Acetylenic compounds from Bidens graveolens

Bidens graveolens afforded, in addition to known compounds, two new acetylenic esters and a monoterpene diol. Other species only gave known compoun     

Cortex resin monoterpene composition in Pinus brutia provenances grown in Israel

Cortex resin collected from 7-year-old trees of Pinus brutia from different seed sources growing in experimental plots was analyzed by GLC and GC-MS. The monoterpene composition of the cortex resin Pinus brutia subsp, brutia differs markedly from that of Pinus brutia subsp; eldarica, and of Pinus halepensis Mill. trees of the same age. Within a provenance, monoterpene composition varies considerably, yet the provenances differ significantly when analyzed by multiple analysis of variance and Duncan's Multiple Range Test. Five chemotypes were identified using the Fastclus procedure; one of which has a monoterpene composition which corresponds only to the mean monoterpene composition of the subsp. elderica. Most of the subsp. brutia provenances include a range of chemotypes, thereby implying the occurrence of genotypic variation. Cluster analysis discriminates conspicuously between subsp. eldarica and subsp. brutia. Subsp. brutia provenances are arranged into two groups, the dividing line between them being approximately the 35°E meridian.     

Distribution and chemotaxonomic significance of acetylenic fatty acids in mosses of the dicranales

Thirty-eight moss species from four families of the order Dicranales were analysed for the fatty acid composition of their acyl lipids. In the Ditrichaceae and the Dicranaceae numerous species were found to contain acetylenic fatty acids in their triglycerides, 9,12,15-Octadecatrien-6-ynoic acid was the major component, often accounting for more than 80 mol%, whereas 9,12-octadecadien-6-ynoic acid was found in small amounts of less than 5 mol%. In some genera, all the species examined contained acetylenic fatty acids, e.g.Dicranella andDicranum, whereas in the genusCampylopus all five species tested were free of acetylenic compounds. Two genera, Ditrichum andDicranoweisia, were found to have a non-homogeous distribution of acetylenic fatty acids. The chemotaxonomic significance of the fatty acid composition in relation to morphological characters is discussed.     

Factors Affecting the Emission of Monoterpenes from Red Pine (Pinus densiflora)

The mechanism of monoterpene emission from Pinus densiflora was studied using an environmentally controlled gas cabinet. It was found that monoterpene emission rate increases exponentially with temperature and is also influenced by light. These observations were explained reasonably by a mechanism whereby monoterpene emission rate depends on the monoterpene amount in the leaf oil and its saturated vapor pressure.     

Syntheses of long-chain acids,part X acetylenic hydroxy-acids and 8,9,13-trihydroxydocosanoic acid

The dilithio-derivative of a terminal acetylenic secondary alcohol reacts with alkyl halide to form the long-chain acetylenic alcohol by C-alkylation. Similar condensation with the NN-dimethylamide of an ω-bromo-acid, followed by hydrolysis, gives the acetylenic hydroxy-acid in low yield. 13-Hydroxydocos-8-ynoic acid is obtained by this route and, more satisfactorily, by condensation of 7-bromo-NN-dimethylheptanamide with the lithium derivative of pentadec-1-yn-6-one ethylene glycol ketal, with subsequent hydrolysis and reduction. Catalytic partial hydrogenation of the acetylenic hydroxy-acid, and then cis-hydroxylation with potassium permanganate, gives two isomers of (±)-8,9 (erythro) 13-trihydroxydocosanoic acid. One of these corresponds to the (+)-8,9,13-trihydroxydocosanoic acid isolated by Stodola and his co-workers from the extracellular lipid produced by a yeast obtained from the frass of white spruce.     

Fourteen heliangolides from Calea species

The investigation of two further Calea species afforded, in addition to known compounds, fourteen new heliangolides, most of them being 11,13-epoxides. One lactone is a new type, a heliangolide substituted with a monoterpene residue. Furthermore, a new chromene and a new dithienyl derivative were isolated. The structures were elucidated by spectroscopic methods. The chemotaxonomic situation is discussed briefly.     

