Phytochemical Analysis of Pseudocedrela Kotschyi Harms. (Meliaceae) and Harungana Madagascariensis Lam. (Clusiaceae) Stem Barks

Agboola, Olubunmi Isaiah (2015-03-31)

Thesis

The study was aimed at isolating and characterising compounds from the ethylacetate extracts of tl-.e stem barks of Pseudocerela kotschyi and Harugana madagascariensis, already established to have larvicidal properties. The stem barks of the plants were separately extracted with 70 % aqueous ethanol and the solvent removed in vacuo. The extracts were partitioned between H2O and EtOAc to obtain ethylacetate extracts. The extracts from each plant were respectively subjected to various chromatographic techniques that included, Accelerated Gradient (AGC), Column (CC), Vacuum Liquid (VLC) and Preparative Thin Layer (PTLC) chromatographies, to obtain some pure compounds. The compounds were thereafter characterised using spectroscopic methods of Infra Red (IR), Ultraviolet (UV) and Nuclear Magnetic Resonance (NMR) as well as colour reactions with detecting reagents. The compounds isolated from P. kotschyi gave reddish colour with vanillin/H2SO4 spray reagent suggesting their phenolic nature. They however polymerized to brown flakes before further spectroscopic studies could be done. These results suggested that they were likely to be polyphenolics (tannins). Harugana madagascariensis gave eleven compounds, one of which was fully characterized and the probable structures of two others were suggested. Using the 1 D and 2 D spectroscopic methods of Homonuclear Correlations (Homocosy) and Hetero-Molecular .Bond Connectivity (HMBC), Distortionless Enhanced Proton Test (DEPT) and Attached Proton Test (APT), the first compound was found to be a triterpenoic (C30) acid with a terminal olefinic group. It was identified as betulinic acid by comparing its data with those in the literature. The second compound was reddish brown colour with a melting point of 110-114 °C. It had two aromatic systems and its structure was proposed to be a substituted tetrahydro anthranol. The third compound was a C29 phenolic ester. The study concluded that the main compounds isolated from the active ethylacetate extracts were phenols that are known to have larvicidal activity.

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