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Bioassay-Directed Isolation and Identification of Phytotoxic and Fungitoxic Acetylenes from Conyza canadensis
Abstract
Conyza canadensis (L.) Cronquist syn. (horseweed) is a problematic and invasive weed with reported allelopathic properties. To identify the phytotoxic constituents of the aerial parts, a systematic bioactivity-guided fractionation of the dichloromethane extract was performed. Three active enyne derivatives, (2Z,8Z)-matricaria acid methyl ester, (4Z,8Z)-matricaria lactone, and (4Z)-lachnophyllum lactone, were identified. The lactones inhibited growth of the monocot Agrostis stolonifera (bentgrass) and the dicot Lactuca sativa (lettuce) at 1 mg mL(-1), while the (2Z,8Z)-matricaria acid methyl ester was less active. In a dose-response screening of the lactones for growth inhibitory activity against Lemna paucicostata , (4Z)-lachnophyllum lactone was the most active with an IC(50) of 104 μM, while the (4Z,8Z)-matricaria lactone was less active (IC(50) of 220 μM). In a fungal direct bioautography assay, the two lactones at 10 and 100 μg/spot inhibited growth of the plant pathogenic fungi Colletotrichum acutatum , Colletotrichum fragariae , and Colletotrichum gloeosporioides . In a dose-response screening of the lactones against six different plant pathogenic fungi, (4Z,8Z)-matricaria lactone was more active than the commercial fungicide azoxystrobin on Col. acutatum , Col. fragariae , and Col. gloeosporioides at 30 μM and about as active as the commercial fungicide captan against Col. gloeosporioides , while (4Z)-lachnophyllum lactone was less active.
... Other authors observed that aqueous extracts of C. canadensis (whole plant), in different concentrations, weakened the root activity of Arabidopsis thaliana and caused the accumulation of reactive oxygen species [38]. The lactones, (4Z,8Z)-matricaria lactone and (4Z)-lachnophyllum lactone, found in the aerial part of C. canadensis, inhibited the growth of the monocot Agrostis stolonifera and the dicot Lactuca sativa [39]. ...
... Some studies indicate that allelochemical compounds, as well as environmental factors, are also capable of significantly influencing photosynthesis [17]. It is known that C. canadensis, as well as other species of the genus Conyza, contains several allelochemical compounds that contribute to the phytotoxicity of its exudates and extracts, inhibiting the germination of plants around it [28,32,36,37,51] and promoting resistance to both herbicides [51][52][53] and pathogenic microorganisms [39,54,55]. Furthermore, it has been demonstrated that C. canadensis root exudates are capable of modifying nutrient cycling, enzymatic activity, and soil microbiota under different occupancy densities [28]. ...
... The major volatile compounds identified in the organic extract by GC-MS were the well-known (2Z,8Z)-matricaria acid methyl ester (C11H10O2 (M + , m/z 174)); (4Z,8Z)-matricaria lactone (C10H8O2 (M + , m/z 160)); (4Z)-lachnophyllum lactone (C10H10O2 (M + , m/z 162.)); and cis-lachnophyllum ester (C11H12O2; (M + , m/z 176)). The mass spectra are in accordance with those previously described by [39,61]. These compounds have antifungal and herbicidal activities. ...
Cyclamen (Cyclamen persicum Mill.) is an ornamental plant that is highly susceptible to pathogens, requiring high amounts of phytosanitary products. Therefore, the development of more sustainable alternatives has been required. The present study aimed to analyze the effect of C. canadensis root extract (aqueous and with dichloromethane) applied via foliar or soil, in C. persicum, on gas exchange and the SPAD index and on the biomass of cyclamen. The aqueous extract treatment increased net CO2 assimilation, the transpiration rates, and instantaneous carboxylation efficiency. The water use efficiency values were reduced in the treatments with both extracts. The greatest increases in the SPAD index were provided by the aqueous extract. The cyclamens that received the aqueous extract applied in soil or the dichloromethane extract applied in leaves showed an increase in total biomass and number of leaves. To identify the compounds present in the extracts, CG-MS and LC-MS/MS analyses were performed. The positive effects obtained indicated a high biostimulant effect of C. Canadensis. Thus, the root extracts of C. Canadensis, particularly the aqueous extracts, have the potential to be used to reduce the use of mineral fertilizers and pesticides, promoting agroecological practices and contributing to sustainable agriculture.
... Thus, compound 2 was identified as (4Z)-lachnophyllum lactone [24], whereas compounds 3 and 4 were analogues of compound 2 containing a double bond in positions C8 = C9, whose structure corresponds with that of matricaria lactone. By comparing the 1 H NMR spectra of compounds 3 and 4 with the data available in the literature for matricaria lactone, the main difference observed was that H-5 appeared 0.43 ppm higher in compound 3. Thus, it was concluded that compounds 3 and 4 were geometric isomers at their C4 = C5 double bonds, being identified as (4Z,8Z)matricaria lactone (3) and (4E,8Z)-matricaria lactone (4) [26,27]. ...
... Thus, compound 2 was identified as (4Z)-lachnophyllum lactone [24], whereas compounds 3 and 4 were analogues of compound 2 containing a double bond in positions C 8 = C 9 , whose structure corresponds with that of matricaria lactone. By comparing the 1 H NMR spectra of compounds 3 and 4 with the data available in the literature for matricaria lactone, the main difference observed was that H-5 appeared 0.43 ppm higher in compound 3. Thus, it was concluded that compounds 3 and 4 were geometric isomers at their C 4 = C 5 double bonds, being identified as (4Z,8Z)-matricaria lactone (3) and (4E,8Z)-matricaria lactone (4) [26,27]. ...
... From the structural point of view, it could be concluded that the high inhibition activity levels showed by the lactones (4Z)-lachnophyllum lactone (2) and (4Z,8Z)-matricaria lactone (3) decrease to a high extent when the lactonic ring is opened (compound 1). This conclusion is in agreement with the results reported in a previous study for the same compounds in inhibition growth bioassays on monocot and dicot species [26]. Comparing the activity levels of compounds 3 (4Z) and 4 (4E), a strong effect of the geometry of the C 4 = C 5 double bond can also be attributed to the loss of activity of compound 4. ...
The study of allelopathic activity of plants and the isolation and characterization of the responsible allelochemicals can lead to the development of environment friendly alternative approaches to weed control. Conyza species are invasive weeds that use allelopathic activity as part of a successful strategy to outcompete neighboring plants. Broomrape weeds are parasitic plants that use host-induced germination and the formation of a haustorium as strategies to infect host plants. The control of broomrape infection in most affected crops is limited or non-existing. In the current study, we investigated the allelopathic activity of Conyza bonariensis organic extracts in suicidal germination and radicle growth of four broomrape species (Orobanche crenata, Orobanche cumana, Orobanche minor and Phelipanche ramosa). A bioactivity-driven fractionation of Conyza bonariensis extracts led to the identification of two germination-inducing molecules and two growth-inhibitory compounds. The germination-inducing metabolites had species-specific activity being hispidulin active on seeds of O. cumana and methyl 4-hydroxybenzoate active in P. ramosa. The growth-inhibitory metabolites (4Z)-lachnophyllum lactone and (4Z,8Z)-matricaria lactone strongly inhibited the radicle growth of all parasitic weed species studied. Some structure–activity relationships were found as result of the study herein presented.
... Species of Conyza are sources of abundant phytotoxic compounds such as catechol, gallic acid, syringic acid and vanillic acid [24]. In vitro phytotoxicity of the closely related species Conyza canadensis against Lactuca sativa and Agrostis stolonifera was previously identified at 1 mg/mL [26]. To the best of our knowledge, there are no previous reports on phytotoxicity from any Conyza species against Cuscuta seedlings. ...
... The investigation of the active fraction CBB, by the study of the 1 H NMR and ESI-MS spectra, revealed that it consisted in a pure compound, which was identified as (4Z)lachnophyllum lactone, the (Z)-5-(hex-2-yn-1-ylidene)furan-2(5H)-one ( Figure 6, R f = 0.76, 5.10 mg). Its structure was confirmed by comparison of the 1 H-NMR data with those reported in the literature [26,37,38]. The configuration of the double bond was deduced from the presence of coupling between H-5 with H-3 and H-2 in the NOESY spectrum ( Figure S1). ...
... This structure was confirmed by the data of its ESI-MS spectrum which showed the sodiated adduct [2M + Na] + and protonated [2M + H] + dimers, and protonated [M + H] + ions at m/z 347, 325 and 163, respectively. This lactone with unspecified configuration was previously reported from different plant species [26,37,38,42]. The 1 H NMR data of the (Z) and (E) isomers of the acetylenic lactone were reported when both the compounds were isolated from Baccharis paniculata. ...
Cuscuta species are obligate parasitic plants that infect the stems of a wide range of hosts including many crop and weed species causing severe agricultural problems. Using in vitro experiments to screen organic extracts prepared from fifteen autotrophic weed species found in agricultural fields infested with Cuscuta campestris, we have identified for the first time a strong phytotoxic activity in Conyza bonariensis extract against C. campestris. Additional pot experiments revealed that seven day-old Cuscuta seedlings had reduced capacity to coil and properly attach on Conyza plants, leading to reduced parasitic weed infection. Via activity-guided fractionation of Conyza extracts, we isolated and identified the acetylenic furanone (4Z)-lachnophyllum lactone as the major active component, with a concentration required to achieve reduction of 50% Cuscuta seedling growth (IC50) of 24.8 µg/mL. The discovery of (4Z)-lachnophyllum lactone bioactivity could aid the development of efficient and sustainable management strategies for C. campestris, whose control is limited or non-existent.
... Sphingolipids 1,3,5-trihydroxy-2-hexadecanoylamino-(6E,9E)-heptacosdiene (131), 1,3,5-trihydroxy-2hexadecanoylamino-(6E,9E)-heptacosdiene-1-O-glucopyranoside (132), 1,3-dihydroxy-2-hexanoylamino-(4E)heptadecene (133) and bonaroside (134) were also reported. Other componds include 9,12,13-trihydroxy-10(E)octadecenoic acid (135), 2,3-dihydroxylpropyl hexacosanoate (136), n-triacontanol (137) and an alkaloid 4hydroxypyridin-3-carboxylic acid 4-O-glucopyranoside (138 (125) C. bonariensis 80,59 Allelochemicals, antimicrobial, antioxidant 80 185 (4Z)-lachnophyllum lactone (126) C. bonariensis, C. canadensis 59,80184,186 Allelopathetic, antimicrobial, cytotoxic ) 80,186 (2Z,8Z)-matricaria acid methyl ester (127) C. bonariensis, C. canadensis 59,184,186 Allelopathetic, antimicrobial 186 8,9-dihydroxymatricarine methyl ester (128) C. canadensis 152 Antimicrobial 152 (4Z,8Z)-matricaria lactone (129) C. bonariensis, C. canadensis 79,184,80,186 Allelopathetic, antimicrobial 80,186 4E,8Z-matricaria lactone (130) C. bonariensis , C. canadensis 79,80 Allelochemicals 80 1,3,5-trihydroxy-2-hexadecanoylamino-(6E,9E)heptacosdiene (131) C. canadensis 123 1,3,5-trihydroxy-2-hexadecanoylamino-(6E,9E)heptacosdiene-1-O-glucopyranoside (132) C. canadensis 123 1,3-dihydroxy-2-hexanoylamino-(4E)heptadecene (133) C. canadensis 123 ...
