Allelopathic activity of buckwheat: Isolation and characterization of phenolics

Laboratory and field experiments were conducted to assess the allelopathic potential of buckwheat. In the field, buckwheat demonstrated strong inhibitory activity by suppressing weeds. In laboratory studies, aqueous and organic solvent extracts of the aerial parts of common buckwheat inhibited the root and shoot growth of lettuce seedlings. The chloroform and ethyl acetate extracts showed maximum activity, and plants grown in the presence of the ethyl acetate extract showed severe root browning. The allelopathic constituents of the ethyl acetate phase were isolated and identified as gallic acid and (+)-catechin by nuclear magnetic resonance spectroscopy. Gallic acid and (+)-catechin were present in the upper part of buckwheat at concentrations of 0.02 and 0.01%, of fresh weight, respectively. Gallic acid was found to be selectively and strongly inhibitory to root and shoot growth of tested plants at 100 and 10 μg ml^-1. (+)-Catechin, however, inhibited plant growth to a lesser extent. These results suggest that buckwheat may have allelopathic potential and that when used as a ground cover crop or green manure may produce inhibitors, which could suppress weeds.