Sainfoin proanthocyanidins (PAs) are complex mixtures of homo- and hetero- polymers consisting of B-type procyanidins and prodelphinidins. Direct analysis by thiolytic degradation revealed a wide range of PA contents and compositions within the HealthyHay germplasm collection (46 accessions). PA contents varied from 0.57% to 2.80% (g PAl100g freeze-dried samples). PAs polymer size ranged from 12 to 84 flavan-3-ol units in terms of their mean degree of polymerisation. Prodelphinidin/procyanidin ratios ranged from 53/47 to 95/5 and trans/cis ratios varied from 12/88 to 34/66. Purified PAs fractions from 4 selected accessions showed a positive correlation between polymer size and prodelphinidin content within each accession (R2 from 0.69 to 0.92). Careful selection of MALDI-TOF MS matrices and analytical conditions made it possible to detect PAs up to 12 subunits and also ion signals that could be assigned to A-type and rarely reported glycosylated A-type PAs. For detecting and confirming the polymer size of underivatised higher molecular weight PAs a new HPLC-GPC technique consisting in a single calibration curve for galloyl glucoses, ellagitannins and PAs was developed. Peak-average molecular weights of sainfoin PA fractions were overestimated by 42.0% at 2436 Dalton and underestimated by 13.9% at 8318 Dalton. Number-average molecular weights were overestimated by 30.0% and underestimated by 25.8%, respectively. Cluster analysis of the HealthyHay germplasm collection revealed that accessions clustered into two main clusters, Western Europe and Eastern Europe/Asia, and that accessions from Armenia, Canada and USA clustered into another group. This seems to be in agreement with the strong links between geographic origin and accession performance found in the HealthyHay sainfoin germplasm. This research made significant contributions to the fields of PA analysis and germplasm screening in terms of novel analytical techniques for determining the average molecular weight distribution, content, subunit composition and linkages, purification and fractionation of proanthocyanidins in sainfoin.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:553034 |
| Date | January 2011 |
| Creators | Stringano, Elisabetta |
| Publisher | University of Reading |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
Page generated in 0.0017 seconds