Galactomannans with novel structures from the lichen Roccella decipiens Darb

Two homogeneous galactomannan fractions were isolated from the lichen, Roccella decipiens, one (FP) containing Man and Gal in an 81:19 molar ratio and the other (RFS), having Man, Gal, and Glc in a 43:56:1 molar ratio. FP consisted of a main chain with (1-->4)-linked alpha-D-Manp units, most of which were substituted at O-2 with side chains consisting of nonreducing end-, 2-O- and 6-O-substituted alpha-Manp units. The latter appeared to be substituted by single-unit beta-D-Galf nonreducing ends. RFS contained a similar alpha-D-Manp core structure, but with side chains containing nonreducing end, 5-O-, 6-O-, and 5,6-di-O-substituted beta-D-Galf units. Such polysaccharide structures have not been previously reported.     

Phytotoxic polyacetylenes from roots of Russian knapweed (Acroptilon repens (L.) DC.)

There are several factors thought to assist invasive weeds in colonization of ecosystems. One of these factors is allelopathy, the negative effect of chemicals produced by one plant on neighboring plants, frequently mediated through root exudates and other plant leachates. Acroptilon repens (Asteraceae) is one of the most invasive and ecologically threatening weed species in western North America. A bioassay-guided fractionation of the root extracts of this plant led to the isolation of five polyacetylenic compounds, of which one [5′-methoxy-1′-(5-prop-1-yn-1-yl-2-thienyl)-hexa-2′,4′-diyin-6′-yl acetate] was hitherto unknown. The structures of these compounds were elucidated on the basis of spectroscopic analysis (IR, ESIMS, ¹H, ¹³C NMR and 2D NMR). All of the compounds obtained, except 1-chloro-4-(5-penta-1,3-diyn-1-yl-2-thienyl)but-3-yn-2-ol, showed phytotoxic activity against Arabidopsis thaliana seedlings. The presence of 4′-chloro-1′-(5-penta-1,3-diyn-1-yl-2-thienyl)-but-2′-yn-3′-ol was detected in the root exudates of aeroponically grown A. repens plants. None of the polyacetylenes isolated in this study were found in Colorado soils collected between September 2006 and July 2007 in an A. repens colonized site. However, polyacetylene 5 in A. repens infested soil from Washington was found in June, 2007. Contrary to our previous report, the compound 7,8-benzoflavone (6) was not detected in root exudates, nor was it encountered in extracts of roots, aerial parts or infested soil. Since we could not repeat this work, the original report has been retracted [Stermitz, F.R., Bais, H.P., Foderaro, T.A., Vivanco, J.M., 2003. 7,8-Benzoflavone: a phytotoxin from root exudates of invasive Russian knapweed [A retraction]. Phytochemistry 64, 493-497.].     

Tetranortriterpenoid derivatives from Turraea parvifolia (Meliaceae)

The methanol extract of the seeds of Turraea parvifolia has yielded seven novel triterpenoid derivatives: 12alpha-acetoxyazadironolide, turraparvin A (12alpha-acetoxy-7alpha,23-dihydroxy-24,25,26,27-tetranor-3-oxoapotirucalla-1,14,20(22)-trien-21,23-olide), turraparvin B (12alpha-acetoxy-7alpha,21-dihydroxy-24,25,26,27-tetranor-3-oxoapotirucalla-1,14,20(22)-trien-23,21-olide), turraparvin C (7alpha,12alpha-diacetoxy-21-hydroxy-24,25,26,27-tetranor-3-oxoapotirucalla-1,14,20(22)-trien-23,21-olide), 11-epi-21-hydroxytoonacilide, 11-epi-23-hydroxytoonacilide and turraparvin D (12alpha-acetoxy-7alpha-hydroxy-24,25,26,27-tetranor-3-oxoapotirucalla-1,14,20(22)-trien-21,23-lactam).     

O-Methylated mannogalactan from the microalga Coccomyxa mucigena, symbiotic partner of the lichenized fungus Peltigera aphthosa

A structural study of the carbohydrates from Coccomyxa mucigena, the symbiotic algal partner of the lichenized fungus Peltigera aphthosa, was carried out. It produced an O-methylated mannogalactan, with a (1 → 6)-linked β-galactopyranose main-chain partially substituted at O-3 by β-Galp, 3-OMe-α-Manp or α-Manp units. There were no similarities with polysaccharides previously found in the lichen thallus of P. aphthosa. Moreover, the influence of lichenization in polysaccharide production by symbiotic microalgae and the nature of the photobiont in carbohydrate production in lichen symbiosis are also discussed.     

Prenylated xanthone glucosides from Ural's lichen Umbilicaria proboscidea

Two new compounds isolated from an extract of a Central Asian lichen [Umbilicaria proboscidea (L.) Schrader=Syn.: Gyrophora proboscidea (L.) Ach.] are glucosides with mono- and di-prenylated xanthones as the aglycones and a saccharide moiety from two glucoses linked at C-7. The structures were elucidated on the basis of extensive spectroscopic analysis (1D and 2D NMR, MS, IR and UV) and by hydrolysis.     

