The use of and search for drugs and dietary supplements derived from plants have accelerated in recent years. Ethnopharmacologists, botanists, microbiologists, and natural-products chemists are combing the Earth for phytochemicals and “leads” which could be developed for treatment of infectious diseases. While 25 to 50% of current pharmaceuticals are derived from plants, none are used as antimicrobials. Traditional healers have long used plants to prevent or cure infectious conditions; Western medicine is trying to duplicate their successes. Plants are rich in a wide variety of secondary metabolites, such as tannins, terpenoids, alkaloids, and flavonoids, which have been found in vitro to have antimicrobial properties. This review attempts to summarize the current status of botanical screening efforts, as well as in vivo studies of their effectiveness and toxicity. The structure and antimicrobial properties of phytochemicals are also addressed. Since many of these compounds are currently available as unregulated botanical preparations and their use by the public is increasing rapidly, clinicians need to consider the consequences of patients self-medicating with these preparations.

Plant Products as Antimicrobial Agents

Bacteria that colonize the mammalian intestine collectively possess a far larger repertoire of degradative enzymes and metabolic capabilities than their hosts. Microbial fermentation of complex non...

https://www.tandfonline.com/doi/pdf/10.4161/gmic.19897

Microbial degradation of complex carbohydrates in the gut

Effects and fate of tannins in ruminant animals, adaptation to tannins, and strategies to overcome detrimental effects of feeding tannin-rich feeds

A variety of nutritional management strategies that reduce enteric methane (CH4) production are discussed. Strategies such as increasing the level of grain in the diet, inclusion of lipids and supplementation with ionophores (>24 ppm) are most likely to be implemented by farmers because there is a high probability that they reduce CH4 emissions in addition to improving production efficiency. Improved pasture management, replacing grass silage with maize silage and using legumes hold some promise for CH4 mitigation but as yet their impact is not sufficiently documented. Several new strategies including dietary supplementation with saponins and tannins, selection of yeast cultures and use of fibre-digesting enzymes may mitigate CH4, but these still require extensive research. Most of the studies on reductions in CH4 from ruminants due to diet management are short-term and focussed only on changes in enteric emissions. Future research must examine long-term sustainability of reductions in CH4 production and impacts on the entire farm greenhouse gas budget.

Nutritional management for enteric methane abatement: A review

The effect of condensed tannins on the nutrition and health of ruminants fed fresh temperate forages: a review

Direct microscopic examination of the rumen and its contents shows microbial populations largely attached to feed particles in the digesta Most feeds contain a surface layer that is resistant to attachment and therefore to digestion Infiltration of these recalcitrant epidermal layers through damage sites or through focused enzymatic attack is essential for initiation of the digestive process Proliferation of primary colonizing cells produces glycocalyx-enclosed microcolonies Secondary colonizers from the ruminal fluid associate with microcolonies, resulting in the formation of multispecies microbial biofilms These metabolically related organisms associate with their preferred substrates and produce the myriad of enzymes necessary for the digestion of chemically and structurally complex plant tissues Upon accessing the internal, enzyme-susceptible tissues, microbial "digestive consortia" attach to a variety of nutrients, including protein, cellulose, and starch and digest insoluble feed materials from the inside out Substances that prevent microbial attachment or promote detachment (eg, condensed tannins, methylcellulose) can completely inhibit cellulose digestion As the microbial consortium matures and adapts to a particular type of feed, it becomes inherently stable and its participant microorganisms are notoriously difficult to manipulate due to the impenetrable nature of biofilms Properties of feed that place constraints on microbial attachment and biofilm formation can have a profound effect on both the rate and extent of feed digestion in the rumen Developments in feed processing (ie, chemical and physical), plant breeding, and genetic engineering (both of ruminal microorganisms and plants) that overcome these constraints through the promotion of microbial attachment and biofilm formation could substantially benefit ruminant production

Microbial attachment and feed digestion in the rumen.

Sainfoin leaf condensed tannins inhibited growth and protease activity in Butyrivibrio fibrisolvens A38 and Streptococcus bovis 45S1 but had little effect on Prevotella ruminicola B(1)4 or Ruminobacter amylophilus WP225 Tannins bound to cell coat polymers in all strains Morphological changes in B fibrisolvens and S bovis implicated the cell wall as a target of tannin toxicity

Effects of Sainfoin (Onobrychis viciifolia Scop.) Condensed Tannins on Growth and Proteolysis by Four Strains of Ruminal Bacteria