... Sphingolipids 1,3,5-trihydroxy-2-hexadecanoylamino-(6E,9E)-heptacosdiene (131), 1,3,5-trihydroxy-2hexadecanoylamino-(6E,9E)-heptacosdiene-1-O-glucopyranoside (132), 1,3-dihydroxy-2-hexanoylamino-(4E)heptadecene (133) and bonaroside (134) were also reported. Other componds include 9,12,13-trihydroxy-10(E)octadecenoic acid (135), 2,3-dihydroxylpropyl hexacosanoate (136), n-triacontanol (137) and an alkaloid 4hydroxypyridin-3-carboxylic acid 4-O-glucopyranoside (138 (125) C. bonariensis 80,59 Allelochemicals, antimicrobial, antioxidant 80 185 (4Z)-lachnophyllum lactone (126) C. bonariensis, C. canadensis 59,80184,186 Allelopathetic, antimicrobial, cytotoxic ) 80,186 (2Z,8Z)-matricaria acid methyl ester (127) C. bonariensis, C. canadensis 59,184,186 Allelopathetic, antimicrobial 186 8,9-dihydroxymatricarine methyl ester (128) C. canadensis 152 Antimicrobial 152 (4Z,8Z)-matricaria lactone (129) C. bonariensis, C. canadensis 79,184,80,186 Allelopathetic, antimicrobial 80,186 4E,8Z-matricaria lactone (130) C. bonariensis , C. canadensis 79,80 Allelochemicals 80 1,3,5-trihydroxy-2-hexadecanoylamino-(6E,9E)heptacosdiene (131) C. canadensis 123 1,3,5-trihydroxy-2-hexadecanoylamino-(6E,9E)heptacosdiene-1-O-glucopyranoside (132) C. canadensis 123 1,3-dihydroxy-2-hexanoylamino-(4E)heptadecene (133) C. canadensis 123 ...
A large proportion of the African population's primary healthcare requirements are still mostly met by traditional medicine. Previous studies have demonstrated the potential of plant extracts disease management. Conyza species are traditionally used for a variety of pharmacological applications including treatment of malaria, smallpox, chickenpox, sore throat, ringworm and other skin related infections, toothache and wounds. The aim of this study was to provide a review of the chemical compounds from Conyza species and their bioactivities. Extracts from Conyza species have a wide range of bioactivities including antioxidant, anti-inflammatory, antimicrobial, antitumor, analgesic, antiplasmodial, wound healing, insecticidal, allopathic, antidiabetic, antiviral, anticonvulsant and anti-amnesic effects. These bioactivities are attributed to the bioactive secondary metabolite including terpenoids, phenolic acids, flavonoids and tannins, saponins and steroids which are biosynthesized by the plants. Previous phytochemical test have shown that Conyza species are rich in alkaloids. However, the information about the alkaloids previously isolated from Conyza species is scanty in literature. Further studies should be done isolate and characterize the alkaloids from the plants.
... It is native to North America and has become an invasive plant in temperate and subtropical regions worldwide (Bajwa et al. 2016, Pyšek et al. 2017. The invasion success of E. canadensis in non-native ranges is often attributed to several intrinsic biotic characteristics, such as high seed production, efficient seed dispersal, high adaptive ability to diverse climatic conditions, allelopathic effects, genetic diversity, and evolutionary adaptation (Main et al. 2004, Nandula et al. 2006, Dauer et al. 2007, Queiroz et al. 2012, Wang et al. 2018). However, how abiotic factors, such as resource fluctuation, affect E. canadensis invasion is largely unknown. ...
... However, how abiotic factors, such as resource fluctuation, affect E. canadensis invasion is largely unknown. In invasive ranges, E. canadensis is a serious invader in disturbed habitats, such as roadsides, old fields, and abandoned lands (Weaver 2001, Queiroz et al. 2012. Furthermore, it also intensively invades agricultural fields, including cereal, legume, forage, fruits, and vegetable crops (Holm et al. 1997). ...
Human activities can cause resource fluctuations through reducing uptake by the resident vegetation (e.g. disturbance) or through changing external resource supply (e.g. fertilization). Resource fluctuations often occur as pulses which are low frequency, large magnitude and short duration and now are recognized as an important driver of plant invasions. However, resource pulses often vary dramatically in a number of attributes, yet how these attributes mediate the impacts of resource pulses on plant invasions remains unclear. Erigeron canadensis is a serious invader of disturbed habitats and agricultural fields in China. Thus, it experiences nutrient pulses with different magnitudes and timings. Here, we grew E. canadensis and six co-occurring native plant species with three different magnitudes of nutrient enrichment (low, medium, or high). For each magnitude, we added equivalent amounts of nutrients with a constant supply as a control or one of three pulses with different timings (early, middle, or late stages). We found that pulse magnitude, timing and their interaction significantly affected E. canadensis growth (biomass production) and invasion (proportion of biomass in a pot). For each timing, E. candensis growth and invasion increased with nutrient magnitude. At low magnitude, middle and late pulses promoted E. canadensis growth and invasion. At medium magnitude, late pulses suppressed E. canadensis growth, but did not affect its invasion. At high magnitude, early and middle pulses strongly suppressed E. canadensis growth and invasion. In contrast, natives generally exhibited different responses to nutrient pulses. Our study shows that plant responses are not just dependent on the presence of a resource pulse but also on its attributes. In contrast to theory and many empirical studies, our results show that resource fluctuation does not always promote plant invasion. We highlight that the attributes of resource pulses are key to understanding the impact of resource fluctuations on plant invasion.
... Conyza canadensis (commonly known as horseweed) is a globally distributed invasive weed, which has been shown to cause considerable impacts on the structure, biodiversity and functioning of many ecosystems, including huge economic losses in agriculture by overgrowing into a dense monoculture and preventing regeneration of other species (Wiese et al., 1995;Queiroz et al., 2012). Worldwide, C. canadensis has been affecting more than 40 main crops, invading orchards, vineyards, hay crops, pastures, rangeland and field crops such as corn, soybean and cotton, particularly where conservation tillage or no-till systems are used (Bruce and Kells, 1990;Buhler, 1992;Wiese et al., 1995;Holm et al., 1997;Weaver, 2001). ...
... In China, C. canadensis encroaches a large number of varied agricultural fields from the northeast to the south (Weber et al., 2008). Several studies have identified the factors that contribute to the spread of C. canadensis into new habitats and regions, and these include genetic diversity (Main et al., 2004;Circunvis et al., 2014), evolutionary adaptation (Nandula et al., 2006;Shah et al., 2015) and allelopathic effects (Djurdjevi� c et al., 2011;Queiroz et al., 2012;Zhang, 2017). The density of C. canadensis has also been found to be significantly correlated with soil properties (Shontz and Oosting, 1970), and the herbicide resistance of this species has been associated with biotic components in the soil (Schafer et al., 2013). ...
Modifications in soil fertility and microbiota structure driven by invasive plants can initiate a self-promoting mechanism that facilitates their invasion process. This study aimed to resolve how the progression of invasion affects the chemical, biochemical and microbial properties of soil using Conyza canadensis, a widespread and noxious invasive farmland weed, as a model. Different stages of the invasion process were simulated by growing C. canadensis and a non-invasive crop, Lactuca sativa, at different relative densities. Increasing invasion levels (i.e. increasing invader relative densities) resulted in altered properties of the soil, with an overall increase in nutrient supply and enzymatic activities as invasion intensified. Threshold changes in available nitrogen, organic matter and catalase activity in the soil were identified at invasion levels of 69%, 50% and 47%, respectively. Increasing invasion levels also affected the structure of the soil microbiota, with substantial changes occurring in the relative abundance for a number of bacterial and fungal taxa, including some that are relevant to nutrient cycling. Such changes in soil abiotic and biotic composition driven by C. canadensis might lead to positive plant-soil feedbacks that could promote the establishment and spread of the invasive weed.
... Plant species have historically been a valuable source of biologically active compounds, or templates for the synthesis of more potent bioactive candidates. Bioassay-guided isolation is the most common strategy for screening a large pool of active plant extracts and fractions to find active principles [5,6]. The genus Ambrosia L. is comprised of more than 40 species and belongs to one of the largest botanical families, Asteraceae. ...
... 1D and 2D NMR spectra were recorded on a Bruker NMR spectrometer (Billerica, MA, USA) operating at 400 MHz ( 1 H) and 100 MHz ( 13 C) at 25 • C. Samples were run in MeOH-d 4 , CHCl 3 -d, or DMSO-d 6 . The chemical shifts were reported in δ (ppm) and were referenced to residual solvent signals. ...
The discovery of potent natural and ecofriendly pesticides is one of the focuses of the agrochemical industry, and plant species are a source of many potentially active compounds. We describe the bioassay-guided isolation of antifungal and phytotoxic compounds from the ethyl acetate extract of Ambrosia salsola twigs and leaves. With this methodology, we isolated and identified twelve compounds (four chalcones, six flavonols and two pseudoguaianolide sesquiterpene lactones). Three new chalcones were elucidated as (S)-β-Hydroxy-2′,3,4,6′-tetrahydroxy-5-methoxydihydrochalcone (salsolol A),(S)-β-Hydroxy-2′,4,4′,6'-tetrahydroxy-3-methoxydihydrochalcone (salsolol B), and (R)-α, (R)-β-Dihydroxy-2′,3,4,4′,6′-pentahydroxydihydrochalcone (salsolol C) together with nine known compounds: balanochalcone, six quercetin derivatives, confertin, and neoambrosin. Chemical structures were determined based on comprehensive direct analysis in real time-high resolution mass spectrometry (HR-DART-MS), as well as 1D and 2D NMR experiments: Cosy Double Quantum Filter (DQFCOSY), Heteronuclear Multiple Quantum Coherence (HMQC) and Heteronuclear Multiple Bond Coherence (HMBC), and the absolute configurations of the chalcones were confirmed by CD spectra analysis. Crystal structure of confertin was determined by X-ray diffraction. The phytotoxicity of purified compounds was evaluated, and neoambrosim was active against Agrostis stolonifera at 1 mM, while confertin was active against both, Lactuca sativa and A. stolonifera at 1 mM and 100 µM, respectively. Confertin and salsolol A and B had IC50 values of 261, 275, and 251 µM, respectively, against Lemna pausicotata (duckweed). The antifungal activity was also tested against Colletotrichum fragariae Brooks using a thin layer chromatography bioautography assay. Both confertin and neoambrosin were antifungal at 100 µM, with a higher confertin activity than that of neoambrosin at this concentration.
... The major serious ecological consequence is that it adversely affects the biodiversity of local ecosystem (38). Numerous studies have shown that C. canadensis interferes with the growth and establishment of native plants through allelopathy (14,16,32) due to presence of many compounds, when extracted with organic solvents (14,15,49). Extracting the plant tissue with organic solvents may dissolve the cell wall and bring out substances, which cannot be released into the environment under normal conditions (46). ...
... Chloroform extract inhibited the root growth of A. stolonifera (Fig. 3A) and slightly promoted the shoot growth of L. sativa (Fig. 3B). Ethyl acetate and n-butyl alcohol extracts of C. canadensis severely inhibited the seed germination and growth of A. stolonifera and L. sativa, conforming the previous findings (16,32). The inhibitory effects indicated the involvement of allelopathic interactions and the existence of phytotoxic constituents in these extracts of C. canadensis. ...
