Stability and radical scavenging activity of betalains, biosynthesized by Beta vulgaris hairy root culture were investigated at different pH values, bile salts concentration, as well as at the in vitro conditions of gastrointestinal tract. It was established that pH below 3 and concentrations of the bile salts up to 4% had no great influence on betalains stability. At the in vitro conditions of gastrointestinal tract betalains are relatively stable, as their radical scavenging activity decrease from 75% inhibition of 2,2-diphenyl-1-picrylhydrazyl (DPPH*) to about 38%.