Abstract The liver-protecting activity of melanin-like pigment (MLP) derived from tea was studied using hydrazine intoxication. The non-reduced MLP demonstrated the lack of activity. Reduction of MLP caused an increase in the number of phenol groups. Administration of reduced MLP (rMLP) to rats (i.p., 20 mg/kg, 30 min before hydrazine) to rats prevented development of heavy liver intoxication. Pretreatment of animals with rMLP prevented the rise of serum alanine transferase activity and the decrease of glutathione level in the liver challenged by hydrazine. It also lowered the hepatic malondialdehyde concentration. Reduced MLP significantly restored the ability for rats to metabolize antipyrine. The introduction of MLP alone did not affect pharmacokinetics of antipyrine nor introduce toxicity to rats. Biochemical and pharmacokinetical data proved that the rMLP protects the liver against hydrazine-induced injury.