Characterization of carotenoids and flavonoids in Yangxian pigmented rice varieties through LC‒MS/MS-based targeted metabolomics and multivariate statistics

Pigmented rice is widely popular because of its abundant phytochemicals and various health benefits. This study investigated the variations in the carotenoids and flavonoids of Yangxian-pigmented rice (black, green, purple, yellow, and red) through LC‒MS/MS targeted metabolomics. A total of 20 carotenoids were identified, with 18 xanthophylls (90 %) and 2 carotenes (10 %). Principal component analysis (PCA) demonstrated that PC1 and PC2 accounted for 55.4 % and 26.4 %, respectively, of the variance among pigmented rice samples. PLS-DA revealed 5 significantly different carotenoids (VIP >1 and P value < 0.05) across these rice varieties. Additionally, 378 metabolites, consisting of 361 flavonoids (95.5 %) and 17 tannic acids (4.5 %), were detected. PCA revealed that PC1 and PC2 contributed 52.5 % and 24.8 % of the variance, respectively, and PLS-DA identified 147 significantly differential flavonoids (VIP >1 and P < 0.05) among the samples. Multivariate statistical analysis revealed variation within the groups and separation among the groups, suggesting relatively significant differences in carotenoids and flavonoids among pigmented rice. KEGG pathway analysis mapped 5 carotenoid metabolites to three metabolic pathways (carotenoid biosynthesis, metabolic pathways, and secondary metabolite biosynthesis) and 22 flavonoid metabolites to five pathways (secondary metabolite biosynthesis, metabolic pathways, flavonoid biosynthesis, flavonoid and flavonol biosynthesis, and anthocyanin biosynthesis). These findings can support research on bioactive compounds and functional food processing in pigmented rice.