Jan Schlauer

Droserone from cell cultures of Triphyophyllum peltatum (Dioncophyllaceae) and its biosynthetic origin.

The growth and droserone content of callus cultures of Triphyophyllum peltatum grown in liquid 1/5 Linsmaier and Skoog medium was studied. During a lag phase in growth, droserone concentrations in the medium reached a value of 2.1 mg g-1 fr. wt. After this maximum value the concentration decreased slightly to 1.8 mg g-1 fr. wt., while the growth of the calli was enhanced (25% increase in fr. wt. within 7 days). Plumbagin and isoshinanolone were likewise present in the medium. By feeding 13C2-labelled acetate to the cultures the biosynthesis of droserone was elucidated. The incorporation of whole C2-units unambiguously shows its acetogenic origin and fits well in the biosynthetic scheme suggested for the structurally--and biogenetically--related naphthylisoquinoline alkaloids.

The polyketide folding mode in the biogenesis of isoshinanolone and plumbagin from Ancistrocladus heyneanus (Ancistrocladaceae)

Abstract The biosynthetic orgins of the tetralone isoshinanolone and the related naphthoquinone plumbagin were investigated by feeding [13C2]-acetate to suspended callus cultures of Ancistrocladus heyneanus. The orientation of the acetate subunits was elucidated by a similar experiment using [2-13C]-acetate. The polyketide folding mode found for isoshinanolone and plumbagin constitutes a further hint at the acetogenic nature of the naphthylisoquinoline alkaloids, which are typical of A. heyneanus and other species of Ancistrocladaceae and Dioncophyllaceae.

Identification of the regions of porcine VCP preventing its function in Saccharomyces cerevisiae

Cdc48p is essential for homotypic endoplasmic reticular fusion in Saccharomyces cerevisiae. It is localized at the endoplasmic reticulum during most of the cell division cycle but concentrates in the nucleus at the G1/S-transition. Its mammalian homologue VCP alternates between the endoplasmic reticulum and the centrosome in dependence of the cell cycle. Though Cdc48p and porcine VCP show a high sequence conservation--almost 70% of their amino acid residues are identical the VCP gene fails to complement a disruption of CDC48. Complementation studies with CDC48 and VCP gene hybrids show that an exchange of the central Cdc48p domain for the central VCP domain prevents a complementation of a CDC48 disruption, although this is the best conserved region between the two proteins. Protein chimeras containing the N-terminal part of VCP only complement a disruption of CDC48 when expressed at high levels. The respective yeast strain shows a nucleus devoid of Cdc48p. In contrast to VCP, Cdc48p contains an almost perfect nuclear targeting sequence in this region. Exchange of the C-terminal Cdc48p domain for the C-terminus of VCP leads to normal viability of the cell, even at low expression levels.

Revised Structure of Antidesmone, an Unusual Alkaloid from Tropical Antidesma Plants (Euphorbiaceae)

Abstract The structure of antidesmone, an alkaloid from Antidesma membranaceum Mull. Arg. and A. venosum E. Mey. (Euphorbiaceae), was revised to be (S)-4,8-dioxo-3-methoxy-2-methyl-5-n-octyl-1,4,5,6,7,8-hexahydroquinoline [(S)-2], not the isoquinoline derivative 1, as assumed previously. The revision was initiated by biosynthetic feeding experiments of one of our groups.

Carnivorous plant chemistry

Abstract Phytochemical data are contrasted with phylogenetic relationships of carnivorous plants. Naphthoquinone profiles of a representative set of Nepenthes species are evaluated in comparison with previously published chemical data for Nepenthales (containing four distinct carnivorous plant families). The iridoids sarracenin and aucubin are identified as valuable chemical markers of Sarraceniaceae and Scrophulariales, respectively. The latter order (that contains the carnivorous Lentibulariaceae and Byblidaceae) is also characterized by the common occurrence of the phenylethanoid caffeic acid glycoside acteoside. No taxonomically relevant metabolite is known from Cephalotaceae so far.

In vitro propagation of Ancistrocladus abbreviatus Airy Shaw (Ancistrocladaceae)

Ancistrocladus abbreviatus Airy Shaw (Ancistrocladaceae), a West African liana producing naphthylisoquinoline alkaloids, was successfully raised from seeds in vitro. Clonal propagation was best achieved growing nodal stem segments on 1/5 Linsmaier and Skoog medium with full strength organics and supplemented with 0.02 μM thidiazuron, 4.44 μM 6-benzylaminopurine and 0.05 μM 1-naphthaleneacetic acid. Detached axillary shoots were grown on Andersons Rhododendron medium devoid of phytohormones and rooted within one month when dipped in 4.92 μM indole-3-butyric acid. Rooted plants became acclimatized to nonsterile greenhouse conditions.

Acetogenic isoquinoline alkaloids. CXII. Separation and identification of dimeric naphthylisoquinoline alkaloids by liquid chromatography coupled to electrospray ionization mass spectrometry

The atropodiastereomeric dimeric naphthylisoquinoline alkaloids, michellamines A (1a), B (1b) and C (1c), together with their monomers, korupensamines A (2a) and B (2b), were investigated using electrospray ionization tandem mass spectrometry coupled to liquid chromatography (LC-ESI-MS-MS). From the spectra obtained, characteristic product ions were chosen to monitor the chromatographic separation achieved on an RP-18 column. Under acidic conditions required for chromatographic analysis, the monomeric alkaloids 2a and 2b yielded protonated molecules [M + H]+, while the dimers, the michellamines, exhibited doubly protonated [M + 2H]2+ molecules. In addition, the coeluting alkaloids 1b and 2b were identified unambiguously be means of tandem mass spectrometry. Thus, together with the retention times of the alkaloids, the product ion spectra allowed us the identification of michellamines in the presence of their presumed biogenetic monomeric precursors. Application of the HPLC-MS-MS method successfully proved the enzymatic formation of michellamine C (1c) by in vitro dimerization of korupensamine B (2b).