- Isolation and structure elucidation of tetrameric procyanidins from unripe apples (Malus pumila cv. Fuji) by NMR spectroscopy
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Procyanidins are plant secondary metabolites widely consumed and known to have various physiological functions, but their bioavailability and mechanism of action are still unclear especially for larger oligomers. One of the reasons is scarce information about the detailed structure of oligomeric procyanidins. As for apple, structures of procyanidin components larger than trimers are scarcely known. In this study, 11 tetrameric procyanidins including two known compounds were isolated from unripe apples (Malus pumila cv. Fuji) and identified by NMR spectroscopic analysis and phloroglucinol degradation. As a result, the detailed structural diversity of tetrameric procyanidins in apple was established.
- Nakashima, Shohei,Oda, Chihiro,Masuda, Susumu,Tagashira, Motoyuki,Kanda, Tomomasa
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p. 144 - 152
(2012/11/13)
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- Structural identification and distribution of proanthocyanidins in 13 different hops
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Ten newly isolated hop proanthocyanidin oligomers and flavan-3-ol monomers from 13 different hops have been identified as gallocatechin, gallocatechin-(4α→8)-catechin, gallocatechin-(4α→6)- catechin, catechin-(4α→8)-gallocatechin, catechin-(4α→6)- gallocatechin, afzelechin-(4α→8)-catechin, catechin-(4α→8) -catechin-(4α→8)-catechin, epicatechin-(4β→8)-epicatechin- (4β→8)-catechin, catechin-(4α→8)-gallocatechin- (4α→8)-catechin, and gallocatechin-(4α→8)-gallocatechin- (4α→8)-catechin, together with seven previously isolated oligomers, namely, catechin, epicatechin, epicatechin-(4β→8)-catechin, epicatechin-(4β→8)-epicatechin, catechin-(4α→8)-catechin, catechin-(4α→8)-epicatechin, and epicatechin-(4β→8)- catechin-(4α→8)-catechin. These compounds were subjected to acid-catalyzed degradation in the presence of phloroglucinol or by partial or complete acid-catalyzed degradation and reaction with benzyl mercaptan followed by desulfurization. The resultant adducts when compared to authentic samples by high-performance liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry and high-performance liquid chromatography-electrospray ionization tandem mass spectrometry served to identify the precursors. The composition of proanthocyanidins from 13 different hops was similar, but the concentration of individual compounds showed some differences, which indicated that hop proanthocyanidin profiles are affected by geographic origin and are variable depending on the cultivars.
- Li, Hui-Jing,Deinzer, Max L.
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p. 4048 - 4056
(2007/10/03)
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- Synthesis of Condensed Tannins. Part 1. Stereoselective and Stereospecific Syntheses of Optically Pure 4-Arylflavan-3-ols, and Assessment of their Absolute Stereochemistry at C-4 by means of Circular Dichroism
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Stereoselective and also stereospecific condensation at C-4 of flavan-3,4-diols of known absolute configuration with phloroglucinol and resorcinol in acid medium proceeds at ambient temperatures with partial retention of configuration for 2,3-trans-isomers and with inversion for 2,3-cis-analogues.Circular dichroism spectra of the resultant 4-arylflavan-3-ols all exhibit multiple Cotton effects.The sign of high intensity Cotton effects to low wavelength, contributed by aryl chromophores at C-4, may almost invariably be correlated with the absolute configuration at this chiral centre of 2,3-trans-3,4-trans, 2,3-trans-3,4-cis, and 2,3-cis-3,4-trans-isomers.
- Botha, Jacobus J.,Young, Desmond A.,Ferreira, Daneel,Roux, David G.
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p. 1213 - 1219
(2007/10/02)
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