Catechin and epicatechin gallate (ECg) were found only in common buckwheat.
Quercetin was observed only in tartary buckwheat.
The highest antioxidant activity was observed in tartary groats.
ECg was the main contributor to antioxidant activity of common buckwheat hull.
Rutin, orientin, and/or ECg contents were highly correlated with the antioxidant activity.