Biosynthesis of plant papanridins -A group of novel oligomeric flavonoids

Discovery of novel flavonoids and their biosynthesis are fundamental to understand their roles in plants and benefits to human and animal health. Herein, we report a new polymerization pathway of a group of novel oligomeric flavonoids in plants. We have engineered red cells for discovering genes of interest involved in the flavonoid pathway and identified a gene that encodes a novel flavanol polymerase (FP) localized in the central vacuole. FP catalyzes the polymerization of flavanols, such as epicatechin and catechin, to produce yellowish dimers or oligomers. Structural elucidation show that these compounds are featured with a novel oligomeric flaven-flavan (FF) skeleton linked by interflavan-flaven and interflaven bonds, which are different from proanthocyanidins and dehydrodicatechins. Detailed chemical and physical characterizations further demonstrate that FFs are novel flavonoids. Mechanistic investigations show that FP polymerizes flavan-3-ols and flav-2-en-3-ol carbocation to form dimeric or oligomeric flaven-4[->]8-flavans, termed as papanridins. Data from transgenic, mutation, metabolic profiling, and phylogenetic analyses demonstrate that the biosynthesis of papanridins is prevalent in cacao, grape, blue berry, corn, rice, Arabidopsis and others in the plant kingdom. Given that these findings are the first report, many questions remain for answers. For instance, what are roles of papanridins in plants and what benefits do they have for human and animal health? We anticipate that these findings will promote investigations across plant, nutritional, and animal sciences to understand papanridins in plants and food products. TeaserPlant flavanol polymerase catalyzes the biosynthesis of novel oligomeric flavonoids in the plant kingdom.