Interspecies comparative features of trichomes in Ocimum reveal insights for biosynthesis of specialized essential oil metabolites

Essential oil and Waste Hydrosol of Ocimum Tenuiflorum L.: A Low-Cost Raw Material Source of Eugenol, Botanical Pesticides, and Therapeutic Potentiality

In this study, essential oils and waste hydrosols of leaves of Ocimum tenuiflorum in four different geographical locations were extracted by hydrodistillation method and using gas chromatography/mass spectrometry (GC/MS) for chemical composition analysis. All four essential oil samples contained the main components (E)-β-caryophyllene (27.8-49.0 %), trans-β-elemene (20.3-37.1 %) and eugenol (9.0-44.0 %). Three of the four hydrosol samples had eugenol in absolute content (94.5-98.6 %), while the remaining hydrosol sample had two main components, elemicin (77.8 %) and eugenol (14.2 %). Essential oils and hydrosols demonstrated larvicidal activities against four important disease-transmitting mosquito species including Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, and Culex fuscocephala with 24-h LC50 values in the range 15.42-56.01 μg/mL and 53.88-97.80 μg/mL for the essential oils and the hydrosols, respectively. Essential oils and hydrosols strongly inhibited the acetylcholinesterase (AChE) enzyme of electric eels with IC50 values in the range of 25.35-107.19 μg/mL. Microemulsion (ME) can be considered as a sustainable pesticide formulation over 300 days and has improved larvicidal activity compared to free essential oil. The O. tenuiflorum in Vietnam can be considered a low-cost source of eugenol, botanical pesticides that control disease-transmitting mosquitoes, as well as having therapeutic potential to be further investigated.

Comparative microscopic investigations of leaf epidermis in four Ajuga species from Korea

The genus Ajuga is widely distributed in temperate to subtropical regions, and four species are currently recognized in Korea (A. decumbens, A. multiflora, A. nipponensis, and A. spectabilis), but epidermal anatomical differences across these species have never been described. A comparative study of the leaf micromorphological characteristics of Korean Ajuga species was performed using light microscopy (LM) and scanning electron microscopy (SEM) to elucidate their taxonomic usefulness and to assess leaf micromorphological diversity. Considerable diversity in epidermal and stomatal anatomy was observed across Korean Ajuga species. Species had both hypostomatic or amphistomatic leaves, with anomocytic, anisocytic, diactyic, or actinocytic stomatal complexes. Guard cell length across species ranged from 17.66 ± 0.57 μm to 32.50 ± 2.38 μm and correlated with genome size. Abnormal stomata were frequently observed in three species (A. decumbens, A. multiflora, and A. nipponensis) but not in A. spectabilis. Three types of glandular trichomes were found: peltate in all species, short-stalked in all species, and long-stalked glandular trichomes in A. multiflora. Among the investigated leaf micromophological characters, trichome type, epidermal cell shape, and stomatal morphology were all taxonomically informative traits at a species level. RESEARCH HIGHLIGHTS: A comprehensive micromorphological description of the leaf surface is provided for Korean Ajuga species using scanning electron microscopic (SEM) and light microscopic (LM) analyses. The diverse range of stomatal development and the occurrence of polymorphic stomatal types are documented for the first time in Korean Ajuga species. The great diversity in stomatal and trichome morphology in Korean Ajuga species are taxonomically useful traits for species identification.

Rapid Identification and Quantification of Adulteration in Methyl Eugenol using Raman Spectroscopy Coupled with Multivariate Data Analysis

Identification of adulterants in commercial samples of methyl eugenol is necessary because it is a botanical insecticide, a tephritid male attractant lure that is used to attract and kill invasive pests such as oriental fruit flies and melon flies on crops. In this study, Raman spectroscopy was used to qualitatively and quantitatively assess commercial methyl eugenol along with adulterants. For this purpose, commercial methyl eugenol was adulterated with different concentrations of xylene. The Raman spectral features of methyl eugenol and xylene in liquid formulations were examined, and Raman peaks were identified as associated with the methyl eugenol and adulterant. Principal component analysis (PCA) and partial least-squares regression analysis (PLSR) have been used to qualitatively and quantitatively analyze the Raman spectral features. PCA was applied to differentiate Raman spectral data for various concentrations of methyl eugenol and xylene. Additionally, PLSR has been used to develop a predictive model to observe a quantitative relationship between various concentrations of adulterated methyl eugenol and their Raman spectral data sets. The root-mean-square errors of calibration and prediction were calculated using this model, and the results were found to be 1.90 and 3.86, respectively. The goodness of fit of the PLSR model is found to be 0.99. The proposed approach showed excellent potential for the rapid, quantitative detection of adulterants in methyl eugenol, and it may be applied to the analysis of a range of pesticide products.

