Streblus asper Lour. (Moraceae) is a small tree occurring in dry regions of India, Sri Lanka, Malaya, Vietnam and Thailand. Various parts of this tree have been used in Ayurvedic medicine for cardiac disorders, epilepsy, and edema. Reichstein and co-workers have isolated more than twenty cardiac glycosides from the root bark of S. asper and were able to structurally characterize about fifteen such compounds mainly via degradative techniques. An investigation on the stem bark resulted in the isolation of α-amyrin, lupeol and their acetates, as well as β-sitosterol. In a continuing search for tumor inhibitors from plants, KB cytotoxicity was concentrated sequentially into MeOH and CH₂Cl₂ extracts of S. asper stem bark. Fractionation of the CH₂Cl₂ extracts over silica gel by gravity column chromatography and purification by preparative TLC afforded two cytotoxic cardiac glycosides, strebloside (1) and mansonin (2), which are respectively the 2,3-di-O-methyl-β-D-fucopyranoside and the 2,3-di-O-methyl-6-deoxy-β-D-glucopyranoside of strophanthidin (3). Strebloside (1), a Kedde reagent-positive compound, was identified by direct comparison (mmp, ir, ¹H nmr, co-tlc) with an authentic sample previously isolated from S. asper stem bark. Since no ¹H nmr data had been reported for 1, double irradiation studies and a two-dimensional ¹H-¹H homonuclear shift correlated (COSY) experiment were conducted to assign the protons of its sugar portion. A second Kedde reagent-positive isolate (2) exhibited closely comparable uv, ir, and mass spectral parameters to 1. On hydrolysis of 2 with 2 N trifluoroacetic acid, its aglycone strophanthidin (3) was obtained. The identity of 2 as mansonin—previously only isolated from the seeds of Mansonia altissima A. Chev. (Sterculiaceae)—was confirmed by comparison with an authentic sample via mmp and ir.