Deglycosylation of isoflavone <i>C</i>&#x2010;glycosides by newly isolated human intestinal bacteria

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P><P><B>BACKGROUND</B></P><P>Plant isoflavones are mostly present in the glycoside form. Isoflavone aglycones produced by intestinal microflora are reported to be more bioactive than the glycoside form. However, the deglycosylation of isoflavone <I>C</I>‐glycosides is known to be rare, and is less studied.</P><P><B>RESULTS</B></P><P>Three new bacteria were isolated from human faecal samples, two of which hydrolysed the <I>C</I>‐glycosidic bond of puerarin, daidzein‐8‐<I>C</I>‐glucoside. They were identified as two <I>Lactococcus</I> species, herein designated as MRG‐IFC‐1 and MRG‐IFC‐3, and an <I>Enterococcus</I> species, herein designated MRG‐IFC‐2, based on their 16S rDNA sequences. From a reactivity study, it was found that <I>Lactococcus</I> sp. MRG‐IFC‐1 and <I>Enterococcus</I> sp. MRG‐IFC‐2 hydrolysed isoflavone <I>C</I>‐ and <I>O</I>‐glycosides, as well as the flavone <I>O</I>‐glycoside apigetrin, but could not hydrolyse the flavone <I>C</I>‐glycosidic bond of vitexin. The other <I>Lactococcus</I> sp., MRG‐IF‐3, could not hydrolyse the <I>C</I>‐glycosidic linkage of puerarin, while it showed a broad substrate spectrum of <I>O</I>‐glycosidase activity similar to the other two bacteria. Puerarin was completely converted to daidzein within 100 min by <I>Lactococcus</I> sp. MRG‐IFC‐1 and <I>Enterococcus</I> sp. MRG‐IFC‐2, which is the fastest conversion among the reported human intestinal bacteria.</P><P><B>CONCLUSION</B></P><P>Two new puerarin‐metabolising human intestinal bacteria were isolated and identified, and the deglycosylation activity for various flavonoid glycosides was investigated. The results could facilitate the study of <I>C</I>‐glycosidase reaction mechanisms, as well as the pharmacokinetics of bioactive <I>C</I>‐glycoside natural products. © 2014 Society of Chemical Industry</P>