Isolation and Characterisation of a New Allelochemical from Parthenium Hysterophorus L

Parthenium hysterophorus L. is commonly known as “Gajar ghas" in Hindi and belongs to family Composite. It is an annual herb erect up to 1.5 m in hight. Its stems is branched and covered with trichomes. Its leaves are pale green, branched and covered with soft fine hairs. In Homoeopathy system, allergies caused by Parthenium can be treated by a drug prepared from Parthenium. Root decoction is useful in dysentery. In the present paper, we report the isolation and structurel elucidation of a new allelochemical identified (I) as 3 , 5, 7, 4′ tetrahydroxy-3'-methoxyflavone-3O--L-galactopyranosyl-(1→3)-O--D-arabinopyranosyl-7-O--Lrhamnopyranoside alongwith two known compounds Lutexin (II) and Cirsilineol (III) from methanolic extract of the stems of this plant by several colour reactions, chemical degradations and spectral analysis. INTRODUCTION: Parthenium hysterophorus L. is commonly known as “Gajar ghas" in Hindi which belongs to family Composite. It is an annual herb erect up to 1.5 m in hight. Its stems is branched and covered with trichomes. Its leaves are pale green, branched and covered with soft fine hairs. The small white flowers have five distinct corners and grow on the stem tips. It is considered a highly invasive weed. It releases chemicals that inhibit the germination and growth of pasture grasses and other plants. This weed is common throughout the World. In Homoeopathy system, allergies caused by Parthenium can be treated by a drug prepared from Parthenium. Root decoction is useful in dysentery. Earlier workers 4-8 have reported the presence of various constituents from this plant. In the present paper, we report the isolation and structure elucidation of a new allelochemical (I) identified as 3 , 5, 7, 4′ tetrahydroxy-3'-methoxyflavone-3-O--Lgalactopyranosyl-(1→3)-O--D-arabinopyranosyl-7-O-L-rhamnopyranoside by several colour reactions, chemical degradations and spectral analysis. EXPERIMENTAL SECTION: General experimental procedure: All the m.p. were determined on a thermoelectrically melting point apparatus and are uncorrected. The IR spectra were recorded in KBr disc; H-NMR spectra at 300 MHz in CDCl3 using TMS as internal standard; C-NMR spectra were recorded at 300 MHz using CDCl3 as solvent; UV spectra were determined in MeOH and Mass spectra on a Jeol D-300 mass spectrometer.