Compounds and methods of preparing compounds represented by structural formula (I):
wherein X represents any suitable counter-anion;
R1 and R2 independently represent hydrogen, C1-6 alkoxy or nitro;
R3, R4, R5 and R6 each independently represents hydrogen, hydroxy, halo, C1-6 alkyl,
C2-6 alkenyl or C1-6 alkoxy; and
R7, R8, R9 and R10 each independently represents hydrogen, hydroxy, halo, C1-6 alkyl, C2-6 alkenyl or C1-6 alkoxy.
Compounds represented by structural formula (I) are useful in treating or preventing free radical-associated diseases or conditions in mammals.