Ludger Witte

Patterns of quinolizidine alkaloids in 56 species of the genus Lupinus

Abstract The alkaloid composition of 56 species (90 taxa if all subspecies and chemotypes are included) of the genus Lupinus was studied by capillary gas-liquid chromatography and GLC-mass spectrometry (GC-EIMS). The distribution of 100 alkaloids (quinolizidines, piperidines, dipiperidines and simple indoles) and their relative abundances in leaves and seeds (if available) are recorded.

Comparative analysis of pyrrolizidine alkaloids from natural sources by gas chromatography-mass spectrometry

Abstract Underivatized pyrrolizidine alkaloids (PAs) from natural sources (plants and insects) were analysed by capillary gas chromatography-mass spectrometry. GC-MS data (retention indices and [M]+) of ca 100 PAs separated on different fused-silica columns in two laboratories are presented and compared. The results suggest that polydimethylsiloxane coated columns (OV-1, DB-1) are well suited for comparative studies in different laboratories. Separation of PAs using either OV-1 or DB-1 in different laboratories even under slightly different conditions revealed almost identical RIs. Application of these columns and the combination of RI, [M]+ and group-specific MS fragmentation allows in many cases the unequivocal assignment of PAs from complex mixtures even in the presence of different geometrical isomers. Furthermore, it encourages a reliable comparison and exchange of data between laboratories.

Chemical and Physical Characterization of Four Interfacial-Active Rhamnolipids from Pseudomonas spec. DSM 2874 Grown on n-Alkanes

Four extracellular glycolipids produced under growth-limiting conditions were isolated from the culture broth of Pseudomonas spec. DSM 2874. After purification by column and thick-layer chromatography they were identified as anionic rhamnolipids. 1H and 13C-NMR studies showed that two of these, β(β(2-O-α-ʟ-rhamnopyranosyloxy)decanoyl)decanoic acid and β(β(2-O-α-ʟ- rhamnopyranosyl-α-ʟ-rhamnopyranosyloxy)decanoyloxy)decanoic acid, were identical with compounds described previously, while the other more hydrophilic compounds, β(2-O-α-ʟ-rhamno- pyranosyloxy)decanoic acid and β(2-O-β-ʟ-rhamnopyranosyl-a-ʟ-rhamnopyranosyloxy)decanoic acid, were new compounds. Surface and interfacial activity of the organic crude extract and of the purified components were determined in different aqueous solutions. The pH-dependence of surface and interfacial properties of the two previously described rhamnolipids (4. 20. 23) were examined in Teorell- Stenhagen-buffer (supplemented with 10% NaCl) at pH 3.0 and pH 9.0. All rhamnolipids reduced the surface-tension from 72 to about 30 mɴ/m and the interfacial-tension from 42 to about 1 mɴ/m. The critical micelle concentrations were of the order of 5 to 200 mg/l depending on the structure of the molecule.

Turnover and transport of quinolizidine alkaloids. Diurnal fluctuations of lupanine in the phloem sap, leaves and fruits of Lupinus albus L.

Quinolizidine alkaloids formed in the leaves of Lupinus albus L. are translocated via the phloem to the other plant organs, especially the maturing fruits. Compared with amino-acid transport in the phloem, the alkaloids contribute about 8% to the overall nitrogen being exported from the leaf. Since it is likely that the alkaloids are subsequently degraded in the target tissues a minor role of quinolizidine alkaloids might be nitrogen transport. A marked diurnal fluctuation of alkaloids was observed in the leaves, the phloem sap, the roots and the fruits with an increase during the day and an amplitude of several hundred percent thus providing evidence for a rapid turnover of endogenous alkaloids.

Pyrrolizidine alkaloids in Chromolaena odorata. Chemical and chemoecological aspects

Abstract The tropical weed Chromolaena odorata contains the N -oxides of five pyrrolizidine alkaloids (PAs): 7- and 9-angeloylretronecine, intermedine, rinderine and 3′-acetylrinderine. Highest concentrations occur in roots and mature flower heads, while leaves and stems are almost devoid of alkaloids, and no PAs are present in nectar. The polyphagous grasshopper Zonocerus variegatus sequesters intermedine and rinderine from Chromolaena flowers and transforms up to 20% of these PAs into lycopsamine and echinatine, respectively, by inversion of configuration at C-3′. Pure rinderine injected into the haemolymph of Zonocerus is partly converted into intermedine, indicating inversion of configuration at C-7.

Chemotypes of two pyrrolizidine alkaloid-containing Senecio species

Evaluation of the pyrrolizidine alkaloids (PAs) of more than 100 populations of Senecio jacobaea and of ca 25 populations of S. erucifolius from different geographic locations revealed the existence of different chemotypes. Two chemotypes were established within each species. They are for S. jacobaea, (a) ‘jacobine chemotype’ with jacobine and its derivatives as major PAs, representing the well known ‘classical’ PA pattern of this species. (b)‘erucifoline chemotype’, with erucifoline and O-acetylerucifoline as dominating PAs, and for S. erucifolius, (a) ‘erucifoline chemotype’, erucifoline and O-acetylerucifoline as major PAs. (b) ‘eruciflorine chemotype’, with eruciflorine (21-hydroxyintegerrimine) as dominating PA. Eruciflorine was identified as a novel PA. Its structure was elucidated by means of NMR and mass spectrometry. Individual populations representing the different chemotypes within the respective species are indistinguishable from their morphological characters.

