Epimerization and Conjugation of 14C-Labeled Epibraßinolide in Cucumber Seedlings

Summary When 14 C-24epibrasinolide ( 24 C-EBR) was applied to the roots of cucumber seedlings, 14 C-EBR was metabolized to les polar and polar metabolites. Chemical characterization of these metabolites was investigated by acid and alkali hydrolysis. The sterol obtained from these hydrolysates was a unique sterol (EBR*) having higher polarity than the original EBR. These results indicate that EBR was metabolized to EBR*, and then EBR* was conjugated with fatty acid and/or sugar in cucumber seedlings. The chemical structure of EBR* was determined to be 2,24-diepibrasinolide, which was a 2-epimer of EBR, by liquid chromatography-mas spectrometry (LC-MS)and gas chromatography-mas spectrometry (GC-MS). It is suggested that 2,24-diepibrasinolide was an important intermediate to form conjugates.