Publications (4)4.31 Total impact
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Article: The influence of plant polyphenols on lipolysis and biohydrogenation in dried forages at different phenological stages: in vitro study.
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ABSTRACT: It is known that forage legumes show a higher transfer efficiency of polyunsaturated fatty acids (PUFA) to ruminant dairy products in comparison with grasses. Legumes are usually characterised by moderate levels of plant secondary metabolites, which can have an effect on lipolysis and biohydrogenation in the rumen. An in vitro study was carried out to compare two species with different plant phenol compositions, Vicia sativa (VS, common vetch, cv. Jose) and Trifolium incarnatum (TI, crimson clover, cv. Viterbo) cut at the vegetative (Veg) and reproductive (Rep) stages, on lipolysis and PUFA biohydrogenation in the rumen. The study showed that forage species and phenological stage affected the levels of bound phenols (BP) and tannic polyphenols (TP). VS was characterised by a higher level of TP than TI at both Veg and Rep stages, whereas BP levels were low in both forages. BP and TP had a negative effect on lipolysis and biohydrogenation, but TP showed a greater negative correlation than BP for both forages. These results showed that lipolysis and biohydrogenation of PUFA could be affected by plant phenols, particularly TP.Journal of the Science of Food and Agriculture 04/2010; 90(5):829-35. · 1.44 Impact Factor -
Article: Immunogold labelling to localize polyphenol oxidase (PPO) during wilting of red clover leaf tissue and the effect of removing cellular matrices on PPO protection of glycerol-based lipid in the rumen.
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ABSTRACT: The enzyme polyphenol oxidase (PPO) reduces the extent of proteolysis and lipolysis within red clover fed to ruminants. PPO catalyses the conversion of phenols to quinones, which can react with nucleophilic cellular constituents (e.g. proteins) forming protein-phenol complexes that may reduce protein solubility, bioavailability to rumen microbes and deactivate plant enzymes. In this study, we localized PPO in red clover leaf tissue by immunogold labelling and investigated whether red clover lipid was protected in the absence of PPO-induced protein-phenol complexes and plant enzymes (lipases). PPO protein was detected to a greater extent (P < 0.001) within the chloroplasts of mesophyll cells in stressed (cut/crushed and wilted for 1 h) than freshly cut leaves for both palisade (61.6 and 25.6 Au label per chloroplast, respectively) and spongy mesophyll cells (94.5 and 40.6 Au label per chloroplast, respectively). Hydrolysis of lipid and C18 polyunsaturated fatty acid biohydrogenation during in vitro batch culture was lower (P < 0.05) for wild-type red clover than for red clover with PPO expression reduced to undetectable levels but only when cellular matrices containing protein-phenol complexes were present. Damaging of the leaves resulted in over a doubling of PPO detected within mesophyll cells, potentially as a consequence of conversion of the enzyme from latent to active form. PPO reduction of microbial lipolysis was apparent in macerated red clover tissue but not in the absence of the proteinaceous cellular matrix, suggesting that the PPO mechanism for reducing lipolysis may be primarily through the entrapment of lipid within protein-phenol complexes.Journal of the Science of Food and Agriculture 02/2010; 90(3):503-10. · 1.44 Impact Factor -
Article: Polyphenol oxidase activity in grass and its effect on plant‐mediated lipolysis and proteolysis of Dactylis glomerata (cocksfoot) in a simulated rumen environment
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ABSTRACT: Little is known about the level or activity of polyphenol oxidase (PPO) in grasses and its potential impact on proteolysis and lipolysis. Six grass species were initially screened for PPO activity (740.6, 291.9, 213.6, 119.0, 16.3 and 6.5 U g−1 fresh weight (FW) for cocksfoot, hybrid ryegrass, Italian ryegrass, perennial ryegrass, timothy and tall fescue respectively). Cocksfoot, which expressed the highest activity, was then used to determine the effect of PPO on plant-mediated proteolysis and lipolysis in a simulated rumen environment. Sourced cocksfoot was macerated and incubated in an antibiotic-containing anaerobic medium with or without ascorbate to deactivate PPO in the dark at 39 °C over five time points. At each time point (0, 1, 2, 6 and 24 h), six replicate samples were destructively harvested; three of the replicates were used for lipid analysis and the other three for protein, free amino acid and bound phenol determination. Characterisation of the herbage showed PPO activities of 649.6 and 0 U g−1 FW, which were reflected in the extent of phenol (derived from quinones) binding to protein after 24 h of incubation, namely 65.1 and 29.6 mg bound phenol g−1 protein (P < 0.001) for cocksfoot and cocksfoot + ascorbate respectively. Proteolysis, measured as free amino acids released into the incubation buffer, was significantly reduced (P < 0.001) with increasing PPO activity, with values after the 24 h incubation of 0.03 and 0.07 mmol L−1 g−1 FW for cocksfoot and cocksfoot + ascorbate respectively. Lipolysis, measured as the proportional decline in the membrane lipid polar fraction, was likewise reduced (P < 0.001) with increasing PPO activity, with values after the 24 h incubation of 0.43 and 0.65 for cocksfoot and cocksfoot + ascorbate respectively. Changes that occurred in protein and the lipid fractions (polar fraction, monoacylglycerol + diacylglycerol, triacylglycerol and free fatty acids) during the incubations are also reported and discussed. These results support the selection of forages high in PPO activity to reduce protein and lipid losses in silo and potentially in the rumen. Copyright © 2006 Society of Chemical IndustryJournal of the Science of Food and Agriculture 08/2006; 86(10):1503 - 1511. · 1.44 Impact Factor -
Article: Ruminal micro-organisms do not adapt to increase utilization of poly-phenol oxidase protected red clover protein and glycerol-based lipid.
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ABSTRACT: BACKGROUND: The enzyme polyphenol oxidase (PPO) reduces the extent of proteolysis and lipolysis within red clover fed to ruminants with subsequent increases in the efficiency of N utilization and the level of beneficial polyunsaturated fatty acids in their products (meat and milk). It has also been reported that red clover feeding alters the rumen microbial population compared to grass feeding. This study investigated whether the observed shifts in the microbial population of the rumen when ruminants are fed red clover silage (RC) as opposed to grass silage (G) represented an adaptation by the micro-organisms to increase the utilization of PPO-protected protein and glycerol-based lipid.RESULTS: The experiment consisted of two periods where ruminally fistulated dairy cows were offered either RC or G for 2 weeks, followed by collection of rumen fluid, which was then used in in vitro incubations to investigate lipolysis and proteolysis over time in plant material derived from red clover plants with either wild type PPO expression (PPO+) or PPO expression reduced to undetectable levels by gene silencing (PPO-). Proteolysis and lipolysis (P < 0.05) were lower after 24 h of incubation in the PPO+ treatment than the PPO- treatment irrespective of rumen fluid. Biohydrogenation of C18 polyunsaturated fatty acids was also lower on the PPO+ treatment than the PPO- treatment, with no effect of rumen fluid.CONCLUSION: These results suggest that microbial changes to red clover feeding did not result in an increased ability of the micro-organisms in the present study to utilize either PPO-protected protein or glycerol-based lipid.
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Institutions
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2010
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Aberystwyth University
- Institute of Biological, Environmental and Rural Sciences
Aberystwyth, WLS, United Kingdom -
Agris Sardegna
Sardagna, Trentino-Alto Adige, Italy
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