Antioxidant oligomeric proanthocyanidins from Cistus salvifolius

The purified proanthocyanidin oligomers of Cistus salvifolius herb extract accounted for 78% of the total proanthocyanidins and 73% of the total antioxidant activity of this extract [1]. To elucidate the structure of the oligomer, it was depolymerized by acid catalysis in the presence of phloroglucinol [2]. The structures of the resulting flavan-3-ols and phloroglucinol adducts were determined on the basis of 1D-and reverse 2D-NMR (HSQC, HMBC) experiments of their peracetylated derivatives, MALDI-TOF-MS and CD- spectroscopy [3]. These observations resulting from the degradation with phloroglucinol were confirmed by 13 C-NMR spectroscopy of the oligomer (4). The mean molecular weight of the higher oligomeric fraction was estimated to be 5–6 flavan-3-ol-units. Acknowledgment s: F Qa'dan would like to acknowedge gratefully the DAAD and the Deanship of Research at the University of Petra for funds and grants (Grant No.1/5/2002). We wish to acknowlege also the help of Dr.H.Lahl, Ms.M.Heim (Inst.f. Pharmazeutische Chemie, Münster) and Dr. Brian Lockwood (School of Pharmacy, Manchester) for the NMR-spectra. References : 1. Al-Khalil, S. (1995), Int. J. Pharmacognosy 33(4): 317–323. 2. Kennedy, J.A., Graham, P.J. (2001), J. Agric. Food Chem. 49:1740–1746. 3. Balas, L., Vercauteren, J. (1994), Magn. Reson. Chem. 32: 386–393. 4. Eberhardt, T., Young, R.A. (1994), J. Agric. Food Chem. 42: 1704–1708.