Two new proanthocyanidin trimers isolated from <i>Cistus incanus</i> L. demonstrate potent anti-inflammatory activity and selectivity to cyclooxygenase isoenzymes inhibition

<p>Two new proanthocyanidin trimers have been isolated from <i>Cistus incanus</i> herb; gallocatechin-(4α→6)-gallocatechin-(4α→8)-gallocatechin (compound <b>1</b>) and epigallocatechin-3-O-gallate-(4ß→8)-epigallocatechin-3-O-gallate-(4ß→8)-gallocatechin (compound <b>2</b>). The structures were determined on the basis of 1D- and 2D-NMR (HSQC, HMBC) of their peracetylated derivatives, MALDI-TOF-MS and by acid-catalysed degradation with phloroglucinol. A more abundant proanthocyanidin oligomer was also isolated, purified and its chemical constitution studied by ¹³C-NMR and phloroglucinol degradation. The mean molecular weight of the polymer was estimated to be about 7 to 8 flavan-3-ol-units with a ratio of procyanidin : prodelphinidin units at 1:5, some of which are derivatised by gallic acid. Water extract and higher oligomeric proanthocyanidin fractions of <i>C. incanus</i> significantly inhibited TPA-induced oedema when applied topically at doses of 0.5 and 1 mg/ear in mice. Furthermore, the extracts and the pure compounds inhibited COX-1 and COX-2 activities. In addition, compound <b>2</b> exhibited an IC₅₀ of 4.5 μM against COX-2 indicating its high selectivity towards COX-2.</p

1H–13C HSQC NMR Spectroscopy for Estimating Procyanidin/Prodelphinidin and cis/trans-Flavan-3-ol Ratios of Condensed Tannin Samples: Correlation with Thiolysis

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 1H–13C 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 (R2 = 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 (R2 = 0.89). Overall, 1H–13C 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