We identified the bioactive flavonoids from the aqueous leachates of Conyza canadensis and investigated their allelopathic potential on the seed germination and seedling growth of two recipient spp. Agrostis stolonifera and Lactuca sativa. In bioassay-directed isolation of phytotoxic constituents in the aqueous leachates of C. canadensis, it was extracted with various organic solvents (n-hexane, chloroform, ethyl acetate and n-butyl alcohol). The ethyl acetate and n-butyl alcohol extracts from the aqueous leachates of C. canadensis inhibited the seed germination and seedling growth of both recipient spp. Agrostis stolonifera and Lactuca sativa. Besides, two flavonoids (luteolin and eriodictyol) were identified from the ethyl acetate and n-butyl alcohol extracts of C. canadensis via HPLC-PDA/ESI-MS² and spectral characteristics analysis. The luteolin and eriodictyol significantly decreased the seed germination and seedling growth of A. stolonifera and L. sativa at 15.8 mg/L and 20.3 mg/L, respectively. Furthermore, the lueolin at 40 mg/L and eriodictyol at 60 mg/L significantly inhibited the growth of plant pathogenic fungi Rhizoctonia solani. Our results suggested that luteolin and eriodictyol from C. canadensis allelochemicals, may help to suppress the tested organisms. © 2017, International Allelopathy Foundation. All rights reserved.
... C. bonariensis and C. canadensis are highly allelopathic in nature and, thus, suppress growth and development of crops and other native species through the release of potent allelochemicals (Thabit et al. 2014). A large number of allelochemicals have been sourced from these two weed species (Kong et al. 2001;Djurdjevic et al. 2011;Queiroz et al. 2012). Some studies have also quantified the allelopathic suppression of different agronomic and horticultural crops by C. bonariensis and C. canadensis. ...
... Mainly, p-coumaric, ferulic, p-hydroxybenzoic, vanillic and syringic acids were identified as major phenolic acids produced by C. canadensis (Djurdjevic et al. 2011). Three acetylenes having allelopathic potential were also isolated from dichlomethane extract of C. canadensis (Queiroz et al. 2012). ...
Weed management is one of the prime concerns for sustainable crop production. Conyza bonariensis and Conyza canadensis are two of the most problematic, noxious, invasive, and widespread weeds in modern day agriculture. The biology, ecology, and interference of C. bonariensis and C. canadensis have been reviewed here to highlight pragmatic management options. Both these species share a unique set of biological features, which enables them to invade and adapt a wide range of environmental conditions. Distinct reproductive biology and an efficient seed dispersal mechanism help these species to spread rapidly. Ability to interfere strongly and to host crop pests make these two species worst weeds of cropping systems. These weed species cause 28-68% yield loss in important field crops such as soybean and cotton every year. These weeds are more prevalent in no-till systems and, thus, becoming a major issue in conservation agriculture. Cultural practices such as crop rotations, seed rate manipulation, mulching, inter row tillage, and narrow row spacing may provide an effective control of these species. However, such methods are not feasible and applicable under all types of conditions. Different herbicides also provide a varying degree of control depending on crop, agronomic practices, herbicide dose, application time, and season. However, both these species have evolved resistance against multiple herbicides, including glyphosate and paraquat. The use of alternative herbicides and integrated management strategies may provide better control of herbicide-resistant C. bonariensis and C. canadensis. Management plans based on the eco-biological interactions of these species may prove sustainable in future.
... The petroleum ether extract also showed phytotoxicity against agrostis with a ranking of 4 at 1 mg/ml, where 0 = no effect and 5 = no growth or no germination of the seeds (Table 5). Bergapten was reported in the literature to have strong activity against Lactuca sativa and Agrostis stolonifera [22], therefore further research in herbicide activity was not conducted. * Ranking based on scale of 0 to 5 (0 = no effect, 5 = no growth) ...
... Bergapten showed significant antifungal activities against P. viticola and P. obscurans. In addition, potent herbicidal activity of bergapten has been previously reported [22]. Suberosin showed significant antifungal activities against P. obscurans, and it was the most effective compound against L. donovani, the causative agent for visceral leishmaniasis. ...
Angelica dahurica (Fisch. Ex Hoffm) is an important traditional Chinese herb which is widely used in curing acne, ulcers, carbuncles, rheumatism, headaches and toothaches. A systematic antifungal bioassay-guided fractionation of the ethyl acetate extract from A. dahurica led to the isolation of six coumarins, namely, suberosin, bergapten, alloimperatorin, xanthotoxol, 5-methoxy-8-hydroxypsoralen and pabulenol. These coumarins were subsequently subjected to evaluation for antifungal, antibacterial, antimalarial, antileishmanial and mosquito larvicidal activities. Bergapten and xanthotoxol showed good antifungal activity against Phomopsis viticola, with 99.8% and 73.0% fungal growth inhibition at the concentration of 30 μM. Among all the compounds tested against Phomopsis obscurans, bergapten and suberosin showed the highest antifungal activity with 61.0% and 88.3% inhibition at a 30 μM concentration, respectively. 5-Methoxy-8-hydroxypsoralen displayed toxicity against Streptococcus iniae with an IC50 of 11.6 mg/L and MIC values of 2.32 mg/L. Suberosin and alloimperatorin displayed moderate activity against Leishmania donovani promastigotes with IC50 of 4.43 μg/mL and 20.43 μg/mL. Herein, the antifungal activities of suberosin against P. obscurans and xanthotoxol against P. viticola, the antileishmanial activities of suberosin and alloimperatorin, and the antibacterial activity 5-methoxy-8-hydroxy-psoralen against the fresh water fish pathogen S. iniae were reported for the first time.
... This compound rendered the characteristic even ion at m/z 82.0050 as base peak, which is originated from the lactone ring cleavage [41]. Lachnophyllum lactone has been reported in the literature as a bioactive component with allelopathic [42], fungitoxic [43] and repellent properties [44]. The presence of this compound in B. palustris essential oil even at trace level, might contribute to its potential bioactivity, which need to be evaluated further. ...
... To isolate more acetylenic compounds, we performed a preparative HPLC on the diethyl ether extract that gave different fractions. Fortunately, a fraction showed to be a pure Lachnophyllum lactone as confirmed by mass spectrometry analysis and 1 H, 13 [20] [21]; also in the essential oil of root of Erigeron acris [22]. ...
... This compound rendered the characteristic even ion of m/z 82.0050 as II Simpósio Sul-Brasileiro de Farmacognosia 25 e 26 de outubro de 2022 -Universidade Estadual de Ponta Grossa/PR 4 base peak, which is originated from the lactone ring cleavage (RIVERA et al., 1989). Lachnophyllum lactone have been reported as a bioactive component: allelopathic (FERNÁNDEZ-APARICIO et al., 2022), fungitoxic (QUEIROZ et al., 2012) and repellent (NAWAMAKI et al., 1979). The presence of this compound in BPEO even at trace level, might contribute to its potential bioactivity (MINTEGUIAGA et al., 2018), which need to be evaluated in further studies. ...
Polyacetylenes, a group of specialized bioactive metabolites potentially useful in
therapy as antitumorals, are present in plants mostly from the Asteraceae family.
Baccharis L. is a known source of C10 and C17-polyacetylenes, despite so far, their
presence in essential oils is extremely rare. Previously we studied the unusual composition of B. palustris hydrodistilled essential oil (BPEO) from Southern Uruguay identifying a series of volatile C9-polyacetylenes. In this work, we re-analyze BPEO conducting GC/MS (ISO standard), GC/HRMS-TOF and GCxGC/HRMS-TOF analyses with the aim to find new components. In full, 42 compounds were identified or tentatively identified, most of them monoterpenoids and sesquiterpenoids. Ten minor oxygenated terpenoids were detected for the first time in BPEO (α-pinene epoxide, trans-β-ocimene epoxide, epicubebol, cubebol, germacrene D-4-ol, junenol, epi-α-cadinol, epi-α-muurolol, germacra- 4(15),5,10(14)-trien-1-β-ol and oplopanone), several of them co-eluting with major components. The C9-polyacetylenes baccharisdyine and the 7-dehydro-baccharisdyine geometric isomers were the main BPEO components, while 1-nonen-3-yne and 3-ethylidene-2-methyl-1-hexen-4-yne (two isomers) were tentatively identified. Finally, applying GCxGC/HRMS-TOF it was possible to identify the lachnophyllum lactone (undefined stereochemistry) in the second chromatographic dimension through deconvolution of the cis -lachnophyllum acid methyl ester peak. Being B. palustris a highly endangered species, our results might contribute to its preservation as a valuable source of polyacetylenes whose bioactivities need to be studied further.
... C. canadensis had the lowest concentration of total identified phenolic compounds ( Table 1, Supplementary Table S1). According to Queiroz et al. [50], this species contains acetylenes, which could be responsible for its allelopathic activity. The highest concentration of a single group of compounds we recorded in E. annuus-naringenin hexosides, at a concentration of 32.07 ± 3.01 mg/g DW (Table 1). ...
Invasive plants’ phytochemicals are important for their invasiveness, enabling them to spread in new environments. However, these chemicals could offer many pharmaceutical compounds or active ingredients for herbal preparations. This study provides the first LC–MS phytochemical screening of six invasive alien plant species (IAPS) in the Istria region (Croatia): Ailanthus altissima, Ambrosia artemisiifolia, Conyza canadensis, Dittrichia viscosa, Erigeron annuus, and Xanthium strumarium. The study aims to identify and quantify the phenolic content of their leaf extracts and assess their antimicrobial and cytotoxic potential. A total of 32 species-specific compounds were recorded. Neochlorogenic, chlorogenic, and 5-p-coumaroylquinic acids, quercetin-3-glucoside, and kaempferol hexoside were detected in all the tested IAPS. Hydroxycinnamic acid derivatives were the main components in all the tested IAPS, except in E. annuus, where flavanones dominated with a share of 70%. X. strumarium extract had the best activity against the tested bacteria, with an average MIC value of 0.11 mg/mL, while A. altissima and X. strumarium extracts had the best activity against the tested fungi, with an average MIC value of 0.21 mg/mL in both cases. All the plant extracts studied, except X. strumarium, were less cytotoxic than the positive control. The results provided additional information on the phytochemical properties of IAPS and their potential for use as antimicrobial agents.
... At the same time, certified standards are not required for the detection of phytotoxins. Bioassays is a commonly used technique in ecotoxicology research to detect and determine phytotoxins or bioavailable phytotoxic residues of pesticides [48]. One of the main disadvantages of using bioassays in phytotoxin studies is their weakness in identifying phytotoxic compounds [49]. ...
Nowadays, phytotoxins as natural compounds extracted from different plants are widely used as growth regulators or growth inhibitors for other plants or microorganisms. Furthermore, phytotoxin study may lead to the synthesis of new products with various biological activities. Therefore, the detection and identification of these compounds is very important in the study of their effects on living organisms and the environment. Different methods have been used for the identification and characterization of phytotoxins. This study is devoted to reviewing various methods for the extraction, purification, detection, and identification of phytotoxins from different plant species. The most common methods for detecting plant toxins include a variety of bioassays (plant, cell, and enzyme assay) and the application of a wide range of chemical and analytical methods (especially chromatographic techniques). Both types of methods will be discussed in more details. Moreover, applications of these methods in the study of phytotoxin interaction from recent studies are exemplified to aid understanding f these interactions. It can be concluded that bioassay and analytical methods are the two fundamental techniques for phytotoxin analysis. In addition, new advanced techniques that can enable better understanding of phytotoxins and their functions and which are based on biochemistry, robotics, biosensors, nanotechnology, and enzyme-based methods will be developed in the near future.
... The invasive plant species, Conyza canadensis (synonym of Erigeron canadensis, commonly known as horseweed), is native to North and Central America, and is widely naturalized in agricultural areas and temperate ecosystems throughout Eurasia and Australia (Gonzáleztorralva et al. 2017). Previous studies have shown that C. canadensis is allelopathic towards other plant species, including crops (Djurdjević et al. 2011;Queiroz et al. 2012). Conyza canadensis has been found to possess many allelochemicals, such as phenolics, ketones, flavonoids, alcohols, aldehydes, esters, and terpenes (Djurdjević et al. 2011;Zhou et al. 2013;Zhang et al. 2017a). ...