To identify simple screening tools for selecting condensed tannin (CT)-containing forages as candidate sources for further study, CT were isolated from nine legumes, and their molecular weights (MW), chromophore production, capacity to precipitate bovine serum albumin (BSA) and Fraction 1 protein (Rubisco) isolated from alfalfa, and inhibition of filter paper digestion were compared. Sources were as follows: leaves of sericea lespedeza (Lespedeza cuneata Dum.-Cours.), crown vetch (Coronilla varia L.), and sainfoin (Onobrychis viciifolia Scop.); stems of hedysarum (Hedysarum alpinum L.); seeds of alfalfa (Medicago sativa L.); and whole plants of birdsfoot trefoil (Lotus corniculatus var. corniculatus L.) and three varieties of big trefoil (Lotus pedunculatus Cav.), viz., Lotus uliginosus Schkuhr, L. uliginosus var. glabriusculus, and L. uliginosus var. villosus. Molecular weights and sizes (degrees of polymerization) of the CT varied considerably within and among plant species. Average MW ranged from 3036 Da (crown vetch) to 7143 Da (lespedeza). All CT exhibited greater capacity (w/w basis) to bind alfalfa Rubisco than BSA. Relative astringencies (μg CT required to precipitate 1 mg protein) against BSA ranged from 262.5 for CT from lespedeza to 435.5 for CT from L. corniculatus, and against Rubisco, from 49.6 (sainfoin) to 108.2 (alfalfa seed). Including CT at 300 μg/ml in cultures of Fibrobacter succinogenes reduced digestion of cellulose filter paper by 19.8% (sainfoin) to 92.4% (crown vetch) and increased the specific activity of cell-associated endoglucanase. There were no correlations between inhibitory effects of CT on filter paper digestion and (1) chromophore formation during CT assay by butanol–HCl, vanillin–HCl, or H2SO4; (2) precipitation of BSA or alfalfa Rubisco; and (3) MW of CT. The most inhibitory CT for cellulose digestion included those with broad and with narrow MW distributions. Sainfoin was the most desirable source of CT, as it had the highest capacity to bind alfalfa protein and was least inhibitory to cellulose digestion by F. succinogenes. This study suggests that these properties are not easily defined via chemical means, and that biological assays using rumen bacteria may help identify those CT with properties of nutritional interest.

Characterization of condensed tannins purified from legume forages: chromophore production, protein precipitation, and inhibitory effects on cellulose digestion.

The effects of sainfoin (Onobrychis viciifolia) on digestion of alfalfa (Medicago sativa) were investigated in vitro and in vivo. Fresh alfalfa and sainfoin were incubated in an artificial rumen (Rusitec) in ratios of 100:0, 75:25, 50:50, 25:75 and 0:100 (as-fed). Disappearances of dry matter and N from sainfoin were 77 and 65% of those from alfalfa, respectively. Protease and endoglucanase activities, NH3-N and methane production declined (P   0.05), but cells incorporated more 15NH3N as sainfoin in the diet increased. Chopped leaves (100:0, 95:5 and 90:10 alfalfa:sainfoin) were incubated for 48 h with diluted ruminal fluid containing 0 or 50 mg polyethylene glycol, which binds tannins. Gas and volatile fatty acid productions were similar (P > 0.05) across treatments, but including 10% sainfoin (without polyethylene glycol) reduced (P < 0.05) NH3 concentrations between 8 and 24 h. Sainfoin tannins reduced degradation...

Effect of sainfoin on in vitro digestion of fresh alfalfa and bloat in steers

Beef was packaged under CO2 containing < 500 ppm O2 (MAP), vacuum, or air and stored at 0, 2, or 4°C Samples were analyzed weekly for bacterial numbers using anaerobic plate count (pre-reduced medium and anaerobic chamber), -aerobic plate count, and anaerobic jar plate count (MAP samples only) methods For both MAP and vacuum packaged samples, the anaerobic plate count was consistently greater than the aerobic plate count and for MAP samples the anaerobic plate count was consistently higher than the anaerobic jar plate count Differences between plating methods were most frequent during the latter third of 0 and 2°C storage Anaerobic isolates from MAP samples were most often lactic acid cocci and staphylococci No clostridia were isolated from any of the treatments

G. A. Jones

Papers

Microbial attachment and feed digestion in the rumen.

Effects of Sainfoin (Onobrychis viciifolia Scop.) Condensed Tannins on Growth and Proteolysis by Four Strains of Ruminal Bacteria

Characterization of condensed tannins purified from legume forages: chromophore production, protein precipitation, and inhibitory effects on cellulose digestion.

Effect of sainfoin on in vitro digestion of fresh alfalfa and bloat in steers

Anaerobic microbiology of fresh beef packaged under modified atmosphere or vacuum