Larvicidal efficacy of monoterpenes against the larvae of Anopheles gambiae

Objective:To evaluate the larvicidal efficacy of eight volatile components of essential oils against 3rd instar larvae of Anopheles gambiae s.s.Methods:Larvicidal effects of each compound were evaluated in both laboratory and semi-field trials.Stock solution was prepared and serial dilutions were made in six concentrations for each compound.A total of 20 larvae were exposed to larvicides for each replicate and monitored at intervals of 12,24,48 and 72 h.Larvae monitoring was done on basis of dead and live larvae in all intervals.Results:All assayed compounds were larvicides and presented varying degrees of larval toxicity,with LC50 values ranging from 1.28 to 1 938.92 mg/L depending on the treatment time(12,24,48 or 72 h).(-)-Perillyl alcohol presented the strongest larvicidal activity towards Anopheles gambiae larvae,with LC_(50) values of 73.60,18.36,1.72 and1.28 mg/L after 12,24,48 and 72 h of exposure,respectively.The next strongest were(-)-isopulegol(LC_(50)= 135.10,49.39,34.39 and 20.22 mg/L) and(-)-carvone epoxide(LC_(50)= 168.86,124.74,80.84 and 23.46 mg/L).After 12,24 and 48 h of treatment,hydroxydihydrocarvone was the least toxic compound,with LC_(50) values of 1 938.92,1 172.18 and 401.03 mg/L,respectively.Conclusions:The data obtained in this study suggest that all evaluated monoterpenes,especially(-)-perillyl alcohol,have remarkable larvicidal effects and may be considered as potential sources for the development of suitable natural larvicides for mosquito management programs.Further small-scale field trials should be conducted.

Highly Oxygenated Monoterpenes from Eupatorium fortunei

A pair of epimers of highly-oxygenated monoterpenes were isolated from the traditional Chinese medicine Eupatorium fortunei. Their structures were elucidated on the basis of the spectral analysis as （1R＊, 2S＊, 3R＊, 4R＊, 6S＊）-1, 2, 3, 6-tetrehydroxy-p-menthane （1） and （1S＊, 2S＊, 3S＊, 4R＊, 6R＊）-1, 2, 3, 6-tetrehydroxy-p-menthane （2）.

Cyclization mechanism of monoterpenes catalyzed by monoterpene synthases in dipterocarpaceae

Monoterpenoids are typically present in the secretory tissues of higher plants,and their biosynthesis is catalyzed by the action of monoterpene synthases(MTSs).However,the knowledge about these enzymes is restricted in a few plant species.MTSs are responsible for the complex cyclization of monoterpene precursors,resulting in the production of diverse monoterpene products.These enzymatic reactions are considered exceptionally complex in nature.Therefore,it is crucial to understand the catalytic mechanism of MTSs to elucidate their ability to produce diverse or specific monoterpenoid products.In our study,we analyzed thirteen genomes of Dipterocarpaceae and identified 38 MTSs that generate a variety of monoterpene products.By focusing on four MTSs with different product spectra and analyzing the formation mechanism of acyclic,monocyclic and bicyclic products in MTSs,we observed that even a single amino acid mutation can change the specificity and diversity of MTS products,which is due to the synergistic effect between the shape of the active cavity and the stabilization of carbon-positive intermediates that the mutation changing.Notably,residues N340,I448,and phosphoric acid groups were found to be significant contributors to the stabilization of intermediate terpinyl and pinene cations.Alterations in these residues,either directly or indirectly,can impact the synthesis of single monoterpenes or their mixtures.By revealing the role of key residues in the catalytic process and establishing the interaction model between specific residues and complex monoterpenes in MTSs,it will be possible to reasonably design and engineer different catalytic activities into existing MTSs,laying a foundation for the artificial design and industrial application of MTSs.

