The Electronic Properties of Cordycepin in the Adenine Nucleoside Landscape: A Theoretical Approach

The anticancer activity of 3'-deoxyadenosine (Cordycepin, or dCor) is known to be linked to the inhibition of the MAPK/ERK signalling and Hedgehog pathways, as well as the termination of primer elongation by primase in DNA lagging-strand synthesis. In this study, the electronic properties of dCor, 7,8-dihydro-8-oxo-3'-deoxyadenosine (^OXOdCor), and 8-hydroxy-3'deoxyadenosie (^HOdCor), together with their spin densities, charge distributions, and global reactive descriptors, have been taken into consideration at the M06-2x/6-31++G** level of theory in the aqueous phase. It was found that dCor predominantly adopts a <i>3'-endo,anti</i> conformation, while ^OXOdCor and ^HOdCor adopt a <i>2'-endo,syn</i> conformation. Also, the keto form of oxidised dCor was found to be energetically preferred to its enolic form. The adiabatic ionisation potentials (AIPs) were noted as follows (in eV): 6.29 for dCor, 6.21 for ^OXOdCor, and 6.17 for ^HOdCor. The lowest adiabatic electron affinity among all the discussed adenine nucleosides analogues was assigned for ^OXOdCor at 1.12 eV. A thorough analysis of the spin density distribution of the adiabatic radical cation reveals that it has a higher accumulation at N6 > C5 > C8 > 3 of dCor, C5 > N6 > N7 > O8 of ^OXOdCor, and N6 > C5 > C8 > C2 of ^HOdCor. The results suggest that Cordycepin is more easily converted to ^OXOdCor and ^HOdCor than canonical adenine nucleosides. Much like typical drugs, after its administration and release, Cordycepin is exposed to various physiological factors and can be exposed to ionisation radiation during combined therapy. These factors can influence the therapeutic potential of Cordycepin. Therefore, further studies on its stability are of utmost importance.