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The content and accumulation patterns of flavonoids in response to light were investigated in common buckwheat (Fagopyrum esculentum) sprouts over the course of 9 days. Buckwheat sprouts were grown under fluorescent (FL), red (RL), and blue (BL) light sources, as well as in darkness, and their extracts were analyzed. Sprout elongation and chlorophyll content were high in the presence of red light. The contents of the major buckwheat sprout flavonoids, orientin, isoorientin, vetexin, isovetexin, and rutin all peaked 5 days after germination under all four growth conditions, then gradually decreased. Sprouting cotyledons accumulated around 1.5-fold more orientin, isoorientin, quercetin-3-O-robinobioside, and rutin in the presence of red light, including from the RL and FL light sources, than in blue light alone. The C-glycosyl flavones, orientin, isoorientin, vetexin, and isovetexin, were not detected in the stem tissues of the hypocotyls, but C-glycosyl flavonols, such as quercetin-3-O-robinobioside and rutin, were present, and were twice as abundant under BL and FL than in the RL and darkness conditions. In the root tissues, a small amount of C-glycosyl flavonols was detected after BL exposure only; however, the other flavonoids were not detected at all. These results indicated that red light induces flavonoid biosynthesis in the cotyledons of buckwheat seedlings, but blue light has a greater effect on the accumulation of C-glycosyl flavonols in other seedling tissues. [ABSTRACT FROM AUTHOR]

Buckwheat sprouts that are synthesized during the germination process are rich in flavonoids, including orientin, vitexin, rutin, and their isomers (isoorientin, isovitexin, and quercetin-3-O-robinobioside, respectively). The purpose of this study was to optimize and validate an analytical method for separating flavonoid isomers in common buckwheat sprout extract (CSE). Factors, such as range, linearity, precision, accuracy, limit of detection, and limit of quantification, were evaluated for each standard using high-performance liquid chromatography (HPLC). On the basis of resolution and symmetry, a column temperature of 40 °C with 0.1% (v/v) acidic water and acetonitrile as mobile phases, at a flow rate of 1 mL min−1 were determined to be the optimal analytical conditions. Calibration curves for orientin, isoorientin, vitexin, isovitexin, and rutin exhibited good linearity with correlation coefficients of 0.9999 over the 6.25−100.00 μg mL−1 range. Recovery values of 96.67−103.60% confirmed that the method was accurate for all flavonoids. The relative standard deviations of intra-day repeatability and inter-day reproducibility confirmed method preciseness, with values of less than 5.21% and 5.40%, respectively. The developed method was used to analyze flavonoids in CSE, with isomers satisfactorily separated and simultaneously quantified. We demonstrated that the developed HPLC method can be used to monitor flavonoids in buckwheat sprouts.

Buckwheat sprouts that are synthesized during the germination process are rich in flavonoids, including orientin, vitexin, rutin, and their isomers (isoorientin, isovitexin, and quercetin-3- O -robinobioside, respectively). The purpose of this study was to optimize and validate an analytical method for separating flavonoid isomers in common buckwheat sprout extract (CSE). Factors, such as range, linearity, precision, accuracy, limit of detection, and limit of quantification, were evaluated for each standard using high-performance liquid chromatography (HPLC). On the basis of resolution and symmetry, a column temperature of 40 °C with 0.1% ( v / v ) acidic water and acetonitrile as mobile phases, at a flow rate of 1 mL min -1 were determined to be the optimal analytical conditions. Calibration curves for orientin, isoorientin, vitexin, isovitexin, and rutin exhibited good linearity with correlation coefficients of 0.9999 over the 6.25-100.00 μg mL -1 range. Recovery values of 96.67-103.60% confirmed that the method was accurate for all flavonoids. The relative standard deviations of intra-day repeatability and inter-day reproducibility confirmed method preciseness, with values of less than 5.21% and 5.40%, respectively. The developed method was used to analyze flavonoids in CSE, with isomers satisfactorily separated and simultaneously quantified. We demonstrated that the developed HPLC method can be used to monitor flavonoids in buckwheat sprouts.

It is known that common buckwheat sprouts contain several flavonoids, including orientin, isoorientin, vitexin, isovitexin, rutin, and quercetrin, whereas tartary buckwheat sprouts contain only rutin. In this study, we evaluated flavonoids present in buckwheat sprouts and identified a previously unreported flavonoid. Simultaneous detection by HPLC was used to separate rutin and a compound that was not separated in previous studies. We used a novel HPLC elution gradient method to successfully separate rutin and the previously unidentified compound, for which we performed structural analysis. The identification of six flavonoids by HPLC was confirmed using HPLC-ESI-MS/MS analysis. The newly identified compound, [M+H](+) =611.17, was identified by NMR as the rutin epimer quercetin-3-O-robinobioside. Unlike common buckwheat sprout, tartary buckwheat sprout contained rutin as a main flavonoid, whereas other flavonoids appeared only in trace amounts or were not detected. Quercetin-3-O-robinobioside was not detected in tartary buckwheat sprout., (Copyright © 2014 Elsevier Ltd. All rights reserved.)