The present topics concentrate on three areas:
Classical steroid hormones are known to bind to receptors in cell nuclei. When the steroid-receptor complex is attached to the steroid-binding site of DNA, the latter changes its conformation and the hormone response is launched. Recently, a new class of steroid hormones was discovered: they bind to membrane receptors of various neurotransmitters, thus modulating - in a positive or negative sense - action of the transmitters. This gives synthetic chemists many options to verify their expertise: haptens may be constructed to enable endocrinologists develop new diagnostic methods, new derivatives may be prepared for physiological studies, new analogues may be produced to improve their biological activity. Our team has been active in all these spheres.
There are several classes of plant growth regulators in nature: auxins, cytokinins, gibberelins, brassinosteroids, abscisic acid etc. Brassinolide is the first brassinosteroid isolated from plant - from the pollen of Brassica napus. It is a very efficient plant growth regulator, its activity makes it possible to detect up to several fentomoles per one plant. Physiologically it multiplies the number of plant cells and prolongs their length, although almost nothing more is known about its physiology. In practice, it stimulates plant stem growth, increases the green and dry mass of plants, the number of flowers, the number and mass of seeds, and has an effect on the root growth, too. A great attention has also been devoted to its antistress activity, especially against the low and high temperature, insufficient amounts of nutrients, water deficit, action of salt, herbicides, pesticides etc.
Brassinosteroids, analogues of brassinolide, either natural or synthetic ones, form a group of very active compounds with a special structural feature: usually steroidal B ring is a lactone ring, and the molecule contains several hydroxyl groups, e.g. brassinolide contains 2a,3a,22R,23R hydroxyls. Very important seems to be also their antistress activity. The great ecological and economical promise of these compounds stimulates interest of many world chemical, botanical, and genetic laboratories.
The classical steroid skeleton can be viewed as a very rigid building block of significant chirality. Methods of partial modification of individual functional groups, developed over the past decades, make it possible to build supramolecules containing several steroid units linked in various arrangement, thus producing larger compounds with increased chirality and new complexation potential.
