title: ¹H-¹³C HSQC NMR spectroscopy for estimating procyanidin/prodelphinidin and cis/trans-flavan-3-ol ratios of condensed tannin samples: correlation with thiolysis.
abstract: Studies with a diverse array of 22 purified condensed tannin (CT) samples from nine plant species demonstrated that procyanidin/prodelphinidin (PC/PD) and cis/trans-flavan-3-ol ratios can be appraised by (1)H-(13)C HSQC NMR spectroscopy. The method was developed from samples containing 44-∼100% CT, PC/PD ratios ranging from 0/100 to 99/1, and cis/trans ratios ranging from 58/42 to 95/5 as determined by thiolysis with benzyl mercaptan. Integration of cross-peak contours of H/C-6' signals from PC and of H/C-2',6' signals from PD yielded nuclei-adjusted estimates that were highly correlated with PC/PD ratios obtained by thiolysis (R(2) = 0.99). cis/trans-Flavan-3-ol ratios, obtained by integration of the respective H/C-4 cross-peak contours, were also related to determinations made by thiolysis (R(2) = 0.89). Overall, (1)H-(13)C HSQC NMR spectroscopy appears to be a viable alternative to thiolysis for estimating PC/PD and cis/trans ratios of CT if precautions are taken to avoid integration of cross-peak contours of contaminants.
authors: U.S. Dairy Forage Research Center, Agricultural Research Service, U.S. Department of Agriculture , 1925 Linden Drive West, Madison, Wisconsin 53706, United States.
authors: Wayne E
authors: WE
authors: Zeller
authors: Aina
authors: A
authors: Ramsay
authors: Honorata M
authors: HM
authors: Ropiak
authors: Christos
authors: C
authors: Fryganas
authors: Irene
authors: I
authors: Mueller-Harvey
authors: Ronald H
authors: RH
authors: Brown
authors: Chris
authors: C
authors: Drake
authors: John H
authors: JH
authors: Grabber
mesh_terms: D044946:Biflavonoids / Q000737:chemistry*; D002392:Catechin / Q000737:chemistry*; D005419:Flavonoids / Q000737:chemistry*; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D010936:Plant Extracts / Q000737:chemistry*; D010944:Plants / Q000737:chemistry*; D044945:Proanthocyanidins / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D044946:Biflavonoids; D005419:Flavonoids; D010936:Plant Extracts; D044945:Proanthocyanidins; D013438:Sulfhydryl Compounds; C013221:proanthocyanidin; C404987:flavan-3-ol; C017674:procyanidin; D002392:Catechin
keywords: NMR; condensed tannins; nuclear magnetic resonance spectroscopy; proanthocyanidins; procyanidins; prodelphinidins; thiolysis