Low-temperature perception and modulations in Ocimum basilicum commercial cultivar CIM-Shishir: Biosynthetic potential with insight towards climate-smart resilience

The newly released interspecific hybrid variety CIM-Shishir, resulting from a cross between Ocimum basilicum and Ocimum kilimandscharicum claims to be a multicut, lodging resistant, cold tolerant, high essential oil yielding with linalool rich variety. It has a purple-green stem and has a unique feature and advantage of better survival in the winter season than other O. basilicum varieties, illustrating its physiological mechanisms for cold tolerance. In this study, we subjected both the CIM-Shishir variety and a control plant to cold stress to investigate the impact of low temperatures on various physiological, trichome developments, secondary metabolite constitution aspects related to essential oil production, and gene expression. The analysis revealed a significantly higher density and altered morphology of trichomes on the leaf surface of the variety subjected to low temperatures, indicating its adaptation to cold conditions. Furthermore, when comparing the treated plants under low-temperature stress, it was observed that the relative electrolyte leakage and Malondialdehyde (MDA) contents substantially increased in the control in contrast to the CIM-Shishir variety. This finding suggests that CIM-Shishir exhibits superior cold tolerance. Additionally, an increase in proline content was noted in the variety exposed to low temperatures compared to the control. Moreover, the chlorophyll and anthocyanin content gradually increased with prolonged exposure to low-temperature stress in the newly developed variety, indicating its ability to maintain photosynthetic capacity and adapt to cold conditions. The activities of superoxide dismutase (SOD) also increased under low-temperature conditions in the CIM-Shishir variety, further highlighting its cold tolerance behaviour. In our research, we investigated the comprehensive molecular mechanisms of cold response in Ocimum. We analyzed the expression of key genes associated with cold tolerance in two plant groups: the newly developed hybrid variety known as CIM-Shishir Ocimum, which exhibits cold tolerance, and the control plants susceptible to cold climates that include WRKY53, ICE1, HOS1, COR47, LOS15, DREB5, CBF4, LTI6, KIN, and ERD2. These genes exhibited significantly higher expression levels in the CIM-Shishir variety compared to the control, shedding light on the genetic basis of its cold tolerance. The need for climate-smart, resilient high-yielding genotype is of high importance due to varied climatic conditions as this will hit the yield drastically and further to the economic sectors including farmers and many industries that are dependent on the bioactive constituents of Ocimum.

Enhancing growth, vitality, and aromatic richness: unveiling the dual magic of silicon dioxide and titanium dioxide nanoparticles in Ocimum tenuiflorum L

Ocimum tenuiflorum, commonly known as "Holy basil," is renowned for its notable medicinal and aromatic attributes. Its unique fragrance attributes to specific volatile phytochemicals, primarily belonging to terpenoid and/or phenylpropanoid classes, found within their essential oils. The use of nanoparticles (NPs) in agriculture has attracted attention among plant researchers. However, the impact of NPs on the modulation of morpho-physiological aspects and essential oil production in medicinal plants has received limited attention. Consequently, the present study aimed to explore the effect of silicon dioxide (SiO2) and titanium dioxide (TiO2) nanoparticles at various concentrations (viz., DDW (control), Si50+Ti50, Si100+Ti50, Si100+Ti100, Si200+Ti100, Si100+Ti200 and Si200+Ti200 mg L-1) on growth, physiology and essential oil production of O. tenuiflorum at 120 days after planting (DAP). The results demonstrated that the combined application of Si and Ti (Si100+Ti100 mg L-1) exhibited the most favourable outcomes compared to the other combinational treatments. This optimal treatment significantly increased the vegetative growth parameters (root length (33.5%), shoot length (39.2%), fresh weight (62.7%) and dry weight (28.5%)), photosynthetic parameters, enzymatic activities (nitrate reductase and carbonic anhydrase), the overall area of PGTs (peltate glandular trichomes) and essential oil content (172.4%) and yield (323.1%), compared to the control plants. Furthermore, the GCMS analysis showed optimal treatment (Si100+Ti100) significantly improved the content (43.3%) and yield (151.3%) of eugenol, the primary active component of the essential oil. This study uncovers a remarkable and optimal combination of SiO2 and TiO2 nanoparticles that effectively enhances the growth, physiology, and essential oil production in Holy basil. These findings offer valuable insights into maximizing the potential benefits of its use in industrial applications.

