Xanthones from formosan Gentianaceous plants

A reinvestigation of the whole plants ofTripterospermum lanceolatum gave, in addition to compounds isolated previously, two new xanthones, named lanceolin and methyllanceolin, respectively. The compound previously reported to be oleanolic acid was re-examined and identified as ursolic acid by a¹³C NMR study. An isomeric mixture, oleanolic acid and ursolic acid, and sweroside were isolated from the whole plants ofSwertia arisanensis.     

Biosynthesis of fomannoxin in the root rotting pathogen Heterobasidion occidentale

Fomannoxin is a biologically active benzohydrofuran, which has been suggested to be involved in the pathogenicity of the root rotting fungus Heterobasidion annosum sensu lato. The biosynthesis of fomannoxin was investigated through an isotopic enrichment study utilizing [1-¹³C]glucose as metabolic tracer. ¹³C NMR spectroscopic analysis revealed the labeling pattern and showed that the isoprene building block originates from the mevalonic acid pathway, whereas the aromatic motif is formed via the shikimic acid route by elimination of pyruvate from chorismic acid. A natural product, 4-hydroxy-3-(3-methylbut-2-enyl)benzaldehyde (1), was isolated and characterized, and was suggested to be a key intermediate in the biosynthesis of fomannoxin and related secondary metabolites previously identified from the H. annosum fungal species complex.     

Stereochemistry of 2-aminopimelic acid and related amino acids in three species of asplenium

We previously reported two free D-amino acids, D-2-aminopimelic acid (D-APA) and trans-3,4-dehydro-D-2-aminopimelic acid (D-Δ-APA), from Asplenium unilaterale. In the present work we isolated 4-hydroxy-2-aminopimelic acid (OH-APA) from the same plant and determined it to be the α-L-form. We also investigated the configurations of these amino acids isolated from A. prolongatum and A. wilfordii which are morphologically distinct from A. unilaterale. In A. prolongatum, APA was the D- and OH-APA was the L-isomer. In contrast, APA from A. wilfordii was partially racemized and the degree of racemization was significantly different in plant material collected in July and November, L:D = 3:2 and 3:7, respectively. In A. wilfordii OH-APA was almost pure L- and Δ-APA was mostly the D-isomer.     

Three cadinene derivatives and a prostaglandin-like acid from Chromolaena species

An investigation of the aerial parts of Chromolaena chasleae afforded a prostaglandin-like acid, whose structure followed from the ¹H NMR spectral data and from the reaction with periodate, which afforded a hemiacetal. From a new Chromolaena species, three novel cadinene derivatives were isolated, which were closely related to those isolated previously from this genus.     

Molecular cloning of cDNA for lysenin,a novel protein in the earthworm Eisenia foetida that causes contraction of rat vascular smooth muscle

Lysenin, which causes contraction of rat vascular smooth muscle, is a protein that was isolated from the earthworm Eisenia foetida. A cDNA encoding lysenin was isolated by use of a partial cDNA probe that had been generated by the PCR with a primer designed by reference to an internal peptide sequence of lysenin. This clone had an ORF encoding 297 amino acid residues. The amino acid sequence deduced from the cDNA revealed the absence of any significant homology to those of previously characterized vasoactive substances. The recombinant lysenin was produced in Escherichia coli. This protein and native lysenin isolated from the earthworm had similar contractive activities when tested on rat aorta. Northern blot analysis of the RNA from various tissues of the earthworm indicated that lysenin is produced by the coelomocytes.     

2-amino-4-acetylaminobutyric acid, 2,4-diaminobutyric acid and 2-amino-6N-oxalylureidopropionic acid (oxalylalbizziine) in seeds of acacia angustissima

A new amino acid previously detected in 17 species of Acacia has been isolated from seeds of Acacia angustissima and identified as oxalylalbizziine. These seeds also contain more than 6% dry weight of 2-amino-4-acetylaminobutyric acid, which has not been reported previously in a legume, and lower concentrations of 2,4-diaminobutyric acid.     

A naturally-occurring structural analogue of the phytotoxin coronatine

Chlorosis-inducing compounds in liquid cultures of the phytopathogenic bacterium Pseudomonas syringae pv. atropurpurea have been investigated. In addition to coronatine as previously reported, a new compound was discovered. This gave a mass spectral fragmentation pattern which indicated that it was, like coronatine, an amide of coronafacic acid. Acid-hydrolysis of the new toxin liberated the amino acid valine. This observation, together with mass spectral and NMR data, established the structure of the new toxin as N-coronafacoylvaline. Some implications to biosynthesis are discussed. Along with the two chlorosis-inducing compounds, the biologically inactive coronafacic acid was also isolated from the growth medium.     