Atmospheric isoprene and monoterpenes in a typical urban area of Beijing： Pollution characterization, chemical reactivity and source identification

Continuous observation of isoprene, β-pinene and β-pinene was carried out in a typical urban area of Beijing from March 2014 to February 2015, using an AirmoVOC online analyzer. Based on the analysis of the ambient level and variation characteristics of isoprene, β-pinene and β- pinene, the chemical reactivity was studied, and their sources were identified. Results showed that the concentrations of isoprene, α-pinene and β-pinene in the urban area of Beijing were lower than those in richly vegetated areas; the concentrations of isoprene were at a moderate level compared with those of previous studies of Beijing. Concentrations of isoprene, α-pinene and β-pinene showed different seasonal, monthly, daily and diurnal variations, and all of the three species showed higher level at night than those in the daytime as a whole, the variations of isoprene, α-pinene and β-pinene mainly influenced by emission of sources, photochemical reaction, and meteorological parameters. Isoprene was the largest contributor to the total OFP values than β-pinene and β-pinene. α-Pinene was the largest contributor to the total SOAFP values than isoprene and β-pinene in autumn, while isoprene was the largest one in other seasons. Isoprene, α-pinene and β-pinene were derived mainly from biological sources; and α- pinene level were also affected by industrial sources. To reduce the concentrations of isoprene, α-pinene and β-pinene, it is necessary to scientifically select urban green plant species, and more strict control measures should be taken to reduce the emission of β-pinene from industrial sources, such as artificial flavors and resins synthesis processes.

Characteristics and possible origins of atmospheric monoterpenes from nonliving plants in Guangzhou

Monoterpenes in ambient air were determined in various sites in Guangzhou, and it was revealed that monoterpene concentrations in some special sites, like landfills, were even higher than those in locations with much more vegetation. On the average, monoterpene contents in samples from streets and highways were 1.9 μg/m3; from gardens, plantations and wooded lands, 2.2 μg/m3; from farmlands, 1.5 μg/m3; but from landfills, 4.1 μg/m3. So other sources like landfills, apart from living plants, might also contribute to the biogenic non-methane hydrocarbons (NMHCs) in the atmospheric environment. On the other hand, the composition pattern of monoterpenes in air samples from landfills were obviously different compared with those from living plants, this might result from the different synthesis pathways of monoterpenes, the oxygen-depleted environment and the microbiogenic process might affect the synthesis in landfills.

Spruce budworm feeding and oviposition are stimulated by monoterpenes in white spruce epicuticular waxes

Monoterpenes, source of the distinctive odor of conifers, are generally considered plant defensive compounds. However, they are also known to act as long-range insect attractants, as they are volatile and permeate forest airspaces. Moreover, they are lipid soluble and can be absorbed into plant epicuticular waxes. We test their role in short-range host plant choice by both adult females and larvae of a folivorous forest pest （Choristoneura fumiferana）. We conducted laboratory assays testing the responses of Eastern spruce budworm to an artificial monoterpene mix （α-pinene, β-pinene, limonene, myrcene） and to white spruce （Picea glauca） epicuticular waxes in closed arenas. Ovipositing females pre- ferred filter paper discs treated with P. glauca waxes to controls, and preferred the waxes ＋ monoterpenes treatment to waxes alone. However, females showed no preference between the monoterpene-treated disc and the control when presented without waxes. Feeding larvae prefered wax discs to control discs. They also consumed discs treated with realistic monoterpene concentrations and wax preferentially over wax-only discs, but showed no preference between extremely high monoterpene concentrations and wax-only controls. In an insect-free assay, P. glauca epicuticular wax decreased monoterpene volatilization. These results suggest that P. glauca waxes and realistic concentrations of monoterpenes are stimulatory to both egg-laying females and feeding larvae, and that their effects are synergistic.

Identification of key gene networks controlling monoterpene biosynthesis during grape ripening by integrating transcriptome and metabolite profiling

