Biosyn this of Brassinosteroids in Plant

分别用胆甾醇和胆甾醇还原法制备了氚标记的油菜素内酯和castasterone。放射性还原产物经薄层高效液相色谱纯化，得到放射性标记的油菜素内酯和castasterone，比放射性约为4Ci/mM。3叶期水稻幼苗通过根部饲喂（<^3H>）castasterone 6小时。部分处理过的幼苗在不含castasterone的培养基中进一步孵育10天。对这些植物材料进行castasterone代谢产物分析。因此，发现castasterone被根吸收并运输到芽。还发现castasterone可以迅速转化为水溶性代谢物。经色谱分析和水解分析，它们的结构似为酸性偶联物，而非糖苷类。处理10 d后，吸收的大部分卡斯特酮转化为极性代谢物，未改变的卡斯特酮仅占0.43%。油菜素内酯的假设前体Castasterone从未转化为油菜素内酯。对（< 3H>）油菜素的命运进行了类似的研究，结果与卡斯特酮相似。

Tritium-labelled brassinolide and castasterone were prepared by reduction of dolicholide and dolichosterone respectively. Radioactive reduction products were purified by thin-layer and high performanceliquid chromatography, affording radio-labelled brassinolide and castasterone: specipic radioactivity of them was about 4Ci/mM.3-leaf-stage rice seedlings were fed with ( <^3H> )castasterone for 6 hr through the roots. Portion of the treated seedlings were further incubated for 10 days in castasterone-free medium. These plant materials were analysed for the metabolites of castasterone. Thus, it was found that castasterone is absorbed by roots and transported to shoots. It was also found that castasterone was found to be rapidly converted into water-soluble metabolites. The structures of them seemed to be acidic conjugates rather than glycosides on the basis of chromatographic analysis and hydrolysis. Ten days after the treatment, most of castasterone absorbed was changed into polar metabolites, while unchanged castasterone accounted for only 0.43%. Castasterone, a hypothetical precursor of brassinolide was never changed into brassinolide. Fate of ( <^3H> )brassinlode was similarly pursued and the result was analogous to that of castasterone.