Isolation of two new bioactive proanthocyanidins from Cistus salvifolius herb extract

Two new proanthocyanidins, epigallocatechin-3-O-p-hydroxybenzoate-(4 beta -> 8)-epigallocatechin (1) and epigallocatechin-3-O-p-hydroxybenzoate-(4 beta -> 8)-epigallocatechin-3-O-gallate (2) in addition to the known compound epigallocatechin-(4 beta -> 6)-epigallocatechin-3-O-gallate (3), were isolated from the air-dried herb of Cistus salvifolius. The chemical structures were determined on the basis of 1 D-and 2D-NMR-spectra (HSQC, HMBC) of their peracetylated derivatives, MALDI-TOF-mass spectra, and by acid-catalysed degradation with phloroglucinol. The isolated compounds 1-3 and the water extract of C. salvifolius herb were tested for their inhibitory activities against COX-1 and COX-2. Compound 2 showed the strongest inhibitory effect on COX-2 followed by compound 3, compound 1 and the water extract, while compounds 1-3 exhibited moderate in vitro inhibition against COX-1.