ORTHO-TOPOLIN-9-GLUCOSIDE, AN AROMATIC CYTOKININ FROM POPULUS X CANADENSIS CV ROBUSTA LEAVES

A new natural cytokinin was isolated from Populus x canadensis Moench cv Robusta leaves. Its structure was established as -(o-hydroxybenzyla mino)-9-O-beta-D-glucopyranosylp urine (termed ortho-topolin-9-glucosi de) by UV and mass spectrometry and confirmed by synthesis. This cytok inin exhibited comparatively low biological activity in three common b ioassays. It was quantified in the leaf extract by combined high perfo rmance liquid chromatography-enzyme linked immunoassay. Amounting to 5 0 pmol g(-1) fresh weight, ortho-topolin-9-glucoside was the dominant aromatic cytokinin in poplar leaves collected 2 hr after sunrise.