S04 - Session O1 - Keynote: Modern cytokinin derivatives – synthesis, bioactivity and use in tissue cultures

Authors: Magdalena Bryksova *, Lucie Plihalova, Karel Dolezal

Plant hormones, such as cytokinins (CKs), regulate many aspects of plant growth and development. The CKs have long been known to play an important role during the cell cycle and influence many developmental processes. Aromatic CKs and their endogenous metabolites can adversely affect shoot proliferation, acclimatisation or inhibition of rooting in some plant species, making micropropagation processes more difficult, especially in rare and sensitive medicinal plants. One of them, 6-benzylaminopurine (BAP) is an important and affordable cytokinin, but its drawbacks and negative effect in certain crops and micropropagation techniques limit its use in the agricultural and biotechnological areas. Therefore, many CK derivatives are prepared to avoid the unfavourable properties of BAP. Moreover, the wide variety of the adenine moiety allows substitution at different positions, such as N1, C2, N3, N6, N7, C8 and N9, and also their combination opens possibilities for preparing a wide range of derivatives with targeted biological applications. Based on these studies, a series of CK derivatives were prepared, substituted at the N9 position by various sugars and tetrahydropyranyl/tetrahydrofuranyl protecting groups, to enhance their specific biological functions that are already routinely used in plant micropropagation. Recently, the group of N9-substituted CK derivatives with fluorinated carbohydrate group has been synthesised and their bioactivity evaluated. The replacement of the hydroxyl group by a fluorine atom on the sugar moiety has a significant effect on the stereo-electronic properties and also changes the physical and chemical properties compared to their non-fluorinated counterparts. It is clear that the application of fluorinated compounds seems to be a good approach to increase biological activity and it might present a breakthrough in the in vitro micropropagation of some plant species.