Evaluation of the radical scavenging activity of some representative isoprenoid and aromatic cytokinin ribosides (N⁶-substituted adenosines) by in vitro chemical assays

Cytokinins are naturally occurring adenine derivatives whose physiological role is that of growth regulators in plants and that show also many other activities either in plants and in mammalian cells. In plants, they can be found mainly as free bases ((N⁶-substituted adenines, CKs), but also as the corresponding N⁹- ribosides (N⁶-substituted adenosines, CKRs). In mammalian cells, CKRs are, in general, more active than CKs. In order to evaluate the intrinsic in vitro antioxidant capacity of some significant CKRs, their scavenging activity against synthetic radicals that are at the basis of well-established antioxidant assays (ORAC, TEAC, DPPH) has been evaluated. The results of the in vitro scavenging activity of biologically relevant radicals such as hydroxyl (HO^•), superoxide (O₂^.-) and lipid peroxides (R-OO^.) are reported and discussed.