Electrochemical monitoring of the interaction of cisplatin with cystine and ascorbic acid

The interaction of cisplatin with cystine (RSSR) and ascorbic acid (AA) has been investigated in aqueous solution at physiological pH, using drug conc entration of 0.835 x 10(-6) M to 46.76 x 10(-6) M with RSSR concentration o f 6.5 x 10(-5) M by voltammetric techniques. Voltammetric results show that at low drug concentration (< 0.835 x 10(-6) M), the interaction between ci splatin and RSSR occurs slightly, while at higher drug concentrations (grea ter than or equal to 0.835 x 10(-6) M), cisplatin binds to RSSR and gives a n unseparated-reduction peak at -0.610 V. Based on the voltammetric behavio ur of RSSR, it has been suggested that binding of cisplatin to RSSR occurs mainly at the disulphide bond. It has been shown that the interaction of ci splatin with RSSR in the presence of AA is very rapid with regards to the i nteraction without AA, and a new peak, probably corresponding to the intera ction of cisplatin with RSSR and AA is appeared at - 0.970 V. The fractiona l coefficient for the binding of cisplatin to RSSR with or without AA was c alculated to be 0.031 and 0.055, respectively. (C) 2000 Elsevier Science S. A. All rights reserved.