Browsing by Author "Wekesa, Ingrid"

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    Antiplasmodial Quinones from the Rhizomes of Kniphofia foliosa
    (Natural product communications, 2013) Induli, Martha; Gebru, Meron; Abdissa, Negera Abdissa; Akala, Hosea; Wekesa, Ingrid; Byamukama, Robert; Heydenreich, Matthias; Murunga, Sylvia; Dagne, Ermias; Yenesew, Abiy
    Extracts of the rhizomes of Kniphofia foliosa exhibited antiplasmodial activities against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC50 values of 3–5 g/mL. A phenyloxanthrone, named 10-acetonylknipholone cyclooxanthrone (1) and an anthraquinoneanthrone dimer, chryslandicin 10-methyl ether (2), were isolated from the rhizomes, along with known quinones, including the rare phenylanthraquinone dimers, joziknipholones A and B. The structures of these compounds were determined based on spectroscopic data. This is the second report on the occurrence of the dimeric phenylanthraquinones in nature. In an in vitro antiplasmodial assay of the isolated compounds, activity was observed for phenylanthraquinones, anthraquinone-anthrone dimers and dimeric phenylanthraquinones, with joziknipholone A being the most active. The new compound, 10-acetonylknipholonecyclooxanthrone, also showed anti-plasmodial activity. In an in vivo assay, knipholone anthrone displayed marginal antimalarial activity
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    Naphthoquinones from the Roots of Aloe Secundiflora
    (Phytochemistry Letters, 2012) Indul, Martha; Cheloti, Michael; Wasuna, Antonina; Wekesa, Ingrid; Wanjohi, John M.; Byamukama, Robert; Heydenrich, Matthias; Makayoto, Moses; Yenesew, Abiy
    Two new naphthoquinones, 5-hydroxy-3,6-dimethoxy-2-methylnaphthalene-1,4-dione and 5,8-dihydroxy- 3-methoxy-2-methylnaphthalene-1,4-dione, were isolated from the roots of Aloe secundiflora together with the known compounds chrysophanol, helminthosporin, isoxanthorin, ancistroquinone C, aloesaponarins I and II, aloesaponols I and II, laccaic acid D methyl ester and asphodelin. The structures were elucidated based on spectroscopic evidence. This appears to be the first report on the occurrence of naphthoquinones in the genus Aloe. Aloesaponarin I and 5-hydroxy-3,6-dimethoxy-2-methylnaphthalene- 1,4-dione showed anti-bacterial activity against Mycobacterium tuberculosis with MIC values of 21– 23 mg/mL in the Microplate Alamar Blue Assay (MABA) and Low Oxygen Recovery Assay (LORA); 5- hydroxy-3,6-dimethoxy-2-methylnaphthalene-1,4-dione also showed cytotoxicity against the Vero cell line (IC50 = 10.2 mg/mL).