Monoterpenes are typical aroma components of muscat grape cultivars,providing pleasant floral and fruity aromas to grapes and wines.However,the molecular mechanism of monoterpene biosynthesis between muscat and non-muscat grape remains unclear.Here,the muscat grape cultivar‘Jumeigui’and the non-muscat grape cultivar‘Kyoho’were chosen as plant materials for a comprehensive transcriptome and metabolite analysis.The gas chromatography-mass spectrometry(GC-MS)analysis demonstrated that a total of 27 and 23 monoterpene compounds were identified and quantified in the‘Jumeigui’and‘Kyoho’grape,respectively.‘Jumeigui’grape accumulated significantly higher concentrations of monoterpenes than‘Kyoho’grape.Furthermore,geraniol,linalool,geranic acid,and β-citronellol might be important odorants contributing to the floral character of the‘Jumeigui’grape due to the high levels odor activity values(OAVs).Transcriptome analysis demonstrated that the expression profiles of VvDXS,VvGGPPS.SSU1,Vv TPS-b/g showed a positive correlation with monoterpene accumulation in grapes.In addition,the expression patterns of the genes involved in jasmonic acid(JA)synthesis and signal were also positively correlated with monoterpene accumulation.All these results will help guide the functional verification of candidate genes related to monoterpene biosynthesis,as well as identify the master transcriptional and hormonal regulators of this pathway in grapes.

Uncarialines A-E,new alkaloids from Uncaria rhynchophylla and their anticoagulant activity

Uncarialines A-E(1-5),five undescribed monoterpene indole alkaloids,together with five known analogues were obtained from the stems of Uncaria rhynchophylla.Alkaloids 1-3 were unique 3,4-seco-tricyclic alkaloids with a 6/5/10 ring system,while 4 and 5 possessed a rare rearranged scaffold originated from corynantheine-type alkaloids with C-2/C-7 oxidation.Their structures were characterized by a comprehensive analysis of MS,NMR,and ECD.Their effects on blood clotting times of human plasma were evaluated and alkaloid 5 had a slight prolongation effect on both thrombin time and activated partial thromboplastin time(p<0.001).

Antifungal activity and antidiarrheal activity via antimotility mechanisms of (-)-fenchone in experimental models

BACKGROUND(-)-Fenchone is a bicyclic monoterpene present in essential oils of plant species,such as Foeniculum vulgare and Peumus boldus,used to treatment of gastrointestinal diseases.Pharmacological studies report its anti-inflammatory,antioxidant,and antinociceptive activity.AIM To investigate antidiarrheal activity related to gastrointestinal motility,intestinal secretion and antimicrobial activity.METHODS A castor oil-induced diarrhea model was used to evaluate antidiarrheal activity.Intestinal transit and gastric emptying protocols were used to assess a possible antimotility effect.Muscarinic receptors,presynaptic α2-adrenergic and tissue adrenergic receptors,KATP channels,nitric oxide were investigated to uncover antimotility mechanisms of action and castor oil-induced enteropooling to elucidate antisecretory mechanisms.The antimicrobial activity was evaluated in the minimum inhibitory concentration model,the fractional inhibitory concentration index using the(-)-fenchone association method with standard antifungal agents.RESULTS(-)-Fenchone(75,150 and 300 mg/kg)showed antidiarrheal activity,with a significant decrease in the evacuation index.This activity is possibly related to a percentage of reduced intestinal transit(75,150 and 300 mg/kg).The antimotility effect of(-)-fenchone decreased in the presence of pilocarpine,yohimbine,propranolol,L-NG-nitroarginine methyl ester or glibenclamide.In the enteropooling model,no reduction in intestinal fluid weight was observed.(-)-Fenchone did not show antibacterial activity;on the other hand,inhibits the growth of strains of fungi with a minimum fungicide concentration of 32μg/mL.However,when it was associated with amphotericin B,no synergism was observed.CONCLUSION The antidiarrheal effect of(-)-fenchone in this study involves antimotility effect and not involve antisecretory mechanisms.(-)-Fenchone presents antifungal activity;however,it did not show antibacterial activity.

Chemical diversity of essential oils from flowers,leaves,and stems of Rhanterium epapposum Oliv. growing in northern border region of Saudi Arabia

