Effect of germination conditions on total phenolic and flavonoid contents and antioxidant capacity of buckwheat seeds (Fagopyrum Esculentum Moench)

Abstract

Buckwheat grains contain high amount of flavonoid rutin which are beneficial to human health. In this study, the buckwheat grains were germinated under limited moisture content at different durations (0, 8, 16, 24, 36 and 48 h). The total phenolic and flavonoid contents and antioxidant capacity of the extracts were examined to determine the effect of germination time on the bioactive compounds of the germinated buckwheat grains. The results indicated that total phenolic and flavonoid contents of both free and bound phenolic extracts of germinated buckwheat significantly increased from 0 to 48 h of germination. The total phenolic content was sharply increased from 10.58 ± 0.094 mg ferulic acid equivalent (FAE)/g flour in the control to 13.54 ± 0.12 mg FAE/g flour after 48 h of germination. Likewise, the total flavonoid content was from 5.82 ± 0.038 mg rutin equivalent (RE)/g to 7.28 ± 0.036 mg RE/g flour when the germination lengthened from 0 to 48 h. In addition, the rutin content steadily declined from 203 ± 13.1 to 189 ± 12.7 μg/g flour in the initial stage of germination at 16 h, then slightly increased to 236 ± 13.2 μg/g flour after 48 h of germination. In contrast, the quercetin content gradually rose from 11.9 ± 2.7 to 26.2 ± 0.8 μg/g flour at the first 16 h of germination, and then steadily decreased to 13.4 ± 0.6 μg/g flour after 48 h of germination. Consequently, the antioxidant capacity was considerably improved from 85.3% and 10.69% of free and bound phenolic extracts in non-germinated buckwheat to 97.3% and 19.2% after germination for 48 h, respectively. As a result, the buckwheat grains germinated at 48 h was the good source of flavonoid compounds which can be used as functional foods. Keywords: antioxidant capacity, buckwheat, Fagopyrum esculentum Moench, flavonoids, germination, phenolics.