title: A study of the structure-activity relationship of oligomeric ellagitannins on ruminal fermentation in vitro.
abstract: The aim of this study was to investigate how the degree of oligomerization of ellagitannins (ET) influences their ability to alter ruminal fermentation. Dimeric to heptameric ET were isolated from rosebay willowherb (Epilobium angustifolium) flowers and purified. Ellagitannins were tested in vitro on a mixture of grass silage and buffered rumen fluid. Total gas production was measured in real time using an automated pressure evaluation system. Methane production was monitored at regular interval by gas chromatography for 72h. The effect of ET was evaluated on 2 sources of rumen fluid using a randomized block design. Ammonia nitrogen, volatile fatty acid concentration, and pH were measured at the end of the experiment. Results show that oligomeric ET decreased gas production and total volatile fatty acid concentration proportionally to their degree of oligomerization. Methane production was also decreased by all the tested compounds and dimer was less effective than the larger ET, which showed similar levels of activity. Additionally, willowherb's oligomeric ET decreased ammonia-nitrogen and branched-chain volatile fatty acid concentrations, thus indicating reduced protein degradation by ruminal bacteria. This effect showed a quadratic relationship with the degree of oligomerization and was maximal with the tetramer. In conclusion, this study shows that the degree of oligomerization of ET has more than a simple linear effect on fermentation parameters in vitro. Large oligomers, in fact, have more detrimental effects on volatile fatty acid and gas production than small ones, while being similarly effective at inhibiting methane production.
authors: Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, Turku FI-20014, Finland. Electronic address: nicolas.baert@utu.fi.
authors: Nicolas
authors: N
authors: Baert
authors: Animal Nutrition Group, Department of Animal Sciences, Wageningen University, PO Box 338, NL-6700 AH Wageningen, the Netherlands.
authors: Wilbert F
authors: WF
authors: Pellikaan
authors: Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, Turku FI-20014, Finland.
authors: Maarit
authors: M
authors: Karonen
authors: Laboratory of Organic Chemistry and Chemical Biology, Department of Chemistry, University of Turku, Turku FI-20014, Finland.
authors: Juha-Pekka
authors: JP
authors: Salminen
mesh_terms: D000641:Ammonia / Q000032:analysis; D000818:Animals; D002417:Cattle; D005232:Fatty Acids, Volatile / Q000032:analysis; D005285:Fermentation; D000069196:Gastrointestinal Microbiome; D006863:Hydrogen-Ion Concentration; D047348:Hydrolyzable Tannins / Q000494:pharmacology*; D008697:Methane / Q000378:metabolism; D015394:Molecular Structure; D006109:Poaceae / Q000737:chemistry; D012417:Rumen / Q000187:drug effects* / Q000378:metabolism / Q000382:microbiology; D012820:Silage / Q000032:analysis; D013329:Structure-Activity Relationship
chemical_list: D005232:Fatty Acids, Volatile; D047348:Hydrolyzable Tannins; D000641:Ammonia; D008697:Methane
keywords: gas production technique; methane; structure-activity relationship; willowherb