Allelopathic substances in alfalfa plants (Medicago sativa L.) were pu
rified from methanol extracts of alfalfa shoots. The methanol extracts
were fractionated into an acidic fraction, and the sample was divided
into 10 fractions by thinlayer chromatography (TLC). Growth of radish
seedlings was inhibited by the substances obtained from Rf values of
0.5 approximately 0.6 and 0.6 approximately 0.7.These fractions were e
luted with distilled water, and the eluates were analyzed by high-perf
ormance liquid chromatography (HPLC). Six peaks were detected on the c
hromatogram. Growth of radish seedlings was inhibited on three peaks.
Of these peaks, two were identified using HPLC, a mass-spectrometer, I
R, and 1NMR as follows: peak b, ferulic acid and peak f, salicylic aci
d. The growth of alfalfa and radish seedlings was inhibited at lower c
oncentrations of these substances.