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In vivo transformations of dihydro-epi-deoxyarteannuin B in Artemisia annua plants

Brown, G.D. and Sy, L.K. (2007) In vivo transformations of dihydro-epi-deoxyarteannuin B in Artemisia annua plants. Tetrahedron, 63 (38). pp. 9536-9547. ISSN 0040-4020

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To link to this item DOI: 10.1016/j.tet.2007.06.016

Abstract/Summary

[15-(CH3)-C-13-H-2]-dihydro-epi-deoxyarteannuin B (4a) has been fed to intact Artemisia annua plants via the root and three labeled metabolites (17a-19a) have been identified by 1D- and 2D-NMR spectroscopies. The in vivo transformations of 4a in A. annua are proposed to involve enzymatically-mediated processes in addition to possible spontaneous autoxidation. In the hypothetical spontaneous autoxidation pathway, the tri-substituted double bond in 4a appears to have undergone 'ene-type' reaction with oxygen to form an allylic hydroperoxide, which subsequently rearranges to the allylic hydroxyl group in the metabolite 3 alpha-hydroxy-dihydro-epi-deoxyarteannuin B (17a). In the enzymatically-mediated pathways, compound 17a has then been converted to its acetyl derivative, 3 alpha-acetoxy-dihydro-epi-deoxyarteannuin B (18a), while oxidation of 4a at the 'unactivated' 9-position has yielded 9 beta-hydroxy-dihydro-epi-deoxyarteannuin B (19a). Although all of the natural products artemisinin ( 1), arteannuin K ( 7), arteannuin L ( 8), and arteannuin M ( 9) have been suggested previously as hypothetical metabolites from dihydro-epi-deoxyarteannuin B in A. annua, none were isolated in labeled form in this study. It is argued that the nature of the transformations undergone by compound 4a are more consistent with a degradative metabolism, designed to eliminate this compound from the plant, rather than with a role as a late precursor in the biosynthesis of artemisinin or other natural products from A. annua. (C) 2007 Elsevier Ltd. All rights reserved.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
ID Code:11064
Uncontrolled Keywords:terpenes and terpenoids, biogenesis, autoxidation, NMR, DIHYDROARTEMISINIC ACID, ARTEANNUIN-B, QINGHAOSU ARTEMISININ, MICROBIAL-METABOLISM, BIOSYNTHESIS, IDENTIFICATION, MECHANISM, BEHAVIOR, IRON(II)

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