研究主題
Profiling Of Anthocyanidins And Flavonoids, Proanthocyanidins In Colored Rice – A Metabolomic Approach
研究摘要
Flavonoids are well-known for their antioxidant activities and serve as pigments. Flavones and flavonols occur in monomeric forms in nature. Flavan-3-ols, which are structural components of proanthocyanidins, exist in monomers, oligomers, and polymers. Anthocyanidins, flavylium cation structured, are responsible for the coloration of colored rice. However, the relationship between the distribution of flavonoids and their synthesis in rice needs to be further investigated. In this study, we used ultra-high performance liquid chromatography – tandem mass spectrometry (UHPLC–MS/MS) to analyze flavonoid components in the rice varieties in black, purple, red, and brown colors. To reveal their relationship, we matched flavonoids detected in selected samples to the synthesis pathways of the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Naringenin is a central flavonoid building block in the synthetic pathway. From naringenin, two main pathways diverge. One pathway uses leucoanthocyanidin reductase (LAR) to convert the intermediate compound, leucoanthocyanidin, into flavan-3-ols. These flavan-3-ols then link together to form oligomers, specifically B-type and A-type proanthocyanidins, which are most abundant in red rice and typically consist of 2 to 6 linked units (degree of polymerization). The other pathway from leucoanthocyanidin uses a different enzyme, anthocyanidin synthase (ANS), to produce anthocyanidins. These anthocyanidins, such as cyanidin-3-O glucoside and peonidin-3-O-glucoside, along with other related compounds, are the main flavonoids found in black and purple rice. This suggests that in these rice varieties, both ANS and another enzyme called flavonoid 3-O-glycosyltransferase are active. In contrast to red, black, and purple rice, brown rice primarily contains flavones. Specifically, downstream products of naringenin in brown rice include three different apigenin glycosides and two different luteolin glycosides. Previous research has largely concentrated on specific rice colors; however, our results present the first comprehensive mapping of flavonoid varieties across four colored rice types. Furthermore, the structural identification of these compounds enhances our understanding of the biosynthesis of flavonoids in rice, and the relationship between flavonoids and coloration.
作者
國立臺灣大學食品科學系博士生 Hsin-Jo Chang (張心柔)
發表研討會
21st ICC Conference – Celebrating 70 Years of ICC