Lipids of Fontinalis antipyretica

Fatty acid compositions of the lipids of Fontinalis antipyretica shows the presence of octadeca-9, 12-dien-6-ynoic, octadeca-9,12,15-trien- 6-ynoic and eicosa-11,14-dien-8-ynoic acids as the major components of the triglycerides. These acetylenic acids were not present in the galactosyl diglycerides. The moss lipids also contained relatively large amounts of two novel acetylenic methyl ketones with an unsaturation pattern analogous to that of the C₁₈ acetylenic acids.     

Synthesis,antimalarial and antitubercular activity of acetylenic chalcones

A series of acetylenic chalcones were evaluated for antimalarial and antitubercular activity. The antimalarial data for this series suggests that growth inhibition of the W2 strain of Plasmodium falciparum can be imparted by the introduction of a methoxy group ortho to the acetylenic group. Most compounds were more active against non-replicating than replicating cultures of Mycobacterium tuberculosis H₃₇Rv, an unusual pattern with respect to existing anti-TB agents.     

Defense mechanisms of conifers : relationship of monoterpene cyclase activity to anatomical specialization and oleoresin monoterpene content

Cell-free extracts from Pinus ponderosa Lawson (ponderosa pine) and Pinus sylvestris L. (Scotch pine) wood exhibited high levels of monoterpene synthase (cyclase) activity, whereas bark extracts of these species contained no detectable activity, and they inhibited cyclase activity when added to extracts from wood, unless polyvinylpyrrolidone was included in the preparation. The molecular mass of the polyvinylpyrrolidone added was of little consequence; however, polyvinylpolypyrrolidone (a cross-linked insoluble form of the polymer) was ineffective in protecting enzyme activity. Based on these observations, methods were developed for the efficient extraction and assay of monoterpene cyclase activity from conifer stem (wood and bark) tissue. The level of monoterpene cyclase activity for a given conifer species was shown to correlate closely with the monoterpene content of the oleoresin and with the degree of anatomical complexity of the specialized resin-secreting structures. Cyclase activity and monoterpene content were lowest in the stems of species containing only isolated resin cells, such as western red cedar (Thuja plicata D. Don). Increasing levels of cyclase activity and oleoresin monoterpenes were observed in advancing from species with multicellular resin blisters (true firs [Abies]) to those with organized resin passages, such as western larch (Larix occidentalis Nutt.), Colorado blue spruce (Picea pungens Engelm.) and Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco). The highest levels of cyclase activity and oleoresin monoterpenes were noted in Pinus species that contain the most highly developed resin duct systems. The relationship between biosynthetic capacity, as measured by cyclase activity, monoterpene content, and the degree of organization of the secretory structures for a given species, may reflect the total number of specialized resin-producing cells per unit mass of stem tissue.     

Sesquiterpenoid and acetylenic constituents of seven Clibadium species

The investigation of seven Clibadium species resulted in the isolation of a new germacrolide from C. surinamense, trans-β-bergamotene, a new sesquiterpene from C. asperum and a new C-17 acetylenic alcohol from C. glomeratum. Five known acetylenic compounds were present in some members of the genus. In good agreement with morphological data, the presence of ichthyothereol and its acetate in several members of Clibadium suggest affiliation with the genus Ichthyothere within the subtribe Milleriinae (Heliantheae-Compositae).     

Variations in the halogenated monoterpene metabolites of Plocamium cartilagineum and P. violaceum

Observed variations in the halogenated monoterpene content of Aplysia californica were due to digestion of Plocamium cartilagineum and Plocamium violaceum. Whereas Plocamium violaceum was chemically homogeneous, some variation in the composition of halogenated monoterpene composition of individual plants of P. cartilagineum was observed.     