Prelunularic acid in liverworts

Prelunularic acid, the first example of an intermediate with a ‘pre-aromatic’ structure in the phenylpropanoid-polymalonate pathway, was isolated from suspension-cultured cells of Marchantia polymorpha. Its structure, including its absolute configuration, was assigned on the basis of spectral properties, direct conversion into lunularic acid, and CD measurements on the bis(p-dimethylaminobenzoate) of the methyl ester. Prelunularic acid was also detected in several liverworts of Marchantiales and Jungermanniales, and appears to be the immediate precursor of lunularic acid instead of the previously postulated hydrangenol or hydrangeic acid.     

Alkaloids of ethiopian Calpurnia aurea subsp. aurea

Two novel alkaloids 3β,4α,13α-trihydroxylupanine and 3β,4α-dihydroxy 13α-O-(2'-pyrrolylcarbonyl)-lupanine (calpaurine) have been isolated from the leaves of Ethiopian Calpurnia aurea subsp. aurea. In addition, lupinine and epilupinine (both new for the genus), calpurmenine and calpurmenine pyrrolecarboxylic acid ester (previously found in subsp. sylvatica but not in subsp. aruea) have been isolated together with 13-hydroxylupanine, its tiglate and pyrrolecarboxylic acid esters (calpumine), virgiline and virgiline pyrrolecarboxylic acid ester, alkaloids which have been reported previously from subsp. aruea.     

Taraxacoside,a type of acylated γ-butyrolactone glycoside from taraxacum officinale

In addition to the four new sesquiterpene lactones previously identified, a new acylated γ-butyrolactone glucoside, taraxacoside, was isolated from the roots of Taraxacum officinale. Its structure was elucidated mainly by ¹H and ¹³C NMR studies as β-O-[4-O-(p-hydroxyphenylacetyl]β-D-glucopyranosyl]-β-hydroxy-γ-butyrolactone. This seems to be the first instance of the detection of a monocyclic five-membered, saturated lactone O-glycoside. Additionally, p-hydroxyphenylacetic acid was identified for the first time as an acylating acid in a sugar ester.     

A revised structure for the diterpene rosmanol

The diterpene rosmanol, previously isolated from Rosmarinus officinalis, has been isolated from the flowers of Salvia canariensis and its structure revised as 7α,11,12-trihydroxyabieta-8,11,13-trien-20-oic acid 20,6-lactone, on the basis of chemical evidence and an X-ray diffraction analysis.     

Iridoids from Galium mollugo

From Galium mollugo, two new iridoids, gardenosidic acid and 10-hydroxymorroniside as well as 10-hydroxyloganin have been isolated, along with seven known iridoids, secogalioside, asperuloside, asperulosidic acid, daphylloside, monotropein, scandoside and scandoside methyl ester. 10-Hydroxyloganin, a compound which was previously considered to be the key biosynthetic intermediate of secoiridoids, was obtained for the first time from a natural source.     

Dimeric guaianolides and other constituents from Gochnatia species

The roots of Gochnatia polymorpha afforded two new bisabolene derivatives and four dimeric guaianolides, two of them being isolated previously from G. paniculata. The aerial parts gave two further dimeric guaianolides. The aerial parts of G. hypoleuca afforded three new germacran-8,12-olides, a germacranolide acid and four additional dimeric guaianolides, which may be characteristic for this genus, while the presence of oxygenated germacranolides seems to be typical for the whole subtribe.     

Expanding the Cyanuric Acid Hydrolase Protein Family to the Fungal Kingdom

The known enzymes that open the s-triazine ring, the cyanuric acid hydrolases, have been confined almost exclusively to the kingdom Bacteria and are all homologous members of the rare cyanuric acid hydrolase/barbiturase protein family. In the present study, a filamentous fungus, Sarocladium sp. strain CA, was isolated from soil by enrichment culturing using cyanuric acid as the sole source of nitrogen. A reverse-genetic approach identified a fungal cyanuric acid hydrolase gene composed of two exons and one intron. The translated spliced sequence was 39 to 53% identical to previously characterized bacterial cyanuric acid hydrolases. The sequence was used to generate a gene optimized for expression in Escherichia coli and encoding an N-terminally histidine-tagged protein. The protein was purified by nickel affinity and anion-exchange chromatography. The purified protein was shown by ¹³C nuclear magnetic resonance (¹³C-NMR) to produce carboxybiuret as the product, which spontaneously decarboxylated to yield biuret and carbon dioxide. The protein was very narrow in substrate specificity, showing activity only with cyanuric acid and N-methyl cyanuric acid. Barbituric acid was an inhibitor of enzyme activity. Sequence analysis identified genes with introns in other fungi from the Ascomycota that, if spliced, are predicted to encode proteins with cyanuric acid hydrolase activity. The Ascomycota cyanuric acid hydrolase homologs are most closely related to cyanuric acid hydrolases from Actinobacteria.     

Further diterpenoids from Plectranthus ornatus and P. grandidentatus

A new halimane diterpenoid and the previously known labdane rhinocerotinoic acid were isolated from Plectranthus ornatus Codd. In addition, a new monoacetyl derivative of the abietane coleon U was found among the constituents of Plectranthus grandidentatus Gürke. These diterpenes could be significant from both chemotaxonomic and biogenetic points of view.     

