Brassinolide chemical structure

Structure-activity relationship Biosynthesis and Metabolism Biosynthesis of castasterone Biosynthesis of brassinolide from castasterone Regulation of biosynthesis Metabolism and its regulation Physiology and Signal Transduction Physiology Signal transduction Jasmonates and Oxylipins Introduction Chemistry Chemical structure Chemical stability... 

The isolation and structural determination of brassinolide [BR] was reported in Nature by Dr. N. B. Mandava and co-workers at the USDA in 1979(5), and was subsequently announced in Chem, Eng, News 6). The steroidal skeleton of the chemical structure of BR prompted us to examine the effect on the LJT. (225,235)-homobrassinolide was synthesized by Mori in 1980( 7) at our request just after the structural determination of BR. BR itself was also produced by Ikekawa and his co-workers the same year(3). Wada, a co-worker in our group, tested the activity of BR and homobrassinolide on rice lamina inclination and found that both compounds dramatically induced the inclination of laminae (see Table I) as expected(5). These findings strongly suggested... 

Among the compounds that have been isolated from the brassins were a new group of glucosyl esters of fatty acids, the structures of which were established by spectral methods (254, 255) as well as by chemical and biochemical synthesis (256, 257, 258). Although these esters were much less active than brassinolide in the bean second internode bioassay, their presence may be essential for seed germination since the enzymatic synthesis of these esters was correlated to germination (257, 258). 

Brassinosteroids are grouped into C, Cg, and steroids like the typical phytosterols. These classifications result basically from different alkyl substitutions in the side chain, that is no substituent in steroids (14, 15 ), a methyl (1, 3,5, 7-9, 16-22,29) or an exomethylene ( 2,4, 6) at C24 in steroids, and an ethyl at C24 (12 )or an ethylidene at C24 ( 10,11, 13) or an exomethylene at C24 with a methyl at C25 ( 23-28 ) in steroids. The structure-activity relationship reveals that alkylation in the side chain is necessary for biological activity. More especially, the presence of a saturated alkyl ( a methyl or an ethyl ) at C24 and a methyl at C25 makes brassinosteroids biologically more active. Thus, 25-methylbrassinolide bearing both 24-methyl and 25-methyl functions has been chemically synthesized and it is more potent than brassinolide which, until now, had been considered to be the most potent brassinosteroid (44). 

The chemical identify and biological activity has beeen verified through the use of synthetic brassinolide. A number of biologically active epimers and biologically inactive isomers were used in the study of structure activity relationships (11,12). 

Brassinosteroid Production. As soon as the structure for brassinolide had been proved, an immediate search followed to find systems that would give greater quantities for practical applications. This followed two routes examination of organisms that produced not only brassinolide but, hopefiilly, other brassinostnoids possessing high specific activity and, concomitantly, chemical synthesis. 

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