Buckwheat is a pseudocereal whose seeds are rich in numerous health-positive phytochemicals including polyphenols. Several methods for extracting these compounds can be found in the literature. The objective of the study was to compare the total polyphenol content (TPC) of seven common buckwheat (Fagopyrum esculentum Moench) varieties obtained using different extraction methods/procedures and to assess the impact of the extraction methods on various varieties. The Folin–Ciocalteu spectrophotometric assay was used to measure the TPC. The results showed that TPC was significantly dependent on the extraction solvent and the efficiency of the solvents may be ordered from high to low efficacy as follows: 80% acetone > 0.1% HCl in methanol > 80% methanol = 80% ethanol > 100% methanol > water = 100% ethanol. TPC increased with increasing temperature during extraction and procedures based on alkaline hydrolysis proved to be more effective than those based on the acidic one. The responses of different buckwheat varieties to various extract preparations slightly differed, which could be attributed to each variety’s specific composition of extractable and bound polyphenols. It can be suggested that using more than one extraction method gives more robust information for good characterizing of buckwheat varieties according to their TPC for breeding and food use purposes.

Barley is a good source of dietary fibre, vitamins, and minerals. Moreover, it is a source of polyphenols, which recently have been studied for their antioxidant properties. Barley generally is not eaten in its raw form, and the necessary processing influences the polyphenol content. This study evaluated the content of polyphenol compounds and antioxidant activity before and after thermal treatment typical for that carried out in households (i.e., boiling and subsequent microwave heating). Six genetic materials of hull-less barley were chosen for this study. The results showed that all tested barley genotypes were good sources of polyphenols. The studied thermal processes led to certain reductions in polyphenol content. The antioxidant activity of soluble phenolic compounds and the effects of heat treatment, as analysed by Trolox equivalent antioxidant activity (TEAC) and 2,2-diphenyl-1-picrylhydrazyl assay (DPPH) methods, differed. In the case of the DPPH method, the boiling and subsequent microwave heating indicated growth in antioxidant activity for almost all genotypes. When using the TEAC method, the results were not so clear, as the indicated activity both increased and declined. In the case of insoluble polyphenols, the antioxidant activity decreased for almost all genotypes regardless of the measurement method used.