Effect of phenolic aldehydes and flavonoids on growth and inactivation of Oenococcus oeni and Lactobacillus hilgardii

The aim of this work was to investigate the effect of wine phenolic aldehydes, flavonoids and tannins on growth and viability of strains of Oenococcus oeni and Lactobacillus hilgardii. Cultures were grown in ethanol-containing MRS/TJ medium supplemented with different concentrations of phenolic aldehydes or flavonoids and monitored spectrophotometrically. The effect of tannins was evaluated by monitoring the progressive inactivation of cells in ethanol-containing phosphate buffer supplemented with grape seed extracts with different molecular weight tannins. Of the phenolic aldehydes tested, sinapaldehyde, coniferaldehyde, p-hydroxybenzaldehyde, 3,4-dihydroxybenzaldehyde and 3,4,5-trihydroxybenzaldehyde significantly inhibited the growth of O. oeni VF, while vanillin and syringaldehyde had no effect at the concentrations tested. Lact. hilgardii 5 was only inhibited by sinapaldehyde and coniferaldehyde. Among the flavonoids, quercetin and kaempferol exerted an inhibitory effect especially on O. oeni VF. Myricetin and the flavan-3-ols studied (catechin and epicatechin) did not affect considerably the growth of both strains. Condensed tannins (particularly tetramers and pentamers) were found to strongly affect cell viability, especially in the case of O. oeni VF. In general, this strain was found to be more sensitive than Lact. hilgardii 5 to the phenolic compounds studied. This work contributes to the knowledge of the effect of different phenolic compounds on the activity of wine lactic acid bacteria, which, especially in the case of aldehydes and of different molecular weight fractions of tannins, is very scarce.     

Removal of metal ions by modified Pinus radiata bark and tannins from water solutions

Pinus radiata bark and tannins, chemically modified with an acidified formaldehyde solution were used for removing metal ions from aqueous solutions and copper mine acidic residual waters. The adsorption ability to different metal ions [V(V), Re(VII), Mo(VI), Ge(IV), As(V), Cd(II), Hg(II), Al(III), Pb(II), Fe(II), Fe(III), Cu(II)] and the factors affecting their removal from solutions were investigated. Effect of pH on the adsorption, desorption, maximum adsorption capacity of the adsorbents, and selectivity experiments with metal ion solutions and waste waters from copper mine were carried out. The adsorbents considerably varied in the adsorption ability to each metal ion. The adsorption depends largely upon the pH of the solution. Modified tannins showed lower adsorption values than the modified bark. For the same adsorbent, the maximum capacity at pH 3 for the different ions were very different, ranging for modified bark from 6.8 meqg⁻¹ for V to 0.93 meqg⁻¹ for Hg. Waste waters were extracted with modified bark as adsorbent and at pH 2. The ions Cu(II) (35.2 mgL⁻¹), Fe(III) (198 mgL⁻¹), Al(III) (83.5 mgL⁻¹) and Cd(II) (0.15 mgL⁻¹) were removed in 15.6%, 46.9%, 83.7% and 3.3%, respectively, by using 1 g of adsorbent/10 mL of waste water. In general, a continuous adsorption on a packed column gave higher adsorbed values than those observed in the batchwise experiment.     

Reassessment of interaction between gut detergents and tannins in lepidoptera and significance for gypsy moth larvae

Surface-active lysophospholipids are thought to interfere with tannin-protein interactions and may comprise an adaptation in Lepidoptera to tannin-rich diets. We found several lysophospholipids and phospholipids at about eight times the critical micelle concentration (CMC) in the midguts of gypsy moth larvae, which exhibited appropriately reduced surface tensions. We confirmed the interfering activity of lysophosphatidylcholine (lysolecithin) in a model astringency assay using tannic acid and hemoglobin (hemanalysis), but discovered that tannic acid and red oak tannin extracts precipitate the lipid from simulated midgut solutions quantitatively, even at pH 10. Leaf tannin extracts from trees on which gypsy moths grew and reproduced poorly precipitated lysolecithin more effectively than did extracts from trees on which gypsy moths performed well. Adding tannic acid to midgut fluid elevated surface tension, and about 25% of larvae feeding on oak leaves exhibited elevated midgut surface tension, suggesting a loss of surfactants. Larvae appear able to replace lost surfactants to a limited degree. An important effect of leaf tannins, and perhaps other phenolics, may be to reduce concentrations of surface-active phospholipids in the midgut and produce lipid or other dietary deficiencies in insects.     

