In vitro protein degradation of 38 sainfoin accessions and its relationship to tannin content by different assays

Comparison of the Effects between Tannins Extracted from Different Natural Plants on Growth Performance, Antioxidant Capacity, Immunity, and Intestinal Flora of Broiler Chickens

In this study, four plant tannins, including AT (Acacia mearnsii tannin, 68%), CT (Castanea sativa tannin, 60%), QT (Schinopsis lorenzii tannin, 73%) and TT (Caesalpinia spinosa tannin, 50%) were added to broiler diets for 42 days to evaluate and compare their effects on growth performance, antioxidant capacity, immune performance and gut microbiota in broilers. The results showed that the supplementation of five tannins could increase the production of T-AOC, GSH-Px, SOD and CAT and reduce the production of MDA in the serum of broilers (p < 0.01), but the antioxidant effect of the AT group was lower than that of the other three groups (p < 0.01). All four tannins decreased the level of the pro-inflammatory factor IL-1β and increased the level of the anti-inflammatory factor IL-10 (p < 0.01). CT, QT and TT decreased the levels of pro-inflammatory factors IL-6 and TNF-α (p < 0.01), while AT and CT increased the level of IL-2 in serum (p < 0.01). Supplementation with four tannins also increased the levels of IgG, IgM, IgA and sIgA in serum (p < 0.01) and the levels of ZO-1, claudin-1 and occludin in the jejunum (p < 0.01). The detection results of ALT and AST showed that CT, QT and TT decreased the concentrations of ALT and AST in serum (p < 0.01). The results of the gut microbiota showed that the abundance of Clostridia and Subdoligranulum increased, and the abundance of Oscillospiraceae decreased, compared to the control group after adding the four tannins to the diets (p > 0.05). In addition, CT, QT and TT decreased the abundance of Lactobacillus and increased the abundance of Bacteroides compared to the control group, while AT showed the opposite result (p > 0.05). Overall, our study shows that tannins derived from different plants have their own unique effects on broilers. AT and CT can promote broilers' growth better than other tannins, CT has the best ability to improve immune and antioxidant properties, and QT and TT have the best effect on broilers' liver protection.

Direct versus Sequential Analysis of Procyanidin- and Prodelphinidin-Based Condensed Tannins by the HCl-Butanol-Acetone-Iron Assay

In this study, we optimized the HCl-butanol-acetone-iron (HBAI) assay for the analysis of B-linked procyanidin (PC) and prodelphinidin (PD) condensed tannins (CTs) by direct analysis of whole tissue and sequential analysis of acetone-water extracts and insoluble residues prepared from forage, woody plant, food, and food byproduct samples. Yields of anthocyanidins (cyanidin and delphinidin) were optimized by heating ≤0.25 mg mL^-1 CT standards, 1 mg mL^-1 tissue, or 1-2 mg mL^-1 acetone-water fractioned tissue for 3 h at 70 °C in medium containing 5% concentrated HCl, 6.7% total water, 50% acetone, 42% n-butanol, and 0.15% ammonium iron(III) sulfate dodecahydrate. Accurate quantitation required CT standards of known purity sourced from the same tissue being analyzed. Both analysis methods provided comparable estimates of total CTs for most PD-rich samples, but only the sequential method gave good recovery and accurate estimates of CTs in most PC-rich samples.

Evaluation of direct phloroglucinolysis and colorimetric depolymerization assays and their applicability for determining condensed tannins in grape marc

To determine the optimum methods for determining condensed tannin (CT) content in grape marc, butanol-hydrochloric acid assays and phloroglucinolysis were adapted for use, applied to a range of grape marc types, and the methods compared. Porter's assay (butanol-HCl) was found to give unreliable results due to nonlinear color responses to grape skin and seed tannin concentrations, whereas the modification to include acetone (Grabber's assay) overcame this. Differences between skin and seed tannin responses highlighted the need to adequately select the correct grape tannin standard, and the formation of pH-dependent color was accounted for through acidification of blank samples. For phloroglucinolysis, the inability to remove highly bound tannins from cell wall material was highlighted, although a measure of tannins remaining post-phloroglucinolysis (Grabber's assay) showed a trend with the level of exposure to oxidative storage or processing conditions. The comparison of CT concentrations from phloroglucinolysis and Grabber's assay gave poor correlation coefficients.

Acetone enhances the direct analysis of procyanidin- and prodelphinidin-based condensed tannins in lotus species by the butanol-HCl-iron assay

The butanol-HCl spectrophotometric assay is widely used for quantifying extractable and insoluble condensed tannins (CT, syn. proanthocyanidins) in foods, feeds, and foliage of herbaceous and woody plants, but the method underestimates total CT content when applied directly to plant material. To improve CT quantitation, we tested various cosolvents with butanol-HCl and found that acetone increased anthocyanidin yields from two forage Lotus species having contrasting procyanidin and prodelphinidin compositions. A butanol-HCl-iron assay run with 50% (v/v) acetone gave linear responses with Lotus CT standards and increased estimates of total CT in Lotus herbage and leaves by up to 3.2-fold over the conventional method run without acetone. The use of thiolysis to determine the purity of CT standards further improved quantitation. Gel-state (13)C and (1)H-(13)C HSQC NMR spectra of insoluble residues collected after butanol-HCl assays revealed that acetone increased anthocyanidin yields by facilitating complete solubilization of CT from tissue.