A 34-seco-ambrosanolide from Ambrosia artemisiifolia

A new 3,4-seco-ambrosanolide was isolated from Ambrosia artemisiifolia and identified by means of spectroscopic evidence ¹H and ¹³C NMR, IR and MS).     

Granilin and ivasperin from Ambrosia polystachya. 13C-NMR spectra of hydroxylated isoalantones

The eudesmanolides granilin and ivasperin were isolated from Ambrosia polystachya DC. ¹³C-NMR spectra are reported for these and other naturally-occurring ring A-hydroxylated isoalantolactones.     

Sesquiterpene lactones from Ambrosia maritima (Damssissa)

Six sesquiterpene lactones were isolated from the aerial parts of Ambrosia maritima. Four pseudoguaianolides were isolated for the first time in addition to parthenin and neoambrosin.     

Neue guajen-derivate aus Parthenium hysterophorus und ein weiteres pseudoguajanolid aus Ambrosia cumanensis

From the roots of Parthenium hysterophorus two new guaienes and from the aereal parts of Ambrosia cumanensis a further ambrosin derivative have been isolated. The structures have been elucidated by spectroscopic methods. The chemotaxonomic significance of these results is discussed.     

A water potential threshold for the increase of abscisic Acid in leaves

A relationship between abscisic acid concentration and leaf water status is reported. Water potentials were measured in leaves of Ambrosia artemisiifolia L. and Ambrosia trifida L. throughout a period of dehydration of intact plants. Tissues from the same leaves were analyzed for abscisic acid. For both species, abscisic acid began to increase in a critical water potential range (−10 to −12 atmospheres). These data suggest a threshold water potential that stimulates abscisic acid synthesis. The data support the hypothesis that a small change in water potential could affect stomatal resistance to water loss by means of a very sensitive chemical feedback control mechanism.     

Sesquiterpene lactones of Ambrosia chamissonis

A study of a large number of populations of Ambrosia chamissonis ranging from Southern California to British Columbia, has disclosed chemical differences within the species. Six germacranolides, in addition to chamissonin, have been found in the various populations.     

Ambrosanolides and secoambrosanolides from Ambrosia tenuifolia

Populations of Ambrosia tenuifolia from four regions of North Central Argentina differed substantially in sesquiterpene lactone content. Lactones and lactone derivatives isolated were peruvin, ambrosic acid, cumanin, psilostachyin, psilostachyins B and C, dihydropsilostachyin C, altamisin and altamisic acid.     

Sesquiterpene lactones of diploid and tetraploid Ambrosia camphorata

Diploid and tetraploid specimens of Ambrosia camphorata have distinct sesquiterpene lactone patterns; however, no direct correlation between chemistry and morphological patterns is detectable.     

Megasporogenesis, female gametophyte development and embryonic development of Ambrosia L. in China

The megasporogenesis, female gametophyte development and embryonic development of Ambrosia artemisiifolia L. and Ambrosia trifida L. of genus Ambrosia L. in China were studied using conventional paraffin section technology and optical microscopy. The results show that both A. artemisiifolia L. and A. trifida L. have a bilobed pistil stigma, two carpels, one chamber, basal placenta, unitegmic, tenuinucellate, anatropous ovule, and well-developed integumentary tapetum. Megaspore mother cells are directly developed from archesporial cells originated from the nucellar cells under the nucellar epidermis and further undergo meiosis to form linear tetrads. The megaspore at the chalazal end develops into a functional megaspore and the other three megaspores are degraded. The development of embryo sac is monosporic type. After three consecutive mitosis, mononucleate embryo sac becomes a mature embryo sac with two synergids and one egg cell at the micropylar end, a central cell at the center and three antipodal cells at the chalazal end. Most antipodal cells are mononucleate or binucleate, only few are trinucleate. The embryonic development process contains four stages: globular embryo, heart-stage embryo, torpedo-stage embryo and mature embryo. The development of endosperm is cellular type.     

