title: In situ analysis and structural elucidation of sainfoin (Onobrychis viciifolia) tannins for high-throughput germplasm screening.
abstract: A rapid thiolytic degradation and cleanup procedure was developed for analyzing tannins directly in chlorophyll-containing sainfoin ( Onobrychis viciifolia ) plants. The technique proved suitable for complex tannin mixtures containing catechin, epicatechin, gallocatechin, and epigallocatechin flavan-3-ol units. The reaction time was standardized at 60 min to minimize the loss of structural information as a result of epimerization and degradation of terminal flavan-3-ol units. The results were evaluated by separate analysis of extractable and unextractable tannins, which accounted for 63.6-113.7% of the in situ plant tannins. It is of note that 70% aqueous acetone extracted tannins with a lower mean degree of polymerization (mDP) than was found for tannins analyzed in situ. Extractable tannins had between 4 and 29 lower mDP values. The method was validated by comparing results from individual and mixed sample sets. The tannin composition of different sainfoin accessions covered a range of mDP values from 16 to 83, procyanidin/prodelphinidin (PC/PD) ratios from 19.2/80.8 to 45.6/54.4, and cis/trans ratios from 74.1/25.9 to 88.0/12.0. This is the first high-throughput screening method that is suitable for analyzing condensed tannin contents and structural composition directly in green plant tissue.
authors.affiliation: Chemistry and Biochemistry Laboratory, Department of Agriculture, University of Reading, 1 Earley Gate, Post Office Box 236, Reading RG6 6AT, United Kingdom.
authors.forename: An
authors.initials: A
authors.lastname: Gea
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Stringano
authors.forename: Ron H
authors.initials: RH
authors.lastname: Brown
authors.forename: Irene
authors.initials: I
authors.lastname: Mueller-Harvey
mesh_terms: D007887:Fabaceae / Q000737:chemistry*; D055993:Germ Cells, Plant / Q000737:chemistry; D057166:High-Throughput Screening Assays / Q000379:methods*; D015394:Molecular Structure; D010936:Plant Extracts / Q000737:chemistry*; D013634:Tannins / Q000737:chemistry*
chemical_list: D010936:Plant Extracts; D013634:Tannins