The molecular mechanisms underlying allelopathy and their role in the interactions between invasive weeds and native species remain unclear. In this study, we aimed to explore the physiological and molecular response of plant roots of a native species to allelopathy from an invasive weed. We examined the growth and development of roots of native Arabidopsis thaliana for a 2-week period after being treated with aqueous extracts at different concentrations from invasive Conyza canadensis. Extracts with higher concentration in the Murashige and Skoog (MS) media (i.e., 4 mg of extract/mL of MS) significantly affected the root growth of A. thaliana. Roots of A. thaliana displayed weakened root tip activity and an accumulation of reactive oxygen species (ROS) in response to extracts from C. canadensis. The transcriptome analysis of A. thaliana roots exposed to phytotoxicity revealed differentially expressed genes (DEGs) involved in cell wall formation, abiotic stress, transporter genes and signal transduction. We found that genes associated with nutrient transport, such as major facilitator superfamily (MFS) and amino acid permease (AAP3) transporters as well as genes involved in stress response, including leucine-rich repeat receptor-like protein kinases (LRR-RLKs) were down-regulated. In addition, we found that many transcription factors associated with plant stress (such as APETALA2/ethylene response factors) were up-regulated while others (e.g., zinc-finger proteins) were down-regulated. Allelochemicals from C. canadensis also induced the up-regulation of detoxification (DTX) genes, ROS related genes, calcineurin B-like interacting protein kinases (CIPKs) and calmodulin. Overall, our findings provided insights into allelopathy in C. canadensis at the molecular level, and contributes to our understanding of invasion mechanisms of alien plant species.
Clinical trials registration
This study does not contain any studies with clinical trials performed by any of the authors.
... Several papers are on the isolation, structural characterization, and biological activity of secondary compounds from Sponges (100), plants (103,105,106,118,128,130,136,149,150,157,158,180,187,194,204), fungi (132,140,156,175,176,179,188,189,195,198,199,203,205) and insects (154,174). Other papers have dealt with the interactions of synthetic pesticides with bio-pesticides (119) and secondary compounds as pharmaceuticals (126). ...
... atividade elevada para o fungo Trichophyton Foto: Daniel Terao interdigitale e para a levedura Cryptococcus neoformans. Edziri et al. (2011) observaram que o extrato de C. canadensis, contendo etil acetato, clorofórmio, butanol e metano apresentaram potente atividade antiviral contra os vírus humanos, citomegalovírus (HCMV) e o enterovírus Cox-B3.Queiroz et al. (2012) realizaram o fracionamento sistemático guiado por bioensaios nos extratos de C. canadensis e identificou três substâncias com atividade antifúngica, dentre elas (4Z)-lachnophyllum lactona (LACH) (Figura 3). ...
... About antifungal mechanisms, it was reported that the compound 22 is a fungal endo-β-(1,3)- glucanase inhibitor (Vargas-Arispuru et al., 2009). Others active compounds (Figure 1) are acetylenic lactone (27) (Queiroz et al., 2012), 2-phenylethanol ester (28) (Labbé et ...
Various pathogenic microorganisms affect plants. However, most diseases are caused by fungi, which have an enormous reproductive capacity and possess metabolic mechanisms capable to develop resistance to commercial fungicides. Fungi produce mycotoxins on crops and this represents a considerable risk to human and animal health. The most important genera of phytopathogenic fungi of the American continent are: Aspergillus, Alternaria, Botrytis, Colletotrichum, Fusarium, Phytophthora, Penicillium and Pythium, among others. Different strategies have been used for phytopatogenic fungi control, mainly by using synthetic fungicides. Currently, a great deal of attention has been paid towards exploitation of higher plant products as an innovative alternative in crops protection. The use of plant derived natural products has many advantages, such as little or no harmful side effects, rare cases of resistance, long-term control and completely or substantially eliminates the use of synthetic fungicides. Several plants belonging to the Anacardiaceae, Asteraceae, Caprifoliaceae, Lamiaceae, Liliaceae, Papilionacea, Poaceae, Verbenaceae, families, have showed fungicide potential. Therefore, this review addresses occurrence of the most important phytopatogenic fungi and the current state of research regarding the potential of vegetable biodiversity in the development of plant derived natural products for the management of these pathogens in the American continent.
(2Z)-Lachnophyllum methyl ester and (4Z)-Lachnophyllum lactone were recently identified as major components in essential oils and extracts of Conyza bonariensis from Togo. Extended biological evaluation of these acetylenic compounds was however hampered by the reduced amounts isolated. A synthetic route was designed providing access to larger quantities of these two natural products as well as to original non-natural analogs with the prospect of exploring for the first time the structure-activity relationships in this series. Using LC/MS analysis, synthetic samples allowed confirming the presence of the two previously isolated natural products in plant extracts obtained by the accelerated solvent extraction technique. The nematocidal activity of the synthesized compounds confirmed the potency of the natural products, which remain the most active among all analogs tested. The synthesized compounds were also assessed against Leishmania infantum axenic amastigotes and the Mycobacterium tuberculosis H37Rv pathogenic strain. (2Z)-Lachnophyllum methyl ester, (4Z)-Lachnophyllum lactone and lactone analogs exhibited the strongest antileishmanial potency. As expected, a longer alkyl chain was necessary to observe significant antimycobacterial activity. The lactone analog bearing a C10 lipophilic appendage displayed the highest antimycobacterial potency. The notable activities of lactones, naturally occurring or analogs, either nematicidal, antileishmanial or antimycobacterial, were compared to their cytotoxicity for mammalian cells and revealed moderate selectivity index values. In this regard, the innocuous (2Z)-Lachnophyllum methyl ester and its analogs open up more promising perspectives for the discovery of bioactive agents to protect both agricultural crops and human health.
In this investigation, the chemical composition of the hydro-distilled essential oil (HD-EO), obtained from the fresh aerial parts (inflorescence heads (Inf), leaves (L), and stems (St)) of Conyza canadensis growing wild in Jordan was determined by GC/MS. Additionally, the methanolic extract obtained from the whole aerial parts of C. canadensis (CCM) was examined for its total phenolic content (TPC), total flavonoids content (TFC), DPPH radical scavenging activity, iron chelating activity and was then analyzed with LC-MS/MS for the presence of certain selected phenolic compounds and flavonoids. The GC/MS analysis of CCHD-EOs obtained from the different aerial parts revealed the presence of (2E, 8Z)-matricaria ester as the main component, amounting to 15.4% (Inf), 60.7% (L), and 31.6% (St) of the total content. Oxygenated monoterpenes were the main class of volatile compounds detected in the Inf-CCHD-EO. However, oils obtained from the leaves and stems were rich in polyacetylene derivatives. The evaluation of the CCM extract showed a richness in phenolic content (95.59 ± 0.40 mg GAE/g extract), flavonoids contents (467.0 ± 10.5 mg QE/ g extract), moderate DPPH radical scavenging power (IC 50 of 23.75 ± 0.86 µg/mL) and low iron chelating activity (IC 50 = 5396.07 ± 15.05 µg/mL). The LC-MS/MS profiling of the CCM extract allowed for the detection of twenty-five phenolic compounds and flavonoids. Results revealed that the CCM extract contained high concentration levels of rosmarinic acid (1441.1 mg/kg plant), in addition to caffeic acid phenethyl ester (231.8 mg/kg plant). An antimicrobial activity assessment of the CCM extract against a set of Gram-positive and Gram-negative bacteria, in addition to two other fungal species including Candida and Cryptococcus, showed significant antibacterial activity of the extract against S. aureus with MIC value of 3.125 µg/mL. The current study is the first phytochemical screening for the essential oil and methanolic extract composition of C. canadensis growing in Jordan, its antioxidant and antimicrobial activity.
The genus Conyza (Asteraceae) comprises about 50 species and found in the tropical and warm regions. Extracts from Conyza species have numerous pharmacological applications. The aim of this study was review the chemical composition and biological activity of Conyza species. Extracts from the plants have antimicrobial, antioxidant, cytotoxic, anti-inflammatory, antiplasmodial, analgesic, antiviral, allelopathic and insecticidal activities. The constituents of essential oils from Conyza species include limonene and β
Soil health is a key factor for the global food security. One of the main bottlenecks for the efficient utilization of farmland soil is the accumulation of allelochemicals excreted by plant roots, leached and volatilized from plants, and released during the decomposition of plant residues. The negative impacts derived from allelochemicals include: decreasing soil fertility, breaking the balance of soil microbial community, reducing seed germination rate and crop yield, and interfering with the growth of neighboring or successive plants. Recently, biochar, a soil amendment with low cost and high performance, is extensively studied on its functions and effects on farmland systems. In this review, we focused on the potential role of biochar in controlling the environmental fate and risk of allelochemicals in soils. The source and potential toxicity of allelochemicals in farmland and the deficiencies in current methods for alleviating the allelopathy were summarized first, followed by the discussion on their sorption and degradation by biochar as well as the impact of biochar properties on the performance and mechanism. At the same time, the generation of allelochemicals regulated by biochar through improving plant growth conditions was analyzed. The modification of biochar for alleviating the allelopathy and then overcoming the obstacles of agricultural production was also addressed. Future research directions, such as targeted biochar production, the interactions between different allelochemicals and biochar investigated by simulations and modeling, negative effects and stability of biochar or modified biochar, were then proposed. This review will provide useful theoretical and technical supports for targeted biochar applications in soils with allelopathy.
Graphical abstract
Green mould, caused by Penicillium digitatum, is the major postharvest disease of citrus in all producing countries. The control of this disease is carried out by fungicides in postharvest treatments, which can leave toxic residues in fruits. Therefore, the interest in cleaner technologies and alternatives to the use of fungicides, such as biopesticides, has grown in recent years. Conyza canadensis, an herbaceous weed spread all over the world, contains compounds which have significant activity against P. digitatum. Thus, the present research aimed to evaluate (4Z)-lachnophyllum lactone (LACH), isolated from C. canadensis, in combination with hot water brushing (HWB) and UV-C treatments, to control green mould and to preserve the quality of the fruit. LACH efficiently controlled green mould in orange cv. Valencia. The level of control improved from 24% to 42% according to the dose of LACH adopted, ranging from 10 to 100 µg ml⁻¹ respectively. When in combination with HWB or UV-C, the efficiency of the control was enhanced from 50% to 78% with the lowest dose of LACH (10 µg ml⁻¹) and UV-C at 1.5 kJ m⁻², which showed no significant difference when the highest dose of LACH (100 µg ml⁻¹) was applied alone. This treatment delayed the onset of the disease symptoms. A biofungicide based on C. canadensis combined with UV-C and HWB is a potential natural control of green mould.
Eragrostis plana (Nees) is an allelopathic plant with invasive potential in South American pastures. To isolate and identify phytotoxic compounds from leaves and roots of E. plana, a bioassay-directed isolation of the bioactive constituents was performed. This is the first report on a new diterpene carbon skeleton, the neocassanes, and of three new neocassane diterpenes, neocassa-1,12(13),15-triene-3,14-dione, 1, 19-norneocassa-1,12(13),15-triene-3,14-dione, 2, and 14-hydroxyneocassa-1,12(17),15-triene-3-one, 3, identified from the roots. Compounds 1, 2, and 3 inhibited the growth of duckweed 50% at concentrations of 109 ± 28, 200 ± 37, and 59 ± 15 µM, respectively. Compound 2 was fungicidal to Colletotrichum fragariae, C. acutatum and C. gloeosporioides. The compounds identified here could explain the allelopathy of E. plana. The description of the newly discovered compounds, besides contributing to the chemical characterization of the species, may be the first step in the study of the potential of these compounds as bioherbicides.
