthases (TPSs) with different specificities, none of which has been identified. As the first step in identifying TPSs responsible for terpenoid chemodiversity in A. archangelica, we produced a transcriptome catalogue using the mRNAs extracted from the leaves, tap roots, and dry seeds of the plant; 11 putative TPS genes were identified (AaTPS1-AaTPS11). Phylogenetic analysis predicted that AaTPS1-AaTPS5, AaTPS6-AaTPS10, and AaTPS11 belong to the monoterpene synthase (monoTPS), sesquiterpene synthase (sesquiTPS), and diterpene synthase clusters, respectively. We then performed in vivo enzyme assays of the AaTPSs using recombinant Escherichia coli systems to examine their enzymatic activities and specificities. Nine recombinant enzymes (AaTPS2-AaTPS10) displayed TPS activities with specificities consistent with their phylogenetics; however, AaTPS5 exhibited a strong sesquiTPS activity along with a weak monoTPS activity. We also analyzed terpenoid volatiles in the flowers, immature and mature seeds, leaves, and tap roots of A. archangelica using gas chromatography-mass spectrometry; 14 monoterpenoids and 13 sesquiterpenoids were identified. The mature seeds accumulated the highest levels of monoterpenoids, with β-phellandrene being the most prominent. α-Pinene and β-myrcene were abundant in all organs examined. The in vivo assay results suggest that the AaTPSs functionally identified in this study are at least partly involved in the chemodiversity of terpenoid volatiles in A. archangelica.

Metabolite Profiling and Bioassay-Guided Fractionation of Zataria multiflora Boiss. Hydroethanolic Leaf Extracts for Identification of Broad-Spectrum Pre and Postharvest Antifungal Agents

Hydroethanolic leaf extracts of 14 Iranian Zataria multiflora Boiss. populations were screened for their antifungal activity against five plant pathogenic fungi and metabolically profiled using a non-targeted workflow based on UHPLC/ESI-QTOFMS. Detailed tandem mass-spectrometric analyses of one of the most active hydroethanolic leaf extracts led to the annotation of 68 non-volatile semi-polar secondary metabolites, including 33 flavonoids, 9 hydroxycinnamic acid derivatives, 14 terpenoids, and 12 other metabolites. Rank correlation analyses using the abundances of the annotated metabolites in crude leaf extracts and their antifungal activity revealed four O-methylated flavones, two flavanones, two dihydroflavonols, five thymohydroquinone glycoconjugates, and five putative phenolic diterpenoids as putative antifungal metabolites. After bioassay-guided fractionation, a number of mono-, di- and tri-O-methylated flavones, as well as three of unidentified phenolic diterpenoids, were found in the most active subfractions. These metabolites are promising candidates for the development of new natural fungicides for the protection of agro-food crops.

Chromosome-level assembly and analysis of the Thymus genome provide insights into glandular secretory trichome formation and monoterpenoid biosynthesis in thyme

Thyme has medicinal and aromatic value because of its potent antimicrobial and antioxidant properties. However, the absence of a fully sequenced thyme genome limits functional genomic studies of Chinese native thymes. Thymus quinquecostatus Čelak., which contains large amounts of bioactive monoterpenes such as thymol and carvacrol, is an important wild medicinal and aromatic plant in China. Monoterpenoids are abundant in glandular secretory trichomes. Here, high-fidelity and chromatin conformation capture technologies were used to assemble and annotate the T. quinquecostatus genome at the chromosome level. The 13 chromosomes of T. quinquecostatus had a total length of 528.66 Mb, a contig N50 of 8.06 Mb, and a BUSCO score of 97.34%. We found that T. quinquecostatus had experienced two whole-genome duplications, with the most recent event occurring ∼4.34 million years ago. Deep analyses of the genome, in conjunction with comparative genomic, phylogenetic, transcriptomic, and metabonomic studies, uncovered many regulatory factors and genes related to monoterpenoids and glandular secretory trichome development. Genes encoding terpene synthase (TPS), cytochrome P450 monooxygenases (CYPs), short-chain dehydrogenase/reductase (SDR), R2R3-MYB, and homeodomain-leucine zipper (HD-ZIP) IV were among those present in the T. quinquecostatus genome. Notably, Tq02G002290.1 (TqTPS1) was shown to encode the terpene synthase responsible for catalyzing production of the main monoterpene product γ-terpinene from geranyl diphosphate (GPP). Our study provides significant insight into the mechanisms of glandular secretory trichome formation and monoterpenoid biosynthesis in thyme. This work will facilitate the development of molecular breeding tools to enhance the production of bioactive secondary metabolites in Lamiaceae.

Fingerprinting based on gas chromatography-Orbitrap high-resolution mass spectrometry and chemometrics to reveal geographical origin, processing, and volatile markers for thyme authentication

Thyme is an aromatic herb traditionally used for food purposes due to its organoleptic characteristics and medicinal properties, which is highly susceptible to food fraud. In this study, GC-HRMS-based fingerprinting was applied for the first time to determine the geographical traceability of thyme based on different origins (Spain, Poland, and Morocco), as well as to assess its processing by comparing sterilized vs. non-sterilized thyme. Unsupervised chemometric methods (PCA and HCA) revealed a predominant influence of the geographical origin on thyme fingerprints rather than processing effects. Supervised PLS-DA and OPLS-DA were used for discrimination purposes, revealing high predictive ability for further samples (100%), and allowing the identification of differential compounds (markers). A total of 24 markers were putatively identified (13 metabolites were confirmed) belonging to different classes: monoterpenoids, diterpenoids, sesquiterpenoids, alkenylbenzenes, and other miscellaneous compounds. This study outlines the potential of combining untargeted analysis by GC-HRMS with chemometrics for thyme authenticity and traceability.