Combined application of SiO2 and TiO2 nanoparticles enhances growth characters, physiological attributes and essential oil production of Coleus aromatics Benth

Nanoparticles (NPs) have gained considerable interest among researchers in the field of plant biology, particularly in the agricultural sector. Among the numerous NPs, the individual application of silicon (Si) or titanium (Ti), in their oxide forms, had a positive influence on growth, physiochemical and yield attributes of plants. However, the synergetic application of both these NPs has not been studied yet. Therefore, the current study was aimed to investigate the effect of combined application of silicon dioxide (SiO2) and titanium dioxide (TiO2) NPs on the growth characters, physiological parameters, and essential oil quality and production of Coleus aromatics Benth. Aqueous solutions of nanoparticles were applied to the foliage of the plants at varying combinations (Si50+Ti50, Si100+Ti50, Si100+Ti100, Si200+Ti100, Si100+Ti200 and Si200+Ti200 mg L-1). Various morpho-physiological, biochemical and yield attributes were assessed at 120 days after planting. The results demonstrated that both Si and Ti NPs improved the growth and photosynthetic efficiency in a dose dependent manner. The best results were obtained by the combined application of Si100+Ti100 mg L-1, and thereafter, the values declined progressively. The maximum improvement in fresh weight (39.5 %) and dry weight (40.8 %) of shoot, fresh weight (45.7 %) and dry weight (49.4 %) of root was observed as compared to respective controls. Moreover, the exogenous application of Si100+Ti100 mg L-1 increased photosynthetic attributes such as total content of chlorophyll (41.7 %), carotenoids (43.7 %), chlorophyll fluorescence (7.1 %), and carbonic anhydrase (23.8 %). All of these contributed to the highest accumulation in the content (129.0 %) and yield (215.5 %) of essential oil (EO), in comparison to the control. Thus, results encouraged the use of SiO2 and TiO2 NPs to be applied in combined form to boost the essential oil production of Coleus aromaticus. The findings of this study may serve agronomists to determine the optimal concentrations of NPs for enhanced production of bioactive compounds with a wide range of industrial applications.

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.

Characterization and the comprehensive expression analysis of tobacco valine-glutamine genes in response to trichomes development and stress tolerance

Valine-glutamine genes (VQ) acted as transcription regulators and played the important roles in plant growth and development, and stress tolerance through interacting with transcription factors and other co-regulators. In this study, sixty-one VQ genes containing the FxxxVQxxTG motif were identified and updated in the Nicotiana tobacum genome. Phylogenetic analysis indicated that NtVQ genes were divided into seven groups and genes of each group had highly conserved exon-intron structure. Expression patterns analysis firstly showed that NtVQ genes expressed individually in different tobacco tissues including mixed-trichome (mT), glandular-trichome (gT), and nonglandular-trichome (nT), and the expression levels were also distinguishing in response to methyl jasmonate (MeJA), salicylic acid (SA), gibberellic acid (GA), ethylene (ETH), high salinity and PEG stresses. Besides, only NtVQ17 of its gene family was verified to have acquired autoactivating activity. This work will not only lead a foundation on revealing the functions of NtVQ genes in tobacco trichomes but also provided references to VQ genes related stress tolerance research in more crops.

Plant Secondary Metabolites: The Weapons for Biotic Stress Management

The rise in global temperature also favors the multiplication of pests and pathogens, which calls into question global food security. Plants have developed special coping mechanisms since they are sessile and lack an immune system. These mechanisms use a variety of secondary metabolites as weapons to avoid obstacles, adapt to their changing environment, and survive in less-than-ideal circumstances. Plant secondary metabolites include phenolic compounds, alkaloids, glycosides, and terpenoids, which are stored in specialized structures such as latex, trichomes, resin ducts, etc. Secondary metabolites help the plants to be safe from biotic stressors, either by repelling them or attracting their enemies, or exerting toxic effects on them. Modern omics technologies enable the elucidation of the structural and functional properties of these metabolites along with their biosynthesis. A better understanding of the enzymatic regulations and molecular mechanisms aids in the exploitation of secondary metabolites in modern pest management approaches such as biopesticides and integrated pest management. The current review provides an overview of the major plant secondary metabolites that play significant roles in enhancing biotic stress tolerance. It examines their involvement in both indirect and direct defense mechanisms, as well as their storage within plant tissues. Additionally, this review explores the importance of metabolomics approaches in elucidating the significance of secondary metabolites in biotic stress tolerance. The application of metabolic engineering in breeding for biotic stress resistance is discussed, along with the exploitation of secondary metabolites for sustainable pest management.

