Streblus asper is a rich source of cardiac glycosides. Reichstein and co-workers (15–18) have isolated more than 20 cardiac glycosides from the root bark of S. asper and were able to structurally characterize ∼15 such compounds, mainly as a result of the application of degradative techniques, namely kamloside, asperoside, strebloside, indroside, cannodimemoside, strophalloside, strophanolloside, 16-O-acetyl-glucogitomethoside, glucogitodimethoside, glucokamloside, sarmethoside and glucostrebloside. The other glycosides reported from the roots include β-sitosterol-3-O-β-d-arabinofuranosyl-O-α-l-rhamnopyranosyl-O-β-d-glucopyranoside (19), lupanol-3-O-β-d-glucopyranosyl-[1-5]-O-β-d-xylofuranoside (20) and vijaloside, i.e. periplogenin-3-O-β-d-glucopyranosyl-[1-5]-O-β-d-xylopyranoside (21).
From the stem bark of this plant, α-amyrin acetate, lupeol acetate, β-sitosterol, α-amyrin, lupeol and diol (22), strebloside and mansonin (23) have been isolated. A pregnane glycoside named sioraside (24) has also been isolated. n-Triacontane, tetraiacontan-3-one, β-sitosterol, stigmasterol, betulin and oleanolic acid were identified from the aerial parts (25). An unidentified cardenolide (26), β-sitosterol, α-amyrin and lupeol were isolated from root bark and leaves (27). Figure 2 gives the structures of a few biologically active compounds that have been isolated from S. asper.
The volatile oil (28) from fresh leaves of S. asper was obtained in 0.005% yield as a brown liquid. The major constituents of the volatile oil were phytol (45.1%), α-farnesene (6.4%), trans-farnesyl acetate (5.8%), caryophyllene (4.9%) and trans-trans-α-farnesene (2.0%). The other constituents were α-copaene, β-elemene, caryophyllene, geranyl acetone, germacrene, δ-cadinene, caryophyllene oxide and 8-heptadecene.