Reinvestigation of the Alkaloid Composition of Atropa belladonna Plants, Root Cultures, and Cell Suspension Cultures.

The alkaloid composition of ATROPA BELLADONNA was analyzed by high resolution GLC and GLC-MS. A total of 13 alkaloids, most new for ATROPA, were identified from roots. The aboveground parts of the plant revealed 7 alkaloids; the hygrines were completely absent. The alkaloid pattern of root cultures was almost identical with the pattern of roots from intact plants. The patterns differed only quantitatively. Scopolamine which in A. BELLADONNA seems to be synthesized in the roots only, was preferably excreted into the culture medium. Norhyoscyamine was found frequently in plant shoots. The occurrence of hyoscyamine N-oxide in various plant organs could be confirmed. Cell suspension cultures produced trace amounts of hyoscyamine, 3alpha-acetoxytropane and 3alpha-tigloyloxytropane. The last two ester alkaloids were not detectable in intact plants.

Interrelationship between Quinolizidine Alkaloid Producing Legumes and Infesting Insects: Exploitation of the Alkaloid- Containing Phloem Sap of Cytisus scoparius by the Broom Aphid Aphis cytisorum

Abstract Aphids (Aphis cytisorum) which infest broom plants (Cytisus scoparius) accumulate up to 500 μg alkaloid/g fr. wt. The alkaloids, which are similar to those of the plants, consist of 17-oxo-sparteine, sparteine, 12,13-dehydrosparteine, and lupanine. Infested plants contain > 50% less alkaloids than aphid-free plants. In Lupinus aphid resistance which is due to their high alkaloid content is more expressed: Whereas bitter varieties are free from aphids, only the sweet alkaloid-free plants are susceptible to aphid infestation. The accumulation of alkaloids in aphids indicates that the quinolizidine alkaloids are translocated via the phloem in legume plants. This assumption is supported by direct evidence: analysis of phloem sap from Lupinus contains up to 5 mg alkaloid whereas xylem sap is virtually free of alkaloids. The interrelationship between quinolizidine alkaloids and hervivores is discussed.

An insecticidal rocaglamide derivatives and related compounds from Aglaia odorata (Meliaceae)

Organic extracts of the twigs and leaves of Aglaia odorata yielded eight insecticidal cyclopentatetrahydrobenzofuran rocaglamide derivatives including three congeners which proved to be new natural products. Moreover, four new cyclopentatetrahydrobenzopyran aglain derivatives, as well as the known aminopyrrolidine odorine and odorinol, syringaresinol and flavonoid derivatives were also isolated. Structure elucidation of the new compounds is described and a rationale of the biosynthesis of the rocaglamide and aglain congeners is considered. The isolated rocaglamide derivatives exhibited strong insecticidal activity towards neonate larvae of the polyphagous pest insect Spodoptera littoralis when incorporated into artificial diet with LC50 values varying from 1.0‐8.0 ppm. The most active compounds showed LC50 values between 1.0 and 1.1 ppm, comparable to those of the insecticide azadirachtin, which was used as a positive control. The remaining compounds isolated from A. odorata were inactive with regard to insecticidal activity. # 1999 Elsevier Science Ltd. All rights reserved.

Levels and tissue distribution of loline alkaloids in endophyte-infected Festuca pratensis

Festuca pratensis (meadow fescue) infected with the endophyte Acremonium uncinatum produces loline alkaloids (1-aminopyrrolizidines) that are not found in the uninfected grass or the fungus alone. Five alkaloids were identified by capillary GC and GC-MS: N-formylloline as the major compound, followed by N-acetylloline, N-acetylnorloline and trace amounts of loline and N-methylloline. A routine procedure for the extraction and sensitive quantitative analysis of loline alkaloids by capillary GC is described. The loline alkaloid levels and concentrations were followed quantitatively over the growing season of the grass-endophyte association. A detailed analysis of the tissue distribution of the alkaloids is given. The total alkaloid level per plant increases from almost zero in early spring and reaches its highest level during seed maturation. It drops to almost zero with seed dispersal and stalk senescence but increases again during the subsequent period of vegetative growth in late summer. The highest alkaloid concentrations were found in young leaves in early spring, and in panicles (spikelets, seeds) and leaf pseudostems during the period of vegetative growth in late summer and autumn. During seed germination loline alkaloids are not degraded, however, a significant proportion (about 20%) are lost by leaching, mainly during seed imbibition. Within a seed the embryo was found to contain a two-fold higher alkaloid concentration than the remaining seed tissue.