The objective was to evaluate the effect of fodder tree species (FTS) with condensed tannin contents: Cordia elaeagnoides, Platymiscium lasiocarpum, Vitex mollis, and Haematoxylon brasiletto, on in vitro methane (CH4) production at 24 h post incubation. The analysis was performed using the in vitro gas production technique, with three levels of inclusion/species: 600, 800, and 1,000 mg and with 4 replicates/species/level of inclusion. The substrate was incubated at 39°C, and the gas and CH4 production were recorded at 4, 8, 12, and 24 h post incubation. The data collected was analyzed through Pearson correlation, polinomial regression and fixed effects models. There were negative correlations between FTS-total gas volume (r = -0.40; p<0.001); FTS-volume of CH4 produced (r = -0.40; p<0.001) and between the inclusion level-volume of CH4 produced (r = -0.20; p<0.001). As well as a positive correlation between hours post incubation-total gas volume (r = 0.42; p<0.001) and between hours post incubation-volume of CH4 produced (r = 0.48; p<0.001). The FTS: C. elaeagnoides, V. mollis, and H. brasiletto have potential, in the three inclusion levels analyzed, to reduce CH4 emission on in vitro trials (>32.7%), taking into account the total CH4 production at 24 h of the forage used as reference (Avena sativa). It’s suggested that C. elaeagnoides-according to its crude protein, neutral detergent fiber, and condensed tannins content- is the best alternative within the FTS analyzed, for feeding ruminants and for the control of CH4 emissions during the dry season.

Lotus pedunculatus (cv. Grasslands Maku) grown on acid low-fertility soil and containing high concentrations of condensed tannin (76-90 g/kg dry matter (DM] was grazed by growing sheep for 31-42 d periods in three experiments. In Expt 2 an additional group of lambs grazed areas oversown with white clover (Trifolium repens) and red clover (Trifolium pratense). Lambs were transferred from grazing ryegrass (Lolium perenne)-white clover straight on to lotus in all experiments (unconditioned sheep). In Expt 3 a second group was included which had grazed high-tannin lotus for a pre-experimental period of 8 weeks (conditioned sheep). Effects of condensed tannin on body and wool growth were assessed by studying responses to daily oral administration of polyethylene glycol (PEG; molecular weight 3350, 75-100 g/d). PEG forms a complex with condensed tannin, which is assumed to be inert in its passage through the digestive system, and so effectively reduces the nutritional effects attributable to high condensed-tannin concentrations. Live-weight gain (LWG) in the absence of PEG was low (27-125 g/d) for sheep grazing high-tannin lotus, and PEG administration increased LWG by 41-61 g/d and increased wool growth. In Expt 3, responses to PEG supplementation tended to be less with conditioned than with unconditioned sheep, indicating that conditioned sheep had partially adapted to the high-tannin diet. PEG supplementation had no effect on either LWG or wool growth of sheep grazing areas oversown with mixed clovers, confirming its effects as specific to forages containing condensed tannins. These experiments therefore conclusively show that high concentrations of condensed tannin induced by growing Lotus pedunculatus under low soil fertility conditions prevent maximum expression of LWG and wool growth in grazing sheep. These results contrast with high LWG (153-315 g/d) observed in growing sheep grazing the same lotus cultivar grown in high fertility soil and containing 20 g condensed tannin/kg DM, a level considered to be nutritionally beneficial.

We applied a taxonomic approach to select the Eugenia dysenterica (Myrtaceae) leaf extract, known in Brazil as “cagaita,” and evaluated its gastroprotective effect. The ability of the extract or carbenoxolone to protect the gastric mucosa from ethanol/HCl-induced lesions was evaluated in mice. The contributions of nitric oxide (NO), endogenous sulfhydryl (SH) groups and alterations in HCl production to the extract’s gastroprotective effect were investigated. We also determined the antioxidant activity of the extract and the possible contribution of tannins to the cytoprotective effect. The extract and carbenoxolone protected the gastric mucosa from ethanol/HCl-induced ulcers, and the former also decreased HCl production. The blockage of SH groups but not the inhibition of NO synthesis abolished the gastroprotective action of the extract. Tannins are present in the extract, which was analyzed by matrix assisted laser desorption/ionization (MALDI); the tannins identified by fragmentation pattern (MS/MS) were condensed type-B, coupled up to eleven flavan-3-ol units and were predominantly procyanidin and prodelphinidin units. Partial removal of tannins from the extract abolished the cytoprotective actions of the extract. The extract exhibits free-radical-scavenging activity in vitro, and the extract/FeCl3 sequence stained gastric surface epithelial cells dark-gray. Therefore, E. dysenterica leaf extract has gastroprotective effects that appear to be linked to the inhibition of HCl production, the antioxidant activity and the endogenous SH-containing compounds. These pleiotropic actions appear to be dependent on the condensed tannins contained in the extract, which bind to mucins in the gastric mucosa forming a protective coating against damaging agents. Our study highlights the biopharmaceutical potential of E. dysenterica.

While the importance of plant secondary metabolites to belowground functioning is gaining recognition, the perception remains that secondary metabolites are produced for herbivore defense, whereas their belowground impacts are ecological by-products, or ‘afterlife’ effects. However, plants invest a significant amount of resources into production of secondary metabolites that have minimal effects on herbivore resistance (e.g. condensed tannins and insect herbivores). We show that genetically mediated variation in condensed tannin concentration is correlated with plant nitrogen recovery following a severe defoliation event. We used single-tree mesocosms labeled with (15) N to track nitrogen through both the frass and litter cycling pathways. High concentrations of leaf tannins in Populus tremuloides were correlated with (15) N recovery from frass within the same growing season and in the following growing season. Likewise, leaf tannin concentrations were also correlated with (15) N recovery from the litter of defoliated trees in the growing season following the defoliation event. Conversely, tannins were not well correlated with nitrogen uptake under conditions of nominal herbivory. Our results suggest that tannins may confer benefits in response to herbivore pressure through conserved belowground nitrogen cycling, rather than via defensive properties. Consequently, tannins may be considered as chemical mediators of tolerance rather than resistance.

© 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Anthelmintic activity of condensed tannins (CT) was evaluated both in vitro and in vivo. In vitro tests included egg hatch test and paralysis/mortality assay on adult Haemonchus contortus. In vivo anthelmintic effect was determined by faecal egg count reduction test in lambs. To this end, 18 lambs were divided into three groups (low tannin, high tannin and control). The lambs of low and high tannin groups were fed diets containing 2 and 3% CT while the control group was fed on diets without CT. In vitro trials showed a dose-dependent inhibition of nematode egg hatching; whereas, there was no effect of CT on adult H. contortus. In vivo trials indicated reduction in faecal egg counts in lambs fed diets containing CT. Feed intake and nutrient digestibility of CT-fed sheep was lower and nitrogen balance was higher as compared to control. Maximum weight gain was observed in animals fed diets containing 3% CT. The direct anthelmintic effect of CT, therefore, was evidenced by inhibited egg hatching; whereas, faecal egg counts reduction in sheep was through improved nutrient utilization.