Effect of Low-Frequency Static Magnetic Field on Enrichment of Phenolics and Hypoglycemic Activity of Germinated Maize (Zea mays L.)

Maize kernels (cv. ‘Jidan 66’) were exposed to different intensities (2.5, 3.5 and 4.5 mT) of low-frequency static magnetic fields for different time periods (12, 24, 36, 48, 60 and 72 h) and germinated at 25 ℃ for 96 h. The changes in the growth indices, the phenolic contents, the hypoglycemic activity of phenolic compounds and the key enzyme activities related to polyphenol metabolism in germinated maize kernels were investigated. The results showed that the sprout length and germination rate of maize seeds treated at magnetic field intensity of 3.5 mT for 60 h were significantly increased, and the contents of bound and free phenols were increased by 72.72% and 47.16%, and the contents of syringic acid and p-coumaric acid were also significantly increased compared to the untreated control (P < 0.05). In addition, the activity of phenylalanine ammonia lyase (PAL), 4-coumaric acid-CoA ligase (4CL), and cinnamate 4-hydroxylase (C4H) were improved under low frequency static magnetic field, and the α-glucosidase and α-amylase inhibitory activity of bound and free phenolics were enhanced. These pieces of evidence indicated that low frequency static magnetic field can promote the growth of maize seeds and the accumulation of phenolic compounds, and improve the hypoglycemic activity of phenolic compounds in germinated maize seeds .