The role of human gut bacteria in bioactivation of polyphenolic isoflavones and pyranoanthocyanins

植物来源的类黄酮和其他多酚被认为对人类健康具有有益作用。肠道微生物群可能在食物和膳食补充剂摄入后多酚化合物的转化中发挥关键作用。存在于人类肠道中的细菌已被证明不仅催化多酚的去糖基化和去缀合，而且催化所得糖苷配基的转化。由此形成的细菌代谢物可能具有与母体化合物不同的生物活性。该项目旨在阐明人类肠道细菌在饮食中摄入的选定的甘草酮和吡喃花青素的生物活化中的作用。在雌马酮中，已知大豆苷元仅被肠道细菌激活为雌马酚。将分离雌马酚形成菌株，并使用无菌大鼠模型在体内验证其活性。虽然已知大豆苷元在人体肠道中从O-糖苷释放，但其从C-糖苷形成仍需证明。因此，相关的细菌黄豆苷元形成从其8-C-葡萄糖苷，葛根素，将澄清在体外发酵实验。类似地，肠道细菌的O-去糖基化活性可能导致吡喃花青素的生物活化。为了验证这一假设，这些花青素衍生的色素的成员，如皮诺廷A，将被纳入与细菌去糖基化和进一步转化有关的研究。在项目中获得的数据将有助于测试多酚的效益/风险评估。

Plant-derived flavonoids and other polyphenols are proposed to have beneficial effects on human health. The intestinal microbiota may play a key role in the conversion of polyphenolic compounds following their intake with food and dietary supplements. Bacteria present in the human gut have been shown to catalyze not only the deglycosylation and deconjugation of polyphenolics but also the transformation of the resulting aglycones. The bacterial metabolites thereby formed may have biological activities that differ from those of the parent compounds. The project aims to elucidate the role of human gut bacteria in the bioactivation of selected isoflavones and pyranoanthocyanins ingested with diet. Of the isoflavones, daidzein is known to be activated to equol exclusively by intestinal bacteria. Equol-forming strains will be isolated and their activity verified in vivo using a gnotobiotic rat model. Whereas daidzein is known to be released from O-glycosides in the human gut, its formation from C-glycosides still needs to be demonstrated. Thus, the relevance of bacterial daidzein formation from its 8-C-glucoside, puerarin, will be clarified by in vitro fermentation experiments. Similarly, the O-deglycosylating activity of gut bacteria may result in bioactivation of pyranoanthocyanins. To test this hypothesis, members of these anthocyanin-derived pigments, such as pinotin A, will be included in studies relating to bacterial deglycosylation and further conversion. The data obtained within the project will contribute to the benefit/risk assessment of the tested polyphenols.