IDENTIFICATION OF A MAJOR CYTOKININ IN COCONUT MILK

A major cytokinin found in coconut milk was isolated by using the tobacco callus growth-promoting assay as a guide during purification. The structure of the factor was determined to be 14-O-{3-O-[beta-D-galactopyranosyl-(1-->2)-alpha-D-galactopyranosyl-(1-->3)-alpha-L-arabinofuranosyl]-4-O-(alpha-L-arabinofuranosyl)-beta-D-galactopyransyl}-trans-zeatin riboside [G(3)A(2)-ZR] by various NMR techniques, including heteronuclear multiple bond connectivity by 2D multiple quantum NMR (HMBC), as well as mass spectroscopy and sugar analysis. The optimum concentration of G(3)A(2)-ZR for cytokinin activity in the tobacco callus assay was estimated to be 5 x 10(-6) M, so that G(3)A(2)-ZR is one order of magnitude more potent than 1,3-diphenylurea and one order less potent than zeatin riboside. At least 20% of the cytokinin activity of coconut milk could be attributed to G(3)A(2)-ZR.