Sesquiterpene lactone patterns in diploid and polyploid Ambrosia dumosa

Diploid, tetraploid and hexaploid populations of Ambrosia dumosa yielded several different sesquiterpene lactone patterns. The distribution of chemical complements is useful in relating the different levels of this polyploid series.     

Damsinic acid and ambrosanolides from vegetative ambrosia hispida

Ambrosia hispida in the vegetative state furnished large quantities of damsinic acid and smaller amounts of ambrosin and damsin. Also isolated were anhydrocoronopilin, hispidulin and the new compounds 3-hydroxyambrosin damsinate and ent-12-oxokaura-9(11),16-dien-19-oic acid.     

Sesquiterpene lactones and a sesquiterpene diol from jamaican ambrosia peruviana

A new sesquiterpene diol and four pseudoguaianolides have been isolated from the aerial part of a Jamaican collection of Ambrosia peruviana. The structures have been identified as alloaromadendrane-4β, 10α-diol, psilostachyins C and B, ambrosin and damsin, respectively, by chemical and spectroscopic means.     

Sesquiterpene lactones of Ambrosia cordifolia

Extraction of Ambrosia cordifolia (Gray) Payne furnished the modified pseudoguaianolides psilostachyin C (I) and cordilin. The latter was shown to be a stereoisomer IV of psilostachyin (II). Dicorea brandegei Gray and D. canescens T. &. G. yielded no crystalline lactone components.     

Establishment of trophic associations of native leaf beetle species (Coleoptera,Chrysomelidae) with Ambrosia artemisiifolia (Asteraceae) in Primorskii Territory of Russia

The establishment of trophic associations between the native leaf beetle species and the adventive ragweed Ambrosia artemisiifolia in the territory of southern Primorskii Territory of Russia is considered. The native leaf beetles Neocrepidodera obscuritarsis (Motschulsky, 1859) and Chrysolina aurichalcea (Gebler in Mannerheim, 1825) feed on A. artemisiifolia despite their trophic preferences for native plants.     

Distribution map of Ambrosia artemisiifolia L. (Asteraceae) in Italy

The spread of the invasive and allergenic Ambrosia artemisiifolia L. in Italy was analysed and mapped using distribution data from a wide range of sources. Ambrosia artemisiifolia occupies 1057 floristic quadrants which are mostly distributed in the Po plain. The distribution obtained represents the basis to implement urgent management strategies.     

A novel eudesmane sesquiterpene glycoside from Ambrosia artemisiifolia L.

A new eudesmane sesquiterpene glycoside (1), five known eudesmane sesquiterpenoids (2–6), and seven known compounds (7–13), were obtained from Ambrosia artemisiifolia. Their structures were elucidated mainly by NMR and MS methods. Among them, compounds 1–4 and 6–9 were isolated from the A. artemisiifolia for the first time and the chemotaxonomic significance of these compounds was summarized.     

Mode of Action of the Sesquiterpene Lactones Psilostachyin and Psilostachyin C on Trypanosoma cruzi

Trypanosoma cruzi is the causative agent of Chagas’ disease, which is a major endemic disease in Latin America and is recognized by the WHO as one of the 17 neglected tropical diseases in the world. Psilostachyin and psilostachyin C, two sesquiterpene lactones isolated from Ambrosia spp., have been demonstrated to have trypanocidal activity. Considering both the potential therapeutic targets present in the parasite, and the several mechanisms of action proposed for sesquiterpene lactones, the aim of this work was to characterize the mode of action of psilostachyin and psilostachyin C on Trypanosoma cruzi and to identify the possible targets for these molecules. Psilostachyin and psilostachyin C were isolated from Ambrosia tenuifolia and Ambrosia scabra, respectively. Interaction of sesquiterpene lactones with hemin, the induction of oxidative stress, the inhibition of cruzipain and trypanothione reductase and their ability to inhibit sterol biosynthesis were evaluated. The induction of cell death by apoptosis was also evaluated by analyzing phosphatidylserine exposure detected using annexin-V/propidium iodide, decreased mitochondrial membrane potential, assessed with Rhodamine 123 and nuclear DNA fragmentation evaluated by the TUNEL assay. Both STLs were capable of interacting with hemin. Psilostachyin increased about 5 times the generation of reactive oxygen species in Trypanosoma cruzi after a 4h treatment, unlike psilostachyin C which induced an increase in reactive oxygen species levels of only 1.5 times. Only psilostachyin C was able to inhibit the biosynthesis of ergosterol, causing an accumulation of squalene. Both sesquiterpene lactones induced parasite death by apoptosis. Upon evaluating the combination of both compounds, and additive trypanocidal effect was observed. Despite their structural similarity, both sesquiterpene lactones exerted their anti-T. cruzi activity through interaction with different targets. Psilostachyin accomplished its antiparasitic effect by interacting with hemin, while psilostachyin C interfered with sterol synthesis.     