Lavandula Species, Their Bioactive Phytochemicals, and Their Biosynthetic Regulation

Lavandula species are one of the most useful aromatic and medicinal plants and have great economic potential. The phytopharmaceutical contribution of the secondary metabolites of the species is unquestionable. Most recent studies have been focusing on the elucidation of the genetic background of secondary metabolite production in lavender species. Therefore, knowledge of not only genetic but especially epigenetic mechanisms for the regulation of secondary metabolites is necessary for the modification of those biosynthesis processes and the understanding of genotypic differences in the content and compositional variability of these products. The review discusses the genetic diversity of Lavandula species in relation to the geographic area, occurrence, and morphogenetic factors. The role of microRNAs in secondary-metabolites biosynthesis is described.

Trichome-Specific Analysis and Weighted Gene Co-Expression Correlation Network Analysis (WGCNA) Reveal Potential Regulation Mechanism of Artemisinin Biosynthesis in Artemisia annua

Trichomes are attractive cells for terpenoid biosynthesis and accumulation in Artemisia annua. However, the molecular process underlying the trichome of A. annua is not yet fully elucidated. In this study, an analysis of multi-tissue transcriptome data was performed to examine trichome-specific expression patterns. A total of 6646 genes were screened and highly expressed in trichomes, including artemisinin biosynthetic genes such as amorpha-4,11-diene synthase (ADS) and cytochrome P450 monooxygenase (CYP71AV1). Mapman and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that trichome-specific genes were mainly enriched in lipid metabolism and terpenoid metabolism. These trichome-specific genes were analyzed by a weighted gene co-expression network analysis (WGCNA), and the blue module linked to terpenoid backbone biosynthesis was determined. Hub genes correlated with the artemisinin biosynthetic genes were selected based on TOM value. ORA, Benzoate carboxyl methyltransferase (BAMT), Lysine histidine transporter-like 8 (AATL1), Ubiquitin-like protease 1 (Ulp1) and TUBBY were revealed as key hub genes induced by methyl jasmonate (MeJA) for regulating artemisinin biosynthesis. In summary, the identified trichome-specific genes, modules, pathways and hub genes provide clues and shed light on the potential regulatory mechanisms of artemisinin biosynthesis in trichomes in A. annua.

Current Trends for Lavender (Lavandula angustifolia Mill.) Crops and Products with Emphasis on Essential Oil Quality

Lavender is in the research spotlight due to its increasing economic importance, while market demand is expected to continue to grow. Among the hundreds of essential-oil-bearing plants, Lavandula angustifolia Mill. remains one of the most valuable. This paper explores the lavender chain timeline from crop to products, examining the expanding knowledge on the characteristics, phytochemical profile and functional potential of lavender that could lead to new products and uses. Lavender crops can be expanded without competing for productive land, instead using marginal, contaminated or unproductive land. A novel cultivation trend proposes leveraging agri-background biodiversity, arbuscular mycorrhiza and the natural enemies of pests for healthy crops. Together with breeding efforts targeting highly performant genotypes with complex volatile profiles coupled with resistance to specific biotic (particularly Phytoplasma) and abiotic (salt, heavy metals) stressors, industry could have a steady supply of high-quality raw material. Besides the expansion of the uses of essential oil in cosmetics, pharmaceuticals, food and environmental and agri-applications, novel channels have appeared for the use of the solid by-product, which is rich in polyphenols and polysaccharides; these channels have the potential to create additional streams of value. The stabilization and optimization of techno-functional delivery systems through the encapsulation of essential oil can extend shelf-life and enhance biological activity efficiency.

Physicochemical Characterization and Prospecting Biological Activity of Some Authentic Transylvanian Essential Oils: Lavender, Sage and Basil

Essential oils are a category of agro-based industrial products experiencing increasing demand. In this research, three essential oils obtained by steam distillation from lavender, sage and basil plants cultivated in temperate continental conditions of Transylvania were investigated for chemical composition, physical characteristics and biological activity (antimicrobial and cytotoxic effect on cancer cell lines). The number of identified compounds varied: 38 for lavender, 29 for sage essential oil and 41 for basil. The volatile profile was dominated by terpenes and terpenoids (>80%). Major components were beta-linalool and linalool acetate in lavender essential oil; thujones and camphor in sage essential oil; beta-linalool, thujone, camphor and eucalyptol in basil essential oil. Refractive index of the essential oils was lowest for lavender and highest for sage. Antibacterial activity was strongest for basil, moderate for lavender and weakest for sage essential oil. The most active on both colon adenocarcinoma (Caco-2) and ovary carcinoma (A2780) was sage essential oil.