В обзоре представлены данные по химическому составу и биологической активности мелколепестника канадского Conisa canadensis (L.) Cronq. (Erigeron canadenasis L.) заносного и натурализовавшегося в Евразии и на других
континентах растения родом из Северной и Центральной Америки.
Биологически активные вещества, входящие в состав мелколепестника канадского, представлены различными группами соединений: эфирным маслом, основным компонентом которого является лимонен, дигидропиранонами,
тритерпенами, сфинголипидами, фенольными веществами, органическими кислотами и их производными и др.
Conisa canadensis Conisa canadensis применяется в традиционной медицине при лечении желудочно-кишечных заболеваний, геморроя, а также как противовоспалительное, вяжущее, мочегонное, стимулирующее менструацию, кровоостанавливающее, тонизирующее и глистогонное средство,проявляет антиоксидантные и антиагрегантные свойства. Настойка Conisa canadensis применяется в гомеопатии.
Эфирное масло мелколепестника обладает фунгицидной и антибактериальной активностью. Экстракты из травы обладают потенциальным антипролиферативным действием на раковые клетки. Мелколепестник канадский является перспективным растением для дальнейшего фитохимического изучения
и создания лекарственных средств противовоспалительного, антипролиферативного, гастрозащитного, антиоксидантного действия.
The aim of this study was to investigate the potential anti-inflammatory effect of Conyzacanadeusis methanol extract (CME) using a cell model of RAW264.7 murine macrophage cell stimulated with lipopolysaccharide (LPS)(1μg/ml). Co-treatment with different concentrations (10, 50 and 100μg/ml) of CME was concentration-dependently reduced the LPS-induced generation of prostaglandin E2 (PGE2), nitric oxide (NO) tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6. In addition, CME also reduced the mRNA expressions of cyclooxygenase-2 (COX-2), inducible nitric oxide (iNOS), TNF-α, IL-1β and IL-6 in LPS-stimulated RAW264.7 cells. These results suggested that CME showed an anti-inflammatory activity through reduced the mRNA expression of COX-2, iNOS, TNF-α IL-1β and IL-6 and also decreased the productions of PGE2, NO, TNF-α IL-1β and IL-6in LPS-stimulated RAW264.7 cells.
Effects-directed biological detection facilitates the identification of targeted substances in complicated matrices by biological detection after separation by planar chromatography. The term “bioautography” is used predominantly when antimicrobial or antifungal properties of the analytes are measured on high-performance thin-layer chromatography plates. However, other types of biological effects can be applied, for example, bioluminescence, antioxidant, enzymatic, or antiestrogenic assays. Increasingly, several modes of biological detection in parallel followed by chemical and/or spectroscopic detection are employed. Such hyphenations give complete information for the compounds of interest. They can be isolated, even from very complicated matrices, identified, and quantified. Additionally, their biological relevance and impact on the environment and human health can be assessed.
With chemical analysis and bioassay testing, information can be obtained about the composition and biological activity of a sample. Because chemical analysis on its own does not return information about bioactivity and bioassay testing of a sample, the extract does not show which compound is responsible for the measured activity. A combination of chemical analysis and biotesting can be a powerful approach for the identification of unknown and emerging bioactives. This is done via so-called effect-directed analysis (EDA) or bioassay-guided fractionation (BGF). In these approaches fractionation is used to reduce the sample complexity down to a few compounds or a single compound per fraction, which allows the pinpointing of bioactives. This chapter discusses sample preparation, fractionation techniques, bioassays, and chemical analysis as well as identification strategies for the research fields of environmental analysis, food analysis, and drug discovery.
Populations of Stellera chamaejasme L. have been increasing constantly in recent years in some areas of the grassland in north China but why this toxic weed has become highly competitive is not clear. In order to determine if any potential allelochemicals are released into the soil environment by S. chamaejasme, we investigated the chemical composition of a water-washed solution of the living roots with rhizosphere soil. This led to the isolation and identification of seven compounds: umbelliferone (1), daphnoretin (2), chamaechromone (3), 7-methoxyneochamaejasmine A (4), mesoneochamaejasmin A (5), neochamaejasmin B (6), dihydrodaphnodorin B (7). All are secondary metabolites of S. chamaejasme. Bioassay showed that 1, 5 and 6 had a strong inhibitory effect on Festuca rubra L. and Medicago sativa seedlings. These compounds were quantified by high performance liquid chromatography in 25 root zone soil samples of S. chamaejasme collected at altitudes between 165 and 4741 m from the northeast to the Tibetan Plateau of China. All samples contained at least one of the phytotoxic compounds. Their content did not correlate with the altitude of the growing site. However, the level of chamaechromone negatively correlated with the soil pH. Principle components analysis indicated that the flavonoids might come from the same source. These potential allelochemicals from root release into the soil might play an important role in the highly competitive nature and broad ecological adaptability of S. chamaejasme in the wild.
Wir berichten über die Entwicklung der ersten direkten Alkinylierung von 2-Vinylphenolen. Das optimierte hypervalente Iodreagens TIPS-EBX* ermöglicht zusammen mit [(Cp*RhCl2)2] als Übergangsmetallkatalysator die Konstruktion einer Vielzahl von hochsubstituierten 1,3-Eninen in Ausbeuten von bis zu 98 %. Diese neue C-H-aktivierende Methode zeichnet sich durch eine exzellente Chemoselektivität und reine (Z)-Stereoselektivität aus, ist dabei besonders mild und toleriert viele funktionelle Gruppen. Des Weiteren wurden Modifikationen der so erhaltenen 1,3-Enine untersucht. Unseres Wissens ist diese Reaktion das erste Beispiel einer OH-dirigierten C-H-Alkinylierung mit hypervalenten Iodreagentien.
The first direct alkynylation of 2-vinylphenols was developed. The rationally optimized hypervalent iodine reagent TIPS-EBX* in combination with [(Cp*RhCl2 )2 ] as a CH-activating transition metal catalyst enables the construction of a variety of highly substituted 1,3-enynes in high yields of up to 98 %. This novel CH activation method shows excellent chemoselectivity and exclusive (Z)-stereoselectivity, and it is also remarkably mild and tolerates a variety of functional groups. Furthermore, synthetic modifications of the resulting 1,3-enynes were demonstrated. To our knowledge, this is the first example for an OH-directed CH alkynylation with hypervalent iodine reagents.
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Six analogous of natural trans-4-butyl-cis-3-oxabicyclo[4.3.0]-nonan-2-one (3) and three derivatives 11, 12, 13 of Vince lactam (10) were synthesized and tested as fungistatic agents against Botritis cinerea AM235, Penicillium citrinum AM354 and six strains of Aspergillus. Moreover, bioresolution carried out with means of whole cells microorganisms and commercially available enzymes afforded opposite enantiomerically enriched (-) and (+) isomers of Vince lactam (10) respectively. The effect of compound structures, stereogenic centers on biological activity has been discussed. The highest fungistatic activity was observed for four lactones: 3, 4, 7, 8 (IC50 = 104.6 - 115.2 g/mL) towards B. cinerea AM235. Cis-5,6-epoxy-2-aza[2.2.1]heptan-3-one (13) indicated significant fungistatic activity (IC50 = 107.1 g/mL) against A. glaucus AM211. Trans-4-butyl-cis-3-oxabicyclo[4.3.0]nonan-2-one (3) and trans-4-butyl-cis-3-oxabicyclo[4.3.0]non-7-en-2-one (7) exhibited high fungistatic activity IC50=143.2 g/mL and 110.2 g/mL respectively against Penicillium citrinum AM354 as well.
Enyne derivatives isolated from terrestrial plants and fungi have recently attracted attention due to their interesting biological activities. It was found that these derivatives possess in general potent antiinflammatory activity which was attributed to the structural similarity of enynes with the natural antiinflammatory agents secreted in the human body. The biosynthesis of some of the isolated enynes has been proposed based on detailed isotope labeling studies. Computational calculations have been utilized to analyze the conformational preferences and forces affecting interaction of some enynes with the target binding sites. Synthesis of enynes has been achieved using several coupling techniques. In the current review we shed some light on the isolation, biological activity, and biosynthetic routes of enynes. We also recounts different synthetic methodologies developed for the synthesis of compounds containing enyne functional group.
This paper reviews the use of TLC-bioautography in the search for antifungal compounds from natural sources. The main methods used for antifungal screening are presented, with special emphasis on bioautography. Different aspects of the technique, including the latest chromatographic developments such as HPTLC and HPLC microfractionation are presented. The present status and recent advances made in antifungal bioautography are discussed, and a comprehensive review of the applications over the last 6 years is presented. Various strategies applied in the search for antifungal compounds from natural sources are discussed, with a highlight on the challenges faced when screening complex crude mixtures. The activities of approximately 100 antifungal compounds of natural origin are presented with their minimum inhibitory quantity. The most active natural source compounds against Candida, Cladosporium, Colletotrichum, and Fusarium species are highlighted, and the compound activities discussed. In addition, perspectives concerning future improvements in bioautography sensitivity and reproducibility are noted.
Based on OSMAC strategy (One Strain - Many Compounds), 14 indole diketopiperazine (DKP) alkaloids, including spirotryprostatins (1-3), tryprostatins (4-6), and cyclotryprostatins (7-14), were isolated from the endophyte Aspergillus fumigatus associated with Melia azedarach L. Their structures were identified by NMR and ESIMS data. All the isolated DKPs were evaluated for plant growth regulation. Among them, a tryprostatin-type compound, brevianamide F (6), was identified as a new type of natural potential plant growing inhibitors against lettuce with higher response index than that of positive control glyphosate, a broad-spectrum systemic herbicide. 6 can also inhibit turnip shoot and root elongation with response indexes -0.76 and -0.70 at 120 ppm, and it strongly inhibit amaranth seedling growth with high response index -0.9 at 40 ppm. Preliminary study of the relationship between indole DKP structures and their allelopathic activities indicated that tryprostatin-type alkaloids with absence of C5 prenyl and methoxy group, give the most potent inhibition to the seedlings growth.
The present study investigated the hypothesis that the coupling of high performance thin layer chromatography with the yeast estrogen screen (planar-YES, p-YES) can be used as a screening tool for effect directed analysis. Therefore, the proposed method was challenged for the first time with several real samples from various origin such as sediment pore water, wastewater and sunscreens. It was possible to detect and quantify estrogenic effects in all investigated sample types, even in the presence of demanding matrices. Furthermore, the specific agonistic effect of the estrogen receptor activation could be detected in samples exhibiting cytotoxic effects and at cytotoxic levels of analyzed estrogenic compounds which is not possible with the classic YES. The analysis of samples by the p-YES results in profiles of estrogenic activity. By means of this profiles samples can be compared qualitatively and quantitatively with respect to different compositions of bio-active compounds in mixtures. In conclusion, the p-YES-approach seems to have a high potential to be used as a valuable screening tool for various applications in effect directed analysis.
