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ARS Home » Northeast Area » Beltsville, Maryland (BHNRC) » Beltsville Human Nutrition Research Center » Food Composition and Methods Development Laboratory » Research » Publications at this Location » Publication #327180
Title: Comprehensive characterization of C-glycosyl flavones in wheat (Triticum aestivum L.) germ using UPLC-PDA-ESI/HRMSn and mass defect filtering

Author
item Geng, Ping
item Sun, Jianghao
item ZHANG, MENGLIANG - Ohio University
item LI, XINGNUO - Zhejiang University
item Harnly, James - Jim
item Chen, Pei

Submitted to: Journal of Mass Spectrometry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2016
Publication Date: 6/24/2016
Citation: Geng, P., Sun, J., Zhang, M., Li, X., Harnly, J.M., Chen, P. 2016. Comprehensive characterization of C-glycosyl flavones in wheat (Triticum aestivum L.) germ using UPLC-PDA-ESI/HRMSn and mass defect filtering. Journal of Mass Spectrometry. 64:4407-4415.

Interpretive Summary: This study applied multi-stage high resolution mass spectrometry (HRMS) combined with a mass defect filter (MDF) to identify sugars attached to flavones by a carbon-carbon bond for the first time. Sugars are generally attached to flavonoids by an oxygen-carbon bond and are easy to identify. Sugars attached by a carbon-carbon bond, or C-glycosyls are harder to detect but provide more interesting information about the flavonoids. MDF performed the initial search of raw data with finely defined mass ranges and mass defect windows to generate noise-reduced data focusing on target flavonoids. Fragments from spectra from up to 4 MS stages facilitated the characterization of C-glycosyl flavones with diverse structures. The high specificity of the exact mass measurement permitted the unambiguous identification of acyl groups (nominal masses of 146, 162 and 176, respectively) and sugars (rhamnose, glucose or galactose and glucuronic acid). A total of 72 flavone C-glycosyl derivatives, including 2 mono-C-glycosides, 34 di-C-glycosides, 14 acyl di-C-glycosides and 7 acyl tri-C-glycosides, were identified in wheat germ. These compounds are important marker compounds yhay allow differentiation of whole grain and refined wheat products.

Technical Abstract: A comprehensive characterization of C-glycosyl flavones in wheat germ has been conducted using multi-stage high resolution mass spectrometry (HRMS) combined with mass defect filter (MDF). MDF performed the initial search of raw data with defined mass ranges and mass defect windows to generate the noise-reduced data focusing on targeted flavonoids. The high specificity of the exact mass measurement permitted the unambiguous discrimination of acyl groups (nominal masses of 146, 162 and 176, respectively) from sugar moieties (rhamnose, glucose or galactose and glucuronic acid). A total of 72 flavone C-glycosyl derivatives, including 2 mono-C-glycosides, 34 di-C-glycosides, 14 acyl di-C-glycosides and 7 acyl tri-C-glycosides, were recognized from wheat germ, which was considered to be the important fraction containing marker compounds in differentiation of whole grain and refined wheat products. The 7 acylated mono-O-glycosyl-di-C-glycosyl flavones and some acylated di-C-glycosyl flavones were reported in wheat for the first time. The frequent occurrence of numerous isomers was a remarkable feature of wheat germ flavones. Both UV and mass spectra were needed to maximize the structure information obtained for data interpretation.