Studies on the electrochemical behaviour of two anti-herpes uridines

Abstract

The electrochemical activities of (E)-5-(2-bromovinyl)-2′-deoxyuridine (BVDU) and 5-iodo-2′-deoxyuridine (idoxuridine) were investigated and a simple diffential-pulse polarographic method was developed for the determination of idoxuridine in ophthalmic solutions and ointments. Both compounds were reduced at the dropping-mercury electrode (D.M.E.). In phosphate buffer (pH 7.0), idoxuridine exhibits a well developed d.c. and differential-pulse polarographic wave with an E_1/2 value of –0.97 V vs. S.C.E. The electroreduction mechanism for this substance involves a two-electron carbon–halogen bond fission. On the other hand, BVDU is reduced in tetraethylammonium bromide solution (pH 5.85) at an applied potential of –1.8 V. The mechanism of reduction for BVDU involves the transfer of four electrons, which has been attributed to the fission of the bromine–carbon bond followed by reduction of the vinyl double bond.

The height of the differential-pulse polarographic peaks for idoxuridine and BVDU varies linearly with the concentration of the depolarisers over the range 1 × 10^–4 to 5 × 10^–4M and each substance exhibits a correlation coefficient of 0.9996. The assay method developed for idoxuridine is simple and has a detection limit of about 2.0 µg ml^–1.