To investigate the effects and mechanism of quercetin on blood pressure,intestinal flora and ventricular remodeling in spontaneously hypertensive rats (SHR).Eight Wistar Kyoto rats were set as the control group (WKY),and 24 SHR were randomly divided into 3 groups:model group (SHR),benazepril group (Ben) and quercetin group (Que),separately given blank solvent,blank solvent,benazepril 10 mg/(kg·d),quercetin 50 mg/(kg·d) by gavage.Blood pressure was monitored every 2 weeks.After 8 weeks,the concentrations of Toll-like receptor 4 (TLR4) and nuclear factor-kappa B p65 (NF-κB p65) in the serum were measured by ELISA.The rat feces in the cecum was acquired for the detection of intestinal flora by 16S - V4 area sequencing.Taking the rat heart to calculate heart weight index,left ventricular weight index.Myocardial fibrosis was observed by VanGieson staining and cardiac collagen volume fraction (CVF) was calculated.The expression of TLR4 protein and mRNA in the myocardium was detected by Western blot and RT-PCR.Compared with WKY,systolic blood pressure,cardiac mass index,left ventricular mass index,CVF,the concentrations of TLR4 and NF-κB p65 in the serum,the expression of TLR4 protein and mRNA in the myocardium,F/B value were increased,while the richness of intestinal flora was decreased in SHR.Compared with SHR,blood pressure was significantly reduced;the degree of myocardial fibrosis was improved;the concentrations of TLR4 and NF-κB p65 in the serum,the expression of TLR4 protein and mRNA in the myocardium were reduced;the intestinal flora abundance was improved both in Ben and Que.Quercetin decreases blood pressure and improves ventricular remodeling in SHR.The mechanism may be by regulating intestinal flora,suppressing TLR4/ NF-κB signaling pathway.