Zur biosynthese des graveolins bei Ruta angustifolia

The carbon skeleton of the quinoline alkaloid graveoline is built up from the aromatic ring and probably the carboxylic group of anthranilic acid and the ring and the C-atoms 2′ and 3′ of a phenylpropane. The nitrogen atom of the alkaloid is derived from that of anthranilic acid. It seems that a benzoylacetic acid derivative which is formed from phenylalanine via cinnamic acids reacts with anthranilic acid with loss of its carboxylic group. The two oxygen atoms of the methylenedioxy group of graveoline are introduced by mixed function oxygenation. The value of the NIH-shift which occurs during this reaction shows that the oxygen in the p-position is introduced before that in the m-position. A monomethylated o-dihydroxy group seems to be the direct precursor of the methylenedioxy structure. The introduction of the oxygen atoms, the methylation and the formation of the methylenedioxy group can proceed at different stages in the pathway of graveoline biosynthesis.     

Furanocoumarin biosynthesis in Ruta graveolens cell cultures

The biosynthetic routes to four linear furanocoumarins—psoralen, xanthotoxin, bergapten. isopimpinellin-co-occurring in Ruta graveolens cell cultures have been investigated with six ¹⁴C-labelled compounds. Mevalonic acid was only poorly incorporated, in contrast to umbelliferone. In support of previous suggestions, 7-demethylsuberosin and (±)-marmesin were very good precursors of the linear furanocoumarins. 7-O-Prenylumbelliferone also was fairly well utilized, but this was probably owing to a prior ether cleavage yielding umbelliferone. Psoralen was well incorporated into bergapten and xanthotoxin, but not into the dimethoxylated isopimpinellin. Differences exist between the organized plant and its cell culture in terms of metabolic products and, by implication, precursor utilization. S(+)-Marmesin was obtained in small quantity from an acid-hydrolysable conjugate present in the culture medium. Syntheses of [2-¹⁴C]7-demethylsuberosin, [2-¹⁴C]osthenol, [2-¹⁴C]7-O-prenylumbelliferone, [3-¹⁴C] (±)-marmesin, and [3-¹⁴C]psoralen are described, as well as an improved method for separation of furanocoumarin mixtures by TLC and GLC.     

Stereochemical aspects of the biological oxidation of aryl isoprenoids. The asymmetric synthesis and absolute configuration of meranzin and of meranzin hydrate

The role of epoxides in the biological oxidation of aryl prenyl derivatives is discussed in terms of the stereochemistry of quinoline alkaloids and coumarins found in species of the Rutaceae and Umbelliferae. Asymmetric synthesis of the epoxide, meranzin and of the diol, meranzin hydrate, have been carried out and the absolute configurations of the two coumarins have been established.     

Somatic embryogenesis,plant regeneration,and the evaluation of camptothecin content in <Emphasis Type="Italic">Nothapodytes foetida</Emphasis>

Summary Somatic embryogenesis and plant regeneration have been achieved in Nothapodytes foetida, which is known for its rich source of anti-cancer and anti-AIDS alkaloids. Callus cultures were initiated from immature zygotic embryos cultured on Murashige and Skoog's (MS) medium supplemented with 2,4-dichlorophenoxyacetic acid, 6-benzyladenine (BA), and kinetin. MS medium devoid of plant growth regulators favored the development of globular somatic embryos that differentiated further into plantlets. Plantlet regeneration efficiency was effectively increased on MS medium supplemented with BA. Over 90% of the in vitro plantlets survived when transferred to the soil. Alkaloids were detected in different stages of somatic embryos, regenerated plantlets, and different parts of the 2-yr-old regenerated plants. The somatic embryos contains camptothecin (0.011% dry weight. DW) and 9-methoxycamptothecin (0.0028% DW). Two-yearold field-grown plants obtained from somatic embryos were analyzed and contained higher levels of camptothecin (0.20% DW) and 9-methoxycamptothecin. (0.097% DW) accumulated in roots, followed by stem and leaves. Alkaloids were quantified and identified by TLC and HPLC.     

Bacteriostatic activity of some coumarin derivatives

The bacteriostatic effect of some mono- and dihydroxy-coumarins and isopropyldihydrofuranocoumarins have been examined and compared with other simple phenols. Most of the coumarins proved to be far more bacteriostatic than the simple phenols.     

