Essential oil constituents and RAPD markers to establish species relationship in Cymbopogon Spreng. (Poaceae)

A Review of Botanical Extracts with Repellent and Insecticidal Activity and Their Suitability for Managing Mosquito-Borne Disease Risk in Mexico

Among the main arboviruses affecting public health in tropical regions are dengue, zika, and chikungunya, transmitted mainly by mosquitoes of the Aedes genus, especially Aedes aegypti. In recent years, outbreaks have posed major challenges to global health, highlighting the need for integrated and innovative strategies for their control and prevention. Prevention strategies include the elimination of vectors and avoiding mosquito bites; this can be achieved through the use of bioinsecticides and repellents based on plant phytochemicals, as they offer sustainable, ecological, and low-cost alternatives. Mexico has a variety of plants from which both extracts and essential oils have been obtained which have demonstrated significant efficacy in repelling and/or killing insect vectors. This review examines the current knowledge on plant species found in Mexico which are promising options concerning synthetic compounds in terms of their repellent and insecticidal properties against mosquitoes of the genus Aedes and that are friendly to the environment and health.

Phytochemical constituents, in-vitro anticancer activity and computational studies of Cymbopogon schoenanthus

The cytotoxic effects of Cymbopogon schoenanthus L. aerial part ethanol extract were examined against some cancer cell lines, and HUVEC normal cell lines using MTT assay. The ethanolic extract was prepared by ultrasonic-assisted extraction and analyzed by GC-MS and HPLC. The extract was found to be rich in terpene compounds. The extract proved to be highly selective and effective against breast and prostate cancer cell lines (MDA-MB-435, MCF-7, and DU 145) with IC50 as low as 0.7913 ± 0.14, 12.841 ± 0.21, and 30.51 ± 0.18 µg/ml, respectively. In silico modeling was performed to investigate the binding orientation and affinity of the major identified compounds against Polo-like kinase (PLK1 protein) a cancer molecular target using molecular docking and molecular dynamic whereas eudesm-5-en-11-ol, piperitone, and 2,3-dihydrobenzofuran displayed better binding affinity and stability against PLK1 compared to the reference drug. These findings encourage further in vivo studies to assess the anti-cancer effects of C. schoenanthus extract and its components.

Development and analysis of de novo transcriptome assemblies of multiple genotypes of Cymbopogon spp. reveal candidate genes involved in the biosynthesis of aromatic monoterpenes

Despite the high economic value of the monoterpene-rich essential oils from different genotypes of Cymbopogon, the knowledge about the genes and metabolic route(s) involved in the biosynthesis of aromatic monoterpenes in this genus is limited. In the present study, a comprehensive transcriptome analysis of four genotypes of Cymbopogon, displaying diverse quantitative and qualitative profiles of volatile monoterpenes in their essential oils has been carried out. The comparative analysis of the deduced protein sequences corresponding to the transcriptomes of the four genotypes revealed 4609 genotype-specific orthogroups, which might contribute in defining genotype-specific phenotypes. The transcriptome data mining led to the identification of unigenes involved in the isoprenogenesis. The homology searches, combined with the phylogenetic and expression analyses provided information about candidate genes concerning the biosynthesis of monoterpene aldehyde, monoterpene alcohol, and monoterpene esters. In addition, the present study suggests a potential role of geranial reductase like enzyme in the biosynthesis of monoterpene aldehyde in Cymbopogon spp. The detailed analysis of the candidate pathway genes suggested that multiple enzymatic routes might be involved in the biosynthesis of aromatic monoterpenes in the genus Cymbopogon. The present study provides deeper insights into the biosynthesis of monoterpenes, which will be useful for the genetic improvement of these aromatic grasses.

The Cytokinins BAP and 2-iP Modulate Different Molecular Mechanisms on Shoot Proliferation and Root Development in Lemongrass (Cymbopogon citratus)

The known activities of cytokinins (CKs) are promoting shoot multiplication, root growth inhibition, and delaying senescence. 6-Benzylaminopurine (BAP) has been the most effective CK to induce shoot proliferation in cereal and grasses. Previously, we reported that in lemongrass (Cymbopogon citratus) micropropagation, BAP 10 µM induces high shoot proliferation, while the natural CK 6-(γ,γ-Dimethylallylamino)purine (2-iP) 10 µM shows less pronounced effects and developed rooting. To understand the molecular mechanisms involved, we perform a protein-protein interaction (PPI) network based on the genes of Brachypodium distachyon involved in shoot proliferation/repression, cell cycle, stem cell maintenance, auxin response factors, and CK signaling to analyze the molecular mechanisms in BAP versus 2-iP plants. A different pattern of gene expression was observed between BAP- versus 2-iP-treated plants. In shoots derived from BAP, we found upregulated genes that have already been demonstrated to be involved in de novo shoot proliferation development in several plant species; CK receptors (AHK3, ARR1), stem cell maintenance (STM, REV and CLV3), cell cycle regulation (CDKA-CYCD3 complex), as well as the auxin response factor (ARF5) and CK metabolism (CKX1). In contrast, in the 2-iP culture medium, there was an upregulation of genes involved in shoot repression (BRC1, MAX3), ARR4, a type A-response regulator (RR), and auxin metabolism (SHY2).