Δ desaturase protein expression and fatty acid composition of longissimus dorsi muscle in lambs fed green herbage or concentrate with or without added tannins

The aims of this study were to investigate the effect of feeding system and of supplementation of tannins (8.93% DM) on the relationship between intramuscular fat content, fatty acid composition and Δ⁹desaturase (Δ⁹d) protein expression in longissimus dorsi muscle of lamb. Twenty-eight Comisana lambs (age 45 days) were fed either vetch (Vicia sativa) or concentrate. The herbage diet was (i) lower in saturated fatty acids (especially in C16:0), C18:1 n−9 and in C18:2 n−6; (ii) higher in C16:1 and C18:3 n−3 when compared to concentrate. Within each feeding system the lambs were divided into two sub-groups, one of which received the diet without tannins supplementation, and the other was fed the diets supplemented with the tannins from Quebracho (Schinopsis lorentzii). The animals were slaughtered at age 105 days. The concentrate feeding system increased (p < 0.01) the total intramuscular fat content and the amount of SFA, MUFA and n−6 PUFA and decreased the level of n−3 PUFA (p = 0.05) when compared to the vetch-fed animals but did not affect Δ⁹ desaturase protein expression. There was no correlation between Δ⁹d protein expression and total intramuscular fatty acids, CLA and MUFA level. It was suggested that in ruminants, in contrast to monogastric animals, Δ⁹d expression does not play the key role in intramuscular fatty acids formation. Tannins supplementation resulted in higher (p < 0.05) muscle levels of transC18:1 and C18:2 n−6. It has also increased Δ⁹d expression in the case of herbage-based diet but not in the case of concentrate-based diet. The mechanism of tannins action on the enzyme expression needs to be elucidated.     

Inhibiting enzymatic starch digestion by hydrolyzable tannins isolated from Eugenia jambolana

Slowing down starch digestion is one method of controlling postprandial hyperglycaemia of diabetes, for which naturally occurring α-amylase inhibitors from edible botanicals have a great potential. We reported herein that Eugenia jambolana, a traditional herbal tea for the treatment of diabetes in South Asia, contains potent α-amylase inhibitors because of monomeric and polymeric hydrolyzable tannins (HT). These compounds demonstrated a dose dependent inhibitory activity against α-amylase (IC₅₀ = 1.1 ± 0.4 μg/mL), which was significantly stronger than acarbose (IC₅₀ = 19.0 ± 2.0 μg/mL). Kinetic studies revealed that the HT were mixed non-competitive inhibitors against α-amylase. Using an in vitro human starch digestion model, incorporation of 0.125 mg/mL HT into a real food system (wheat flour) was effective in delaying enzymatic starch digestion moderately, with a significantly stronger inhibitory effect in the absence of proteins in the food matrix. Pre-incubation of HT with α-amylase prior to substrate addition also significantly enhanced their inhibitory activity. These results provide useful knowledge on HT as potential α-amylase inhibitors, which could potentially alleviate postprandial hyperglycaemia in diabetic patients.     

Failure of tannic acid to inhibit digestion or reduce digestibility of plant protein in gut fluids of insect herbivores

The rate of hydrolysis of the abundant foliar protein, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPC), in enzymatically active gut fluid ofManduca sexta larvae is very rapid and is unaffected by the presence of tannic acid, even when tannic acid is present in the incubation mixture in amounts in excess of the amount of RuBPC. When this protein is dissolved in the denatured gut fluids ofM. sexta larvae orSchistocerca gregaria nymphs, large amounts of tannic acid must be added to bring about the precipitation of significant quantities of protein. The ability of insect gut fluid to prevent the formation of insoluble tannin-protein complexes is due to the presence of surfactants. On the basis of our results and a review of the findings of other investigators, we argue that there is no evidence that tannins reduce the nutritional value of an insect's food by inhibiting digestive enzymes or by reducing the digestibility of ingested proteins and, further, that the failure of tannins to interfere with digestion is readily explained on the basis of well-documented characteristics of the digestive systems of herbivorous insects. In challenging the currently popular notion that tannins are digestibility-reducing substances, we do not challenge the general utility of either the apparency theory or resource availability theory of plant defense. In debating the merits of these two analyses of plant-herbivore interactions, however, the demise of tannins as all-purpose, dose-dependent, digestibility-reducing defensive substances must be taken into account.     

