Plant growth regulators from the roots of Tylophora indica Merr.

Abstract

The preliminary screening results on plant growth regulators of twelve plants indicated that crude extract from the roots of Tylophora indica Merr. Showed the highest inhibitory effect against growth of lettuce seedling (Brassica pekinensis Rupr.). Then the roots of this plant were selected for further investigation on chemical constituents. The bioassay-guided fractionation of dichloromethane and ethyl acetate crude extracts led to the isolation of two mixtures and eight compounds. Their structures were characterized by means of physical properties, chemical reactions and spectroscopic data. They were a new compound, 12-(6’-methoxy-2’-chromeone-7’-yl) dodecanoic acid, along with nine known substances, a mixture of hexadecanoic acid, cis-9-octadecanoic acid and octadecanoic acid, a mixture of stigmasterol and β-sitosterol, stigmasteryl-3-β-D-glucopyranoside, oleanolic acid, ursolic acid, nonanedioic acid, decanedioic acid, 3-demethyl-14α-hydroxyisotylocrebrine and tylophorinidine. The biological activity on lettuce seedling at concentration of 1000 ppm, nonanedioic acid completely inhibited on root growth, followed by decanedioic acid (90%), 3-demethyl-14α-hydroxyisotylocrebrine (86%) and tylophorinidine (70%), respectively. On the other hand, ursolic acid and oleanolic acid showed the significant activity on the inhibition against shoot elongation (69 and 65%, respectively). In addition, 3-demethyl-14α-hydroxyisotylocrebrine, tylophorinidine, nonanedioic acid and decanedioic acid exhibited almost complete inhibition against both root and shoot length of Echinochloa crus-galli Beauv. Seedling at concentration 100 ppm.