Effects of linear furanocoumarins on the herbivore Spodoptera exigua and the parasitoid Archytas marmoratus: host quality and parasitoid success

We assessed the effects of three photoactivated linear furanocoumarins, secondary plant metabolites present in Apium spp. (Apiaceae) and other taxa, on the larval-pupal parasitoid, Archytas marmoratus (Townsend) (Diptera: Tachinidae) and the host Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), in the presence and absence of ultraviolet radiation. These results then were compared with previously described responses of Archytas marmoratus and other hosts to different plant allelochemicals. Ultraviolet radiation had no consistent detrimental effects. Increasing concentrations of linear furanocoumarins (from 0 to 0.029% of fresh weight) increased mortality of both the host and parasitoid. Increasing linear furanocoumarin levels also prolonged larval development of surviving S. exigua, but had no effect on pupal developmental time or pupal mass. Consequently, there was no effect of increasing linear furanocoumarin levels on surviving parasitoid development time (from the time of host pupation) or size. These results indicate the effects of linear furanocoumarins are mediated through effects on the host. Because reported responses of Ar. marmoratus to other allelochemicals (e.g., flavones, methyl ketones) are mediated through host effects, these results support the hypothesis that Ar. marmoratus displays a generalized response to plant allelochemicals that are predictable based on host mediated effects.     

Specific accumulation and revised structures of acridone alkaloid glucosides in the tips of transformed roots of Ruta graveolens

The root tips of Ruta graveolens (common rue) show strong autofluorescence of acridone alkaloids, which are characteristic secondary metabolites of this plant. To study the specific distribution and accumulation of acridone alkaloids in various root segments of Ruta graveolens, root material was harvested from genetically transformed root cultures and extracts were investigated by chromatographic techniques and HPLC-(1)H NMR spectroscopy. The cells of the elongation and differentiation zones contained acridone glucosides and large amounts of acridone alkaloids, mainly rutacridone. Gravacridondiol glucoside was identified as the dominant secondary compound of the root tips and its structure revised by means of spectroscopic methods. In addition, minor acridones, including the structurally revised gravacridontriol glucoside and unknown natural products, were found in the root tip.     

7-Demethylsuberosin and osthenol as intermediates in furanocoumarin biosynthesis

¹⁴C-Labelled 7-demethylsuberosin (DMS) was a precursor of linear furanocoumarins in Conium maculatum and Heracleum lanatum (Umbelliferae), and in Ruta graveolens (Rutaceae), but not in Coronilla glauca (Leguminosae). Trapping experiments with ¹⁴C-umbelliferone over 3- to 24-hr periods revealed that DMS is rapidly metabolized, and that in short experiments its specific activity relative to the linear furano- coumarins′ is that of an intermediate. The specific activity of umbelliferone exhibited anomalies attributed to pool compartmentation. Analogous but less extensive experiments established that osthenol is an intermediate in angular furanocoumarin biosynthesis, but is much less rapidly metabolized than DMS. No significant incorporation into furanocoumarins of ¹⁴C from labelled l-valine, l-leucine, acetate, 2,3-di-hydroxyisovaleric acid, senecioic acid, isopentenylpyrophosphate, or mevalonate could be demonstrated. A synthesis of [1-¹⁴C]2,3-dihydroxyisovaleric acid is described.     

Degradation of quinoline by immobilized Comamonas acidovorans in a three-phase airlift reactor

Quinolie degradation by Comamonas acidovorans was studied in a continuously operated three-phase airlift reactor. Porous glass beads were applied as support matrix for cell imobilization by colonization. Under steady-state conditions (S approximately 0), cell attachment was poor at low dilution rates but imporved considerably with increasing dilution rate. Conversion of quinoline was investigated below and above the washout for suspended culture (D(crit) = mu(max) = 0.42 h(-1)). With immobilized cells the reactor could be operated at D > mu(max), and complete conversion of quinoline was achieved as long as the specific quinoline feed rate D*S(0)/X did not exceed the maximum specific degradation rate (r(S, max)). The biofilm thickness was about 100 mum, and its efficiency was about 54% compared to suspended organisms. If quinoline overloads were supplied to the reactor, quinoline, as overloads were supplied to the reactor, quinoline, as well as its pathway intermediates, appeared in the reactor and conversion was low. Hence, the immobilized microorganisms remained viable and active. They could survive quinoline overloads. If the quinoline feed rate was reduced agains, complete conversion was reestablished. (c) 1995 John Wiley & Sons, Inc.     

Synthesis of aurachins B and H

The synthesis of aurachin B, an antibiotic that features a C3-oxygen-substituted quinoline N-oxide nucleus bearing a farnesyl side chain at C4, was accomplished in 60% overall yield from o-nitrotoluene by a concise five-step sequence. An enantioselective synthesis of aurachin H was also achieved for the first time in only two steps from an optically active epoxy iodide.