Abstract/Summary

Proanthocyanidins (PA) in some forage legumes have been linked to contradictory effects in animal health and nutrition. Ruminants fed with PA-containing plants do not suffer from bloat and can also reduce gastrointestinal parasite infections, improve protein use efficiency and reduce greenhouse gas emissions. Plants have a wide range of PA contents and compositions. Therefore, screening tools are required to determine the optimal contents and types to exploit PA bioactivities on farms. This research initially focused on the identification and isolation of PAs with contrasting characteristics from various plant species. These samples were then used to develop novel methods such as UPLC-ESI-MS/MS and 13C HSQC NMR for extractable PAs and 13C CPMAS NMR for PAs within plants, and to probe structure-activity relationships. These PAs were also subjected to complementary analytical methods, which demonstrated that depolymerisation techniques can provide quantitative information on PA contents and compositions and mass spectrometric techniques on molecular distributions. These analyses revealed an enormous range of molecular profiles. This diversity, however, led to good but not excellent correlations between the degradation methods. It also affected mass spectrometric and liquid-state NMR responses. In particular, there were some discrepancies between thiolysis-HPLC and UPLC-ESI-MS/MS results of sainfoin PA extracts. For solid-state NMR, the PAs from model plants proved too homogeneous for the analysis of the highly complex PAs in sainfoin plants. Nevertheless, this method could rank accessions on the basis of PA composition and discriminated between plant organs via signature spectra. Therefore, final decisions on which of these methods to use will depend on the research objectives and sample numbers. Finally, anti-parasitic assays discovered that the in vitro exsheathement inhibition of the abomasal parasite, Haemonchus contortus was dependent on the average molecular size of purified PA mixtures. In addition, collaborative studies showed that prodelphinidins or PA size also affected some anti-parasitic and ruminal fermentation results.