Sesquiterpene lactones from a texas population of Helianthus maximiliani

A population of Helianthus maximiliani from south-central Texas was shown to have a sesquiterpene lactone chemistry which was completely different from that reported for collections of this species from Kansas and north-central Texas. A series of five new guaianolides, two germacrolides (trans, trans-1(10),4(5)-germacradienolides), one of which is new, and a known labdane diterpene acid were isolated from a chloroform extract. Structures were determined by spectral and chemical methods. The structure of one guaianolide had been previously determined by X-ray crystallography.     

Ddi1-like protein from Leishmania major is an active aspartyl proteinase

Eukaryotic cells respond to DNA damage by activating damage checkpoint pathways, which arrest cell cycle progression and induce gene expression. We isolated a full-length cDNA encoding a 49-kDa protein from Leishmania major, which exhibited significant deduced amino acid sequence homology with the annotated Leishmania sp. DNA damage-inducible (Ddi1-like) protein, as well as with the Ddi1 protein from Saccharomyces cerevisiae. In contrast to the previously described Ddi1 protein, the protein from L. major displays three domains: (1) an NH2-terminal ubiquitin like; (2) a COOH terminal ubiquitin-associated; (3) a retroviral aspartyl proteinase, containing the typical D[S/T]G signature. The function of the L. major Ddi1-like recombinant protein was investigated after expression in baculovirus/insect cells and biochemical analysis, revealing preferential substrate selectivity for aspartyl proteinase A₂ family substrates, with optimal activity in acidic conditions. The proteolytic activity was inhibited by aspartyl proteinase inhibitors. Molecular modeling of the retroviral domain of the Ddi1-like Leishmania protein revealed a dimer structure that contained a double Asp-Ser-Gly-Ala amino acid sequence motif, in an almost identical geometry to the exhibited by the homologous retroviral aspartyl protease domain of yeast Ddi1 protein. Our results indicate that the isolated Ddi1-like protein is a functional aspartyl proteinase in L. major, opening possibility to be considered as a potential target for novel antiparasitic drugs.     

Detection,isolation and structure elucidation of a chlorophyll a catabolite from autumnal senescent leaves of Cercidiphyllum japonicum

Extracts of autumnal leaves of the dicotyledonous, deciduous tree Cercidiphyllum japonicum cultivated at the Botanical Garden of Fribourg, Switzerland, were screened for chlorophyll catabolites by TLC utilizing the chromic acid degradation test. The constitution of the isolated material was elucidated by spectroscopy. The structure, an optically active bile-pigment-like 19-formyl-1[21H,22H]bilinone derivative, reveals that this compound originates from chlorophyll a and resembles the structures of previously isolated chlorophyll catabolites from the green alga Chlorella protothecoides and from the angiosperms, the monocot Hordeum vulgare and the dicot Brassica napus.     

Some properties of Photosystem II preparations from the cyanobacterium Synechococcus sp. — presence of an l-amino acid oxidase in Photosystem II complexes from Synechococcus sp.

A highly active O₂-evolving Photosystem II complex has been purified from the cyanobacterium Synechococcus sp., and this complex has been compared with the Photosystem II complex previously isolated from this cyanobacterium (Ohno, T., Satoh, K. and Katoh, S. (1986) Biochim. Biophys. Acta 852, 1–8). Further treatment of the O₂-evolving complex with the detergent sodium taurodesoxycholate resulted in a complex which consisted mainly of the 47 and 40 kDa peptides and which had lost the O₂-evolving activity, but which could still reduce 2,6-dichlorophenolindophenol with 1,5-diphenylcarbazide. Previously, we have shown that a flavoprotein of 49 kDa which has an l-amino acid oxidase activity under certain conditions, is a component of highly active Photosystem II preparations from the cyanobacterium Anacystis nidulans (Pistorius, E.K. and Gau, A.E. (1986) FEBS Lett. 206, 243–248). Based on immunological studies with the antiserum raised against the l-amino acid oxidase protein from A. nidulans, we show that a protein which cross-reacts with this antiserum is present in the highly purified Photosystem II preparations from Synechococcus sp. Moreover, an l-amino acid oxidase activity could also be detected in Photosystem II preparations from Synechococcus sp. The enzyme preferentially oxidizes basic l-amino acids as l-arginine, l-ornithine, 2,3-diamino propionic acid and l-citrulline. In contrast to the enzyme from A. nidulansl-lysine is not oxidized. The here shown presence of an l-amino acid oxidase protein in Photosystem II preparations from Synechococcus sp. is an additional support of our hypothesis that a flavoprotein is a functional component of the water-oxidizing enzyme complex.     

The benzofuran norwedelic acid from Wedelia calendulaceae

A new compound norwedelic acid [5,6-dihydroxy-2(2′,4′,6′-trihydroxyphenyl)-benzofuran-3-carboxylic acid] has been isolated from fresh leaves of Wedelia calendulaceae apart from norwedelolactone, a compound previously found in Eclipta alba.