Quantitative analysis of the phenolic compounds and antioxidant activities of six quinoa seed grains with different colors

To improve understanding of the potential benefits of quinoa as a staple food, the chemical composition, bioactive compounds, and total antioxidant capacity of six different colored quinoa cultivars were studied. The findings revealed that yellow quinoa exhibited a higher protein content, while white and red quinoa seeds contained greater amounts of starch, and black quinoa seeds were richer in fiber. A total of 20 phenolic compounds were identified, encompassing 13 phenolic acid variants and 7 flavonoid variants. The levels of phenolic acids (131.96–223.28 μg/g) and flavonoids (91.86–131.14 μg/g) exhibited variations based on seed color, with crimson and yellow quinoa seeds demonstrating the highest concentrations of both phenolic acids and flavonoids. Notably, crimson quinoa seeds displayed the highest content of betalains (36.17 μg/g). Saponin content was highest in yellow (178.82 mg/100 g), while the lowest in black (106.5 mg/100 g). Furthermore, it was observed that the phenolic acids present in red quinoa seeds exhibited the most potent DPPH free radical-scavenging ability. Conversely, black quinoa seeds displayed the highest iron-reducing antioxidant activity and ABTS free radical scavenging ability among all the samples examined. Moreover, black quinoa seeds demonstrated the highest overall antioxidant activity compared to other quinoa varieties This study suggests that colored quinoa seeds are rich in phenolic and betalains compounds with antioxidant capacity. The correlation analysis indicated a significant positive relationship between antioxidant activity and phenolic compounds up to a certain degree. As a result, colored quinoa can serve as an antioxidant food.