High outcrossing in the annual colonizing species Ambrosia artemisiifolia (Asteraceae)

Background and Aims

Variation in mating patterns may be particularly evident in colonizing species because they commonly experience wide variation in plant density. Here, the role of density for the mating system of Ambrosia artemisiifolia (common ragweed), a wind-pollinated annual colonizing species previously reported as self-compatible, is explored.

Methods

The effect of population density on the proportion of self- and cross-fertilized seeds was examined using allozyme markers and experimental arrays conducted over two seasons in the field. Also the reproductive success of isolated plants located in diverse habitats was measured. The potential occurrence of a physiological mechanism preventing self-fertilization, i.e. self-incompatibility, following controlled self- and cross-pollinations in the glasshouse was examined.

Key Results

Outcrossing rates estimated using allozyme markers were uniformly high, regardless of the spacing between plants. However, when single plants were isolated from congeners they set few seeds. Observations of pollen-tube growth and seed set following controlled pollinations demonstrated that plants of A. artemisiifolia possess a strong self-incompatibility mechanism, contrary to earlier reports and assumptions.

Conclusions

The maintenance of high outcrossing rates in colonizing populations of A. artemisiifolia is likely to be facilitated by the prodigious production of wind-borne pollen, high seed production and extended seed dormancy.Key words: Self-incompatibility, outcrossing rate, density dependence, colonization, wind-pollination, Ambrosia artemisiifolia (ragweed), Asteraceae     

Microsporogenesis,microgametogenesis, and pollen morphology of <Emphasis Type="Italic">Ambrosia artemisiifolia</Emphasis> L. in China

Ambrosia artemisiifolia L. from Ambrosia of the Heliantheae of the Asteraceae family is a recognized harmful weed worldwide and one of the major invasive foreign plants in China. In this study, we investigated its reproductive features, focusing on its microsporogenesis, microgametogenesis, and pollen morphology. The results show that (1) Ambrosia artemisiifolia L. is a dicotyledonous plant and has spherical, tricolpate pollen grains with spiny outer wall; (2) its anther wall comprises four layers, namely epidermis, endothecium, middle layers, and amoeboid tapetum; (3) cytokinesis of microspore mother cells is successive; (4) most of tetrads are tetrahedral; and (5) mature pollen grains are three-celled. In conclusion, although Ambrosia artemisiifolia L. is a dicotyledonous plant with tricolpate pollen, its microsporogenesis is successive, which is different from typical dicots.     

Mycobiota associated with the ambrosia beetle Scolytodes unipunctatus (Coleoptera: Curculionidae, Scolytinae)

Ambrosia beetles (Coleoptera: Scolytinae) are associated with strictly entomochoric and mutualistic fungi. We studied the mycobiota associated with Scolytodes unipunctatus, ambrosia beetles that infest Cecropia trees in Central America. Isolates were characterized using morphology and rDNA sequences (ITS region, LSU, and SSU rDNA). Four species are described here: Raffaelea scolytodis sp. nov. (Ophiostomatales), Gondwanamyces scolytodis sp. nov., Custingophora cecropiae sp. nov., and Graphium sp. (Microascales). The genus Custingophora is emended to include Knoxdaviesia anamorphs of Gondwanamyces based on uniformity of DNA sequences and phenotype.