Essential Oil Derived from Underutilized Plants Cymbopogon khasianus Poses Diverse Biological Activities against "Aspergillosis" and "Mucormycosis"

Palmrosa essential oil (PEO) from Cymbopogon khasianus, is used as complementary and traditional medicine worldwide. The present study aimed at compositional profiling of PEO and molecular docking of PEO bioactive compound geraniol against fungal enzymes chitin synthase (CS), UDP-glycosyltransferase (UDPG) and glucosamine-6-phosphate synthase (GPS), as apposite sites for drug designing against "Aspergillosis" and "Mucormycosis" and in vitro confirmation. Compositional profile of PEO was completed by GC-FID analysis. For molecular docking, Patch-dock tool was conducted. Ligand-enzyme 3D interactions were also calculated. ADMET properties (absorption, distribution, metabolism, excretion and toxicity) were also calculated. GC-FID discovered the occurrence of geraniol as a major component in PEO, thus nominated for docking analysis. Docking analysis specified active binding of geraniol to GPS, CS and UDPG fungal enzymes. Wet-lab authentication was achieved by three fungal strains Aspergillus niger, A. oryzae and Mucor sp. Docking studies revealed that ligand geraniol exhibited intercations with GPS, CS and UDPG fungal enzymes by H-bond and hydrophobic interactions. Geraniol obeyed LIPINSKY rule, and exhibited adequate bioactivity. Wet lab results indicated that PEO was able to inhibit fungal growth against "Aspergillosis" and "Mucormycosis".

Comparative transcriptional analysis of metabolic pathways and mechanisms regulating essential oil biosynthesis in four elite Cymbopogon spp

Cymbopogon is an important aromatic and medicinal grass with several species of ethnopharmaceutical importance. The genus is extremely rich in secondary metabolites, monoterpenes like geraniol and citral being principal constituents, also used as biomarker for classification and identification of Cymbopogon chemotypes. In the light of this, present study involved RNA sequencing and comparison of expression profiles of four contrasting Cymbopogon species namely C. flexuosus var. Chirharit (citral rich and frost resistant), C. martinii var. PRC-1 (geraniol rich), C. pendulus var. Praman (the most stable and citral-rich genotype), and Jamrosa (a hybrid of C. nardus var. confertiflorus × C. jwarancusa (rich in geraniol and geranyl acetate). The transcriptome profiles revealed marked differences in gene expression patterns of 28 differentially expressed genes (DEGs) of terpenoid metabolic pathways between the four Cymbopogon sp. The major DEGs were Carotenoid Cleavage Dioxygenases (CCD), Aspartate aminotransferase (ASP amino), Mevalonate E-4 hydroxy, AKR, GGPS, FDPS, and AAT. In addition, few TFs related to different regulatory pathways were also identified. The gene expression profiles of DEGs were correlated to the EO yield and their monoterpene compositions. Overall, the PRC-1 (C. martinii) shows distinguished gene expression profiles from all other genotypes. Thus, the transcriptome sequence database expanded our understanding of terpenoid metabolism and its molecular regulation in Cymbopogon species. Additionally, this data also serves as an important source of knowledge for enhancing oil yield and quality in Cymbopogon and closely related taxa. KEY MESSAGE: Unfolding the new secretes surrounding EO biosynthesis and regulation in four contrasting Cymbopogon species.

Molecular Fingerprinting and Phytochemical Investigation of Syzygium cumini L. from Different Agro-Ecological Zones of India

Syzygium cumini L. (ver Jamun; BlackBerry) is a native, evergreen multipurpose tree species of India. Besides being a fruit tree and for agroforestry in different regions, it is medicinally important too. This study aimed to determine genetic diversity using molecular and phytochemical markers in sixteen genotypes of Indian S. cumini from different agro-ecological zones. The present study used a combination of ISSR markers and the HPLC technique to explore these genotypes. The results showed a wide genetic diversity range based on the similarity coefficient values observed in S. cumini sixteen accessions from different sites. Four primary phenolic acids were discovered in all the accessions; caffeic acid (CA) was found in high concentrations. The intraspecific association between molecular and phytochemical characteristics was the primary goal of this investigation. By employing gene-specific markers for the route of secondary metabolites (polyphenols) production, it further investigated the progressive research of diversity analysis of polyphenol content in S. cumini accessions, which may also expand its nutraceutical and pharmaceutical utilization.

