Chemical examination of Cuscuta reflexa, Roxb. I. The constituents

Abstract

Cuscuta reflexa (Roxb.), the Hindustani akashbel, is a golden yellow parasitic plant, common throughout India, considered to have purgative properties by native writers. Extn. of 2.5 kg. of sun-dried material from 30 kg. of the freshly collected plant, with boiling alc. gave 25 g. of crude dry cryst. substance contg. a small amt. of yellowish brown wax. Recrystn. from large vols. of EtOH produced white cryst. flakes of cuscutalin (I), C18H10O4, m. 68°, sol. in caustic alkalies. I reduces Tollen's reagent slowly, gives a reddish brown color with alk. K2Fe(CN)5NO. It has no aldehydic or ketone groups and is evidently an α,β-unsatd. lactone (C. A. 21, 99). Pharmacol., I appears to be a potent drug. After the removal of I, the combined alc. exts. were concd. to a greenish red sirup which was extd. with benzene. The ext. was evapd. to dryness and, after washing with cold alc., was crystd. from boiling alc., yielding white flakes of I. The residue was extd. with AcOEt and was then extd. with ice-cold H2O with const. stirring. The brown, difficultly sol. residue was filtered off and dissolved in H2O at room temp. to a golden yellow soln. from which yellow crystals of cuscutin (II), C15H12O9, m. 208-9° (decompn.), sepd. II is sol. in NaHCO3, and forms a Pb salt, and a di-Ac deriv., m. 140°. By treatment with ClCO2Et in pyridine and by methylation with Me2SO4 in the presence of concd. NaOH, dicarbethoxycuscutin, m. 151° (decompn.), and dimethoxycuscutin, m. 193°, were prepd. II gives a neg. test for flavones and is completely decolorized on boiling with NH4OH and Zn dust. It is not glucosidic in character. The above aq. ext. was concd. and was found to contain a large amt. of reducing sugars.