Trifolium pratense, a widespread legume forage plant is reported to exhibit phytotoxic activity on other plants, but the active metabolites have not been clarified so far. A bioassay-guided fractionation of the root extracts led to the isolation of five isoflavonoids, which were elucidated by spectroscopic analysis. All of the purified compounds observably showed phytotoxic activities against Arabidopsis thaliana. Moreover, the inhibitory effects were concentration-dependent. The furan ring linked at C-4 and C-2' positions by an oxygen atom and a 1,3-dioxolane at C-4' and C-5' positions are considered as critical factors for the phytotoxic activity. The concentration of (6aR,11aR)-maackiain and (6aR,11aR)-trifolirhizin, concluded to be allelochemicals from soil around plants of T. pratense, was determined by HPLC and LC-MS to be 4.12 and 2.37 μg/g, respectively. These allelochemicals, which showed remarkable activities against the weed Poa annua may play an important role to assist the widespread occurrence of T. pratense in nature.
TLC bioautography is a method that combines chromatographic separation and in situ biological activity determination. The antimicrobial, antioxidant and enzyme inhibitory activities can be performed on TLC bioautography. This method is mainly used for preliminary screening natural products possessing these biological activities and for the bioactivity-directed fractionation and isolation of active components from complex extracts. This review covers the mechanisms and methodology of the antimicrobial, antioxidant activities, and enzyme inhibition adopted on TLC. It will be in particular discuss the recent advances in these technologies and assess their applications in targeting natural products.
A pytochemical study on the constituents of the roots of Symphyotrichum subulatum led to the isolation of three new compounds including two diacetylenes, asterynes A (1) and B (2), and (E)-4-(3-acetoxyprop-1-enyl)-2-methoxyphenyl (S)-2-methylbutanoate (3) along with twelve known compounds. Their structures were elucidated with spectroscopic analyses. Compound 3 showed anti-inflammatory activity on LPS-induced NO production with an EC50 value of 15.0 µM.
Horseweed (Conyza canadensis) is a common weed in no-till crop production systems. It is problematic because of the frequent occurrence of biorypes resistant to glyphosate and acetolactate synthase (ALS)-inhibiting herbicides and its ability to complete its life cycle as a winter or summer annual weed. Tactics to control horseweed while controlling other winter annual weeds routinely fail; herbicide application timing and spring emergence patterns of horseweed may be responsible. The objectives of this experiment were to (1) determine the influence of fall and spring herbicides with and without Soil residual horseweed activity on spring-emerging glyphosate-resistant (GR) horseweed density and (2) evaluate the efficacy and persistence of saflufenacil on GR horseweed. Field studies were conducted in southern Indiana and Illinois from fall 2006 to Summer 2007 and repeated in 2007 to 2008. Six preplant herbicide treatments were applied at four application timings: early fall, late fall, early spring, and late spring. Horseweed plants were Counted every 2 wk following the First spring application until the first week of July. Horseweed almost exclusively emerged in the spring at both locations. Spring horseweed emergence was higher when 2,4-D + glyphosate was fall-applied and controlled other winter annual weeds. With fall-applied 2,4-D + glyphosate, over 90% of the peak horseweed density was observed before April 25. In contrast, only 25% of the peak horseweed density was observed in the untreated check by April 25. Starting from the initiation of horseweed emergence in late March, chlorimuron + tribenuron applied early fall or early spring, and spring-applied saflufenacil at 100 g ai/ha provided greater than 90% horseweed control for 12 wk. Early spring-applied saflufenacil at 50 g ai/ha provided 8 wk of greater than 90% residual control, and early spring-applied simazine provided 6 wk of greater than 90% control. When applied in]are spring, saflufenacil was the only herbicide treatment that reduced horseweed densities by greater than 90% compared to 2,4-D + glyphosate. We concluded from this research that fall applications of nonresidual herbicides can increase the rate and density of spring emerging horseweed. In addition, spring-applied saflufenacil provides no-cill producers with a new preplant herbicide for foliar and residual control of glyphosate- and ALS-resistant horseweed.
The potential use of natural phytotoxins (including allelochemicals) to develop novel tools for weed management is enhanced by the elucidation of their modes of action. This approach has not been emphasized by the agrochemical industry, although the possibility of discovering new target sites may be promising, since natural products tend to have modes of action different from synthetic herbicides. The approach of testing a compound on all known herbicide molecular target sites for commercial herbicides and other potent phytotoxins is feasible. However, this would preclude the discovery of new mechanisms of action. Discovering new target sites requires more challenging holistic approaches, initiated with physiological and biochemical studies that use whole plant assays. Studying basic plant responses to a compound may yield important clues to the specific physiological processes affected by the compounds and uncover novel mechanisms of action.
We describe an add-on package for the language and environment R which allows simultaneous fitting of several non-linear regression models. The focus is on analysis of dose response curves, but the functionality is applicable to arbitrary non-linear regression models. Features of the package is illustrated in examples.
Bioassay-guided fractionation of the N-hexane and CHCl₃ phases of the methanol extract of the roots of Conyza canadensis (L.) Cronquist led to the isolation of two new dihydropyranones named conyzapyranone A (1) and B (2), and the known 4 Z,8 Z-matricaria- γ-lactone (3), 4 E,8 Z-matricaria- γ-lactone (4), 9,12,13-trihydroxy-10(E)-octadecenoic acid (5), epifriedelanol (6), friedeline (7), taraxerol (8), simiarenol (9), spinasterol (10), stigmasterol, β-sitosterol, and apigenin. The structures were determined by means of ESIMS and 1D and 2D NMR spectroscopy, including ¹H-¹H COSY, NOESY, HSQC, and HMBC experiments. The isolated compounds were evaluated for their antiproliferative activities and were demonstrated to exert considerable cell growth-inhibitory activity against human cervix adenocarcinoma (HeLa), skin carcinoma (A431), and breast adenocarcinoma (MCF-7) cells. Some of the active components, including 2, 4, and 10, proved to be substantially more potent against these cell lines than against noncancerous human foetal fibroblasts (MRC-5) and can therefore be considered selective antiproliferative natural products.
The effects of Conyza canadensis (L.) Cronquist on seed germination and early seedling growth of six test plants namely tomato, radish, wheat, corn, millet and mungbean was investigated. Aqueous extract of C. canadensis at different concentrations (25, 50, 75 and 100% stock solution) inhibited the germination, root and shoot growth of all the six test species. Germination was reduced by the shoot extract in the order: tomato > radish > millet = corn > mungbean > wheat. Both root and shoot growth of the test species were reduced to varying degree and shoot growth was usually affected to a greater degree than the root growth, particularly in tomato. Decaying shoot of C. canadensis in sandy-loam at 5, 10 and 20 g/ 400 g soil substantially inhibited germination and seedling growth of bulrush millet ( Pennisetum americanum ) at all the dosages and no germination occurred at the highest dosage (20 g/400 g soil). Bioassay of the ether extract of C. canadensis disclosed two significant zones of inhibition at R f values of 0.2-0.3 3 and 0.7-0.8. Chromatography for the phenolics revealed the presence of four phenolic compounds: gallic acid, vanillic acid, catechol and syringic acid.
Herbicides are designed to kill plants and their selective use in crops is based on rates that do not harm the crop but effectively control the weeds. Use of dose-response curves and subsequent definitions of relative potency, no observable effect level, estimation of selectivity index are pivotal for the safe and cost-effective use of herbicide in agriculture. Various dose-response curves have been used to describe plant response. The objective of this abstract is to present an R application that makes it easy to analyse bioassays and subsequently performs tests of biological relevance not only in herbicide research and development, but also in other branches of the biological sciences, e.g. toxicology and ecotoxicology. R application In order to automate the fitting and testing of various hypotheses of the dose-response curves we have developed the package ”drc ” which can handle most of the situations common for bioassay work: • Simultaneously fitting of numerous curves. • Testing for similar parameters among some or all simultaneously fitted curves. • Reducing numbers of parameters using likelihood ratio tests.
The allelopathic effects of aqueous extract from Conyza canadesis were tested in Petri dishes in Laboratory and Greenhouse assays. The aqueous extract strongly inhibited the germination, germination speed and seedling growth of sorghum (Sorghum vulgare Pers.), cucumber (Cucumis sativus L), wheat (Triticum aestivum L.), rape (Brassica campestris L.) and radish (Raphanus sativus L.). Rape and radish were more sensitive than other spp. C. canadesis released the allelochemicals mainly as root exudates. The extract inhibited the hypocotyl and root growth of endosperm-removed wheat and sorghum cultivated in darkness, but the inhibitory effect was drastic in sorghum than in endosperm-removed wheat. The aqueous extract decreased the photosynthesis activity but increased the MDA contents of cucumber and radish. Thus allelopathic effects of C canadesis affects non-photosynthesis activity and MDA, but may also affect the photosynthesis activity.
Polyacetylenes and their thiophene derivatives, characteristic secondary metabolites of the Asteraceae, were examined for their effects on herbivorous insects. Three thiophenes (a monothiophene, a bithiophene, and α-terthienyl) and four polyacetylenes (phenylheptatriyne, phenylheptadiynene, phenylheptadiyene acetate, and matricaria lactone) were studied for their phototoxicity and light-independent toxicity to (1) a polyphagous lepidopteran,Ostrinia nubilalis, whose host range includes a number of phototoxic Asteraceae, (2) a polyphagous lepidoteran,Euxoa messoria, whose host range includes very few species of Asteraceae, and (3) an oligophagous lepidopteran,Manduca sexta, which is a specialist on Solanaceae. Several compounds were phototoxic toM. sexta andE. messoria even at very low irradiance levels, but behavioral adaptations, including spinning silk and boring into diet, allowedO. nubilalis to avoid photosensitization. Light-independent activity of the compounds to all three species involved feeding deterrence increasing in the orderO. nubilalis, E. messoria, andM. sexta, and longterm metabolic toxicity in the form of impaired nutrient utilization. The biosynthetically derived thiophenes were more toxic than their acetylenic precursors, and toxicity increased with increasing number of thiophene rings. The results are discussed in terms of plant-insect coevolution.
Field studies were conducted to examine both density and duration of glyphosate-resistant (GR) horseweed interference in cotton. Two studies, one examining the effect of horseweed density and a second the duration of horseweed interference, were conducted on a site with a natural population of horseweed that were treated with glyphosate at 0.84 kg ae ha(-1) prior to planting and at the 2nd and 4th cotton node growth stages. GR horseweed density effect on cotton height, maturity, and lint yield was determined at horseweed densities of 0, 5, 10, 15, 20, and 25 plants m 2. Duration of horseweed interference was evaluated when 20 horseweed m(-2) were allowed to interfere with cotton from emergence to 2nd node, 6th node, 10th node, 12th node, and 1st bloom stage of cotton. The maximum cotton lint yield loss (46%) occurred when horseweed was allowed to compete with cotton from emergence to maturity at the two highest densities (20 and 25 horseweed m(-2)). When the data were fit to the Cousens model the estimated a (maximum yield loss) and i (yield loss per unit density as density approaches zero) were 53 +/- 7.3 and 2.8 +/- 0.6 SE, respectively. In both years of the Study, horseweed interference from emergence to the 2nd cotton node did not reduce cotton lint yields. In 2006, cotton lint yield loss was 28% compared to 39% in 2005 when horseweed interfered with cotton from emergence until the 6th cotton node. Cotton lint yield loss was 37 and 44% when horseweed competed to the 8th cotton node in 2005 and 2006, respectively. Maximum horseweed seed production was 1.34,000 to 148,000 seeds m(-2).
