Effect of free and bound polyphenols from Rosa roxburghii Tratt distiller's grains on moderating fecal microbiota

Abstract

Rosa roxburghii Tratt distiller's grains (R. roxburghii DGs), the main by-product of wine processing, showed functional value and potential for high-value usage which benefited from their rich polyphenols. In this study, the free and bound polyphenols from R. roxburghii DGs were extracted and their potential effect on modulating fecal microbiota was investigated using in vitro fecal fermentation. The free polyphenols (26.32-26.45 mg GAE/g) showed higher antioxidant activity compared to the bound polyphenols (8.76-9.01 mg GAE/g). The free and bound polyphenols significantly improved the fecal microbiota community structure and enhanced short chain fatty acids concentrations after the stimulated colonic fermentation for 24 h. Furthermore, the effect of R. roxburghii DGs polyphenols on modulating fecal microbiota was primarily attributed to quercetin, catechin, kaempferol, cyanidin and baicalin. This research suggests that R. roxburghii DGs are a promising source of natural antioxidants and prebiotic foods.

Keywords: Antioxidant activity; Fecal microbiota; Polyphenols; Rosa roxburghii Tratt distiller’s grains; Short chain fatty acids.

Graphical abstract

Fig. 1

Content of phenolic compounds in R. roxburghii DGs. Including free polyphenols, bound polyphenols and total polyphenols, and the total phenolic content is the sum of free and bound fractions. Two kinds of R. roxburghii DGs named CS and HC were provided by Changshun Dnansoya Rosa roxburghii Farm Co. Ltd. (Guizhou, China) and Guizhou Hongcai Investment Group Co. Ltd. (Guizhou, China), respectively. Results were expressed as means ± SD, n = 3, *: p < 0.05, **: p < 0.01.

Fig. 2

The antioxidant activities of R. roxburghii DGs. (A) The antioxidant activity of the various phenolic extracts of R. roxburghii DGs, including FRAP value, ABTS and DPPH free radical scavenging capacity. The free and bound polyphenols from CS (Changshun Dnansoya Rosa roxburghii Farm Co. Ltd) were named as CS-FP and CS-BP; the free and bound polyphenols from HC (Guizhou Hongcai Investment Group Co. Ltd.) were named as HC-FP and HC-BP, respectively. Results were expressed as means ± SD, n = 3, *: p < 0.05. (B) Redundancy analysis of phenolic contents and antioxidant activity in R. roxburghii DGs. The red vectors represent the antioxidant ability, the length of the line shows the correlation between the ranking axis and the magnitude, and the quadrant in which they are located reflects the positive and negative correlation between the antioxidant and the ranking axis. The blue vectors stand for the individual phenolic compounds of R. roxburghii DGs polyphenols, and their angle with the red vector denotes their relationship to the antioxidant. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

The modulatory effects of R. roxburghii DGs polyphenols on fecal microbiota. (A) The relative abundance of fecal microbiota in R. roxburghii DGs polyphenols treatment after the colonic fermentation. Fermentation for 0 h were set as the corresponding control to evaluate the relative effect of low (20 mg/d), medium (70 mg/d) and high (140 mg/d) doses of CS and HC R. roxburghii DGs polyphenols treatments on fecal microbiota, respectively. Means were higher or lower than 1.00, revealing that the treatment increased or decreased the abundance of specific fecal microbiota, respectively. (B) Correlation analysis of phenolic contents and the relative abundance of fecal microbiota in R. roxburghii DGs. The free and bound polyphenols from CS (Changshun Dnansoya Rosa roxburghii Farm Co. Ltd) were named as CS-FP and CS-BP; the free and bound polyphenols from HC (Guizhou Hongcai Investment Group Co. Ltd.) were named as HC-FP and HC-BP, respectively. Results were expressed as means ± SD, n = 3, *: p < 0.05.

Fig. 4

The effect of R. roxburghii DGs polyphenols on SCFAs production. (A) Effects of R. roxburghii DGs polyphenol treatments on the concentration of SCFAs in the simulated colon fermentation system. This includes acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, and total SCFAs. The bar chart represents the control group, and the broken line chart represents the sample group. (B) Correlation analysis of phenolic contents and acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, and total SCFAs in R. roxburghii DGs. Results were expressed as means ± SD, n = 3, *: p < 0.05. (C) Relationships between contents of phenolic compound of R. roxburghii DGs, relative abundance of fecal microbiota and concentration of SCFAs composition in the simulated colon fermentation system. Comparisons of relative abundance of fecal microbiota and concentration of SCFAs composition in the simulated colon fermentation system are shown, with a color gradient denoting. Spearman’s correlation coefficients. The contents of phenolic compound of R. roxburghii DGs were related to each environmental factors by mantel test.

Fig. 5

The health effects on gut health are supplied by the five important phenolic compounds from R. roxburghii DGs polyphenols, including quercetin, catechin, kaempferol, cyanidin and baicalin. (A) The decrease of intestinal oxidative stress. (B) The modulation of the fecal microbiota's community structure. (C) The increase of SCFAs concentration. The red color denotes the promoting effect, the gray color denotes the inhibiting impact, and the line thickness indicates the intensity of the effect. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)