Objective The aim of research was to study the effects of formononetin (FMN) on the structure and abundance of intestinal microbiota in mice. Methods A total of 12 specific pathogen-free male C57BL/6J mice were randomly divided into control group and FMN group

with 6 mice in each group. The FMN group was given FMN by gavage once daily at a dose of 5 mg/kg for 10 consecutive days

while the control group was given an equal volume of phosphate buffer saline （PBS）. On 11th day

fresh feces of mice were collected in each group

and microbial DNA was extracted using the E.Z.N.A.® soil DNA Kit （Omega Bio-tek

USA）

with the 16S rRNA （V3-V4 region） amplificated using the primers of 338F （5´-ACTCCTACGGGAGGCAGCAG-3´） and 806R （5´-GGACTACHVGGGTWTCTAAT-3´）. Finally

Illumina MiSeq sequencing was performed through using PE300 chemical at Majorbio Bio-Pharm Technology Co.

Ltd. （Shanghai

China）

and the sequencing results were analyzed. Results FMN administration significantly increased the gut microbial richness and diversity in mice

with the Sobs

Chao

Ace and Shannon indices obviously increased. PCoA and Venn analysis demonstrated that the FMN intervention significantly changed the structure of gut microbiota. At the phylum level

the abundance of Bacteroidetes was evidently increased in FMN group

while the abundance of Firmicutes and Proteobacteria was significantly decreased. The abundance of Deferribacteres showed an increasing trend. At the genus level

the FMN treatment group showed significantly increased abundance of Coprococcus

Ruminococcus

unclassified_o__Clostridiales

norank_o__Clostridiales

Odoribacter and norank_o__Bacteroidales

and the abundance of unclassified_f__Lachnospiraceae was remarkably decreased.Conclusion FMN could increase the richness and diversity of gut microbiota in mice and promote the abundance of beneficial bacteria.