Review of phytomedicine, phytochemistry, ethnopharmacology, toxicology, and pharmacological activities of Cymbopogon genus

The Cymbopogon genus belongs to the Andropoganeae family of the family Poaceae, which is famous for its high essential oil concentration. Cymbopogon possesses a diverse set of characteristics that supports its applications in cosmetic, pharmaceuticals and phytotherapy. The purpose of this review is to summarize and connect the evidence supporting the use of phytotherapy, phytomedicine, phytochemistry, ethnopharmacology, toxicology, pharmacological activities, and quality control of the Cymbopogon species and their extracts. To ensure the successful completion of this review, data and studies relating to this review were strategically searched and obtained from scientific databases like PubMed, Google Scholar, ResearchGate, ScienceDirect, and Elsevier. Approximately 120 acceptable reviews, original research articles, and other observational studies were included and incorporated for further analysis. Studies showed that the genus Cymbopogon mainly contained flavonoids and phenolic compounds, which were the pivotal pharmacological active ingredients. When combined with the complex β-cyclodextrin, phytochemicals such as citronellal have been shown to have their own mechanism of action in inhibiting the descending pain pathway. Another mechanism of action described in this review is that of geraniol and citral phytochemicals, which have rose and lemon-like scents and can be exploited in soaps, detergents, mouthwash, cosmetics, and other products. Many other pharmacological effects, such as anti-protozoal, anti-bacterial, anti-inflammatory and anti-cancer have been discussed sequentially, along with how and which phytochemicals are responsible for the observed effect. Cymbopogon species have proven to be extremely valuable, with many applications. Its phytotherapy is proven to be due to its rich phytochemicals, obtained from different parts of the plant like leaves, roots, aerial parts, rhizomes, and even its essential oils. For herbs of Cymbopogon genus as a characteristic plant therapy, significant research is required to ensure their efficacy and safety for a variety of ailments.

Almutairi K, El Sabagh A. Genetic diversity analysis for wild and cultivated accessions of Cymbopogon citratus (D.C.) Stapf using phytochemical and molecular markers

Background

Genetic diversity is being lost because of increasing urbanization and decreasing cultivation land, which leads to the abrupt use of wild resources of medicinally aromatic plants (MAPs). Cymbopogon citratus is a morphologically diverse MAP that is largely exploited in the food, cosmetics, and pharmaceutical industries. However, the intraspecific phytochemical and molecular diversity of C. citratus has yet to be explored.

Methodology

The germplasm was obtained from four different countries representing Pakistan, India, Bangladesh, and the United States. Oil extraction was performed by hydro distillation, and metabolic profiles of different accessions were generated by GC-MS. Seventeen functional molecular markers based on three genes encoding cytochrome P450, uridyl diphosphate glycosyltransferase and the 5S rRNA gene family were used to explore genetic diversity. Principal component analysis (PCA) and heatmaps were constructed using R software with the help of the gg-plot R package v1.0.5 for data validation.

Results

Among the 208 identified metabolites, citral was maximal, with a phytochemical contribution (1.92-27.73%), α-pinene (0.82-15.57%), verbenol (0.24-22.84%), neral (0.23-21.31%) and geranial acetate (0.43-15.65%). In the majority of accessions, citral was the dominant component. The highest concentration of citral was detected in 384541 (27.74%), 384527 (27.52%) belonging to Pakistan and one USA-based accession 38456 (27.71%). Region-specific grouping revealed a relationship between genetic diversity and geographical location. Pakistani accessions 384518, 38452, and 384544 genetically and 384535, 384518, and 384510 were phytochemically diverse.

Conclusion

The genetic diversity was more pronounced in cultivated accessions than in wild accessions. Moreover, it was observed that phytochemical diversity correlated with the altitude and temperature of the region.

