The protective actions of ambroxol, rutin, glutathione and harmaline on oxidative damages of various tissue components were compared. The mechanisms by which they prevent oxidative tissue damages were explored. Lipid peroxidation of liver microsomes induced by combinations of Fe^(2+) and ascorbate or Fe^(3+), ADP and NADPH was inhibited by 50 μM of rutin, ambroxol, harmaline and glutathione. Ambroxol (100 pM) inhibited the degradation of hyaluronic acid by Fe^(2+), H₂O₂ and ascorbate, and it was greater than that of harmaline, whereas hyaluronic acid degradation was not prevented by rutin and glutathione. The compounds used (100 μM) did not protect the degradation of cartilage collagen by xanthine and xanthine oxidase. Rutin, glutathione and harmaline decreased the degradation of IgG by xanthine and xanthine oxidase, while ambroxol did not attenuate degradation of IgG. Glutathione showed a scavenging action on H₂O₂. The compounds all showed scavenging actions on hydroxyl radical. Ambroxol and harmaline exhibited quenching effects on singlet oxygen. In conclusion, ambroxol, rutin, glutathione and harmaline may exert protective effects differently on tissue components against oxidative attack depend on kind of tissue component and free radical.