Bioassays for brassinosteroids

The Rice Lamina Inclination as a Specific Bioassay for Brassinosteroids... 

Some structure-activity relationships, synthesis of new brassinosteroids, and new sensitive bioassays for brassinosteroids are presented. 

Maeda E (1965) Rate of lamina inclination in excised rice leaves. Physiol Plant 18 813-827 Takeno K, Pharis RP (1982) Brassinosteroid-induced bending of the leaf lamina of dwarf rice seedlings an auxin-mediated phenomenon. Plant Cell Physiol 23 1275-1281 54. Wada K, Marumo S, Ikekawa N, Morisaki M, Mori K (1981) Brassinolide and homobras-sinolide promotion of lamina inclination of rice seedlings. Plant Cell Physiol 22 323-325 Wada K, Marumo S, Abe H, Morishita T, Nakamura K, Mori K (1984) A rice lamina inclination test - a microquantitative bioassay for brassinosteroids. Agric Biol Chem 48 719-726... 

We conclude that brassinosteroids may have a slight (if any) agonistic activity in a bioassay for ecdysteroids More importantly, they reveal a significant antagonistic activity. This antagonistic effect is dose dependent and reversible. 

We are able to readily search for naturally occurring brassinosteroid using rice-lamina joint test [LJT] (1) as the bioassay method and GC/MS as the microanalytical method, which was established by Ikekawa and his co-workers as a microanalytical method for BS (2). Plant material was extracted three times in methanol or 80% methanol-H20. After the extract was evaporated under reduced pressure, the resulting aqueous residue was extracted with EtOAc at pH3 and the EtOAc fraction was partitioned with Na2C03-NaHC03 buffer at pH 10 to get neutral substances. 

We developed several methods for construction of the side chain and the A/B ring of brassinosteroids, and synthesized more than fifty analogs (6). In order to obtain the structure-activity relationship, those analogs were subjected to bioassay in the rice-lamina inclination (7), Raphanus, and tomato tests (5). In general, die structural... 

Recently, by the ligand-accelerated osmium catalyzed asymmetric hydroxylation using a cinchona alkaloid derivative, the 22/ ,23/ -epimer was obtained as the major product of the oxidation (77). Thus, epibrassinolide may be ideal for practical use, and, therefore, is one of the most desirable brassinosteroids because of the ease with which it can be synthesized. This compound showed about one tenth the activity of brassinolide in Raphanus and tomato bioassay (5). In field trials, the activity of epibrassinolide was about the same as of brassinolide. Epibrassinolide is a natural sterol. This was confirmed by GC-MS analysis, which identified epibrassinolide, along with co-existing brassinolide, brassinone, and castasterone, from the bee pollen of the broad bean Vida faba obtained in China (72). 

Brassinolide is known as the most potent compound for inducing plant growth promoting activity in various bioassay systems. Many researchers have attempted to demonstrate brassinosteroid application for agricultural use. However, test results have been disappointing in many cases under field conditions. Here, we discuss the capability and problems surrounding the potential practical uses of brassinosteroids. 

Barley field experiments, description for brassin evaluation, 12 Barley leaf cell ultrastructure, protective effect of brassinosteroids under saline stress, 150,152/153,154/ Bean first-intemode bioassay, 321 Bean second-intemode bioassay activities of compounds, 65,68,69-7Of application, 321 brassin purification, 3-4 brassinosteroids, description, 109-110 development, 321 scheme, 63,65,66/... 

The physiological concentrations of BRs in plants are extremely low (ng.Kg Fw), and it can be veiy difficult to analyze their abundance in plant tissues. A wide range of methods are currently employed for the determination and quantification of brassinosteroids in plants, including bioassays, diverse chromatographic procedures, radioimmunoassays [9], and enzyme-linked immunosorbent assays [10-13]. The most widely used bioassays are the second bean intemode bioassay and rice-lamina inclination test. These bioassays have been used in the isolation of brassinolide from rape pollen [1] and castasterone from chestnut insect galls [14]. Gas chromatography-mass spectrometry (GC-MS) analysis is the current standard technique for instrumental analysis of BRs [15-17]. 

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