Stephan Franke

Changes in hydroxamic acid levels of wheat plants induced by aphid feeding

Abstract Seedlings of four wheat cultivars were infested with Metopolophium dirhodum nymphs. After aphids had fed for 40 hr on the plants, the levels of the defense metabolite 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one had changed. The changes depended on the cultivar and the portion of the leaf examined. The increase was greater in cultivars Naofen (45.0% at the tip of the leaf, 96.2% at the base where aphids were feeding) and Quilafen (14.7 and 35.8% respectively). The increase was not significant in cultivars Huenufen and Sonka. A simple and sensitive high performance liquid chromatographic method is described for the quantitation of the above benzoxazinone and its demethoxylated analogue using small amounts of plant tissue.

Molecular markers of anthropogenic activity in sediments of the Havel and Spree Rivers (Germany)

Detailed gas chromatographic/mass spectrometric analyses have been applied to sediment samples of the Havel and Spree River, tributaries to the Elbe River, in order to identify specific molecular markers of anthropogenic activities. Despite a wide variety of lipophilic organic compounds from diffuse anthropogenic contamination, a local emission of an industrial point source was reflected by specific markers including halogenated compounds and nitrogen containing substances (4-ethylnitrobenzene, formyl piperidine, acetyl piperidine). In addition to well-known anthropogenic markers various new molecular tracers were detected and are discussed, namely plasticizers (alkylsulfonic acid aryl esters, tributyl and tricresyl phosphates), synthetic fragrances (galaxolide, tonalide, 4-oxoisophorone), additives of personal care products (4-methoxycinnamic acid 2-ethylhexyl ester, benzyl benzoate, dibenzyl ether, benzophenone), occurring due to sewage treatment plant input.

The distribution of nitrobenzene and other nitroaromatic compounds in the North Sea

Abstract An analytical approach is presented that allows quantification of nitroaromatics below ng l −1 (ppt) levels by fluid-fluid extraction and subsequent GC-AFID detection. Nitrobenzene, 1-chloro-2-nitrobenzene and other nitroaromatic compounds such as musk xylene and musk ketone, synthetic fragrances used on a large scale, were analysed in 33 North Sea water samples in concentrations between 0.05 and 2.5 ng l −1 . This is the first report about the contamination of seawater with nitro musks and the distribution of nitroaromatics in the German Bight and the eastern part of the North Sea.

Cuticular hydrocarbons and aggression in the termite Macrotermes subhyalinus.

Cuticular hydrocarbons are among the prime candidates for nestmate recognition in social insects. We analyzed the variation of cuticular hydrocarbons in the termite species M. subhyalinus in West Africa (Comoë National Park) on a small spatial scale (<1 km). We found considerable variation in the composition of cuticular hydrocarbons among colonies, with four distinct chemical phenotypes. Different phenotypes occurred within each of the four habitats. The difference between these phenotypes is primarily due to unsaturated compounds. A clear correlation between the difference of the hydrocarbon composition and the aggression between colonies was found. This correlation also holds in a multivariate analysis of genetic similarity (measured by AFLPs), morphometric distances (measured by Mahalanobis-distances), as well as geographic distances between colonies. In a more detailed analysis of the correlation between the composition of cuticular hydrocarbons and aggression, we found that no single compound is sufficient to explain variation in aggression between pairings of colonies. Thus, termites seem to use a bouquet of compounds. Multiple regression analysis suggested that many of these compounds are unsaturated hydrocarbons and, thus, may play a key role in colony recognition.

ENANTIOMERIC COMPOSITION OF THE POLYCYCLIC MUSKS HHCB AND AHTN IN DIFFERENT AQUATIC SPECIES

Synthetic polycyclic musk fragrances are mainly represented by the compounds HHCB (Galaxolide(TM)) and AHTN (Tonalide(TM)). Because of their volume of use and their bioaccumulation potential, there is concern with respect to their environmental safety. HHCB and AHTN are chiral compounds, and gas chromatography using modified cyclodextrins as chiral stationary phases coupled to high-resolution mass spectrometry enabled enantioselective analysis even under unfavorable matrix conditions. The gas chromatographic elution order of (4S,7RS)- and (4R,7RS)-HHCB was assigned using synthetic (4S, 7RS)-HHCB. Fish and mussels reared in a pond associated with a municipal waste water treatment plant and semipermeable membrane devices exposed in the pond were analyzed for HHCB and AHTN. The highest lipid concentrations of HHCB and AHTN were observed in mussels (Dreissena polymorpha), tench (Tinca tinca), and crucian carp (Carassius carassius). Pronounced deviations in enantiomeric composition from racemic HHCB were observed in crucian carp and from racemic AHTN in tench. Correlations between lipid levels, enrichment, and enantioselective biotransformation of HHCB or AHTN were not seen. Selective biotransformation depended on both the compound and the species involved. The present study gives the first account of the enantiomeric composition of HHCB and AHTN in aquatic species. The lactone, 1,3,4,6,7,8-hexahydro-4,6,6,7,8, 8-hexamethylcyclopenta[g]-2-benzopyran-1-one, an oxidation product of HHCB, has been identified for the first time in environmental samples. Copyright 1999 Wiley-Liss, Inc.

The discovery of 2,5-dialkylcyclohexan-1,3-diones as a new class of natural products.