Ocimum Species: A Review on Chemical Constituents and Antibacterial Activity

Infection by bacteria is one of the main problems in health. The use of commercial antibiotics is still one of the treatments to overcome these problems. However, high levels of consumption lead to antibiotic resistance. Several types of antibiotics have been reported to experience resistance. One solution that can be given is the use of natural antibacterial products. There have been many studies reporting the potential antibacterial activity of the Ocimum plant. Ocimum is known to be one of the medicinal plants that have been used traditionally by local people. This plant contains components of secondary metabolites such as phenolics, flavonoids, steroids, terpenoids, and alkaloids. Therefore, in this paper, we will discuss five types of Ocimum species, namely O. americanum, O. basilicum, O. gratissimum, O. campechianum, and O. sanctum. The five species are known to contain many chemical constituents and have good antibacterial activity against several pathogenic bacteria.

Morphogenesis, ultrastructure, and chemical profiling of trichomes in Artemisia argyi H. Lév. & Vaniot (Asteraceae)

Glandular trichomes of Artemisia argyi H. Lév. & Vaniot are the key tissues for the production of flavonoid and terpenoid metabolites. Artemisia argyi H. Lév. & Vaniot is an herbaceous perennial plant that has been widely used in traditional medicine for thousands of years. Glandular trichomes (GTs) and nonglandular trichomes (NGTs) have been reported on the leaf surface of A. argyi. The aim of this study was to elucidate the morphogenetic process and to analyze the metabolites of trichomes in A. argyi. The morphogenesis of GTs and NGTs was characterized using light, scanning, and transmission electron microscopy. The constituents of GTs were analyzed using laser microdissection combined with gas and liquid chromatography-mass spectrometry. Five developmental stages of two types of GTs and four developmental stages of one type of NGTs were observed. Two types of mature GT and one type of NGT were composed of 10, 5, and 4-6 cells, respectively. A large storage cavity was detected between the cuticle and cell walls in the first type of mature GT. Large nuclei, nucleoli, and mitochondria were observed in the basal and intermediate cells of the second type of GT. In addition, large vacuoles were observed in the basal and apical cells, and large nuclei were observed in the middle cells of NGTs. One monoterpene and seven flavonoids were identified in GTs of A. argyi. We suggest that GTs are the key tissues for the production of bioactive metabolites in A. argyi. This study provides an important theoretical basis and technical approach for clarifying the regulatory mechanisms for trichome development and bioactive metabolite biosynthesis in A. argyi.

Eugenol inhibits the biological activities of an oral squamous cell carcinoma cell line SCC9 via targeting MIF

BACKGROUND

Oral squamous cell carcinoma (OSCC) is a rampant cancer type in head and neck cancers with a poor prognosis and a high recurrence rate. Eugenol shows anticancer effect in a variety of cancers, but it has been rarely studied in oral squamous cell carcinoma (OSCC).

OBJECTIVE

Therefore, the purpose of this study was to explore the role of Eugenol in OSCC and the underlying mechanism.

METHODS

After different concentrations of Eugenol (0, 200, 400 and 800 μM) treatment, the viability, proliferation, migration and invasion of OSCC cell line SCC9 was measured by CCK-8, colony formation, wound-healing and transwell assays, respectively. TUNEL staining was employed to detect the apoptosis. Western blotting was used to evaluate gene expression at protein level. Molecular docking was used to identify the target of Eugenol.

RESULTS

Eugenol decreased the proliferation, reduced the abilities of invasion and migration along with the expression of matrix metalloproteinases (MMP) 2 and MMP9 in SCC9 cells. On the contrary, the ratio of apoptotic cells was increased by Eugenol. In addition, Eugenol down-regulated B cell lymphoma-2 (Bcl-2) expression, but up-regulated BCL-2 associated X (Bax), cleaved caspase 3 and cleaved poly-ADP ribose polymerase (PARP) expression. Meanwhile, Eugenol exerted its effect on SCC9 cells in a concentration-dependent manner. Eugenol could bind to macrophage migration inhibitory factor (MIF), the expression of which was down-regulated after Eugenol treatment. Besides, overexpression of MIF reversed all the effects of Eugenol on OSCC cells.

CONCLUSION

In summary, Eugenol suppressed the malignant processes of OSCC cells by targeting MIF, which could guide the clinical application of Eugenol in OSCC.