Effect of Processing on Certain Antinutrients in Seeds of Şeker Variety (P. vulgaris L.) Grown in Turkey

Abstract

The effects of different cooking/autoclaving methods were investigated on sucrose, raffinose, stachyose, phytic acid, and tannins content of ?eker bean seeds (Phaseolus vulgaris). All these oligosaccharides and antinutrients decreased under various cooking/autoclaving treatments. Among the different cooking/ autoclaving treatments, 18 h sodium bicarbonate solution soaking followed by autoclaving procedures were the most effective for removing oligosaccharides (65–72%), phytic acid (51%), and tannins (100%). These conditions could be recommended to remove undesirable sugar contents and antinutrients of the ?eker bean used for culinary purposes.     

Protein-precipitating capacity of bearberry-leaf (Arctostaphylos uva-ursi L. Sprengel) polyphenolics

Polyphenolics (PP) from bearberry (Arctostaphylos uva-ursi L. Sprengel) leaves were extracted with 70% (v/v) acetone. The lyophilised crude PP extract was then separated on a Sephadex LH-20 column using first 95% (v/v) ethanol as a mobile phase to elute fraction I low in tannins, and then 50% (v/v) acetone to elute fraction II rich in hydrolysable and condensed tannins. Bovine serum albumin (BSA) was effectively precipitated by PP in the bearberry-leaf crude extract and fraction II at pH values between 3.8 and 4.5. A statistically significant (P = 0.0001) linear relationship exists between the amount of PP-protein complex formed and the quantity of PP added to the reaction mixture. The slope values of these lines indicate that fraction II from the crude extract was a more effective precipitant of proteins than other examined preparations. Based on the quantity of gelatine, fetuin, and BSA required to inhibit 50% of dye-labelled PP–BSA complex precipitation, gelatine was 3–6 times more effective as a precipitation inhibitor than both unlabelled BSA and fetuin.     

Effects of surfactants,pH, and certain cations on precipitation of proteins by tannins

Tannic acid and pin oak tannins precipitate large amounts of the abundant leaf protein, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPC), over a wide pH range (6.15–9.30) in the presence of sodium, potassium, magnesium, and calcium ions at concentrations comparable to those reported in the gut fluids of lepidopteran herbivores. The presence of lysolecithin, a surfactant known to be present in the gut fluids of some insects, significantly reduces the amount of RuBPC precipitated under these conditions. We conclude that high detergency is far more effective than high alkalinity in countering the potential protein-precipitating properties of tannins. We further conclude that tannins do not deserve the status they were once accorded as general, all-purpose, dose-dependent, antidigestive defensive chemicals. We also describe the application of the Schaffner-Weissman protein assay for studying the protein-precipitating capacity of plant extracts. This method is far superior to the one we have used in our earlier studies.     

Characterisation of highly polymerised prodelphinidins from skin and flesh of four cashew apple (Anacardium occidentale L.) genotypes

Tannins were extracted by acetone/water 60:40 from skin and flesh of four cashew apple genotypes from Brazil and Bénin (West Africa), and separated from monomeric phenols. Tannins were submitted to acid-catalysed degradation in the presence of phloroglucinol and the products were analysed by HPLC–DAD/ESI–MS. Both skin and flesh tannins contained high percentages of (-)-epigallocatechin and (-)-epigallocatechin-O-gallate, followed by minor quantities of (-)-epicatechin and (-)-epicatechin-3-O-gallate; 100% of the compounds were the 2,3-cis configuration. Skin tannins were half as galloylated (∼20%) than flesh tannins (∼40%). Their weight-average molecular weight (M_w) was high.