Antioxidant, anti-inflammatory, and antitumor activities of phenolic compounds from white, red, and black Chenopodium quinoa seed

Background and objectives Quinoa (Chenopodium quinoa Willd.) is a promising nutritious cereal known for its rich nutrition and diverse physiological activities. In order to further investigate the profiles and physiological activities of phenolic compounds from quinoa, the composition of free and bound phenolic extracts from white, red, and black quinoa were analyzed, as well as their antioxidant, anti-inflammatory, and antitumor activities. Findings Total phenolic content (TPC) and total flavonoid content (TFC) ranged from 514.03 to 1,409.54 mg gallic acid equivalent (GAE)/100g and 177.49 to 407.75 mg rutin equivalent (RE)/100 g, respectively. TPC existed mainly in bound form in red and black quinoa, but free form in white quinoa. Eight individual phenolic acids were detected, with the total acids amount ranging from 86.21 to 188.76 mu g/g. Protocatechuic acid was the dominant phenolic acid both in red and black quinoa. Red quinoa showed the highest TPC and TFC, while black quinoa had the highest phenolic acids concentration. Red quinoa also showed the best ABTS and DPPH radical scavenging activities. Positive correlations were found among antioxidant activity and phenolic components. Besides, phenolics from red and black quinoa showed better anti-inflammatory and antitumor activity by down-regulating the NO production and inhibiting the proliferation of MCF-7 cells. Conclusions Quinoa seed is rich in phenolic components, especially the red and black one. Higher phenolic contents in red and black quinoa can be responsible for their superior antioxidant, anti-inflammatory, and antitumor activities. With potential health benefits, quinoa phenolics may be used as ingredients for functional food. Significance and novelty Findings of this study revealed useful information on phenolics and bioactivity of quinoa for its cultivation and breeding with functional oriented purpose. The results could be also applied in health food industry for quinoa material selection and processing.