Lead and copper effects on lipid metabolism in cultured lichen photobionts with different phosphorus status

We evaluated the ability of heavy metals (copper, lead) to alter lipid metabolism in four algal lichen photobionts following short term exposure. Metal concentrations (10 microM) were equivalent to environmentally relevant levels that have been reported to have effects on intact algae. The algae were grown under normal or deficient phosphate conditions to assess any interactions with the heavy metal stress. Given the frequent sensitivity of lichens to copper and lead, there were surprisingly small changes on lipid metabolism, as assessed by radiolabelling from [1-14C]acetate. The main effects, which were seen in a number of cases, were an overall inhibition of total lipid labelling and a relative increase in the labelling of triacylglycerols in the non-polar fraction. Both of these changes can be viewed as reflecting general toxicity of heavy metals. The Coccomyxa photobiont species were more sensitive than Trebouxia species, which fits with the general distribution of the latter in lichens inhabiting harsh environments.     

Essential oil composition of Achyrocline flaccida (Weinm.) DC. (Asteraceae) from different locations of Argentina

The qualitative and quantitative composition of the essential oils obtained from the inflorescences of Achyrocline flaccida (Asteraceae) has been investigated for the first time. Plant material was collected from eleven locations in Argentina. The essential oils were obtained by hydrodistillation (0.1–0.8% v/w, dried material) and analyzed by GC–FID–MS. Eighty-three compounds were identified representing more than the 90% of the oils. The major components were α-pinene and β-caryophyllene. Statistical analysis was performed in order to evaluate the variability of the essential oils analyzed. Two groups were formed reflecting only quantitative differences in the content of major compounds. The chemical pattern of essential oils observed for A. flaccida is similar to other Achyrocline species studied, except Achyrocline hyperchlora.     

Xanthones from Swertia punctata

Isolation of 1-O-primeverosyl-3,8-dihydroxy-5-methoxyxanthone and 1-O-gentiobiosyl-3,7-dimethoxy-8-hydroxyxanthone, along with five known xanthones, isobellidifolin, methylbellidifolin, isoswertianin, methylswertianin and norswertianin-1-O-beta-D-glucoside, from the roots of Swertia punctata is reported. In the aerial parts four xanthones, bellidifolin, methylbellidifolin, swertianolin and mangiferin, and flavone-C-glucoside, isoorientin were identified. The chemotaxonomic and pharmacological significance of these results is discussed.     

Carbohydrate, glycolipid, and lipid components from the photobiont (Scytonema sp.) of the lichen, Dictyomema glabratum

The photobiont of the lichen, Dictyonema glabratum (Scytonema sp.), was isolated and cultivated in a soil-extract medium and submitted to chemical analysis. Successive extractions with CHCl3-MeOH, aqueous MeOH, and H2O gave rise to solutions of lipids (25%), low-molecular-weight carbohydrates (22%), and polysaccharides (4%), respectively. TLC of the lipid extract showed the presence of glycolipids, which were further purified and examined by NMR spectroscopy and GC-MS. Monogalactosyldiacylglycerol (1%), digalactosyldiacylglycerol (0.8%), trigalactosyldiacylglycerol (0.4%), and sulfoquinovosyldiacylglycerol (0.5%) were identified. The most abundant fatty acid ester in each fraction was palmitic (C16:0), but a great variation of the ester composition from one to another was found. Others present were those of C12:0, C14:0, C15:0, C16:1, C17:0, C18:0, C18:1, C18:2, C18:3, C22:0, C22:2, and C24:0. The lipid extract was also subjected to acid methanolysis, which gave rise to dodecane, 2-Me-heptadecane, 2,6-Me2-octadecane, and 8-Me-octadecane, methyl esters of C14:0, C15:0, C16:0, C16:1, C17:0, C18:0, C18:1, C18:2, C20:0, and C24:0 fatty acids, and the dimethyl ester of decanedioic acid. The polysaccharide had mainly Glc, Gal, and Man, with small amounts of 3-O-methylrhamnose and 2-O-methylxylose, both found in plants, and unexpectedly, some of the units were beta-galactofuranose, typical of fungal, but not cyanobacterial polysaccharides. The low-molecular-weight carbohydrates showed mannose as the main free reducing sugar, which differs from Nostoc sp. and Trebouxia sp. photobionts.     

Phenolic analogs of the N,C-coupled naphthylisoquinoline alkaloid ancistrocladinium A, from Ancistrocladus cochinchinensis (Ancistrocladaceae), with improved antiprotozoal activities

The first N,8′-coupled naphthylisoquinoline alkaloids with free phenolic OH groups, 4′-O-demethylancistrocladinium A and 6,4′-O-didemethylancistrocladinium A, have been isolated from the leaves and bark of the Vietnamese liana Ancistrocladus cochinchinensis, along with its known, non-phenolic parent compound, ancistrocladinium A, and four C,C-coupled representatives. The structure elucidation was achieved by chemical, spectroscopic, and chiroptical methods. The mono-phenolic alkaloid showed excellent activities in particular against the pathogen causing Chagas’ disease, Trypanosoma cruzi.     

