ISOLATION AND CHARACTERIZATION OF A SECONDARY METABOLITE FROM THE AERIAL PARTS OF Launaea (Lactuca) taraxacifolia

Abstract

Launaea (Lactuca) taraxacifolia also known as wild lettuce is a medicinally important plant of the Asteraceae family. The plant was selected for this study due to its widespread use in traditional medicine and on the basis that the plant is almost going into extinct in Nigeria. The extraction was carried out by subjecting the air dried pulverized plant materials into trichloromethane solvent for a period of some days, followed by filtration and concentration. Separation and purification of the various constituents of the crude were done using thin layer and column chromatography. The mobile phases and solvent blends employed were: normal hexane, trichloromethane, ethyl ethanoate and methanol. The extraction, purification, concentration and chromatographic separations of the extracts were carried out at Post-graduates, chemistry laboratory, Michael Okpara University of Agriculture, Umudike, Nigeria. The NMR spectra analysis was investigated at Monash University Malaysia while the FTIR and GC-MS were carried out at Nanotechnology and Research Institute Malaysia. The NMR analysis was done using a Bruker VSP 500MHZ model machine. The GC-MS was performed using an Agilent 7000 model while the FTIR analysis was carried out on an Agilent 4500 series FTIR system. The structural elucidation of the proposed compound was deduced using GC-MS, FTIR, NMR (13C and 1H) and 2D COSY NMR spectra. This chemical investigation resulted in the isolation of a novel compound SB3 (Octadecahydro-10-(1,2,3,4-tetrahydronaphtalen-3-yl)-4,4-dimethoxy-6b,12b,14b-trimethyl Picen-3-(4H,6bH,14bH)-one. Compound SB3 was isolated using 50% hexane and 50% trichloromethane at an Rf value of 0.692. The MS spectrum of compound SB3 gave a molecular ion peak at m/z 545.81, which corresponded to a molecular formula of C37H53O3.