Raphanin, an Antibacterial Principle of the Radish (Raphanus sativus)

Abstract

In the course of investigation of the watery extracts of different plants by the cylinder plate method on plates seeded with Staphylococcus and Bact. coli, it was found that the extracts of the seeds of radish (Raphanus sativus) gave a very marked zone of inhibition in both cases, whereas the extract of the root and the leaves did not affect the growth of the bacteria. The antibacterial principle of the extract was resistant to heat, and it could even be boiled on a water-bath for 30 minutes without a marked loss of activity. The substance responsible for the activity was isolated from the water extract of the seeds, and a syrupy liquid was obtained of boiling point 135° C. under 0·06 mm. mercury pressure, which could be distilled as a homogeneous substance. The almost colourless, or slightly yellow, distillate proved to be the active antibacterial principle, and has been termed ‘raphanin’ by us. As it was estimated on the basis of antibacterial tests, 1 kgm. of the seeds contains about 6–8 gm. of this active principle, the yield of the raphanin on isolation being about 3 gm. per kgm. of seeds.