Identification and functional characterization of a γ-terpinene synthase in Nigella sativa L (black cumin)

Nigella sativa (Black cumin) has many applications in food and pharmaceutical industries. Thymoquinone has been considered as a main effective compound in N. sativa seeds and attracted researchers' attention mainly due to its medicinal potential. In this study, the essential oil components of leaves, flowers and seed developmental stages including half black seeds, soft black seeds and hard black seeds were analyzed in N. sativa. Whereas no terpenes were detected in flowers and leaves, seeds showed an essential oil composition that increased in its thymoquinone content during seed maturation. To study the proposed first step of thymoquinone biosynthesis, the formation of γ-terpinene from geranyl diphosphate (GDP), we identified and functionally characterized a γ-terpinene synthase (NsTPS1) in N. sativa. This monoterpene synthase was identified in RNA sequence data derived from seeds. After heterologous expression in Escherichia coli, partially purified NsTPS1 converted GDP to γ-terpinene. NsTPS1 is the first functionally characterized terpene synthase from N. sativa and displays a higher similarity to other terpene synthases from Ranunculaceae than known γ-terpinene synthases from more distant plant species. Characterization of NsTPS1 elucidates the first dedicated step in the biosynthesis of thymoquinone in N. sativa and paves the way towards metabolic engineering for high-level thymoquinone production.

Methyl Jasmonate Induces Genes Involved in Linalool Accumulation and Increases the Content of Phenolics in Two Iranian Coriander (Coriandrum sativum L.) Ecotypes

The medicinal herb coriander (Coriandrum sativum L.), with a high linalool (LIN) content, is widely recognized for its therapeutic benefits. As a novel report, the goals of this study were to determine how methyl jasmonate (MeJA) affects total phenolic content (TPC), LIN content, flavonoid content (TFC), and changes in gene expression involved in the linalool biosynthesis pathway (CsγTRPS and CsLINS). Our findings showed that, in comparison to the control samples, MeJA treatment substantially enhanced the TPC, LIN, and TFC content in both ecotypes. Additionally, for both Iranian coriander ecotypes, treatment-induced increases in CsγTRPS and CsLINS expression were connected to LIN accumulation in all treatments. A 24 h treatment with 150 µM MeJA substantially increased the LIN content in the Mashhad and Zanjan ecotypes, which was between 1.48 and 1.69 times greater than that in untreated plants, according to gas chromatography–mass spectrometry (GC-MS) analysis. Our findings demonstrated that MeJA significantly affects the accumulation of LIN, TPC, and TFC in Iranian C. sativum treated with MeJA, which is likely the consequence of gene activation from the monoterpene biosynthesis pathway. Our discoveries have improved the understanding of the molecular mechanisms behind LIN synthesis in coriander plants.

The chemical biogeography of a widespread aromatic plant species shows both spatial and temporal variation

Plants produce a wide variety of secondary metabolites, but intraspecific variation in space and time can alter the ecological interactions these compounds mediate. The aim of this work was to document the spatial and temporal chemical biogeography of Monarda fistulosa. I collected leaves from 1587 M. fistulosa individuals from 86 populations from Colorado to Manitoba, extracted and analyzed their terpenes with gas chromatography, mapped monoterpene chemotypes, and analyzed chemical variation with principal component analysis. I also measured the amounts of terpenes in different plant tissues to examine intraplant variation and monitored leaf terpene chemistry over a single growing season to examine temporal patterns. Finally, I extracted terpenes from herbarium samples up to 125 years old and compared the chemotypes with recent samples from the same sites. M. fistulosa populations consisted mostly of thymol (T) and carvacrol (C) chemotypes, but geraniol (G) and (R)-(-)-linalool (L), a chemotype new to this species, were also present. A principal component analysis showed that most of the chemical variation across populations was due to the amounts of the dominant terpene in plants. Intraplant tissue chemistry revealed that leaves mostly had the greatest amounts of terpenes, followed by floral structures, stems, and roots. Short-term temporal variation in leaf chemistry of T and C plants over a growing season showed that plants produced the highest levels of biosynthetic precursors early in the season and their dominant monoterpenes peaked in mid-summer. Plant chemotype was discernable in the oldest herbarium samples, and 15 of 18 historic samples matched the majority chemotype currently at the site, indicating that population chemotype ratios may remain stable over longer time scales. Overall, the results show that plant species' secondary chemistry can vary both spatially and temporally, which may alter the biological interactions that these compounds mediate over space and time.

Nucleolin: a cell portal for viruses, bacteria, and toxins

The main localization of nucleolin is the nucleolus, but this protein is present in multiple subcellular sites, and it is unconventionally secreted. On the cell surface, nucleolin acts as a receptor for various viruses, some bacteria, and some toxins. Aim of this review is to discuss the characteristics that make nucleolin able to act as receptor or co-receptor of so many and different pathogens. The important features that emerge are its multivalence, and its role as a bridge between the cell surface and the nucleus. Multiple domains, short linear motifs and post-translational modifications confer and modulate nucleolin ability to interact with nucleic acids, with proteins, but also with carbohydrates and lipids. This modular multivalence allows nucleolin to participate in different types of biomolecular condensates and to move to various subcellular locations, where it can act as a kind of molecular glue. It moves from the nucleus to the cell surface and can accompany particles in the reverse direction, from the cell surface into the nucleus, which is the destination of several pathogens to manipulate the cell in their favour.