Evaluation of the In Vitro Antiparasitic Effect of the Essential Oil of Cymbopogon winterianus and Its Chemical Composition Analysis

Cymbopogon winterianus, known as “citronella grass”, is an important aromatic and medicinal tropical herbaceous plant. The essential oil of C. winterianus (EOCw) is popularly used to play an important role in improving human health due to its potential as a bioactive component. The present study aimed to identify the components of the essential oil of C. winterianus and verify its leishmanicidal and trypanocidal potential, as well as the cytotoxicity in mammalian cells, in vitro. The EOCw had geraniol (42.13%), citronellal (17.31%), and citronellol (16.91%) as major constituents. The essential oil only exhibited significant cytotoxicity in mammalian fibroblasts at concentrations greater than 250 μg/mL, while regarding antipromastigote and antiepimastigote activities, they presented values considered clinically relevant, since both had LC50 < 62.5 μg/mL. It can be concluded that this is a pioneer study on the potential of the essential oil of C. winterianus and its use against the parasites T. cruzi and L. brasiliensis, and its importance is also based on this fact. Additionally, according to the results, C. winterianus was effective in presenting values of clinical relevance and low toxicity and, therefore, an indicator of popular use.

NMR Metabolome-Based Classification of Cymbopogon Species: a Prospect for Phyto-equivalency of its Different Accessions Using Chemometric Tools

Cymbopogon species are widely distributed worldwide and known for their high essential oil content with potential commercial and medicinal benefits justifying for their inclusion in food and cosmetics. Most species received scant characterization regarding their full complement of bioactive constituents necessary to explain their medicinal activities. In this study, the metabolite profiles of 5 Cymbopogon species, C. citratus, C. flexuosus, C. procerus, C. martini, and C. nardus, were characterized via NMR-based metabolomics. The results of 13 shoot accessions revealed the identification and quantification of 23 primary and secondary metabolites belonging to various compound classes. Multivariate analyses were used for species classification, though found not successful in discrimination based on geographical origin. Nevertheless, C. citratus was found particularly enriched in neral, geranial, (E)-aconitic acid, isoorientin, and caffeic acid as the major characterizing metabolites compared to other species, while an unknown apigenin derivative appeared to discriminate C. martini. The high essential oil and phenolic content in C. citratus emphasizes its strong antioxidant activity, whereas (E)-aconitic acid accounts for its traditional use as insecticide. This study affords the first insight into metabolite compositional differences among Cymbopogon species. Moreover, antimicrobial, insecticidal, antidiabetic, and antioxidant compounds were identified that can be utilized as biomarkers for species authentication.

p-Menthadienols-rich essential oil from Cymbopogon martini ameliorates skin inflammation

Cymbopogon martini variety sofia, commonly known as ginger-grass, is an important aromatic crop used by the perfumery, medicinal and cosmetic industries worldwide. This study explores the chemical and possible pharmacological profile of hydro-distilled essential oil of C. martini variety sofia against skin inflammation. The essential oil extracted by the hydrodistillation process was analyzed by gas chromatography (GC), gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR) to identify its constituents, and was coded as CMA-01 for further in vitro and in vivo pharmacological study related to skin inflammation. The chemical fingerprint revealed that CMA-01 oil has (E)-p-mentha-2,8-dien-1-ol (21.0%), (E)-p-mentha-1(7),8-dien-2-ol (18.1%), (Z)-p-mentha-1(7),8-dien-2-ol (17.4%), (Z)-p-mentha-2,8-dien-1-ol (9.0%), limonene (7.7%), and (E)-carveol (5.7%) as major components. The pre-treatment of CMA-01 showed significant inhibition of pro-inflammatory markers in activated HaCat cells without cytotoxic effect. The in vivo study revealed the ameliorative impact of CMA-01 against skin inflammation induced by TPA in mouse ears as evidenced by a reduction of ear edema, pro-inflammatory mediators (IL-6, TNF-α), oxidative stress markers (malondialdehyde and nitric-oxide) and histological changes in ear tissues without any skin irritation response on rabbit skin. These findings suggest the suitability of CMA-01 as a valuable therapeutic candidate for the treatment of skin inflammation.

The Essential Oil-Bearing Plants in the United Arab Emirates (UAE): An Overview

Essential Oils (EOs) are expensive hydrocarbons produced exclusively by specific species in the plant kingdom. Their applications have deep roots in traditional herbal medicine, which lacks scientific evidence. Nowadays, more than ever, there is a growing global interest in research-based discoveries that maintain and promote health conditions. Consequently, EOs became a much attractive topic for both research and industry, with revenues reaching billions of dollars annually. In this work, we provide key guidance to all essential oil-bearing plants growing in the United Arab Emirates (UAE). The comprehensive data were collected following an extensive, up-to-date literature review. The results identified 137 plant species, including indigenous and naturalized ones, in the UAE, citing over 180 published research articles. The general overview included plant botanical names, synonyms, common names (Arabic and English), families and taxonomic authority. The study acts as a baseline and accelerator for research, industry and discoveries in multiple disciplines relying on essential oil-bearing plants.

