<p>In this thesis the isolation, synthesis and biological evaluation of natural defense compounds against herbivores or oxidative stress is discussed.</p><p>The first part concerns the metabolites of platyphylloside ((<i>5S</i>)-5-hydroxy-1,7-bis-(4-hydroxyphenyl)-3-heptanone-5-O-β-D-glucopyranoside), a phenolic glucoside found in birch (<i>Betula pendula</i>) that possess digestibility inhibiting activity in herbivores. The structure-activity relationship of platyphylloside analogues were investigated regarding to stereochemistry and substitution pattern on the aromatic rings. The metabolites formed <i>in vitro</i> in rumen fluid were synthesized and the active metabolite determined as (<i>R</i>)-centrolobol (1,7-bis-(4-hydroxyphenyl)-3-heptanol). Treatment of mice and rats with <i>rac</i>-centrolobol did not effect either food intake or body weight. Effect of platyphylloside in moose was also investigated, and the results indicate that there was an <i>in vivo</i> digestibility reducing activity.</p><p>The second part concerns naturally occurring antioxidants. Avenanthramides is a class of phenolic antioxidants found in oat (<i>Avena sativa</i>). Avenanthramides derived from either anthranilic acid or 5-hydroxyanthranilic acid were evaluated for their antioxidative capacity and quantified in oat extracts. Avenanthramides derived from 5-hydroxyanthranilic acid possessed higher activity than those from anthranilic acid. The order of reactivity depending on substitution pattern on the phenolic moiety was found to be 4-hydroxy < 4-hydroxy-3-methoxy < 3,5-dimethoxy-4-hydroxy and 3,4-dihydroxy. A synthesis towards antioxidative compounds such as 4-deoxycarbazomycin was developed.</p><p>The third part concerns the isolation of compounds from Lodgepole pine (<i>Pinus contorta</i>) with antifeedant activity against pine weevil (<i>Hylobius abietis</i>). Two compounds possessing high activity were isolated and identified.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-1074 |
| Date | January 2000 |
| Creators | Bratt, Katharina |
| Publisher | Uppsala University, Department of Chemistry, Uppsala : Acta Universitatis Upsaliensis |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1104-232X ; 567 |
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