Objective:To evaluate the medicinal uses of Rhanterium epapposum Oliv.(R.epapposum) growing in northern border region of Saudi Arabia,through the chemical diversity of essential oils extracted from its flowers,leaves and stems.Methods:Aerial parts of R.epapposum were collected in April 2014.Air dried flowers,leaves,and stems were separately subjected to hydrodistillation in a Clevenger-type apparatus for 4 h to extract the essential oils.Gas chromatography-mass spectrometry analysis of the essential oils was carried out using an Agilent 6890 gas chromatograph equipped with an Agilent 5973 mass spectrometric detector.Results:A total of 51 compounds representing 76.35%–94.86% of flowers,leaves and stems oils composition were identified.The chemical profiles of the studied fractions revealed the dominance of monoterpenes,regardless of qualitative and quantitative differences observed.Limonene,linalool,4-terpineol and a-cadinol represented the major constituents of flowers oil.Leaves oil was dominated by limonene,sabinene,a-pinene and b-myrcene whereas linalool,ionole,a-cadinol,b-eudesmol,4-terpineol,and aterpineol were the major constituents of stems oil.Conclusions:Essential oils from flowers,leaves and stems of R.epapposum growing in northern border region of Saudi Arabia are considered as a rich source of monoterpenes which have biological activities.

Antimicrobial Activity of Essential Oil of <i>Zingiber officinale</i>Roscoe (Zingiberaceae)

Zingiber officinale, commonly known as ginger, is a species native of tropical Asia. It is grown and used in tropical countries of America, including Mexico, where it is used for the treatment of throat infections. The aim of this study was to determine the chemical composition of essential oil of Z. officinale rhizome and evaluate their antimicrobial activity. The essential oil was obtained by hydrodistillation, and the chemical composition of the oil was determined by GC-MS. To determine the antimicrobial activity diffusion, agar dilution and radial growth inhibition methods were employed. Microbial growth curves were performed on the strains most susceptible. It was identified 28 compounds in the essential oil, the most abundant were eudesmol (8.19%), γ-terpinene (7.88 %), a-curcumene (7.28%), alloaromadendrene (6.56%), zingiberene (6.06 %), α-pinene (5.76 %), δ-cadinene (3.84%), elemol (3.39%), farnesal (3.45%), E-β-farnesene (3.57%), neril acetate (2.8%) and β-myrcene (2.94%). In antimicrobial activity, the essential oil inhibited the growth of 15 bacterial strains, 3 of yeast fungi and 4 of mycelia fungi. The most susceptible strains were S. aureus FES-I (MIC = 0.25 mg/mL) S. epidemidis FES-C (MIC = 0.5 mg/mL), E. faecalis ATCC 14506 (MIC = 1.0 mg/mL), C. tropicalis (CMI = 0.125 mg/mL) and T. mentagrophytes (CF50 = 0.08 mg/mL). In the microbial growth curves the essential oil showed bactericidal effect on S. aureus FES-I and S. marcescens ATCC 14756 from the first hour of exposure of the strains to oil, eliminating 99.9% of CFU in concentrations of 0.5 and 0.75 mg/mL respectively. The results validate the medicinal use of Z. officinale in the treatment of diseases of possible infectious origin.

Itoside O,a new linear monoterpene glycoside from the bark and twigs of Itoa orientalis

To investigate the chemical components of the barks and twigs ofltoa orientalis. A new linear monoterpene glycoside named itoside O was isolated from the crude extract of Itoa orientalis together with 11 known compounds. The new compound was identified to be 3,7-dimethyl-1, 6-octadien-3, 10-dihydroxyl-10-O-α-L-arabinopyranosyl （1 -→6）-O-β-D-glucopyranoside by 1D and 2D NMR analysis, and all known compounds were isolated from this plant for the first time.

Investigation of natural VOC emitted from tropical vegetations in China

Twenty three kinds of typical plants in Xishuangbanna, the tropical area of southwestern China, were screened to estimate the emission rates of isoprene and monoterpenes by adopting bag enclosure and curette sampling methods followed by a GC FID analysis. It was found that the Ficus species were mainly emitting isoprene and most tropical vegetations were mainly releasing monoterpenes. The results also showed that the emissions of isoprene were affected by both temperature and PAR(Photosynthetic Active Radiation), while monoterpene emissions were mainly temperature dependent.