Chemical profile, antiproliferative, antioxidant, and enzyme inhibition activities and docking studies of Cymbopogon schoenanthus (L.) Spreng. and Cymbopogon nervatus (Hochst.) Chiov. from Sudan

Essential oils from the inflorescence of Cymbopogon schoenanthus and C. nervatus growing in Northern Sudan were examined for their chemical composition, antiproliferative activity against human breast carcinoma and human colon adenocarcinoma cell lines, antioxidant activity (phosphomolybdenum, antiradical, reducing power, and ferrous chelating), and enzyme inhibition activity against acetylcholinesterase butyrylcholinesterase, tyrosinase, α-glucosidase, and α-amylase. In silico study on the inhibition of tyrosinase and α-amylase was also performed. Piperitone (59.1%) and isomers of para-menthadienols (35.3%) were the main compounds in C. schoenanthus and C. nervatus oils, respectively. Oil from C. nervatus possessed higher antioxidant activity than that from C. schoenanthus except for its metal chelating ability. Both oils showed high antiproliferative activity. In silico study showed that trans-p-mentha-2,8-dien-1-ol and piperitone (both isomers) revealed the best docking scores for α-amylase and tyrosinase, respectively. In conclusion, oils from these two Cymbopogon species could be new natural agents with functional properties for food, cosmetics, and pharmaceutical industries. PRACTICAL APPLICATIONS: Recently, there is a growing tendency to replace synthetic oils by natural ones in the cosmetic, food, and pharmaceutical products. In this context, we investigated the chemical characterization and biological activities of two Cymbopogon species essential oils (C. schoenanthus (L.) Spreng. and C. nervatus). Antioxidant capacity, enzyme inhibition, and antiproliferative effects were tested for biological activities. Chemical characterization was identified by GC-MS. Based on our findings, the Cymbopogon species may be utilized as sources of natural bioactive agents in food industries.

Evaluation of Trace Metal Profile in Cymbopogon validus and Hyparrhenia hirta Used as Traditional Herbs from Environmentally Diverse Region of Komga, South Africa

FAAS was used for the analysis of trace metals in fresh and dry plant parts of Cymbopogon validus and Hyparrhenia hirta species with the aim of determining the trace metals concentrations in selected traditional plants consumed in Eastern Cape, South Africa. The trace metal concentration (mg/kg) in the samples of dry Cymbopogon validus leaves (DCVL) showed Cu of 12.40 ± 1.000; Zn of 2.42 ± 0.401; Fe of 2.50 ± 0.410; Mn of 1.31 ± 0.210; Pb of 3.36 ± 0.401 mg/kg, while the samples of fresh Hyparrhenia hirta flowers (FHHF) gave Cu of 9.77 ± 0.610; Zn of 0.70 ± 0.200; Fe of 2.11 ± 0.200; Mn of 1.15 ± 0.080; Pb of 3.15 ± 0.100 mg/kg. Abundance of metal concentrations follows the order: Cu > Fe > Pb > Mn > Zn in the flower samples of Cymbopogon validus and Hyparrhenia hirta species. The concentrations of trace metals in both plant parts were below the permissible limits (PL) set by WHO. It is suggested that pharmacovigilance be carried out periodically to improve the quality, safety, and efficiency of various herbal products.

Anti-inflammatory activity of the essential oils of Cymbopogon validus (Stapf) Stapf ex Burtt Davy from Eastern Cape, South Africa

OBJECTIVE

To evaluate the essential oil composition and the anti-inflammatory activity of Cymbopogon validus (C. validus) leaves and flowers.

METHODS

A total of 300 g of fresh or dry (leaves and flowers) of C. validus were cut into small pieces and subjected to hydro-distillation method for approximately 5 h using the Clevenger apparatus. The extracted essential oils were then used for testing the anti-inflammatory activity. The anti-inflammatory activity was evaluated by using egg albumin-induced paw edema.

RESULTS

The extracted oils had the following yields 2.2% for fresh leaves, 2.0% for dry leaves and 2.4% v/w for dry flowers. GC-MS results revealed that the oils contained artemisia ketone (37.5%), linalool (3.2%-29.6%), northujane (4.4%-16.8%), verbenone (13.5%), naphthalene (1.7%-9.6%), δ-cadinene (0.5%-8.1%), hedycaryol (5.4%-7.6%) and α-eudesmol (6.5%-6.7%) as the major constituents. C. validus essential oils showed significant (P < 0.05) anti-inflammatory effects from the first 30 min after albumin injection compared to aspirin which had a later onset of effect.

