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Background: Dodonaea angustifolia is used in Ethiopian traditional medicine to treat malaria. The objective of this work was to conduct bioassay guided fractionation of the leaves of D. angustifolia using Plasmodium berghei infected mice.Method: The antiplasmodial activity of the extracts and pure compounds was evaluated using the standard Peter’s four-day suppressive method. The structures of isolated compounds were elucidated using chemical and spectroscopic methods.Results: In this study, the ethyl acetate soluble portion of the 80% aqueous MeOH extract of the leaves significantly suppressed parasitaemia in Plasmodium berghei infected mice (80.28% at 150 mg/kg). Three active compounds which exhibited significant percent suppression of parasitaemia by 81% at 40 mg/kg, 80% at 50 mg/kg and 70% at 40 mg/kg, respectively were identified. These are the flavanone pinocembrin (1), the flavanol santin (2) and the clerodane diterpene 2-hydroxy-15,16-epoxyceloda-3,13(16),14-trien-18-oic acid (3). Under similar conditions, chloroquine suppressed parasitaemia by 100% at 25 mg/kg. Chemical study of the ethanol extract of the leaves yielded 5,7,4'-trihydroxy-3,6-dimethoxyflavone (4), ent-16-hydroxy-labdan-3,8-dihydroxy,13(14)-en-15,16-olide (5) and 5,6,7-trihydroxy-3,4'-dimethoxyflavone (6). Compound 6 has not been reported before as a natural product.Conclusion: From the leaves of D. angustifolia, three compounds with significant antiplasmodial activities were isolated and characterized, with pinocembrin as the most active compound.
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The ethanol extract of the kernel of the endemic plant Moringa stenopetala after silica gel column chromatography led to the isolation of 4-(α-L-rhamnopyranosyloxy)benzyl glucosinolate (1) and sucrose. The oil obtained by Soxhlet extraction with petrol was trans-esterified with BF3-MeOH and analyzed by GC-MS. The results showed the presence of diverse fatty acids namely palmitic (11%), palmitoleic (1.2%), stearic (11%), oleic (63%), linoleic (1.2%), arachidic (6%) and the rare behenic acids (6%). The white glossy seed husk which comprises 25% of the whole seed yielded two compounds namely 4-(σ-L-rhamnosyloxy)benzyl alcohol (2) and allantoin (3). To the best of our knowledge this is the first report of compound 2 as a natural product. Allantoin is reported here for the first time from the genus Moringa.
Publications
Fruiting bodies of the Chilean mushroom Dermocybe nahuelbutenis Garrido & E. Horak (syn.: Cortinariusnahuelbutensis (Garrido & E. Horak) E. Valenz. & G. Moreno) were chemically investigated for the first time andafforded the new dimeric anthraqinone 7,7'-emodinphyscion (1) beside the know anthraquinones dermolutein (2),endocrocin (3), skyrin (4) and the dimeric pre-anthraquinone derivative flavomannin C (5). The chemotaxonomicsignificance of the pigments is discussed.