Chemical Studies, Isolation And Structural Elucidation Of Bioactive Constituents Of Ageratum conyzoides Linn Leaves And Stems

ABSTRACT

This research work was carried out to identify the bioactive constituents of the leaves and stem barks of Ageratum conyzoides Linn, a medicinally important plant of the Asteraceae family. This plant was selected on the basis of its widespread use in traditional herbal medicine.The present study deals with extraction, isolation and characterization of the bioactive compounds from the ethanol extract of leaves and stem barks of Ageratum conyzoides Linn. The extraction was done by macerating the air dried powdered samples into the solvent followed by filtration and concentration. Separation and purification of the various constituents of the crude extracts were done using chromatographic techniques.TLC and Column chromatography were  carried out using  different mobile phases and the solvent blends used were petroleum ether .ethyl acetate, chloroform and Methanol. Qualitative thin layer chromatography was used to monitor the column fractions and also to ascertain the purity of the isolates. The chemical constituents by GC-MS analysis of whole plant extract of Ageratum conyzoides Linn revealed seventy one phytochemicals ranging from high and low molecular weight chemical entities with varying quantities present. The chemical investigation resulted in the isolation of four compounds.  Compound [1] 3-hydroxylup-20(29)-ene  was isolated at R_f 0.69 from the stem bark The MS spectrum showed a molecular ion peak at m/z 426, which corresponded to a molecular formula of C₃₀H₅₀O.  Compound [2] (β-Amyrin acetate) was obtained  from the leaf extract of Ageratum conyzoides Linn with R_f 0.63. The MS spectrum showed a molecular ion peak at m/z 467, which corresponded to a molecular formula of C₃₂H₅₂O₂. Compound [3] 3,3-dimethyl, (1- hydroxy) cyclohexene propanenitrile, 4-benzoate  was obtained from the leaf extract. The MS spectrum showed a molecular ion peak at m/z 297, which corresponded to a molecular formula of  C₁₈H₁₉O_3N FTIR revealed the presence of alcohol (3298 cm-1),  nitrite (2250 cm-1), carbonyl (1726 cm-1), aromatic (1451 cm-1}. Compound [4] ] 3-keto lupane was obtained at R_f of 0.78 from the leaf extract. Mass spectrum gave a molecular ion peak at m/z 424, which was consistent with a molecular formula of C₃₀H₄₈O.The FTIR spectrum showed a carbonyl stretch at 1707 cm-1 and CH stretches at 2922 and 2858 cm-1. The structural elucidation of the compounds   were deduced using   MS, IR, 1D NMR (1H and 13C) along with 2D NMR Spectra ( DEPT ,COSY, HMBC and HSQC). . The antibacterial activity of crude extracts from parts of the plant were tested against four bacteria species; two gram positive pathogens namely (Salmonella typhi,, and Staphylococcus aureus ) and two gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa), using  disc diffusion technique. All the crude plant extracts showed inhibitory activity against the gram positive bacteria, and gram negative bacteria. At concentrations of 12.5-100 mg/ml, the extracts possesses antibacterial activity (from being partially active to very active)