Qualitative and quantitative analysis of characteristic sugars in three colored quinoas based on untargeted and targeted metabolomics

Quinoa is considered as health-promoting food for its high nutritional value. However, little references are focus on the characteristic sugars in quinoa. In this study, characteristic sugars in three colored quinoas (WQ, white quinoa; RQ, red quinoa; BQ, black quinoa) were analyzed based on metabolomics. Results showed a total of 33 sugars including monosaccharaides (21), disaccharides (9) and trisaccharides (3) were identified, and 25 sugars were reported in quinoas for the first time. D-talose (9.49 mg/kg in BQ ~ 45.98 mg/kg in RQ), levoglucosan (17.85 mg/kg in WQ ~ 27.68 mg/kg in RQ), 6-deoxy-D-glucose (8.92 mg/kg in RQ ~ 11.86 mg/kg in BQ) and gentiobiose (8.70 mg/kg in BQ ~ 15.82 mg/kg in RQ) were common in quinoas, and they presented significantly (p < 0.05) different contents among three colored quinoas. Ribose, mannose, lyxose, fructose, xylose, 1-kestose and melibiose respectively showed the highest content in RQ. WQ could be characterized by raffinose, trehalose, maltotriose, galactose, sorbose and D-arabitol. Moreover, sugar profiles and characteristic sugars in different quinoa samples could be well distinguished by principal component analysis (PCA). In conclusion, metabolomics was excellent in the sugar analysis of quinoas which made great contribution to understand the overall nutritional quality of quinoas.