New modified brassinosteroids (BS) with a full set of specific functional groups and with an additional one at C-26 have been synthesized and used as haptens for enzyme-linked immunosorbent assay. The haptens were conjugated to bovine serum albumin (BSA) and the obtained immunoconjugates were applied for production of polyclonal antibodies. A conjugation of the haptens to horseradish peroxidase (HRP) gave the corresponding enzyme-labeled BS-another principal component for immuno-competitive analysis. The steroids were linked to proteins through spacers at the terminal side chain carbon atom (C-26) that made both the cyclic part and the side chain exposed for recognition by antibodies. It allowed maximization of their sensitivity and for the first time made possible immunochemical distinguishing of the most important group of natural BS, B-lactones, from B-ketones and 6-deoxo derivatives. The synthesis of haptens based on a sequence of transformations starting from stigmasterol included Claisen rearrangement of 22-allylic ethers as a key reaction in the side chain construction.

Brassinosteroids are a new group of phytohormones that are widely distributed in plants and play an important role in the processes of plant growth and development. Physiological concentrations of brassinosteroids in plants are extremely low, and their analysis in organs and tissues is very difficult. This study is devoted to the chemical aspects of elaboration and to bioanalytical parameters of an immunoenzymatic system for quantitative determination of the phytohormones 24-epicastasterone and 24-epibrassinolide.

In the mitochondria of animal steroidogenic tissues, cytochrome P450(SCC), encoded by the CYP11A1 gene, catalyzes the conversion of cholesterol into pregnenolone - the general precursor of all steroid hormones. In this work, we study the steroid metabolism in transgenic tobacco plants carrying the CYP11A1 cDNA cytochrome P450(SCC)from the bovine adrenal cortex. The transgenic plants under investigation markedly surpass the control wild-type plants by size and are characterized by a shortened period of vegetative growth (by rapid flowering); their leaves contain pregnenolone - the product of a reaction catalyzed by cytochrome P450(SCC). The level of progesterone in transgenic tobacco leaves is higher than in the control plants of the wild type. The seeds of the transgenic plants contain less (24R)-brassinosteroids than the wild-type tobacco plants. The results obtained indicate that the synthesis of an active P450(SCC) cytochrome in transgenic Nicotiana tabacum plants has a profound effect on steroid metabolism and is responsible for the specific phenotypic features of transgenic plants bearing CYP11A1 cDNA.