By this study, nutritional compositions, phenolic and γ-aminobutyric acid (GABA) contents, and enzyme activities after germination of oats (Avena sativa L.) were evaluated. Protein content significantly increased whilst ash, fat contents and total starch negligibly changed. The total phenolics increased by 0.5 mg ferulic acid equivalents g-1
dry weight in the methanolic extract. In the water extract, it was promoted 0.03 mg ferulic acid equivalents g-1. The GABA content increased > 30% after 5 days of germination. Catechin, eligallocatechin and luteonin were found in only ungerminated seeds, whereas gallic acid, epicatechin, epigallocatechin gallate, ferulic acid were detected only in germinated seeds. Ellagic acid was observed in both ungerminated and germinated oats. The increase of > 30% inhibitory activity of α-amylase and reduction of > 25% of α-glucosidase inhibition proposed that germinated oats is a promising source for safe dietary supplements, despite further elaboration is needed.