CONCLUSIONS

The findings of this study show that the essential oil extracted from C. validus fresh or dry leaves and flowers have anti-inflammatory properties; that might be associated with the major components and the minor components found in the essential oils.

Varietal Discrimination and Genetic Variability Analysis of Cymbopogon Using RAPD and ISSR Markers Analysis

Cymbopogon is an important genus of family Poaceae, cultivated mainly for its essential oils which possess high medicinal and economical value. Several cultivars of Cymbopogon species are available for commercial cultivation in India and identification of these cultivars was conceded by means of morphological markers and essential oil constitution. Since these parameters are highly influenced by environmental factors, in most of the cases, it is difficult to identify Cymbopogon cultivars. In the present study, Random amplified polymorphic DNA (RAPD) and Inter-simple sequence repeat (ISSR) markers were employed to discriminate nine leading varieties of Cymbopogon since prior genomic information is lacking or very little in the genus. Ninety RAPD and 70 ISSR primers were used which generated 63 and 69 % polymorphic amplicons, respectively. Similarity in the pattern of UPGMA-derived dendrogram of RAPD and ISSR analysis revealed the reliability of the markers chosen for the study. Varietal/cultivar-specific markers generated from the study could be utilised for varietal/cultivar authentication, thus monitoring the quality of the essential oil production in Cymbopogon. These markers can also be utilised for the IPR protection of the cultivars. Moreover, the study provides molecular marker tool kit in both random and simple sequence repeats for diverse molecular research in the same or related genera.

Himalayan Aromatic Medicinal Plants: A Review of their Ethnopharmacology, Volatile Phytochemistry, and Biological Activities

Aromatic plants have played key roles in the lives of tribal peoples living in the Himalaya by providing products for both food and medicine. This review presents a summary of aromatic medicinal plants from the Indian Himalaya, Nepal, and Bhutan, focusing on plant species for which volatile compositions have been described. The review summarizes 116 aromatic plant species distributed over 26 families.

De Novo Sequencing and Analysis of Lemongrass Transcriptome Provide First Insights into the Essential Oil Biosynthesis of Aromatic Grasses

Aromatic grasses of the genus Cymbopogon (Poaceae family) represent unique group of plants that produce diverse composition of monoterpene rich essential oils, which have great value in flavor, fragrance, cosmetic, and aromatherapy industries. Despite the commercial importance of these natural aromatic oils, their biosynthesis at the molecular level remains unexplored. As the first step toward understanding the essential oil biosynthesis, we performed de novo transcriptome assembly and analysis of C. flexuosus (lemongrass) by employing Illumina sequencing. Mining of transcriptome data and subsequent phylogenetic analysis led to identification of terpene synthases, pyrophosphatases, alcohol dehydrogenases, aldo-keto reductases, carotenoid cleavage dioxygenases, alcohol acetyltransferases, and aldehyde dehydrogenases, which are potentially involved in essential oil biosynthesis. Comparative essential oil profiling and mRNA expression analysis in three Cymbopogon species (C. flexuosus, aldehyde type; C. martinii, alcohol type; and C. winterianus, intermediate type) with varying essential oil composition indicated the involvement of identified candidate genes in the formation of alcohols, aldehydes, and acetates. Molecular modeling and docking further supported the role of identified protein sequences in aroma formation in Cymbopogon. Also, simple sequence repeats were found in the transcriptome with many linked to terpene pathway genes including the genes potentially involved in aroma biosynthesis. This work provides the first insights into the essential oil biosynthesis of aromatic grasses, and the identified candidate genes and markers can be a great resource for biotechnological and molecular breeding approaches to modulate the essential oil composition.

Could plant extracts have enabled hominins to acquire honey before the control of fire?

Honey is increasingly recognized as an important food item in human evolution, but it remains unclear whether extinct hominins could have overcome the formidable collective stinging defenses of honey bees during honey acquisition. The utility of smoke for this purpose is widely recognized, but little research has explored alternative methods of sting deterrence such as the use of plant secondary compounds. To consider whether hominins could have used plant extracts as a precursor or alternative to smoke, we review the ethnographic, ethnobotanical, and plant chemical ecology literature to examine how humans use plants in combination with, and independently of, smoke during honey collection. Plant secondary compounds are diverse in their physiological and behavioral effects on bees and differ fundamentally from those of smoke. Plants containing these chemicals are widespread and prove to be remarkably effective in facilitating honey collection by honey hunters and beekeepers worldwide. While smoke may be superior as a deterrent to bees, plant extracts represent a plausible precursor or alternative to the use of smoke during honey collection by hominins. Smoke is a sufficient but not necessary condition for acquiring honey in amounts exceeding those typically obtained by chimpanzees, suggesting that significant honey consumption could have predated the control of fire.

