Biomedical subjects
Publications and source records attributed to C Christophersen.
Crude extracts of Haplopappus sonorensis (A. Gray) S.F. Blake (Asteraceae), showed activity against Mycobacterium tuberculosis H(37)Rv. By assay-guided fractionation, 5-hydroxy-3,7,4'-trimethoxyflavone (1). 5,7-dihydroxy-3,4'-dimethoxyflavone (2). and 5,4'-dihydroxy-3,7-dimethoxyflavone (3). were identified as the antimycobacterial principles. Compound 2 was the most active compound.
Cyclic lipopeptides (CLPs) with antibiotic and biosurfactant properties are produced by a number of soil bacteria, including fluorescent Pseudomonas spp. To provide new and efficient strains for the biological control of root-pathogenic fungi in agricultural crops, we isolated approximately 600 fluorescent Pseudomonas spp. from two different agricultural soils by using three different growth media. CLP production was observed in a large proportion of the strains (approximately 60%) inhabiting the sandy soil, compared to a low proportion (approximately 6%) in the loamy soil. Chemical structure analysis revealed that all CLPs could be clustered into two major groups, each consisting of four subgroups. The two major groups varied primarily in the number of amino acids in the cyclic peptide moiety, while each of the subgroups could be differentiated by substitutions of specific amino acids in the peptide moiety. Production of specific CLPs could be affiliated with Pseudomonas fluorescens strain groups belonging to biotype I, V, or VI. In vitro analysis using both purified CLPs and whole-cell P. fluorescens preparations demonstrated that all CLPs exhibited strong biosurfactant properties and that some also had antibiotic properties towards root-pathogenic microfungi. The CLP-producing P. fluorescens strains provide a useful resource for selection of biological control agents, whether a single strain or a consortium of strains was used to maximize the synergistic effect of multiple antagonistic traits in the inoculum.
The crystal structure of the lipoundecapeptide amphisin, presented here as the tetrahydrate, C(66)H(114)N(12)O(20).4H(2)O, originating from non-ribosomal biosynthesis by Pseudomonas sp. strain DSS73, has been solved to a resolution of 0.65 A. The primary structure of amphisin is beta-hydroxydecanoyl-D-Leu-D-Asp-D-allo-Thr-D-Leu-D-Leu-D-Ser-L-Leu-D-Gln-L-Leu-L-Ile-L-Asp (Leu is leucine, Asp is aspartic acid, Thr is threonine, Ser is serine, Gln is glutamine and Ile is isoleucine). The peptide is a lactone, linking Thr4 O(gamma) to the C-terminal. The stereochemistry of the beta-hydroxy acid is R. The peptide is a close analogue of the cyclic lipopeptides tensin and pholipeptin produced by Pseudomonas fluorescens. The structure of amphisin is mainly helical (3(10)-helix), with the cyclic peptide wrapping around a hydrogen-bonded water molecule. This lipopeptide is amphiphilic and has biosurfactant and antifungal properties.
The novel quinazoline metabolite serantrypinone (1) has been isolated from an isolate of the microfungus Penicillium thymicola together with daldinin D (2), a new peracetylated spiro azaphilone derivative. The structures of 1 and 2 were elucidated by analysis of spectroscopic data, including 2D NMR, and comparison with literature data.
A new method for fast and easy monitoring of the presence, isolation, and separation of natural chloro compounds in plants is described. The method relies on the in vivo incorporation of radioactive 36Cl and new enhancement methods in autoradiographic technology. The method allows the time of exposure to be limited to 4 days and is thus suitable for routine purposes.
Two new carboxylic acids, tanzawaic acid E (1) and F (2) in addition to the unknown benzopyran 3,7-dimethyl-1,8-dihydroxy-6-methoxy-isochroman (3), and the known mycotoxin 3,7-dimethyl-8-hydroxy-6-methoxyisochroman (4) were produced by a marine-derived strain of Penicillium steckii isolated from an unidentified tunicate. The carboxylic acids and the benzopyran were identified on the basis of mass spectrometry, and one and two dimensional NMR spectroscopic techniques. The structures 1 and 2 resemble tanzawaic acid A-D, previously isolated from Penicillium citrinum. Screening of isolates of species related to P. citrinum and P. steckii showed that P. citrinum (25 isolates) consistently produced citrinin and tanzawaic acid A, P. steckii (18 isolates) produced isochroman toxins (except 2) and tanzawaic acid E, P. sizovae consistently produced tanzawaic acid A, P. corylophilum (10 isolates) produced citreoisocoumarinol and P. sumatrense (15 isolates) always produced curvularin.
A novel 2,2'-epoxy-terphenyllin, candidusin C, in addition to the well known secondary metabolites terphenyllin, 3-hydroxyterpenyllin and chlorflavonin, has been isolated from the chemically unexplored fungus Aspergillus campestris. The latter three are known secondary metabolites from Aspergillus candidus and therefore a large number of Aspergilli were screened for production of these compounds to see whether they could be regarded as chemotaxonomical indicators of section membership in the monotypic Aspergillus section Candidi. The results indicated that A. campestris and A. taichungensis should be placed in Candidi and this was further confirmed by morphological and physiological similarities. Three species outside the section Candidi produced candidusin related secondary metabolites: Aspergillus arenarius, A. ellipticus and Penicillium raistrickii. Chlorflavonin, however, was only found in section Candidi.
Calafianin (1) and two known compounds, aerothionin and (3, 5-dibromo-2-hydroxy-4-methoxyphenyl)acetic acid, were isolated from the marine sponge Aplysina gerardogreeni. The structure of 1 was determined by NMR analysis and mass spectrometry.
