Identification of an N-Glucoside of cis-Zeatin from Potato Tuber Sprouts

A compound was isolated from potato (Solanum tuberosum L. cv Bintje) tuber sprouts by immunoaffinity chromatography with antibodies against the cytokinins zeatin riboside and isopentenyladenosine. Analysis by ultraviolet spectroscopy and gas chromatography-mass spectrometry of derivatives identified the compound as a 9-glucoside of 6-[(Z)-4-hydroxy-3-methyl-2-butenylamino]purine (cis-zeatin). N-glucosides have often been reported as metabolites of other cytokinins, but to our knowledge, they have never before been found for cis-zeatin. The finding gives proof that cis-zeatin, a modified base in tRNA, also exists as a free substance in plants, since the glucoside, unlike other tRNA-free cis-zeatins described earlier by others, cannot arise by enzymatic degradation of tRNA during plant extraction.