Extraction, isolation and characterization of some limonoids and some constituents of the root bark of Turraea Heterophylla - Smith (Meliaceae)

Abstract

The root bark of the plant Turraea heterophylla belonging to the family Meliaceae was investigated for its chemical constituents. Phytochemical screening of both the methanolic and methylene chloride extracts indicated the presence of tannins, saponnins, terpenes, steroids and about eight different limonoids. Exhaustive extraction, chromatography and spectral analyses led to isolation of three compounds. The spectrometric analyses and the resulting data - including IR, NMR(H-H COSY and 1HNMR) and the LC - ESI - MS spectra and their interpretation helped to propose the structures of the three compounds. Among the isolates, 2 compounds (1&2) are limonoids (tetranortriterpenoids) and the third compound (3) is a diterpenoid. All the compounds are known. The limonoids were elucidated and identified as rohituka-7(1) ( ring A,B-seco), and obacunone (2) (A,D-seco). These tetranortriterpenoids are classified as two different carbon-frame types: (I) Prieurianin limonoid with ring A, B-seco (1), and (II) Obacunol limonoid with rings A, D-seco. The H-NMR shifts of the furan protons were in the range of δHs (7.95 to 6.0 ) and is typical of limonoids.The plant extract had antimicrobial activity against the following bacteria: Staphylococcus aureus, Proteus mirabilis and Pseudomanas aeruginosa. The fungus Candida albican also experienced some growth inhibition.