Characteristics and chemical reactivity of biogenic volatile organic compounds from dominant forest species in the Jing-Jin-Ji area,China

Background:Biogenic volatile organic compounds(BVOCs)play an essential role in tropospheric atmospheric chemical reactions.There are few studies conducted on BVOCs emission of dominant forest species in the Jing-Jin-Ji area of China.Based on the field survey,forest resources data and the measured standard emission factors,the Guenther model developed in 1993(G93)was applied in this paper to estimate the emission of BVOCs from several dominant forest species(Platycladus orientalis,Quercus variabilis,Betula platyphylla,Populus tomentosa,Pinus tabuliformis,Robinia pseudoacacia,Ulmus pumila,Salix babylonica and Larix gmelinii)in the Jing-Jin-Ji area in 2017.Then the spatiotemporal emission characteristics and atmospheric chemical reactivity of these species were extensively evaluated.Results:The results showed that the total annual BVOCs emission was estimated to be 70.8 Gg C·year^(−1),consisting 40.5%(28.7 Gg C·year^(−1))of isoprene,36.0%(25.5 Gg C·year^(−1))of monoterpenes and 23.4%(16.6 Gg C·year^(−1))of other VOCs.The emissions from Platycladus orientalis,Quercus variabilis,Populus tomentosa and Pinus tabulaeformis contributed 56.1%,41.2%,36.0% and 31.1%,respectively.The total BVOCs emission from the Jing-Jin-Ji area accounted for 61.9% and 1.8%in summer and winter,respectively.Up to 28.8% of emission was detected from Chengde followed by Beijing with 24.9%,that mainly distributed in the Taihang Mountains and the Yanshan Mountains.Additionally,the Robinia pseudoacacia,Populus tomentosa,Quercus variabilis,and Pinus tabulaeformis contributed mainly to BVOCs reaction activity.Conclusions:The BVOCs emission peaked in summer(June,July,and August)and bottomed out in winter(December,January,and February).Chengde contributed the most,followed by Beijing.Platycladus orientalis,Quercus variabilis,Populus tomentosa,Pinus tabulaeformis and Robinia pseudoacacia represent the primary contributors to BVOCs emission and atmospheric reactivity,hence the planting of these species should be reduced.

Essential Oil of Phyllanthus reticulatus Poiret from Nigeria

The chemical composition of the essential oil obtained by hydrodistillation from the leaves of Phyllanthus reticulatus Poiret (Euphorbiaceae) growing in Nigeria has been studied. The constituents of the oil were analyzed by means of gas chromatography (GC-FID) and gas chromatography coupled with mass spectrometry (GC-MS). Monoterpenes (64.9%) were the dominant class of compounds, followed by sesquiterpenes (23.0%). The major constituents were α-pinene (6.0%), sabinene (7.6%), β-pinene (18.1%), linalool (6.9%) and camphor (7.7%), among the monoterpenes, and β-caryophyllene (11.9%) and germacrene D (8.6%) among the sesquiterpenes. This is the first report on the volatile constituents of Phyllanthus reticulatus.

Plant VOCs emission： a new strategy of thermotolerance

Plant leaves may emit a substantial amount of volatile organic compounds （VOCs） into the atmosphere, which include isoprene, terpene, alkanes, alkenes, alcohols, aldehydes, eters, esters and carboxylic acids. Furthermore, most of these compounds actively participate in tropospheric chemistry. Great progresses have been made in linking emission of these compounds to climate. However, the VOCs emission function in plant is still not clear. Recently, some evidence has emerged that the production and the emission of VOCs, such as isoprene and monoterpenes, which account for 80% of total VOCs, exhibit plant protection against high temperatures. These increases in VOCs emissions could contribule in a significant way to plant thermotolerance. This perspective summarizes some latest literatures regarding the VOCs emission-dependent thermoprotection in plant species subjected to high temperature stress, presents the achievement in studies concerning plant VOCs emission-dependent thermotolerance, and then exhibits the proposed mechanisms of such plant thermotolerance. Finally open questions regarding the plant VOCs emission were shown, and the future researches were proposed.