Cymbopogon species; ethnopharmacology, phytochemistry and the pharmacological importance

Cymbopogon genus is a member of the family of Gramineae which are herbs known worldwide for their high essential oil content. They are widely distributed across all continents where they are used for various purposes. The commercial and medicinal uses of the various species of Cymbopogon are well documented. Ethnopharmacology evidence shows that they possess a wide array of properties that justifies their use for pest control, in cosmetics and as anti-inflammation agents. These plants may also hold promise as potent anti-tumor and chemopreventive drugs. The chemo-types from this genus have been used as biomarkers for their identification and classification. Pharmacological applications of Cymbopogon citratus are well exploited, though studies show that other species may also useful pharmaceutically. Hence this literature review intends to discuss these species and explore their potential economic importance.

Molluscicidal and larvicidal activities and essential oil composition of Cymbopogon winterianus

CONTEXT. Cymbopogon winterianus Jowitt ex Bor (Poaceae), known as citronella grass, is an aromatic herbaceous plant and the essential oil extracted from this grass is used in cosmetics, perfumes, hygiene and cleanliness products worldwide.

OBJECTIVE

This study investigated the composition and molluscicidal and larvicidal activities of the essential oil of C. winterianus cultivated in North Brazil.

MATERIALS AND METHODS

The oil was obtained by hydrodistillation, analyzed by gas chromatography (GC) and GC-mass spectrometry and then its molluscicidal and larvicidal activities against snails (Biomphalaria glabrata) and hatched larvae of Artemia salina, respectively, were evaluated at concentrations from 10 to 1000 mg/L.

RESULTS

The main constituents of oil were citronellal (26.5%), geraniol (16.2%), elemol (14.5%) and citronellol (7.3%). The molluscicidal test revealed significant lethal concentration (LC) values (LC90=97.0 mg/L, LC50=54.0 mg/L and LC20=22.0 mg/L), indicating the presence of molluscicidal compounds in the oil. In addition, the oil showed moderate larvicidal activity (LC50=181.0 mg/L) against the larvae of A. salina, which could justify its use in the aquatic environment without affecting other living organisms.

DISCUSSION AND CONCLUSION

The results suggest that the oil of C. winterianus could be an effective alternative to control schistosomiasis, with an average margin of safety to other living organisms that coexist with snails.

Chemical and genetic differentiation of two Mediterranean subspecies of Teucrium scorodonia L

Chemical and genetic diversity of Teucrium scorodonia L. subsp. scorodonia from Corsica and T. scorodonia L. subsp. baeticum from western Algeria were investigated. Diversity within and among the two populations of subspecies was assessed according to the chemical composition of their essential oils, and genetic diversity was evaluated using three polymorphic genetic markers. Chemical analysis was performed using a combination of capillary GC-RI and GC/MS after fractionation using column chromatography. Genetic structures were mapped using two chloroplast markers (RPL32-TRNL and TRNL-F) and ribosomal nuclear markers (ITS region). The statistical analysis showed that the two subspecies were clearly distinguished by these chemical and genetic markers. The chemical composition of oil differed qualitatively and quantitatively between the subspecies. Corsican oil samples contained germacrene B (4.2-8.8%) and γ-elemene (2.6-5.7%), which were not detected in Algerian oil samples. The oils of the scorodonia and baeticum subspecies were dominated by sesquiterpene hydrocarbon compounds (75.6-82.9% and 69.6-79.4%, respectively), but they differed in oxygenated sesquiterpene content (3.1-8.9% and 8.4-20.3%, respectively). Neighbor-joining trees constructed from chloroplast DNA and ITS region sequences showed the existence of two groups associated with taxonomic and chemical characteristics. One group consisted of T. scorodonia subsp. scorodonia and the other of T. scorodonia subsp. baeticum, indicating that variation in the essential oil composition of T. scorodonia subspecies depends more on genetic background than environmental characteristics.

