An aqueous ethanol extract of Ziziphus jujuba leaves was fractionated by solvent extraction. The active chloroform-ethanol fraction was separated into two components - ZjE-A, which had surface active properties, and ZjE-B, which did not. Bioassay by psychophysical tests on humans revealed sweetness-modifying activity in ZjE-A, but not in ZjE-B. The combined chemistry and bioassay results indicated that the active component is either closely associated with, or is itself, an amphipathic molecule and supported the notion of a role for surface active properties in the tastemodifying action of Z. jujuba. Thin layer chromatography (TLC) and other data indicated and/or suggested that the active component in Z. jujuba consists of a group of compounds (ziziphins), which probably are triterpene saponin glycosides, as had been indicated previously for the taste-modifying component in Gymnema sylvestre (gymnemic acids). However, the ziziphins differed from the gymnemic acids in TLC mobility and in coloration by a Liebermann-Burchard reagent. Therefore, the ziziphins are not the same compounds as the gymnemic acids. ZjE-A is a potent, purified component, consisting of 60–80% ziziphins, which should be useful for future physiological and chemical studies.