Allelopathy can be defined as an important mechanism of plant interference mediated by the addition of plant-produced secondary products to the soil rhizosphere. Allelochemicals are present in all types of plants and tissues and are released into the soil rhizosphere by a variety of mechanisms, including decomposition of residues, volatilization, and root exudation. Allelochemical structures and modes of action are diverse and may offer potential for the development of future herbicides. We have focused our review on a variety of weed and crop species that establish some form of potent allelopathic interference, either with other crops or weeds, in agricultural settings, in the managed landscape, or in naturalized settings. Recent research suggests that allelopathic properties can render one species more invasive to native species and thus potentially detrimental to both agricultural and naturalized settings. In contrast, allelopathic crops offer strong potential for the development of cultivars that are more highly weed suppressive in managed settings. Both environmental and genotypic effects impact allelochemical production and release over time. A new challenge that exists for future plant scientists is to generate additional information on allelochemical mechanisms of release, selectivity and persistence, mode of action, and genetic regulation. In this manner, we can further protect plant biodiversity and enhance weed management strategies in a variety of ecosystems. Referee: Dr. Steve Weller, Purdue University, Dept. of Horticulture, West Lafayette, IN 47907
Weeds are known to cause enormous losses due to their interference in agroecosystems. Because of environmental and human health concerns, worldwide efforts are being made to reduce the heavy reliance on synthetic herbicides that are used to control weeds. In this regard the phenomenon of allelopathy, which is expressed through the release of chemicals by a plant, has been suggested to be one of the possible alternatives for achieving sustainable weed management. The use of allelopathy for controlling weeds could be either through directly utilizing natural allelopathic interactions, particularly of crop plants, or by using allelochemicals as natural herbicides. In the former case, a number of crop plants with allelopathic potential can be used as cover, smother, and green manure crops for managing weeds by making desired manipulations in the cultural practices and cropping patterns. These can be suitably rotated or intercropped with main crops to manage the target weeds (including parasitic ones) selectively. Even the crop mulch/residues can also give desirable benefits. Not only the terrestrial weeds, even allelopathy can be suitably manipulated for the management of aquatic weeds. The allelochemicals present in the higher plants as well as in the microbes can be directly used for weed management on the pattern of herbicides. Their bioefficacy can be enhanced by structural changes or the synthesis of chemical analogues based on them. Further, in order to enhance the potential of allelopathic crops, several improvements can be made with the use of biotechnology or genomics and proteomics. In this context either the production of allelochemicals can be enhanced or the transgenics with foreign genes encoding for a particular weed-suppressing allelochemical could be produced. In the former, both conventional breeding and molecular genetical techniques are useful. However, with conventional breeding being slow and difficult, more emphasis is laid on the use of modern techniques such as molecular markers and the selection aided by them. Although the progress in this regard is slow, nevertheless some promising results are coming and more are expected in future. This review attempts to discuss all these aspects of allelopathy for the sustainable management of weeds. Referee: Dr. Amrjits S. Basra, Central Plains Crop Technology, 5912 North Meridian Avenue, Wichita, KS 67204
The aerial parts of Chrysoma pauciflosculosa (syn. Solidago pauciflosculosa) gave the known diterpenes, 17-oxygrindelic acid, 17-oxogrindelic acid and 17-carboxygrindelic acid, as well as the new diterpene, 17-hydroxy-7α,8α-epoxygrindelic acid. 17-Oxogrindelic acid decomposes in the presence of air giving three products. The structural data of the diterpenes as well as those of degradation products and derivatives were elucidated by chemical and spectroscopic methods. 17-Oxygrindelic acid and 17-oxogrindelic acid were tested for their effect on the germination and radicle growth of three Florida sandhill species and Lactuca sativa. At concentrations of 12 to 48 ppm, 17-oxogrindelic acid reduced the germination and radicle growth of Schizachyrium scoparium and Leptochloa dubia, two native sandhill grasses, but had no significant effects on germination and only a slight stimulatory effect on radicle growth of Rudbeckia hirta and Lactuca sativa. Mixtures of 17-oxogrindelic acid with an equimolar mixture of three C. pauciflosculosa sesquiterpenes, (+)-curlone, (+)-sesquiphellandrene and (−)-α-trans-bergamontene, did not enhance activity. 17-Oxygrindelic acid was in general less active in reducing germination and growth than 17-oxogrindelic acid.
Two new neoclerodanes diterpenoids paniculadiol [1] and paniculadiol diacetate [2] were isolated from Baccharis paniculata, together with two acetylenic lactones and other known compounds. Their structures were elucidated by chemical and spectroscopic means.
A collection of 39 isolates of Colletotrichum acutatum, C. fragariae and C. gloeosporioides, which cause anthracnose on strawberry, was grouped into species based on the arbitrarily primed polymerase chain reaction (ap-PCR). All isolates used had previously been identified according to classical taxonomic morphology. Ap-PCR amplification of genomic DNA using four different primers allowed for reliable differentiation between isolates of C. acutatum, C. fragariae and two genotypes of C. gloeosporioides. Fifteen of the 18 C. acutatum isolates were very similar, although three isolates which produced a red pigment had distinctly different banding patterns. Nearly identical banding patterns were observed for all nine isolates of C. fragariae. The 12 C. gloeosporioides isolates were more diverse and two separate genotypes, Cgl-1 (six isolates) and Cgl-2 (five isolates) were distinguished by ap-PCR. An additional isolate did not conform to either the Cgl-1 or Cgl-2 genotypes. The utility of ap-PCR compared with other molecular techniques for reliable identification of Colletotrichum isolates pathogenic on strawberry is discussed.
In this review acetylenes and related compounds, such as cumulenes and polyenes, which have been isolated from the tribe Astereae (Asteraceae) are listed. Some of these compounds are widely distributed in Asteraceae, especially in the tribes Anthemideae, Cynareae and Heliantheae and others are characteristic natural products of this tribe. On the basis of their distribution in Astereae, the chemotaxonomy of this tribe is discussed. Furthermore the biosynthesis of some of the isolated compounds is evaluated.
Conyza canaden-sis (L.) Cronq. (Canada fleabane, horseweed, mare's-tail) is a winter or summer annual, native to North America, and found in all provinces of Canada except Newfoundland. It is a weed of orchards, vineyards, roadsides, and arable fields where tillage has been reduced or eliminated. Most seedlings emerge from late August through October and form rosettes which overwinter. Large num-bers of small, wind-dispersed seeds, ranging to over 200 000 seeds per plant, are produced in late summer. Populations of C. canadensis in more than ten countries have evolved resistance to herbicides such as paraquat, atrazine, chlorsulfuron or glyphosate. Several paraquat resistant populations were found in orchards in Essex Country, Ontario. It serves as a wild host of the tarnished plant bug, and of aster yellows, a mycoplasma disease transmitted by the aster leaf hopper. Weaver, S. 2001. Biologie des mauvaises herbes au Canada. 115. Conyza canadensis. Can. J. Plant Sci. 81: 867–875. Conyza canadensis (L.) Cronq. (vergerette du Canada, érigéron du Canada) est une annuelle d'hiver ou d'été indigène à l'Amérique du Nord. On la trouve dans toutes les provinces du Canada sauf Terre-Neuve. Elle envahit les vergers, les vignobles, les bords de route et les terres arables dont on ne travaille plus le sol, ou très peu. La plupart des plantules apparaissent de la fin du mois d'août à octobre et forment des rosettes qui hiverneront. La plante produit au-delà de 200 000 petites graines qui seront dispersées par le vent à la fin de l'été. Dans plus de dix pays, les peuplements de C. canadensis ont acquis une résistance à divers désherbants tels le paraquat, l'atrazine, le chlorsulfuron et le glyphosate. Plusieurs peuplements résistants au paraquat ont été découverts dans des vergers du comté d'Essex, en Ontario. La vergerette du Canada est l'hôte sauvage de la punaise grise et de la jaunisse de l'aster, mycoplasme transmis par la cicadelle de l'aster.
cis-Dehydromatricaria ester (cis-DME) inSolidago altissima, andcis-matricaria ester (cis-ME),trans-matricaria ester (trans-ME), andcis-lachnophyllum ester (cis-LE) inErigeron spp. show strong growth inhibitory effects on other plants. Thecis- andtrans-DMEs were found in soil at the border ofS. altissima communities in concentrations that were inhibitory to test plants. Among four species ofErigeron, the most dominant plant,E floribundus, showed the highest concentrations of the esters. From the results of our experiments, we conclude that these polyacetylenes are probably allelopathic substances with ecological importance.
Paraquat (Pq) inducible transporters are presumed to play a role in the resistance mechanism of horseweed and to function by carrying paraquat to a metabolically inactive compartment. The uptake and intracellular localisation of paraquat, the effect of transporter inhibitors on resistance, and paraquat-induced gene expression were studied to obtain a better understanding of the mechanism of resistance. Investigations proved that paraquat entered the cells of both resistant and susceptible biotypes, approached the maximum within the first hour in chloroplasts, and then declined in all organelle fractions. In the resistant biotype paraquat was located in the vacuoles a day after treatment. Selective transporter inhibitors blocked the sequestration of paraquat, suggesting the participation of not directly energized transporters. Four EST fragments were identified that were expressed in response to paraquat. Two of them are thought to play a role in the general stress response (Ferr2, Myb). The others exhibit a similarity to transporters (EmrE, CAT) and could conceivably be involved in the intracellular transport of paraquat and the mechanism of resistance.
Herbicides with new modes of action are badly needed to manage the evolution of resistance of weeds to existing herbicides. Yet no major new mode of action has been introduced to the market place for about 20 years. There are probably several reasons for this. New potential products may have remained dormant owing to concerns that glyphosate-resistant (GR) crops have reduced the market for a new herbicide. The capture of a large fraction of the herbicide market by glyphosate with GR crops led to significantly diminished herbicide discovery efforts. Some of the reduced herbicide discovery research was also due to company consolidations and the availability of more generic herbicides. Another problem might be that the best herbicide molecular target sites may have already been discovered. However, target sites that are not utilized, for which there are inhibitors that are highly effective at killing plants, suggests that this is not true. Results of modern methods of target site discovery (e.g. gene knockout methods) are mostly not public, but there is no evidence of good herbicides with new target sites coming from these approaches. In summary, there are several reasons for a long dry period for new herbicide target sites; however, the relative magnitude of each is unclear. The economic stimulus to the herbicide industry caused by the evolution of herbicide-resistant weeds, especially GR weeds, may result in one or more new modes of action becoming available in the not too distant future.
A simple bioautographic techniqud according to WELTZIEN', and modified by
DEISHUI JZEN~ for detection of fungitoxic substances has been in use for many years
in this laborattiry. Chromatograms on Whatman No. 3MM paper are develpped with
propanol-water (85: 15) and after drying are sprayed with a conidial suspension of
Glomerella cingzclata. After incubation, clearly visible inhibition zones indicate the
preserice of. fungitoxic compounds. Chromatography thus permits not only the detection
sf fungitoxic substances per se, but also makes the study of the conversion
reactions and of decomposition of such compounds possible.
Horseweed is a weed commonly found in agronomic crops, waste areas and roadsides. Resistance to ALS-inhibiting herbicides in horseweed was first reported in 1993 in a population from Israel. Resistance to ALS-inhibiting herbicides in horseweed is now widespread, but, as of now, the resistance mechanism has not been reported.
Two of three populations evaluated (P116 and P13) were found to be uniform for resistance (>98% of individuals survived 8.8 g AI ha(-1) of cloransulam), whereas a third population, P525, contained about 85% resistant individuals. Cross-resistance to cloransulam, chlorimuron, imazethapyr and bispyribac was observed in the P116 population. P525 and P13 were both sensitive to imazethapyr but resistant to chlorimuron, imazethapyr and bispyribac. Enzyme activity assays indicated that resistance in P13 was due to an altered target site. Southern blot analysis indicated that the ALS target site is encoded by a single copy gene. Overlapping ALS gene regions were amplified and sequenced from each population. Amino acid substitutions of Ser for Pro at position 197 (P197S) was detected from P13, Ala for Pro (P197A) was identified from P525 and substitution of Glu for Asp (D376E) at position 376 was found in P116. Molecular markers were developed to differentiate between wild-type and resistant codons at positions 197 and 376 of horseweed ALS.
