Five compounds (syringic acid, tricin, acacetin, syringoside, and diosmetin) 
were isolated from the aerial parts of wild oats (Avena fatua L.) using 
chromatography columns of silica gel and Sephadex LH-20. Their chemical 
structures were identified by means of electrospray ionization and 
high-resolution mass spectrometry as well as (1)H and (13)C nuclear magnetic 
resonance spectroscopic analyses. Bioassays showed that the five compounds had 
significant allelopathic effects on the germination and seedling growth of wheat 
(Triticum aestivum L.). The five compounds inhibited fresh wheat as well as the 
shoot and root growth of wheat by approximately 50% at a concentration of 100 
mg/kg, except for tricin and syringoside for shoot growth. The results of 
activity testing indicated that the aerial parts of wild oats had strong 
allelopathic potential and could cause different degrees of influence on 
surrounding plants. Moreover, these compounds could be key allelochemicals in 
wild-oat-infested wheat fields and interfere with wheat growth via allelopathy.