Specific and total activities of the allelochemicals identified in buckwheat

The various organs of the Polish cultivars of buckwheat were evaluated for their flavonoid content (rutin, quercetin, (+)-catechin, and (−)-epicatechin) and for their phenolic acid content (chlorogenic, caffeic, ferulic, and gallic acids) to test their contribution to buckwheat allelopathic activity. The main compound found in the above-ground organs of buckwheat was rutin, followed by chlorogenic acid, and then (−)-epicatechin. The allelopathic activity, based on the specific activity of the identified compounds on lettuce seedling growth, was evaluated. Gallic acid had the highest specific activity and quercetin had the lowest. The specific activity of rutin was at the medium level compared to the other examined compounds, but as a consequence of its high concentration, its total activity was very high. The growth inhibitory effects of the aqueous extracts of the buckwheat leaves and inflorescences were higher than that of the stems. The higher inhibitory activity of the extracts compared to the leaves and inflorescences was explained by the high presence of rutin in them. Therefore, based on the total activity, as calculated by its concentration and its growth inhibitory effect, it seems that rutin, among the other tested compounds, is the major allelochemical in Polish buckwheat.