The soil extracts contained at least 10 mg kg-I medicarpin. Medicarpin, 4-methoxymedicarpin, sativan, and 5'-methoxysativan were isolated from alfalfa foliage with 95% ethanol, purified, identified by gas chromatography-mass spectroscopy, and then exogenously applied to alfalfa and velvetleaf (Abutilon theophrasti L.) seeds using an agar bioassay.