Essential Oil Biosynthesis and Regulation in the Genus Cymbopogon

Essential oils distilled from Cymbopogon species are of immense commercial value as flavors and fragrances in the perfumery, cosmetics, soaps, and detergents and in pharmaceutical industries. Two major constituents of the essential oil, geraniol and citral, due to their specific rose and lemon like aromas are widely used as flavors, fragrances and cosmetics. Citral is also used for the synthesis of vitamin A and ionones (for example, β-ionone, methyl ionone). Moreover, Cymbopogon essential oils and constituents possess many useful biological activities including cytotoxic, antiinflammatory and antioxidant. Despite the immense commercial and biological significance of the Cymbopogon essential oils, little is known about their biosynthesis and regulatory mechanisms. So far it is known that essential oils are biosynthesized via the classical acetate-MVA route and existence of a newly discovered MEP pathway in Cymbopogon remains as a topic for investigation. The aim of the present review is to discuss the biosynthesis and regulation of essential oils in the genus Cymbopogon with given emphasis to two elite members, lemongrass (C. flexuosus Nees ex Steud) and palmarosa (C. martinii Roxb.). This article highlights the work done so far towards understanding of essential oil biosynthesis and regulation in the genus Cymbopogon. Also, based on our experiences with Cymbopogon species, we would like to propose C. flexuosus as a model system for the study of essential oil metabolism beyond the much studied plant family Lamiaceae.

Genetic diversity and population structure of Teucrium polium (Lamiaceae) in Tunisia

Random amplified polymorphic DNA markers were used to assess the genetic diversity within and among seven Tunisian diploid and polyploid populations of Teucrium polium L. from five bioclimatic areas. Out of the 141 bands generated from eight selected primers, 124 were polymorphic. The genetic diversity within a population (Shannon's index) was high and varied according both the ploidal levels and bioclimatic zones. The genetic differentiation among populations assessed by G (ST) and Phi(ST) statistics was high, suggesting a low level of gene flow among them. The major proportion of the variation was attributable to individual differences within populations. The UPGMA analysis based on Nei and Li's coefficient showed that individuals from each population clustered together. In a dendrogram using the Phi(ST) distance matrix, population grouping is concordant with bioclimates and cytotypes. Conservation strategies should take into account the level of the genetic diversity of the populations according to their bioclimate and ploidal levels.

Essential Oils and Anxiolytic Aromatherapy

A number of essential oils are currently in use as aromatherapy agents to relieve anxiety, stress, and depression. Popular anxiolytic oils include lavender (Lavandula angustifolia), rose (Rosa damascena), orange (Citrus sinensis), bergamot (Citrus aurantium), lemon (Citrus limon), sandalwood (Santalum album), clary sage (Salvia sclarea), Roman chamomile (Anthemis nobilis), and rose-scented geranium (Pelargonium spp.). This review discusses the chemical constituents and CNS effects of these aromatherapeutic essential oils, as well as recent studies on additional essential oils with anxiolytic activities.

Integrating Plant Essential Oils and Kaolin for the Sustainable Management of Thrips and Tomato Spotted Wilt on Tomato

Thrips-vectored Tomato spotted wilt virus is one of the most devastating pest complexes affecting tomato in the southern United States and elsewhere. Field trials were conducted over 2 years to determine the effects of volatile plant essential oils and kaolin-based particle films on the incidence of tomato spotted wilt and population dynamics of Frankliniella spp. thrips. The essential oils, geraniol (a monoterpene constituent of various plant essential oils), lemongrass (Cymbopogon flexuosus) oil, and tea tree (Melaleuca alternifolii) oil, were compared with a standard insecticide treatment and an untreated control. All treatments were applied with and without kaolin, in a 5 × 2 factorial design. Although the treatments did not clearly affect the abundance of vector species, there were treatment differences in the incidence of tomato spotted wilt. When combined with kaolin, the three essential oils reduced tomato spotted wilt incidence by 32 to 51% in 2005 and by 6 to 25% in 2006 compared with the control. In both years, tea tree oil plus kaolin reduced tomato spotted wilt as well as the standard insecticide treatments. Overall, kaolin significantly increased yield by over 26% compared to treatments without kaolin. When applied with kaolin, the three essential oils produced yields similar to the insecticide standard. Therefore, naturally occurring products, such as essential oils and kaolin, could be used successfully to reduce insecticide use on tomatoes.

Regulation of oil accumulation in single glands of Eucalyptus polybractea

The accumulation of terpenoid oil was examined in the leaves of Eucalyptus polybractea at scales ranging from individual oil glands to the whole plant. Variations in oil composition and concentration of oil were measured and related to both morphological and physiological parameters. Within a plant, all glands produced oil of broadly similar composition that was not regulated by leaf age or the position of the gland within the leaf. There were, however, distinct differences between plants, suggesting that composition is controlled primarily at the whole-plant level. Oil concentration, too, was regulated primarily at the whole-plant level and was limited by gland capacity. Gland capacity was linked to leaf area and thickness, the final products of leaf expansion. Leaf and plant oil composition is determined not by a mosaic of glands specializing in producing a single or a small group of compounds, but rather by glands with remarkably similar capacities for terpenoid biosynthesis, although oil concentration, limited by gland capacity, may be linked to leaf expansion rather than biosynthetic capacity.