Resistance to ALS-inhibiting herbicides in horseweed is conferred by target-site mutations that have also been identified in other weed species. Identification of the mutations within horseweed ALS gene sequence enables molecular assays for rapid detection and resistance diagnosis.
The volatiles from Coriandrum sativum L., Satureja montana L., Santolina chamaecyparissus L., and Thymus vulgaris L. were isolated by hydrodistillation (essential oil) and supercritical fluid extraction (volatile oil). Their effect on seed germination and root and shoot growth of the surviving seedlings of four crops ( Zea mays L., Triticum durum L., Pisum sativum L., and Lactuca sativa L.) and two weeds ( Portulaca oleracea L. and Vicia sativa L.) was investigated and compared with those of two synthetic herbicides, Agrocide and Prowl. The volatile oils of thyme and cotton lavender seemed to be promising alternatives to the synthetic herbicides because they were the least injurious to the crop species. The essential oil of winter savory, on the other hand, affected both crop and weeds and can be appropriate for uncultivated fields.
In the 2009/2010 growing season, Brazil was the second largest world soybean producer, followed by Argentina. Glyphosate-resistant soybeans (GRS) are being cultivated in most of the soybean area in South America. Overall, the GRS system is beneficial to the environment when compared to conventional soybean. GRS resulted in a significant shift toward no-tillage practices in Brazil and Argentina, but weed resistance may reduce this trend. Probably the highest agricultural risk in adopting GRS in Brazil and South America is related to weed resistance due to use of glyphosate. Weed species in GRS fields have shifted in Brazil to those that can more successfully withstand glyphosate or to those that avoid the time of its application. Five weed species, in order of importance, Conyza bonariensis (L.) Cronquist, Conyza canadensis (L.) Cronquist, Lolium multiflorum Lam., Digitaria insularis (L.) Mez ex Ekman, and Euphorbia heterophylla L., have evolved resistance to glyphosate in GRS in Brazil. Conyza spp. are the most difficult to control. A glyphosate-resistant biotype of Sorghum halepense L. has evolved in GRS in Argentina and one of D. insularis in Paraguay. The following actions are proposed to minimize weed resistance problem: (a) rotation of GRS with conventional soybeans in order to rotate herbicide modes of action; (b) avoidance of lower than recommended glyphosate rates; (c) keeping soil covered with a crop or legume at intercrop intervals; (d) keeping machinery free of weed seeds; and (d) use of a preplant nonselective herbicide plus residuals to eliminate early weed interference with the crop and to minimize escapes from later applications of glyphosate due to natural resistance of older weeds and/or incomplete glyphosate coverage.
To discover an active skin depigmenting agent, we isolated a novel inhibitor of melanin biosynthesis from the methanol extract of Erigeron breviscapus using a bioactivity-guided fractionation and identified it as (2Z,8Z)-matricaria acid methyl ester by means of spectroscopic analysis. The compound showed strong whitening activity in melan-a cell. Compared with arbutin (IC(50)=4.0 mM) as a positive control, the depigmentation IC(50) value for (2Z,8Z)-matricaria acid methyl ester was 25.4 muM in B16F10 melanoma cell. Moreover, its inhibitory effect on tyrosinase, the key enzyme of melanogenesis, was examined by in vivo and in vitro tyrosinase assay and Western blot. The results indicate that (2Z,8Z)-matricaria acid methyl ester isolated from Erigeron breviscapus is a promising compound that could be useful for treating hyper-pigmentation as skin-whitening agents.
The tremendous increase in crop yields associated with the 'green' revolution has been possible in part by the discovery and utilization of chemicals for pest control. However, concerns over the potential impact of pesticides on human health and the environment has led to the introduction of new pesticide registration procedures, such as the Food Quality Protection Act in the United States. These new regulations have reduced the number of synthetic pesticides available in agriculture. Therefore, the current paradigm of relying almost exclusively on chemicals for pest control may need to be reconsidered. New pesticides, including natural product-based pesticides are being discovered and developed to replace the compounds lost due to the new registration requirements. This review covers the historical use of natural products in agricultural practices, the impact of natural products on the development of new pesticides, and the future prospects for natural products-based pest management.
Bruceantin and bruceantarin, new antileukemic simaroubolides from Brucea antidysenterica, a plant used in Ethiopia in the treatment of cancer, are shown to have structures 1 and 2, respectively.
Six matricaria esters (MEs) and two matricaria lactones (MLs), isolated from members of the tribe Astereae (Asteraceae), were tested against Mycobacterium tuberculosis and M. avium, using a radiorespirometric bioassay. (2Z,8Z)-ME and (2E-8Z)-ME gave minimum inhibitory concentrations (MICs) of 50 micrograms ml-1 against M. tuberculosis and respective MICs of 25 and 50 micrograms ml-1 against M. avium. The (4Z,8Z)-ML, (2Z)-8-dehydro-ME and (2Z,8Z)-10-angeloyloxy-(2Z,8Z)-ME showed respective MICs of 12.5, 25, 25 micrograms ml-1 against M. tuberculosis and MICs of 50, 25, 25 micrograms ml-1 against M. avium, respectively. The MICs of (2Z,8Z)-10-tigloyloxy-ME and (2E,8Z)-10-angeloyloxy-ME and (4E,8Z)-ML ranged from 50 to > 100 micrograms ml-1 against both pathogenic mycobacteria.
The essential oil profile of Callicarpa americana was examined. Samples were collected from Lafayette county in north central Mississippi, and GC-MS data and retention indices were used to identify 67 oil components. Humulene epoxide II (13.9%), alpha-humulene (10.0%), 7-epi-alpha-eudesmol (9.4%), beta-pinene (8.8%), and 1-octen-3-ol (8.5%) were the major components of the steam-distilled oil. The oil was selectively toxic toward the cyanobacterium Oscillatoria perornata compared to Oscillatoria agardhii and the green alga Selenastrum capricornutum, with complete growth inhibition at 28.5 microgram/mL. The oil was only mildly phytotoxic and antifungal.
A new bioassay has been developed combining the simplicity of direct bioautography with the improved chromatographic resolution of 2D-TLC. Mixtures of structurally diverse antifungal agents were tested to establish the validity and utility of this method in the discovery of new natural products with activity against agriculturally important fungal pathogens.
The steam‐distilled fraction of the aerial parts of Erigeron speciosus (Lindl) DC was tested for activity against strawberry plant pathogenic fungi Botrytis cinerea Pers ex Fr, Colletotrichum acutatum Simmonds, C fragariae Brooks, C gloeosporioides (Penz) Penz & Sacc, and the intermediate host snail Planobdella trivolvis that harbors the trematode, Bolbophorus confusus , that infests and causes severe infections in pond‐raised catfish in the Mississippi Delta region of the USA. Bioautography on silica TLC plates demonstrated antifungal activity in the steam distillate. Preliminary bioassays of the steam distillate indicated the presence of phytochemicals toxic to P trivolvis . The bioactive compounds methyl 2 Z , 8 Z ‐deca‐2,8‐diene‐4,6‐diynoate and its 2 E , 8 E isomer were isolated by bioassay‐guided fractionation and chromatographic techniques and identified by ¹ H NMR spectroscopy.
© 2002 Society of Chemical Industry
Lemna species are widely used in ecotoxicological research to assess the phytotoxicity of environmental compounds. The purpose of the work described in this paper was to further refine the Lemna spp. bioassay, making it more robust and useful in comparing results between laboratories. A nondestructive image analysis method was used to measure growth as affected by herbicides during a time course. We tested 26 herbicides, with as many as 19 different modes of action, on leaf area growth of Lemna paucicostata to establish complete dose-response relationships. By using 3,5-dichlorophenol as a reference compound, different EC50 (concentration that inhibited growth by 50%) values of the herbicides can be compared. The EC50 values ranged from 0.003 microM for sulcotrione to 407 microM for asulam. Complete dose-response parameters were obtained that will better allow comparison of these results to those of other laboratories. These results should give useful information to anyone who works with Lemna species to address questions on herbicide residues in environmental compartments, screening of new herbicidal compounds, or the assessment of phytotoxic side effects of any compound.
Four enyne derivatives (1-4) and quercitrin were isolated during a bioassay-guided chromatographic separation of a methanolic extract of Erigeron apiculatus. Matricarialactone (1) and lachnophyllumlactone (2) showed a high fungitoxic activity against Pyricularia oryzae. Matricaria acid methyl ester (3) and lachnophyllum acid methyl ester (4) were, instead, less active.
Allelopathic effects of Conyza canadesis the germination and growth of wheat, sorghum, cucumber, rape and radish Allelopathic responses of Conyza canadensis (L.) Cronquist: A cosmopolitan weed
- X Gao
- M Li
- Z Gao
- H Zhang
- Z Sun
- S S Shaukat
- N Munir
- I A Siddiqui
Gao, X; Li, M.; Gao, Z.; Zhang, H.; Sun, Z. Allelopathic effects of Conyza canadesis the germination and growth of wheat, sorghum, cucumber, rape and radish. Alellopathy J. 2009, 23, 287−296. (10) Shaukat, S. S.; Munir, N.; Siddiqui, I. A. Allelopathic responses of Conyza canadensis (L.) Cronquist: A cosmopolitan weed. Asian J. Plant Sci. 2003, 14, 1034−1039. (11) Luo, L. H.; Kim, H. J.; Nguyen, D. H.; Lee, H.-B.; Lee, N. H.;
Clerodane diterpenoids and acetylenic lactones from Baccharis paniculata Investigating the mode of action of natural phytotoxins
- A P Rivera
- L Arancibia
- M Castillo
- F E Dayan
- J G Romagni
- S O Duke
Rivera, A. P.; Arancibia, L.; Castillo, M. Clerodane diterpenoids and acetylenic lactones from Baccharis paniculata. J. Nat. Prod. 1989, 52, 433−435. (14) Dayan, F. E.; Romagni, J. G.; Duke, S. O. Investigating the mode of action of natural phytotoxins. J. Chem. Ecol. 2000, 26, 2079−2094.
Bruceantin: A new potent antileukemic simaroubolide from Brucea antidysenterica Acetylenes and related compounds in Asteraceae Naturally Occurring Acetylenes
- S M Kupchan
- G Tsou
- L P Christensen
- J Lam
Kupchan, S. M.; Tsou, G. Bruceantin: A new potent antileukemic simaroubolide from Brucea antidysenterica. J. Org. Chem. 1973, 38, 178−179. (21) Christensen, L. P.; Lam, J. Acetylenes and related compounds in Asteraceae. Phytochemistry 1991, 30, 2453−2476. (22) Bohlmann, F.; Burkhardt, T.; Zdero, C. Naturally Occurring Acetylenes; Academic Press: London, 1973; pp 344−350.
Allelopathic interactions and allelochemicals: New possibilities for sustainable weed management Weed and crop allelopathy
- R K Kohli
- L A Weston
- S O Duke
Kohli, R. K. Allelopathic interactions and allelochemicals: New possibilities for sustainable weed management. Crit. Rev. Plant Sci. 2003, 22, 239−311. (31) Weston, L. A.; Duke, S. O. Weed and crop allelopathy. Crit. Rev. Plant Sci. 2003, 22, 367−389. Journal of Agricultural and Food Chemistry Article dx.doi.org/10.1021/jf3010367 | J. Agric. Food Chem. 2012, 60, 5893−5898