In addition to jaslanceosides B (1) and E (2), and jasminoside (3), a new secoiridoid glucoside, isojasminoside (4) was isolated from the leaves of Jasminum amplexicaule (Oleaceace). The structure of 4 was determined on the basis of spectral analysis and chemical reactions. Chemotaxonomy for some selected plants in Jasminum is also discussed.