| 1. |
- Andreazza, N, et al.
(författare)
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Production of imidazole alkaloids in cell cultures of jaborandi as affected by the medium pH
- 2009
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Ingår i: Biotechnology letters. - : Springer. - 0141-5492 .- 1573-6776. ; 31:4, s. 607-614
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Tidskriftsartikel (refereegranskat)abstract
- The effect of pH (from 4.8 to 9.8) on the production of pilosine and pilocarpine and on their partition between cell and medium was studied in two lineages (P and PP) of Pilocarpus microphyllus cell suspension cultures. Highest mass accumulation was observed at high pHs and both lineages produced pilocarpine while only lineage PP produced pilosine. Both alkaloids were released in the medium but higher accumulation occurred in the cells. The highest production of pilocarpine was at pH 8.8-9.8 in both cell lineages. Other imidazole alkaloids were also identified in both lineages. At all pHs tested, the pH in the media cultures tended to stabilize around 6 after 10-15 days of cultivation. NO(3) (-) and NH(4) (+) variation in the media might partially explain the pH stabilization.
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| 2. |
- Crutsinger, G M, et al.
(författare)
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Ecosystem retrogression leads to increased insect abundance and herbivory across an island chronosequence
- 2008
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Ingår i: Functional Ecology. - : John Wiley & Sons. - 0269-8463 .- 1365-2435. ; 22:5, s. 816-823
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Tidskriftsartikel (refereegranskat)abstract
- 1. Ecosystem retrogression, the decline-phase of ecosystem development, occurs during the long-term absence of catastrophic disturbance. It usually involves increased nutrient limitation over time, and leads to reductions in primary productivity, decomposition, and nutrient cycling.2. As a consequence, retrogression can alter the quality and abundance of host plants as food resources, but little is known about how these changes influence herbivore densities and foliage consumption.3. In this study, we used a 5000-year-old chronosequence of forested islands in northern Sweden on which retrogression occurs in the absence of lightning-induced wildfire. We asked whether retrogression affected the abundance and herbivory of a dominant herbivorous weevil (Deporaus betulae) and the quality and productivity of a dominant host-tree, mountain birch (Betula pubescens).4. Betula pubescens trees on retrogressed islands were less productive and produced smaller, tougher leaves that were lower in nutrients and higher in secondary metabolites than did those trees on earlier-successional islands.5. Despite the lower density and what ecologists might perceive as poorer quality of host plants, we observed several-fold higher weevil abundance and damage on retrogressed islands. This suggests that weevils might prefer the poorer quality leaves with higher secondary metabolites that occur on nutrient stressed host trees.6. Our results show that ecosystem retrogression increases susceptibility of B. pubescens trees to attack by herbivorous weevils.7. Our study provides evidence that ecosystem retrogression and associated shifts in the quantity and quality of available resources can operate as an important driver of abundance of a dominant insect herbivore.
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| 3. |
- Sawaya, Alexandra C H F, et al.
(författare)
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HPLC-ESI-MS/MS of imidazole alkaloids in Pilocarpus microphyllus
- 2008
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Ingår i: Molecules. - Basel, Switzerland : MDPI AG. - 1431-5157 .- 1420-3049. ; 13:7, s. 1518-29
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Tidskriftsartikel (refereegranskat)abstract
- Pilocarpine, an important imidazole alkaloid, is extracted from the leaves of Pilocarpus microphyllus (Rutaceae), known in Brazil as jaborandi and used mainly for the treatment of glaucoma. Jaborandi leaves also contain other imidazole alkaloids, whose pharmacological and physiological properties are unknown, and whose biosynthetic pathways are under investigation. In the present study, a HPLC method coupled with ESI-MS(n) was developed for their qualitative and quantitative analysis. This method permits the chromatographic separation of the imidazole alkaloids found in extracts of jaborandi, as well as the MS/MS analysis of the individual compounds. Thus two samples: leaves of P. microphyllus and a paste that is left over after the industrial extraction of pilocarpine; were compared. The paste was found to contain significant amounts of pilocarpine and other imidazole alkaloids, but had a slightly different alkaloid profile than the leaf extract. The method is suitable for the routine analysis of samples containing these alkaloids, as well as for the separation and identification of known and novel alkaloids from this family, and may be applied to further studies of the biosynthetic pathway of pilocarpine in P. microphyllus.
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