Effect of Viola tricolor flower supplementation on body and intestinal microbiota in rats fed a high-fat diet

The use of herbal medicines, due to their wide therapeutic spectrum and absence or minimal side effects, is an important area of therapy that is used in the treatment of diseases of various etiologies. Garden violet /wild pansy (Viola tricolor L.) is a medicinal plant of the violet family that is widely distributed in Ukraine. The herb of this plant (Violae herba) is used as the official raw material, which is sold in dry form as an independent remedy and as a part of herbal teas. In this study, we determined the overall effect of dry V. tricolor herb as part of a high-fat diet on body weight gain, metabolic processes in model animals, and the effect on their intestinal microbiota. For the experiment, 15 male white laboratory rats were divided into three groups and fed a high-fat diet (15% vegetable fat) supplemented with 0.5% and 2.0% dried V. tricolor herb for 30 days. Consumption of 2.0% of the herb resulted in increased weight gain compared to the control group. The dried herb V. tricolor at a dose of 0.5% in the diet of rats caused an increase in the relative weight of the brain and large intestine (caecum and colon) and a decrease in the weight of the thymus. At a dose of 2.0%, the relative weight of the thymus and caecum increased, but the relative weight of the colon decreased, and the length of the colon and rectum decreased compared to the control group. The diet supplemented with V. tricolor at a dose of 0.5% caused a decrease in globulin concentration and changes in protein ratio, and at a dose of 2.0% – an increase in total protein, albumin, albumin/globulin ratio and a decrease in globulin level. The addition of 0.5% V. tricolor dried herb resulted in an increase in high-density lipoprotein (HDL) cholesterol and a decrease in cholesterol at 2.0%. Regardless of the dose, V. tricolor contributed to a reduction in the plasma atherogenic index. Both doses of violet caused a sharp and significant increase in the De Ritis ratio and a decrease in alkaline phosphatase activity. Adding 0.5% and 2.0% violet herb to high-fat diet helps maintain the quantitative composition of the main intestinal microbiota of laboratory rats (Bifidobacterium, Lactobacillus and typical Escherichia coli). It was found that 2% of violet herb in the diet had a bacteriostatic effect on low-fermenting Escherichia coli and Klebsiella spp. and a bactericidal effect on Enterococcus spp., which can disrupt normal intestinal functions and cause diseases.