Biosynthesis of the Monoterpenes Limonene and Carvone in the Fruit of Caraway : I. Demonstration of Enzyme Activities and Their Changes with Development

The biosynthesis of the monoterpenes limonene and carvone in the fruit of caraway (Carum carvi L.) proceeds from geranyl diphosphate via a three-step pathway. First, geranyl diphosphate is cyclized to (+)-limonene by a monoterpene synthase. Second, this intermediate is stored in the essential oil ducts without further metabolism or is converted by limonene-6-hydroxylase to (+)-trans-carveol. Third, (+)-trans-carveol is oxidized by a dehydrogenase to (+)-carvone. To investigate the regulation of monoterpene formation in caraway, we measured the time course of limonene and carvone accumulation during fruit development and compared it with monoterpene biosynthesis from [U-¹⁴C]Suc and the changes in the activities of the three enzymes. The activities of the enzymes explain the profiles of monoterpene accumulation quite well, with limonene-6-hydroxylase playing a pivotal role in controlling the nature of the end product. In the youngest stages, when limonene-6-hydroxylase is undetectable, only limonene was accumulating in appreciable levels. The appearance of limonene-6-hydroxylase correlates closely with the onset of carvone accumulation. At later stages of fruit development, the activities of all three enzymes declined to low levels. Although this correlates closely with a decrease in monoterpene accumulation, the latter may also be the result of competition with other pathways for substrate.     

Metabolism of Monoterpenes in Cell Cultures of Common Sage (Salvia officinalis) : Biochemical Rationale for the Lack of Monoterpene Accumulation

Leaves of common sage (Salvia officinalis) accumulate monoterpenes in glandular trichomes at levels exceeding 15 milligrams per gram fresh weight at maturity, whereas sage cells in suspension culture did not accumulate detectable levels of monoterpenes (<0.3 nanograms per gram fresh weight) at any stage of the growth cycle, even in the presence of a polystyrene resin trap. Monoterpene biosynthesis from [U-¹⁴C]sucrose was also virtually undetectable in this cell culture system. In vitro assay of each of the enzymes required for the sequential conversion of the ubiquitous isoprenoid precursor geranyl pyrophosphate to (+)-camphor (a major monoterpene product of sage) in soluble extracts of the cells revealed the presence of activity sufficient to produce (+)-camphor at a readily detectable level (>0.3 micrograms per gram fresh weight) at the late log phase of growth. Other monoterpene synthetic enzymes were present as well. In vivo measurement of the ability to catabolize (+)-camphor in these cells indicated that degradative capability exceeded biosynthetic capacity by at least 1000-fold. Therefore, the lack of monoterpene accumulation in undifferentiated sage cultures could be attributed to a low level of biosynthetic activity (relative to the intact plant) coupled to a pronounced capacity for monoterpene catabolism.     

Differences in volatile emissions between healthy and gall-induced branches of Haplopappus foliosus (Asteraceae)

Changes in plant secondary metabolism due to insect galls are one of the frontiers in knowledge of plant-insect interactions, especially concerning volatile organic compounds (VOCs). Here we studied the in vivo VOCs released from healthy apical branches of Haplopappus foliosus DC. (Asteraceae) and compared these volatiles to the VOCs obtained from apical bud galls produced in this host plant when attacked by the gall midge Haplopappusmyiia gregaria (Cecidomyiidae). We field-collected VOCs by dynamic headspace and identified them by gas chromatography coupled to mass spectrometry. We found changes in the relative proportions of different classes of VOC in apical branches vs. apical bud galls. H. foliosus VOCs had mainly monoterpene hydrocarbons such as p-cymene, a recognized herbivore deterrent. We also found oxygenated monoterpenes and sesquiterpenes in the H. foliosus volatile mixture. H. foliosus modifies its fragrance composition when parasitized by gall midges, showing an increased proportion of some monoterpene hydrocarbons, e.g. limonene and camphene, while others such as α-thujene, p-cymene and γ-terpinene were down-expressed in apical bud gall VOCs. We discuss these results considering gall signaling and chemical ecology hypotheses, including the potential role of plant defenses as well as gall midge-derived modification for host plant VOCs, and comment on the ecological relevance of our findings.     

