Effects of Latilactobacillus delbrueckii Fermentation on the Bioconversion and Antioxidant Capacity of Phenolic Compounds in Quinoa Sprouts

Polyphenols, serving as a significant active ingredient, exert a crucial role in the antioxidant effect of quinoa. Nevertheless, the preponderance of research has predominantly centered on quinoa grains, with a conspicuous scarcity of studies dedicated to quinoa sprouts. In this study, quinoa sprouts were used as substrate, and Latilactobacillus delbrueckii subsp. bulgaricus was employed as the fermentation agent. The fermentation parameters of quinoa sprouts were meticulously optimized using a combination of single-factor experiments and response surface analysis, successfully leading to the enrichment of polyphenols. A noteworthy elevation in the total polyphenol and flavonoid contents were observed after fermentation, with increments of 46.56% and 57.28%, respectively. Additionally, a statistically significant (P<0.05) augmentation in antioxidant activity was demonstrated, as measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity, 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) scavenging activity, oxygen radical absorbance capacity (ORAC), and reducing power. To gain further insights, metabolomics analysis was conducted, revealing the identity and quantity of active compounds present in the fermented quinoa sprouts broth. Notably, a marked increase in flavonoids like luteolin and quercetin was evident, whereas a substantial reduction in the levels of certain polyphenols, such as dihydrowogonin and quercetin 3-O-xylosyl-rutinoside, was observed after fermentation. The activities of five key enzymes were quantitatively assayed within the metabolic pathway of polyphenols, revealing significant variations. This comprehensive analysis provides a clearer understanding of the metabolic mechanisms underlying the bioconversion of polyphenols during the fermentation process.