A series of S-nitrosothiols, structurally related to the NO-donor S-nitroso-N- acetylpenicillamine, and of organic nitrate esters that contain amidine groups which specify a recognition via the trypanosomal purine transporter P2, were synthesized and tested for their ability to inhibit the uptake of [2-3H] adenosine on Trypanosoma equiperdum.