A dichloromethane extract of the stem bark of Cryptocarya nigra showed strong in vitro inhibition of Plasmodium falciparum growth, with an IC50 value of 2.82 μg/mL. The phytochemical study of this extract has led to the isolation and characterization of four known alkaloids: (+)-N-methylisococlaurine (1), atherosperminine (2), 2-hydroxyathersperminine (3), and noratherosperminine (4). Structural elucidation of all alkaloids was accomplished by means of high field 1D- and 2D-NMR, IR, UV and LCMS spectral data. The isolated extract constituents (+)-N-methylisococlaurine (1), atherosperminine (2) and 2-hydroxy-atherosperminine (3) showed strong antiplasmodial activity, with IC50 values of 5.40, 5.80 and 0.75 μM, respectively. In addition, (+)-N-methylisocolaurine (1) and atherosperminine (2) showed high antioxidant activity in a DPPH assay with IC50 values of 29.56 ug/mL and 54.53 ug/mL respectively. Compounds 1 and 2 also both showed high antioxidant activity in the FRAP assay, with percentages of 78.54 and 70.66 respectively and in the metal chelating assay, with IC50 values of 50.08 ug/mL and 42.87 ug/mL, respectively.
The 1,3-phosphaazaallene DippTerP = C=NtBu (DippTer = 2,6-(2,6-iPr2C6H3)2-C6H3) is thermally labile towards iso-butene elimination and formation of the corresponding cyanophosphine DippTerP(H)CN (1). In previous work we have shown facile deprotonation of 1 with K[N(SiMe3)2 and formation of cyanophosphide [(DippTerPCN)K]. We now present the alkali metal tethered cyanophosphides [(DippTerPCN)M(crown)] (M = Na, K; crown = 15-c-5, 18-c-6) and their structural diversity in the solid state depending on the metal (M) and the crown ether. Facile oxidation of [DippTerPCN][M(crown)] with O2 yields the formal cyanide adducts of dioxophosphoranes [DippTerPO2(CN)]-. Surprisingly, [DippTerPO2(CN)]- is obtained as a mixture of the cyanide and isocyanide isomers, indicating a coordination isomerism. This phenomenon is corroborated by experimental and theoretical studies revealing the cyanide isomer to be thermodynamically more stable. The oxidation with elemental sulphur gave the corresponding dithiophosphorane cyanide adduct [DippTerPS2(CN)]-, in which no isomerism was observed. This points to a crucial role of triplet oxygen in the isomerisation process. Monooxidation occurs when [DippTerPO2(CN)]- salts were treated with N2O, giving formal anionic phoshinidene monoxide adducts.