Enhancement of the neural response during 40 Hz auditory entrainment in closed-eye state in human prefrontal region.

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.