AIM: To study the antagonistic activity by Pseudomonas fluorescens strain 96.578 on the plant pathogenic fungus Rhizoctonia solani. METHODS AND RESULTS: Strain 96.578 produced a new cyclic lipopeptide, tensin. High tensin production per cell was detected in liquid media with glucose, mannitol or glutamate as growth substrate while fructose, sucrose and asparagine supported low production. Tensin production was nearly constant in media with different initial C levels, while low initial N contents reduced production. When applied to sugar beet seeds, strain 96.578 produced tensin during seed germination. When challenged with strain 96.578 or purified tensin, Rhizoctonia solani reduced radial mycelium extension but increased branching and rosette formation. CONCLUSION: The antagonistic activity of strain 96.578 towards Rhizoctonia solani was caused by tensin. SIGNIFICANCE AND IMPACT OF THE STUDY: When coated onto sugar beet seeds, tensin production by strain 96.578 could be of significant importance for inhibition of mycelial growth and seed infection by Rhizoctonia solani.
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Pseudomonas fluorescens DR54 showed antagonistic properties against plant pathogenic Pythium ultimum and Rhizoctonia solani both in vitro and in planta. Antifungal activity was extractable from spent growth media, and fractionation by semi-preparative HPLC resulted in isolation of an active compound, which was identified as a new bacterial cyclic lipodepsipeptide, viscosinamide, using 1D and 2D 1H-, 13C-NMR and mass spectrometry. The new antibiotic has biosurfactant properties but differs from the known biosurfactant, viscosin, by containing glutamine rather than glutamate at the amino acid position 2 (AA2). No viscosin production was observed, however, when Ps. fluorescens DR54 was cultured in media enriched with glutamate. In vitro tests showed that purified viscosinamide also reduced fungal growth and aerial mycelium development of both P. ultimum and R. solani. Viscosinamide production by Ps. fluorescens DR54 was tightly coupled to cell proliferation in the batch cultures, as the viscosinamide produced per cell mass unit approached a constant value. In batch cultures with variable initial C, N or P nutrient levels, there were no indications of elevated viscosinamide production during starvation or maintenance of the cultures in stationary phase. Analysis of cellular fractions and spent growth media showed that a major fraction of the viscosinamide produced remained bound to the cell membrane of Ps. fluorescens DR54. The isolation, determination of structure and production characteristics of the new compound with both biosurfactant and antibiotic properties have promising perspectives for the application of Ps. fluorescens DR54 in biological control.
Fumiquinazoline F (1) and alantrypinone (2) have been isolated as the two major metabolites of Penicillium thymicola. The structure of 2, which contains a new ring structure, was elucidated by analysis of spectroscopic data including 2D NMR. The absolute configuration of 2 was established by a single-crystal X-ray diffraction study.
A nonswarming Serratia liquefaciens mutant deficient in serrawettin W2 production was constructed by transposon mutagenesis. Sequence homology indicated that insertion had occurred in gene swrA, which encodes a putative peptide synthetase. Expression of swrA is controlled by quorum sensing.
A 56-year-old man, working in a food processing factory, developed contact dermatitis of his hands, forearms, and face after the introduction of a new herb extract (Rosmanox) made from the leaves of rosemary (Rosmarinus officinalis). He reacted to carnosol, the main constituent of Rosmanox. 226 controls were negative. To our knowledge, this is the 1st reported case of contact dermatitis from carnosol.
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Investigation of the ethanolic extracts from Phytolacca rivinoides and P. bogotensis has resulted in the isolation of five new triterpenoid glycosides of serjanic acid. Their structures have been established mainly by spectroscopic methods (FAB-MS, 1H, 13C NMR, COSY, NOESY, TOCSY, HETCOR and J-resolved 1H NMR) as 3-O-(O-beta-D-galactopyranosyl-(1-->3)-O-beta-D-glucopyranosyl)serjan ic acid 28-O-beta-D-glucopyranosyl ester, 3-O-(O-beta-D-glucopyranosyl-(1-->3)-O-[beta-D-galactopyranosyl-(1-->4)] -O- beta-D-glucopyranosyl)serjanic acid 28-O-beta-D-glucopyranosyl ester, 3-O-(O-alpha-L-rhamnopyranosyl-(1-->2)-O-beta-D-glucopyranosyl-(1-->2)- O-beta-glucopyranosyl)serjanic acid 28-O-beta-D-glucopyranosyl ester, 3-O-(O-beta-D-glucopyranosyl-(1-->3)-O-beta-D-galactopyranosyl-(1-->4)- O-beta-D-glucopyranosyl)serjanic acid 28-O-beta-D-glucopyranosyl ester and 3-O-(O-beta-D-galactopyranosyl-(1-->4)-O-[beta-D-glucopyranosyl-(1-->3)] - O-beta-D-glucopyranosyl)serjanic acid.
A new alkaloid, flustramine E [1], with inhibitory activity towards Rhizotonia solani and Botrytis cinerea was isolated by gas-phase extraction from the marine bryozoan Flustra foliacea. The structure was determined as 3a,8a-cis-1-methyl-3a-(3-methyl-2- butenyl)-6-bromo-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b]indole, based on spectroscopic investigations. Another alkaloid, debromoflustramine B [2a], was detected in trace amounts and identified by comparison of the mass spectrum with that of a synthetic sample. The extract also contained the previously reported alkaloids flustramine A and B in the ratio 1:7.