NbJAZ3 is required for jasmonate-meditated glandular trichome development in Nicotiana benthamiana

Exogenous methyl jasmonate (MeJA) treatment induces glandular trichome development in Nicotiana benthamiana, but the function of JAZ proteins, acting as core repressors, and their downstream genes have not been clearly shown in plants. Here, a bioinformatics analysis of 71 JAZ genes from tobacco, Arabidopsis thaliana, and tomato was carried out and shown to share highly conserved domains. Then, the expression profile of 17 NbJAZs in different tissues was analyzed, and NbJAZ3 was highly expressed in trichome. Through transgenic technology, we demonstrated that the glandular trichome density of NbJAZ3-overexpression lines significantly decreased with lower expression levels of NbWo, NbCycB2, and NbMIXTA. In contrast, the trichome density of NbJAZ3 RNAi lines slightly increased with higher expression level of NbWo. Given the negative protein feedback regulation relationship between NbCycB2 and NbWo, we verified that MeJA induced NbWo expression. NbWo was a direct target gene of NbJAZ3 and further demonstrated that NbJAZ3 inhibited the transcriptional activation of NbCycB2 by NbWo. Together, our findings outline a novel JA-meditated glandular trichome development model consisting of the NbJAZ3-NbWo-NbCycB2 axis.

Demystifying therapeutic potential of medicinal plants against chikungunya virus

Viral infections are posing a great threat to humanity for the last few years. Among these, Chikungunya which is a mosquito-borne viral infection has produced enormous epidemics around the world after been rebounded. Although this infection shows a low mortality rate, patients suffer from fever, arthralgia, and maculopapular rashes, which reduce the quality of life for several weeks to years. The currently available treatments only provide symptomatic relief based on analgesics, antipyretics, and anti-inflammatory drugs which are nonspecific without satisfactory results. Medicinal plants are a widely accepted source of new molecules for the treatment of infectious diseases including viral infections. The scientific reports, primarily focusing on the anti-chikungunya activity of plant extracts, natural origin pure compounds, and their synthetic analog published from 2011 to 2021, were selected from PubMed, Google Scholar, and Scopus by using related keywords like anti-chikungunya plants, natural antivirals for Chikungunya. The present review decodes scientific reports on medicinal plants against chikungunya virus (CHIKV) infection and demystifies the potential phytoconstituents which reveals that the screening of flavonoids containing plants and phytochemicals showing efficacy against other arbovirus infections, may prove as a potential lead for drug development against CHIKV. The present article also outlines pathogenesis, clinical aspects, molecular virology, and diagnostic approaches of CHIKV infection.

Interactions of melatonin with the micro-morphological structures and physiological characteristics of lemon balm

Melatonin (MEL) is defined as a plant master regulator. It regulates plant growth and development in various stress environments by increasing in amount. Effects of external MEL application on the content of the secretion products in micro-morphological structures of leaf trichomes of Melissa officinalis L. (lemon balm) without the presence of external stress factors were characterized. The relationships between different MEL concentrations and changes in type, density and size of trichomes, total chlorophyll and proline amounts, and secretion products were defined. Furthermore, monoterpenoids, which are the main products of trichomes that determine the quality of essential oils in lemon balm, varied under the effects of MEL. Especially 100 mM MEL concentration had the most dramatic impact. The highest number of glandular trichomes (GT) were observed at this concentration. 150 mM concentration of MEL had the opposite effect. At this concentration, significant decreases in secondary metabolite content and glandular structures were observed. Thus, it was concluded that MEL had a positive effect on these parameters up to a certain concentration. Changes in the size and number of GT due to MEL application is greatly reflected by the quality and content of secondary metabolites. Total chlorophyll, proline and monoterpene numbers were highest at 100 mM MEL concentration. The effects of MEL application without the presence of any stress conditions were supported by total chlorophyll and proline content. Important information was obtained about the relationship of these effects with the density of peltate trichomes and the chemical compounds and quality of essential oils.

Identification of novel inhibitors of SARS-CoV-2 main protease (Mpro ) from Withania sp. by molecular docking and molecular dynamics simulation

Since December 2019, coronavirus disease (COVID-19) has claimed the lives of millions of people across the globe. To date, no medicine is available for the responsible virus SARS-CoV-2. 3CLpro, that is, 3-chymotrypsin-like protease, the main protease (Mpro ), has an important role in cleaving pp1a and pp1ab polyproteins. This Mpro serves as an important target in drug designing against COVID-19. Herein, the study includes the investigation, screening, and identification of potent leads from (Withania sps.), against SARS-CoV-2, using virtual screening, molecular docking, and molecular dynamics (MD) simulations. Seventy-three natural compounds from this important medicinal plant were screened. The Binding affinity was used to identify the most probable target to inhibit the Mpro , compounds 27-hydroxywithanolide F (W32, -11.5 kcal/mol), withanolide A (W56, -11.4 kcal/mol), and withacoagulin H (W30, -11.1 kcal/mol) showed highest binding energy. Lipinski's rule, followed by drug-likability and likeness screening, resulted in 36 molecules. Further, MD simulation of 50 ns predicted withacoagulin H possessing strong binding affinity and hydrogen-bonding interactions with the active site. The binding free energy calculation showed the most negative energy of withacoagulin H (-63.463 KJ/mol) compared to other selected compounds. The study also compared the bonding energy of already reported repurposed and newly synthesized drugs. Further, absorption, distribution, metabolism, and excretion predictions were made to found a good balance of potency. Hence the following screened compounds from Withania sps. could serve as the potential leads for drug development against COVID-19.

