The antioxidative activity of the mucoregulatory agents: ambroxol, bromhexine and N-acetyl-L-cysteine. A pulse radiolysis study.

Ambroxol and bromhexine are shown to be scavengers of both superoxide and hydroxyl radicals as determined by pulse radiolysis experiments. The dismutation of superoxide was accelerated 3-fold by bromhexine and 2.5-fold by ambroxol over the rate of spontaneous dismutation. The reaction constants of hydroxyl radicals with bromhexine and ambroxol were determined by competition kinetics to be 1.58 +/- 0.15 x 10(10) M-1S-1 and 1.04 +/- 0.1 x 10(10) M-1S-1, respectively. N-acetyl-L-cysteine also reacted with hydroxyl radicals (1.28 +/- 0.14 x 10(10) M-1S-1) but not with superoxide radical. These effects may be clinically relevant in the treatment of oxidant-associated lung damage induced by inflammatory agents and/or environmental pollutants.