Neocapillen,a new acetylenic hydrocarbon from Artemisia capillaris

During an investigation of Artemisia capillaris, a new acetylenic hydrocarbon, neocapillen, was isolated as a minor component and its structure determined.     

Limonene Synthase, the Enzyme Responsible for Monoterpene Biosynthesis in Peppermint, Is Localized to Leucoplasts of Oil Gland Secretory Cells

Circumstantial evidence based on ultrastructural correlation, specific labeling, and subcellular fractionation studies indicates that at least the early steps of monoterpene biosynthesis occur in plastids. (4S)-Limonene synthase, which is responsible for the first dedicated step of monoterpene biosynthesis in mint species, appears to be translated as a preprotein bearing a long plastidial transit peptide. Immunogold labeling using polyclonal antibodies raised to the native enzyme demonstrated the specific localization of limonene synthase to the leucoplasts of peppermint (Mentha × piperita) oil gland secretory cells during the period of essential oil production. Labeling was shown to be absent from all other plastid types examined, including the basal and stalk cell plastids of the secretory phase glandular trichomes. Furthermore, in vitro translation of the preprotein and import experiments with isolated pea chloroplasts were consistent in demonstrating import of the nascent protein to the plastid stroma and proteolytic processing to the mature enzyme at this site. These experiments confirm that the leucoplastidome of the oil gland secretory cells is the exclusive location of limonene synthase, and almost certainly the preceding steps of monoterpene biosynthesis, in peppermint leaves. However, succeeding steps of monoterpene metabolism in mint appear to occur outside the leucoplasts of oil gland cells.     

An acetylenic triol from Hyoseris lucida

The aerial parts of Hyoseris lucida afforded a new acetylenic triol. The structure was elucidated by spectroscopic methods and a few chemical transformations.     

Structure of acacigenin-B,a novel triterpene ester isolated from Acacia concinna

The structure of acacigenin-B, a novel ester genin from the pods of Acacia concinna was established from its PMR and ¹³ C NMR spectra. It was identified as the 21-hydroxy ester of acacic acid; the esterifying acid was a hitherto unknown monoterpene acid of tetrahydrofuranoid structure. This appears to be the first report of a higher terpenoid forming an ester with a monoterpene acid     

Catharanthus biosynthetic enzymes: the road ahead

Alkaloids are one of the most diverse groups of secondary metabolites found in living organisms. The most economically important alkaloids are the bisindole vinblastine, and vincristine. Unraveling the complexity of the genetic, catalytic and transport processes of monoterpene indole alkaloids biosynthesis is one of the most stimulating intellectual challenges in the plant secondary metabolism field. More than 50 metabolic steps are required to synthesize the most important alkaloids in Catharanthus roseus. Until now about only 20 of the 50 enzymes required for their biosynthesis have been determined and characterized. Hence, there are still a number of important enzymes that need to be characterized, beginning with the isolation and cloning of genes. It is also of fundamental importance to elucidate the regulatory aspects of their biosynthesis, both at the cellular and the molecular level, in order to address the question of their function in the plants that are producing them. In this review, we present an analysis of the state of the art related to the biosynthesis of the monoterpene indole alkaloids.     

Monoterpene hydrocarbon biosynthesis by isolated leucoplasts of Citrofortunella mitis

A plastid vesicle preparation isolated from exocarpium of young Citrofortunella mitis (calamondin) fruits was able to synthesise monoterpene hydrocarbons when incubated with isopentenyl pyrophosphate. The electron-microscope comparison between this organelle fraction and the various plastid classes present in the peel tissues has shown the structural identity between these plastid vesicles and the leucoplasts of the epithelial cells lining the secretory pockets. The monoterpene biosynthesis required the presence of dimethylallyl pyrophosphate, Mn²⁺ or Mg²⁺ and was increased by addition of 2-mercaptoethanol. Evidence is provided that the leucoplast vesicles act as a complete system in which occur all the successive steps involved in monoterpene hydrocarbon elaboration from isopentenyl pyrophosphate.