A glance at the chemodiversity of Ocimum species: Trends, implications, and strategies for the quality and yield improvement of essential oil

Ocimum species represent commercially important medicinal and aromatic plants. The essential oil biosynthesized by Ocimum species is enriched with specialized metabolites specifically, terpenoids and phenylpropanoids. Interestingly, various Ocimum species are known to exhibit diverse chemical profiles, and this chemical diversity has been at the center of many studies to identify commercially important chemotypes. Here, we present various chemotypes from the Ocimum species and emphasize trends, implications, and strategies for the quality and yield improvement of essential oil. Globally, many Ocimum species have been analyzed for their essential oil composition in over 50 countries. Asia represents the highest number of chemotypes, followed by Africa, South America, and Europe. Ocimum basilicum L. has been the most widespread and well-studied species, followed by O. gratissimum L., O. tenuiflorum L., O. canum Sims, O. americanum and O. kilimandscharicum Gürke. Moreover, various molecular reasons, benefits, adverse health effects and mechanisms behind this vast chemodiversity have been discussed. Different strategies of plant breeding, metabolic engineering, transgenic, and tissue-culture, along with anatomical modifications, are surveyed to enhance specific chemotypic profiles and essential oil yield in numerous Ocimum species. Consequently, chemical characterization of the essential oil obtained from Ocimum species has become indispensable for its proper utilization. The present chemodiversity knowledge from Ocimum species will help to exploit various applications in the industrial, agriculture, biopharmaceutical, and food sectors.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11101-021-09767-z.

Glandular trichomes of Robinia viscosa Vent. var. hartwigii (Koehne) Ashe (Faboideae, Fabaceae)-morphology, histochemistry and ultrastructure

MAIN CONCLUSION

Permanent glandular trichomes of Robinia viscosa var. hartwigii produce viscous secretion containing several secondary metabolites, as lipids, mucilage, flavonoids, proteins and alkaloids. Robinia viscosa var. hartwigii (Hartweg's locust) is an ornamental tree with high apicultural value. It can be planted in urban greenery and in degraded areas. The shoots, leaves, and inflorescences of this plant are equipped with numerous persistent glandular trichomes producing sticky secretion. The distribution, origin, development, morphology, anatomy, and ultrastructure of glandular trichomes of Hartweg's locust flowers as well as the localisation and composition of their secretory products were investigated for the first time. To this end, light, scanning, and transmission electron microscopy combined with histochemical and fluorescence techniques were used. The massive glandular trichomes differing in the distribution, length, and stage of development were built of a multicellular and multiseriate stalk and a multicellular head. The secretory cells in the stalk and head had large nuclei with nucleoli, numerous chloroplasts with thylakoids and starch grains, mitochondria, endoplasmic reticulum profiles, Golgi apparatus, vesicles, and multivesicular bodies. Many vacuoles contained phenolic compounds dissolved or forming various condensed deposits. The secretion components were transported through symplast elements, and the granulocrine and eccrine modes of nectar secretion were observed. The secretion was accumulated in the subcuticular space at the trichome apex and released through a pore in the cuticle. Histochemical and fluorescence assays showed that the trichomes and secretion contained lipophilic and polyphenol compounds, polysaccharides, proteins, and alkaloids. We suggest that these metabolites may serve an important function in protection of plants against biotic stress conditions and may also be a source of phytopharmaceuticals in the future.

Anthocyanins from Ocimum sanctum L., a promising biomolecule for development of cost-effective and widely applicable pH indicator

A novel cost-effective and widely applicable pH indicator was developed using anthocyanins extracted from the purple subtype of Ocimum sanctum L. and common lab filter paper. This pH indicator was successfully tested to monitor the pH of a wide range of buffers, solutions, irrigation water, and soil solution. Upon testing, the indicator displayed specific colors at corresponding pH ranges. Sucrose showed a stabilizing effect for the color of the extracted anthocyanins. Further, molecular analysis indicated that the leaves from the purple subtypes showed higher transcripts abundance for chalcone synthase, chalcone isomerase, anthocyanidin synthase, and dihydroflavonol 4-reductase than that of the green subtype. Similarly, transcription factors HY5 and a bHLH putatively involved in the biosynthesis of anthocyanins showed up-regulation in the purple subtype of O. sanctum.

