Isolation of natural herbicidal compound from Lantana camara

A flavone glucoside 'vitexin' (C21H20O10) was isolated from the leaves of Lantana camara through bioassay-guided isolation. Kupchan method of solvent-solvent partitioning of crude methanol extract from leaves of L. camara gave ethyl acetate, chloroform, hexane and aqueous fraction. Bio-assay with four fractions at 500 ppm, 1000 ppm and 10,000 ppm indicated chloroform fraction to be most potent phytotoxic against weeds (monocot: Phalaris minor, Avena fatua; Dicot: Chenopodium album, Rumex dentatus). Column chromatography of chloroform fraction with hexane: ethyl acetate (60:40) based on TLC profiling with vanillin visualisation stain and subsequent bioassays indicated sub-fraction (iii) of fraction 23 as most growth inhibitory. The chemical structure of the isolated compound was identified by gas chromatography-mass spectrometry (Shimadzu GC-MS-QP2010 ultra). The natural herbicidal activity of the isolated compound against various weeds in laboratory and field conditions is suggested.