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1.  Antiplasmodial and cytotoxic activities of the constituents of Turraea robusta and Turraea nilotica 
Journal of Ethnopharmacology  2015;174:419-425.
Ethnopharmacological relevance
Turraea robusta and Turraea nilotica are African medicinal plants used for the treatment of a wide variety of diseases, including malaria. The genus Turraea is rich in limonoids and other triterpenoids known to possess various biological activities.
Materials and methods
From the stem bark of T. robusta six compounds, and from various parts of T. nilotica eleven compounds were isolated by the use of a combination of chromatographic techniques. The structures of the isolated compounds were elucidated using NMR and MS, whilst the relative configuration of one of the isolated compounds, toonapubesin F, was established by X-ray crystallography. The antiplasmodial activities of the crude extracts and the isolated constituents against the D6 and W2 strains of Plasmodium falciparum were determined using the semiautomated micro dilution technique that measures the ability of the extracts to inhibit the incorporation of (G-3H, where G is guanine) hypoxanthine into the malaria parasite. The cytotoxicity of the crude extracts and their isolated constituents was evaluated against the mammalian cell lines African monkey kidney (vero), mouse breast cancer (4T1) and human larynx carcinoma (HEp2).
The extracts showed good to moderate antiplasmodial activities, where the extract of the stem bark of T. robusta was also cytotoxic against the 4T1 and the HEp2 cells (IC50<10 μg/ml). The compounds isolated from these extracts were characterized as limonoids, protolimonoids and phytosterol glucosides. These compounds showed good to moderate activities with the most active one being azadironolide, IC50 2.4±0.03 μM and 1.1±0.01 μM against the D6 and W2 strains of Plasmodium falciparum, respectively; all other compounds possessed IC50 14.4–40.5 μM. None of the compounds showed significant cytotoxicity against vero cells, yet four of them were toxic against the 4T1 and HEp2 cancer cell lines with piscidinol A having IC50 8.0±0.03 and 8.4 ±0.01 μM against the 4T1 and HEp2 cells, respectively. Diacetylation of piscidinol A resulted in reduced cytotoxicity.
From the medicinal plants T. robusta and T. nilotica, twelve compounds were isolated and characterized; two of the isolated compounds, namely 11-epi-toonacilin and azadironolide showed good antiplasmodial activity with the highest selectivity indices.
Graphical abstract
Azadironolid islated as an epimeric mixture from Turraea robusta stem bark inhibits growth of plasmodium flac iparum strain(W2) with an IC50 Of 1.1±0.01μM
PMCID: PMC4642656  PMID: 26320684
Turraea robusta; Turraea nilotica; Antiplasmodial activity; Cytotoxicity; Limonoid; Toonapubesins F; Toonacilin; Azadironolide
2.  Hydrogen-bonded network structures in dipyridinium, bis­(2-methyl­pyridinium), bis­(3-methyl­pyridinium) and bis­(4-methyl­pyridinium) dioxidobis(oxydiacetato)uranate(VI) 
Four complexes containing the [UO2(oda)2]2− anion (oda is oxy­diacetate) are reported, namely dipyridinium dioxidobis(oxydiacetato)uranate(VI), (C5H6N)2[U(C4H4O5)2O2], (I), bis(2-methyl­pyridinium) dioxidobis(oxydiacetato)uranate(VI), (C8H8N)2[U(C4H4O5)2O2], (II), bis­(3-methyl­pyridinium) di­oxido­bis(oxydiacetato)uranate(VI), (C8H8N)2[U(C4H4O5)2O2], (III), and bis­(4-methyl­pyridinium) dioxidobis(oxydiacetato)uranate(VI), (C8H8N)2[U(C4H4O5)2O2], (IV). The anions are achiral and are located on a mirror plane in (I) and on inversion centres in (II)–(IV). The four complexes are assembled into three-dimensional structures via N—H⋯O and C—H⋯O inter­actions. Compounds (III) and (IV) are isomorphous; the [UO2(oda)2]2− anions form a porous matrix which is nearly identical in the two structures, and the cations are located in channels formed in this matrix. Compounds (I) and (II) are very different from (III) and (IV): (I) forms a layered structure, while (II) forms ribbons.
PMCID: PMC2855580  PMID: 20203398

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