A major cytokinin found in coconut milk was isolated by using the toba
cco callus growth-promoting assay as a guide during purification. The
structure of the factor was determined to be inofuranosyl)-beta-D-gala
ctopyransyl}-trans-zeatin riboside [G(3)A(2)-ZR] by various NMR techni
ques, including heteronuclear multiple bond connectivity by 2D multipl
e quantum NMR (HMBC), as well as mass spectroscopy and sugar analysis.
The optimum concentration of G(3)A(2)-ZR for cytokinin activity in th
e 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 cytok
inin activity of coconut milk could be attributed to G(3)A(2)-ZR.