Biogenic VOCs emission inventory development of temperate grassland vegetation in Xilin River Basin, Inner Mongolia, China

Given the key role of biogenic volatile organic compounds(VOCs) to tropospheric chemistry and regional air quality, it is important to generate accurate VOCs emission inventories. However, only a less fraction of plant species, in temperate grassland of Inner Mongolia, has been characterized by quantitative measurements. A taxonomic methodology, which assigns VOCs measurements to unmeasured species, is an applicable and inexpensive alternation for extensive VOCs emission survey, although data are needed for additional plant families and genera to further validate the taxonomic approach in grassland vegetation. In this experiment, VOCs emission rates of 178 plant species were measured with a portable photoionization detector(PID). The results showed the most of genera and some families have consistent feature of their VOCs emission, especially for isoprene, and provide the basic premise of taxonomic methodology to develop VOCs emission inventories for temperate grassland. Then, the taxonomic methodology was introduced into assigning emission rate to other 96 species, which no measured emission rates available here. A systematical emission inventory of temperate grassland vegetation in Inner Mongolia was provided and further evidence that taxonomy relationship can serve as a useful guide for generalizing the emissions behavior of many, but not all, plant families and genera to grassland vegetation.

Identification of metabolites of Radix Paeoniae Alba extract in rat bile, plasma and urine by ultra-performance liquid chromatography–quadrupole time-of-flight mass spectrometry

Ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry （UPLC-Q-TOF/MS） was developed to identify the absorbed parent components and metabolites in rat bile, plasma and urine after oral administration of Radix Paeoniae Alba extract （RPAE）. A total of 65 compounds were detected in rat bile, plasma and urine samples, including 11 parent compounds and 54 metabolites. The results indicated that glucuronidation, hydroxylation and methylation were the major metabolic pathways of the components of RPAE. Furthermore, the results of this work demonstrated that UPLC-Q-TOF/MS combined with MetaboLynx？ software and mass defect filtering （MDF） could provide unique high throughput capabilities for drug metabolism study, with excellent MS mass accuracy and enhanced MSE data acquisition. With the MSE technique, both precursor and fragment mass spectra can be simultaneously acquired by alternating between high and low collision energy during a single chromatographic run.

Structural characterization of monoterpene indole alkaloids in ethanolic extracts of Rauwolfia species by liquid chromatography with quadrupole time-of-flight mass spectrometry

Rauwolfia species(Apocynaceae) are medicinal plants well known worldwide due to its potent bioactive monoterpene indole alkaloids(MIAs) such as reserpine,ajmalicine,ajmaline,serpentine and yohimbine.Reserpine,ajmalicine and ajmaline are powerful antihypertensive,tranquilizing agents used in hypertension.Yohimbine is an aphrodisiac used in dietary supplements.As there is no report on the comparative and comprehensive phytochemical investigation of the roots of Rauwolfia species,we have developed an efficient and reliable liquid chromatography-tandem mass spectrometry(LC–MS/MS) method for ethanolic root extract of Rauwolfia species to elucidate the fragmentation pathways for dereplication of bioactive MIAs using highperformance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry(HPLC–ESI–QTOF–MS/MS) in positive ion mode.We identified and established diagnostic fragment ions and fragmentation pathways using reserpine,ajmalicine,ajmaline,serpentine and yohimbine.The MS/MS spectra of reserpine,ajmalicine,and ajmaline showed C-ring-cleavage whereas E-ring cleavage was observed in serpentine via Retro Diels Alder(RDA).A total of 47 bioactive MIAs were identified and characterized on the basis of their molecular formula,exact mass measurements and MS/MS analysis.Reserpine,ajmalicine,ajmaline,serpentine and yohimbine were unambiguously identified by comparison with their authentic standards and other 42 MIAs were tentatively identified and characterized from the roots of Rauwolfia hookeri,Rauwolfia micrantha,Rauwolfia serpentina,Rauwolfia verticillata,Rauwolfia tetraphylla and Rauwolfia vomitoria.Application of LC–MS followed by principal component analysis(PCA) has been successfully used to discriminate among six Rauwolfia species.

Monoterpene Glycosides from the Roots of Paeonia lactiflora

A new monoterpene glycoside, together with nine known ones, 3-O-methylpaeoniflorin, mudanpioside J, paeoniflorin, benzoylpaeoniflorin, oxypaeoniflorin, benzoyloxypaeoniflorin, oxybenzoylpaeoniflorin, albiflorin and lactiflorin, was isolated from the roots of Paeonia lactiflora Pall.. The structure of the new compound was elucidated as galloylalbiflorin by the spectro- scopic evidence including ESI-MS, 1D- and 2D-NMR spectra.