Evaluation of endogenous enzyme-induced chemical transformations of flavonoid glycosides to aglycones and ethyl-rutinoside in different Tartary buckwheat edible tissues

Biotransformation of Bioactive Metabolites in Cassiae Semen by Endogenous Enzymes and Probiotics

The present study evaluated the potential of endogenous enzymes and probiotics in transforming bioactive metabolites to reduce the purgative effect and improve the functional activity of Cassiae Semen and verified and revealed the biotransformation effect of endogenous enzymes. Although probiotics, especially Lactobacillus rhamnosus, exerted the transformation effect, the endogenous enzymes proved to be more effective in transforming the components of Cassiae Semen. After biotransformation by endogenous enzymes for 12 h, the levels of six anthraquinones in Cassiae Semen increased by at least 2.98-fold, and free anthraquinones, total phenolics, and antioxidant activity also showed significant improvement, accompanied by an 82.2% reduction in combined anthraquinones responsible for the purgative effect of Cassiae Semen. Further metabolomic analysis revealed that the biotransformation effect of endogenous enzymes on the bioactive metabolites of Cassiae Semen was complex and diverse, and the biotransformation of quinones and flavonoids was particularly prominent and occurred by three primary mechanisms, hydrolyzation, methylation, and dimerization, might under the action of glycosyl hydrolases, SAM-dependent methyltransferases, and CYP450s. Accordingly, biotransformation by endogenous enzymes emerges as a mild, economical, food safety risk-free, and effective strategy to modify Cassiae Semen into an excellent functional food.

Pectolinarigenin reduces the expression of sterol regulatory element-binding proteins and cellular lipid levels

Sterol regulatory element-binding proteins (SREBPs) are transcription factors that act important roles in the genes involved in lipid biosynthesis. In this study, it was found that the flavonoid pectolinarigenin, reduced the activity of SRE-containing fatty acid synthase (FAS) promoter and the mRNA expressions of SREBP target genes in human hepatoma (Huh-7) cells. Moreover, compared to other flavonoids, pectolinarigenin reduced the mature forms of SREBPs in a dose-dependent manner. The insulin-induced gene (INSIG) and proteasome were not involved in the pectolinarigenin-mediated reduction of mature forms of SREBPs. Pectolinarigenin also reduced the lipid contents in vitro. These results suggest that pectolinarigenin may inhibit lipogenesis through suppressing SREBP activity, at least partially, via the formation of SREBPs mature forms, thereby reducing the expression of their downstream genes related to lipogenesis. To the best of our knowledge, this is the first work that shows how pectolinarigenin affects cellular lipid levels by affecting SREBPs.

Impact of Rutin and Other Phenolic Substances on the Digestibility of Buckwheat Grain Metabolites

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is grown in eastern and central Asia (the Himalayan regions of China, Nepal, Bhutan and India) and in central and eastern Europe (Luxemburg, Germany, Slovenia and Bosnia and Herzegovina). It is known for its high concentration of rutin and other phenolic metabolites. Besides the grain, the other aboveground parts of Tartary buckwheat contain rutin as well. After the mixing of the milled buckwheat products with water, the flavonoid quercetin is obtained in the flour–water mixture, a result of rutin degradation by rutinosidase. Heating by hot water or steam inactivates the rutin-degrading enzymes in buckwheat flour and dough. The low buckwheat protein digestibility is due to the high content of phenolic substances. Phenolic compounds have low absorption after food intake, so, after ingestion, they remain for some time in the gastrointestinal tract. They can act in an inhibitory manner on enzymes, degrading proteins and other food constituents. In common and Tartary buckwheat, the rutin and quercetin complexation with protein and starch molecules has an impact on the in vitro digestibility and the appearance of resistant starch and slowly digestible proteins. Slowly digestible starch and proteins are important for the functional and health-promoting properties of buckwheat products.