Orchids employing sexual deceit attract males of their pollinator species through specific volatile signals that mimic female-released sex pheromones. One of these signals proved to be 2-ethyl-5-propylcyclohexan-1,3-dione (chiloglottone1), a new natural product that was shown to be most important in the relations between orchids of the genus Chiloglottis, native to Australia, and corresponding pollinator species. Systematic investigations on the mass spectrometric fragmentation pattern of 2,5-dialkylcyclohexan-1,3-diones identified key ions providing information about the structures of the substituents at positions 2 and 5. Results enabled us to identify 2-ethyl-5-pentylcyclohexan-1,3-dione (chiloglottone2) and 2-butyl-5-methylcyclohexan-1,3-dione (chiloglottone3) as new natural products that play a decisive role in the pollination syndrome of some Chiloglottis species. During field bioassays, pure synthetic samples of chiloglottone1–3 or mixtures thereof proved to be attractive to the corresponding orchid pollinators. Because of their likely biogenesis from ubiquitous fatty acid precursors, 2,5-dialkylcyclohexan-1,3-diones may represent a hitherto overlooked, widespread class of natural products.

Organic compounds as contaminants of the Elbe River and its tributaries

GC/MS non target screening has been applied to water samples taken during 1992–1994 from the Elbe river and its tributaries Mulde, Saale, Weiße Elster, Schwarze Elster, and Havel. Based on full scan electron impact mass spectra and supplemented by extensive use of chemical ionisation and high resolution data as well as by synthetic reference compounds, several new classes of compounds, whose possible environmental effects are yet unknown at present, have been identified. Tetrachlorinated bis-(propyl)ethers are new among the most prominent contaminants throughout the Elbe river. The confluence with the Mulde river adds a variety of compounds, related to the chemistry of chloro- and nitroaromatics, azo dyes, benzanilides, carbamates, thiophosphates, and pesticides. The combined load of the Weiße Elster and Saale rivers carries oligoformals, oxathiamacrocycles, and dichloro- and trichloro-bis-(propyl)ethers, whereas chloropropylphosphates are introduced via the Schwarze Elster. The majority of these compounds, originating from sources at the tributaries, are still present at the mouth of the Elbe river. In addition to specific industrial emissions, a variety of more generally observed organic compounds like long chain aliphatics, sterols, phenylalkanes, and plasticizers as well as ubiquitous environmental trace pollutants like polycyclic aromatic hydrocarbons, chlorobenzenes, and hexachlorocyclohexane isomers have been encountered throughout the Elbe river drainage system.

A new family of tricyclic alkaloids from Myrmicaria ants

Abstract The poison gland secretion of the African ant, Myrmicaria opaciventris , contains three families of new alkaloids. These alkaloids are represented by a “monomeric” type with 15 carbon atoms in a row forming derivatives of indolizines, while the two other families are “dimers” and “trimers” with 30 and 45 carbon atoms, respectively. The major constituents of the low molecular weight alkaloids are identified to be pyrrolo[2,1,5-cd]indolizines, highly dominated by l-ethyl-3,4,41,5,6,7-hexahydro-2-((1 Z )-1-propenyl)-pyrrolo[2,1,5-cd]indolizine, myrmicarin 215A . The higher molecular weight components show complex oligocyclic structures, which are closely related to the pyrroloindolizines. The alkaloid pattern shows a high degree of intraspecific variation.

Identification of Fungal Sphingolipid C9-methyltransferases by Phylogenetic Profiling

Fungal glucosylceramides play an important role in plant-pathogen interactions enabling plants to recognize the fungal attack and initiate specific defense responses. A prime structural feature distinguishing fungal glucosylceramides from those of plants and animals is a methyl group at the C9-position of the sphingoid base, the biosynthesis of which has never been investigated. Using information on the presence or absence of C9-methylated glucosylceramides in different fungal species, we developed a bioinformatics strategy to identify the gene responsible for the biosynthesis of this C9-methyl group. This phylogenetic profiling allowed the selection of a single candidate out of 24–71 methyltransferase sequences present in each of the fungal species with C9-methylated glucosylceramides. A Pichia pastoris knock-out strain lacking the candidate sphingolipid C9-methyltransferase was generated, and indeed, this strain contained only non-methylated glucosylceramides. In a complementary approach, a Saccharomyces cerevisiae strain was engineered to produce glucosylceramides suitable as a substrate for C9-methylation. C9-methylated sphingolipids were detected in this strain expressing the candidate from P. pastoris, demonstrating its function as a sphingolipid C9-methyltransferase. The enzyme belongs to the superfamily of S-adenosylmethionine-(SAM)-dependent methyltransferases and shows highest sequence similarity to plant and bacterial cyclopropane fatty acid synthases. An in vitro assay showed that sphingolipid C9-methylation is membrane-bound and requires SAM and Δ4,8-desaturated ceramide as substrates.

Structural and chemical ontogeny of the postpharyngeal gland in the desert ant Cataglyphis niger

Abstract. The postpharyngeal gland of Cataglyphis niger (André, 1881) workers is characterized, at the ultrastructural level, by a well‐developed smooth endoplasmic reticulum, Golgi apparatus, and numerous mitochondria and lamellar inclusions suggesting an involvement in lipid metabolism. In addition, the microvillar differentiation of the apical membrane and basal invaginations of the cell imply a transportation process.