ChemInform Abstract: OXIDATIVE KUPPLUNG VON PHENOLEN 3. MITT. ISOLIERUNG UND KONSTITUTIONSBEWEIS EINES 8,6′‐VERKNUEPFTEN DEHYDRO‐DICATECHINS (B4)

Abstract

Bei der enzymatischen Dehydrierung von (+)‐Catechin (I) lassen sich Dehydro‐dicatechin A (10%), Dehydro‐dicatechin B1 ‐B4 (C30H26O12) (0,8; 0,2; 0,2 und 1,0%), die Isomere der Procyanidine der Gruppe B sind, sowie Dehydro‐tricatechin (0,2%) isolieren.

Novel Oxidations of (+)-Catechin by Horseradish Peroxidase and Laccase

“…This carbon resonance indicated that the two flavan-3-ol units were joined via an unusual C-2 f C-8′′ carbon-carbon linkage. The chemical shifts of C-6′′ (δ 109.65) and H-6′′ (δ 6.32) of 3 are similar to those in spectra of related ([2′,8]-and [6′,8]-) bis(+)-catechins coupled via their respective B-and A-rings (13,14). These assignments are supported by HMQC and HMBC spectral data.…”

“…HRP oxidation product 4 gave 611.1403, (M + H) + for C 30 H 27 O 14 , by HRFABMS indicating still another catechin dimer. The 1 H and 13 C NMR spectra of 4 were similar to those for 2. A meta-coupled B-ring with signals at δ 6.92 (d, J ) 1.0 Hz, H-2′) and 7.16 (d, J ) 1.0 Hz, H-6′) confirmed a (+)catechin B-ring coupling at C-5′ as in 2.…”

“…IR spectra (cm -1 ) were obtained using a Nicolet 205 FT-IR spectrometer. 1 H and 13 C NMR spectra were obtained with a Bruker NMR 400 (Bruker Instruments, Billerica, MA), operating at 400 MHz ( 1 H) and 100 MHz ( 13 C). DQF-COSY, ROESY, HMBC, and HMQC NMR experiments were carried out using a Bruker AMX-600 high-field spectrometer equipped with an IBM Aspect-2000 processor and with software VNMR version 4.1.…”

“…2 was obtained as a colorless amorphous powder (11.5 mg): [R] 22 D +64.9 (c 1.00, MeOH); UV (MeOH) λmax (log ) 280 (4.52), 330 (4.22) nm; 1 H NMR (acetone-d6, 600 MHz) δ 5.23 (1H, J ) 7.9 Hz, H-2), 4.69 (1H, m, H-3), 2.97 (1H, dd, J ) 16.2, 5.8 Hz, H-4eq), 2.74 (1H, dd, J ) 16.2, 9.2 Hz, H-4ax), 6.19 (1H, d, J ) 2.5 Hz, H-6), 5.98 (1H, d, J ) 2.5 Hz, H-8), 6.96 (1H, d, J ) 1.1 Hz, H-2′), 7.12 (1H, d, J ) 1.1 Hz, H-6′), 5.06 (1H, J ) 7.5 Hz, H-2′′), 4.29 (1H, m, H-3′′), 2.87 (1H, dd, J ) 16.0, 5.7 Hz, H-4′′eq), 2.71 (1H, dd, J ) 16.0, 8.7 Hz, H-4′′ax), 6.29 (1H, s, H-6′′), 7.43 (1H, d, J ) 2.0 Hz, H-2′′′), 7.20 (1H, d, J ) 8.0 Hz, H-5′′′), 7.26 (1H, dd, J ) 8.0, 2.0 Hz, H-6′′′); 13 Lipid Peroxidation in Rat Brain Homogenates. Lipid peroxides produced in rat brain homogenates in the presence of iron were measured by the thiobarbituric acid method (24) with slight modifications.…”

“…Polymers of (+)-catechin are usually formed by couplings between the A-ring of one unit and the B-ring of another in a so-called "head to tail" polymerization process (6). 8-Hydroxy-(+)-catechin (12) and catechin dimers (dehydrodicatechins) were obtained by both H 2 O 2 -dependent peroxidase (13) and chemical oxidation of (+)-catechin under alkaline conditions (14). Structurally, dehydrodicatechins differ from one another by the biphenyl or phenyl ether (C-C or C-O-C) types of linkage, the position of the interflavan linkage, and the relative conformations of biphenyl or biphenyl ether moieties (6).…”