Monomeric and dimeric dibenzofurans from cultured mycobionts of Lecanora iseana

Spore-derived mycobionts of the lichen Lecanora iseana were cultivated on a malt-yeast extract medium supplemented with 10% sucrose and their metabolites were investigated. Four 3,7-dihydroxy-1,9-dimethyldibenzofuran derivatives along with the known 3,7-dihydroxy-1,9-dimethyldibenzofuran and five norlichexanthone derivatives were isolated. Their structures were determined by spectroscopic methods.     

Phenolic glycosides from Barnettia kerrii

From the leaves and branches Barnettia kerrii, two verbascoside derivatives (6"-O-acetylverbascoside and 4"'-O-acetylverbascoside), as well as two phenolic glycosides (khaephuosides A and B) were isolated together with 15 known compounds. The structural elucidations were based on analyses of spectroscopic data.     

Purification and characterization of malonyl-coenzyme A: 21-hydroxypregnane 21-O-malonyltransferase (Dp21MaT) from leaves of Digitalis purpurea L

With respect to the cardenolide pathway and the characterization of enzymes involved in the formation of cardenolides, a malonyltransferase, termed malonyl-coenzyme A: 21-hydroxypregnane 21-O-malonyltransferase (Dp21MaT) has been purified. The enzyme catalyses the transfer of the malonyl moiety from malonyl-coenzyme A to 21-hydroxypregnane substrates. Malonyltransferase activity was checked in several potential starting materials including fresh leaves and cell suspension cultures from different plants. Fresh Digitalis purpurea L. leaves turned out to be the best enzyme source. The purification protocol included ammonium sulphate precipitation, hydrophobic interaction chromatography on Phenylsepharose 6 FF, ion exchange chromatography on Source 30 Q, affinity chromatography on Cibacron Blue 3GA and gel filtration on Superdex 75. Gel filtration and native SDS-PAGE analysis showed that Dp21MaT exists as a monomer with a molecular mass of 27kDa. Its pI, as determined by isoelectric focusing, was 4.66. The enzyme showed maximal activity at pH 6.5 when incubated at 42 degrees C. The energy of activation was 29.28kJmol(-1), whereas that of inactivation was 48.57kJmol(-1). Dp21MaT was purified 252-fold with a yield of about 1%. Hanes plots of kinetic data indicated K(m) values of 99microM (V(max) 47.57microkatkg(-1)) and 28.44microM (V(max) 39.4microkatkg(-1) protein) for 3beta-benzoyloxy-5beta-pregnane-14beta,21-dihydroxy-20-one and malonyl-CoA, respectively.     

New coumarins from Pterocaulon virgatum (L.) DC

Three new coumarins, 5-hydroxy-6,7-methylenedioxycoumarin, 5-(2-hydroxy-3-methoxy-3-methylbutoxy)-6,7-methylenedioxycoumarin and 5-(2-hydroxy-3-methyl-3-butenyloxy)coumarin, were isolated from the petrol ether extract of the aerial parts of Pterocaulon virgatum. Their structures were elucidated based on spectroscopic evidence.     

Ionic complexation properties of per(3,6-anhydro)cyclodextrin derivatives towards lanthanides

Using per(3,6-anhydro)cyclodextrin derivatives [per(3,6-anhydro)CD], it was possible to produce new lanthanide chelates by careful choice of the size and functional groups. Heptakis(3,6-anhydro-2-O-methyl)cyclomaltoheptaose fulfils the best criteria for complexation of lanthanide ions. Nuclear magnetic resonance was used to derive the association constants and the stoichiometries of these new complexes. Finally, a three-dimensional structure of these complexes consistent with the NMR data is proposed, to ascertain the position of lanthanide in the cavity of the per(3,6-anhydro)CD. For the present purposes, heptakis(2-O-acetyl-3,6-anhydro)cyclomaltoheptaose, octakis(2-O-acetyl-3,6-anhydro)cyclomaltooctaose, heptakis(3,6-anhydro-2-O-methyl)cyclomaltoheptaose and octakis(3,6-anhydro-2-O-methyl)cyclomaltooctaose have been synthesized and purified.     

Three isocoumarins and a benzofuran from the cultured lichen mycobionts of Pyrenula sp

The spore-derived mycobionts of the lichen Pyrenula sp. were cultivated on a malt-yeast extract medium supplemented with 10% sucrose. The investigation of their metabolites resulted in isolation of four compounds, three isocoumarins and a biogenetically related benzofuran; their structures were determined by spectroscopic methods.