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Title: Phytochemical analysis of a willow germplasm collection and its pharmacological activities
Author: Klongsiriwet, Chaweewan
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2016
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Willow (Salix spp.) is a rich source of naturally occurring bioactive compounds. This study focussed specifically on exploring the condensed tannins (CT) in the National Willow Collection, which is a unique germplasm collection held at Rothamsted Research. Willow leaves were analysed by two different tannin methods, thiolysis and acid-butanol-acetone, in order to evaluate their suitability for assessing inter-accession variation and to identify accessions with a potential medicinal use. This is the first report of the tannin contents and compositions of a willow germplasm collection. Large variations were found for tannin contents, i.e. 2.8 to 19.5 g CT/100 g dry weight, and also for composition; mean degrees of polymerisation (mDP) ranged from 4.9 to 12.0, the procyanidin (PC)/prodelphinidin (PD) ratios from 19.1/80.9 to 52.0/48.0 and the cis/trans flavan-3-ol ratios from 13.0/87.0 to 52.1/47.9. Catechin was the major terminal unit and gallocatechin the major extension unit, which clearly distinguishes willow tannins from most other plant tannins. Interestingly, some accessions also had leaves with relatively unusual CT types, i.e. high mDP-values and high molar pcercentages of trans-flavan-3-ols. Cluster analysis succeeded in allocating several accessions into distinct groups that coincided with Salix breeding populations. This study has now laid the foundation for identifying the Salix tannin genome in the future. Given the time-comsuming nature of two tannin analysis methods. This study also evaluated the potential of Near-Infrared Spectroscopy (NIRS), which a much faster method, for predicting CT contents and compositions in these willow leaves. The results confirmed that NIRS is an excellent tool for estimating CT contents, PC/PD and c/s/frans-flavan-3-ol ratios in willow leaves. This finding could be of interest to plant breeders in developing new willow accessions. The final part of the thesis evaluated the antiparasitic potential of willow leaves against an intestinal parasite. CT with contrasting compositions were purified to test their efficacy against Haemonchus contortus, which is a major gastrointestinal parasite of livestock. As expected PD- were more active than PC-tannins. In addition, this study demonstrated for the first time that the PC activity could be synergistically enhanced by some Salix flavonoids.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available