Comparative transcriptome analysis to identify putative genes related to trichome development in Ocimum species

Genus Ocimum is known to have species possessing important therapeutic essential oil. The major phytoconstituents of essential oil in Ocimum species are phenylpropanoids and terpenoids. The essential oil is accumulated in the trichomes; the specialized structures predominantly found on leaves and other tissues. The development of trichome is integrated with development of plant and leaf and also tightly coordinated with the primary and secondary metabolic pathways producing essential oil constituents. In continuation to our studies on elucidating/understanding the mechanism of biosynthesis of  essential oil pathways in Ocimum species, we have performed comparative transcriptome analysis to investigate the role of trichome-related gene expression in the regulation of biosynthetic pathways of essential oil. The essential oil biogenesis is tightly integrated with primary metabolic activities, the analysis for the expression pattern of genes related to primary metabolism and its relationship with secondary metabolism was evaluated in comparative manner. Physiological parameters in relation to primary metabolism such as photosynthetic pigment content, soluble sugar content, and invertase enzymes along with morphological parameters were analysed in O. basilicum and O. sanctum. Differential expression profiling uncovered about 8116 and 2810 differentially expressed transcripts in O. basilicum and O. sanctum, respectively. Enrichment of differentially expressed genes were analysed in relation to metabolic pathways, primary metabolism and secondary metabolism. Trichome related genes identified from the Ocimum species vis-à-vis their expression profiles suggested higher expression in O. basilicum. The findings in this study provide interesting insights into the role of trichome-related transcripts in relation to essential oil content in Ocimum species. The study is valuable as this is the first study on revealing the transcripts and their role in trichome development and essential oil biogenesis in two major species of Ocimum.

The Dynamic Genetic-Hormonal Regulatory Network Controlling the Trichome Development in Leaves

Plant trichomes are outgrowths developed from an epidermal pavement cells of leaves and other organs. Trichomes (also called 'hairs') play well-recognized roles in defense against insect herbivores, forming a physical barrier that obstructs insect movement and mediating chemical defenses. In addition, trichomes can act as a mechanosensory switch, transducing mechanical stimuli (e.g., insect movement) into physiological signals, helping the plant to respond to insect attacks. Hairs can also modulate plant responses to abiotic stresses, such as water loss, an excess of light and temperature, and reflect light to protect plants against UV radiation. The structure of trichomes is species-specific and this trait is generally related to their function. These outgrowths are easily analyzed and their origin represents an outstanding subject to study epidermal cell fate and patterning in plant organs. In leaves, the developmental control of the trichomatous complement has highlighted a regulatory network based on four fundamental elements: (i) genes that activate and/or modify the normal cell cycle of epidermal pavement cells (i.e., endoreduplication cycles); (ii) transcription factors that create an activator/repressor complex with a central role in determining cell fate, initiation, and differentiation of an epidermal cell in trichomes; (iii) evidence that underlines the interplay of the aforesaid complex with different classes of phytohormones; (iv) epigenetic mechanisms involved in trichome development. Here, we reviewed the role of genes in the development of trichomes, as well as the interaction between genes and hormones. Furthermore, we reported basic studies about the regulation of the cell cycle and the complexity of trichomes. Finally, this review focused on the epigenetic factors involved in the initiation and development of hairs, mainly on leaves.

Computational identification of miRNA and their cross kingdom targets from expressed sequence tags of Ocimum basilicum

MicroRNAs (miRNAs) are conserved small non coding RNAs, which are typically 22-24 nucleotides long and play an important role in post transcription regulation andin various biological processes in both animals and plants. Ocimum basilicum is an important medicinal plant having different bioactive compounds eugenol and essential oils that possess numerous therapeutic properties. However, only a few miRNAs of Ocimum basilicum and its function have been studied till date. The present study focusses on the identification of miRNA from expressed sequenced tags by carrying out computational approaches based on the homology search method. A total of 10 potential miRNAs with 8 different families were predicted in O.basilicum. Furthermore, the psRNA target server was used to predict cross kingdom target genes on human transcriptome for identification ofpotential miRNAs. Eight miRNA families were found to modulate the 87 human target genes which were associated with RAS/MAPK signalling cascade, cardiomyopathy, HIV, breast cancer, lung cancer, Alzheimer's diseases and several neurological disorders. Moreover, O.basilicum miRNAs regulate the key human target genes having significance in various diseases and important biological networks with 10 hub nodes interactions. Thus this study gives the pave for further studies to explore the potential of miRNA mediated cross kingdom regulation and treatment of various diseases including cancer.