Effect And Mechanism Of Lights On Content Of Flavonids In Germinated Tartary Buckwheat

Buckwheat (Fagopyrum tataricum L. Gaertn) is a kind of widely edible minor grains. The content of flavonoids in buckwheat is higher, which possess antioxidant, anti-inflammatory and antibiosis activity. Some researchers had found that the flavonoids content in buckwheat can be significantly improved by germination treatment, and enhance the bioactivity. On the basis of these, regulating effect and preliminary effect mechanism of light treatment on the synthesis of flavonoids in germinated buckwheat were investigated in this paper.In this paper, the germinated buckwheat was used as the material. In order to evaluate the influence of light treatment on the flavonoids content in buckwheat sprouts, DPPH free radical scavenging activity of the sprouts, and activity of key enzyme in the synthetic process of flavonoids, the ultraviolet, blue, white, yellow and red light with different frequency were used to treat the buckwheat in the germination process. The preliminarily signal transduction pathway of flavonoids metabolism in the sprouts regulated by light treatment was investigated through several specific inhibitors of calcium signal pathway.The results indicated that total flavonoid and rutin content in buckwheat sprouts was significantly increased under the treatment of ultraviolet, blue, white, yellow and red light in the germination process (compared with the dark treatment), and there was significantly different between the different treatment. After the treatment of UV-C, total flavonoid and rutin contents in buckwheat sprout were the highest, and increased 30.1% and 40.9% compared with the control group, respectively. Moreover, activity of the key enzymes (PAL and CHI) of flavonoids metabolism in buckwheat sprout were significantly increased, and positive correlated with the contents of total flavonoid and rutin, after the treatment of light. These results demonstrated that:after the buckwheat sprout treated with light, the contents of flavonoids were increased by improving the activity of key enzymes in anabolism process of flavonoids. In addition, the DPPH free radical scavenging activity of buckwheat sprout can be increased by the light treatment, and increased up to 35.1% in the process of buckwheat germination. The scavenging activity was positive correlated with the total flavonoids content, and indicated that the flavonoids content in buckwheat sprouts can be increased by the light treatment to improve the antioxidant activity of buckwheat.In the combination of blue light and ultraviolet, blue light could regulate the content of total flavonoids and rutin, only synergistic with UV-C, namely, blue light irradiated first in combination of blue light and UV-C could significantly increase total flavonoids and rutin content, and increased 4.15 and 3.63 mg/g DW respectively, compared with blue light irradiated last. However, blue light in combination of blue light and UV-A did not show this synergistic function. In addition, the activity of CHI and DPPH free radical scavenging activity showed a significant correlation with total flavonoids content. This indicated that blue light synergistic with UV-C increased total flavonoids by increasing the activity of CHI, and then improved the antioxidant activity of buckwheat.In order to investigate the influence of ultraviolet and blue light treatment on flavonoids content and activities of related enzymes, the chelant of Ca2+(EGTA), blocker of Ca2+pathway (AlCl3), inhibitors of IP3 (inositol triphosphate) and ryanodine receptor (neomycin, procaine) were utilized to treat the germinated buckwheat. The results illustrated that:the contents of total flavonoid, rutin and quercetin were significantly decreased in buckwheat sprouts with the treatment of EGTA, AlCl3 and neomycin, and decreased 25.6%,62.3% and 89.6%, compared with the control group. Moreover, activities of the related enzymes of flavonoids metabolism (PAL, CHI and REDs) were inhibited with different degree, and decreased 67.5%,92.3% and 57.1%, compared with control group, respectively. These demonstrated that flavonoids metabolism in buckwheat sprout induced by ultraviolet and blue light was directly related with the signal transduction of Ca2+, and the Ca2+ signal was involved in the metabolic process of flavonoids metabolism in buckwheat sprout induced by ultraviolet and blue light, which was the various Ca2+ signals involved regulation process and based on IP3 pathway.To sum up, the ultraviolet and blue light both can improve the content of flavonoids in germinated buckwheat by enhancing the activity of key enzymes in metabolism process of flavonoids, and further to improve antioxidant activity of the buckwheat sprout; the Ca2+ signal was involved in the metabolic process of flavonoids in buckwheat sprouts induced by ultraviolet and blue light. The treatment of ultraviolet and blue light is a non-residue, non-pollution, simple and effective treatment method. Hence, results of this study not only provide a simple regulatory method for manufacturing, but also offer theory and technical method to accurately adjust and metabolic study of flavonoids in the germinated process of buckwheat.