Isolation and structure elucidation of cistusin: A new ellagitannin from Cistus × incanus L. leaves

Abstract

The leaves of Cistus × incanus L. (pink rock-rose) are used as plant material rich in antioxidants by the pharmaceutical and food industry. The main components which occur in pink rock-rose are polyphenols, especially flavonoids (glycosides of flavonols) and tannins (proanthocyanidins and ellagitannins). Derivatives of flavonols and flavan-3-ols as bioactive compounds of this species were identified previously. However, the full composition of ellagitannins has not been characterized yet. In this context, the study aimed to characterize the chemical composition of pink rock-rose ellagitannins and to identify and elucidate structures of major compounds from this group. In conclusion, the new ellagitannin cistusin together with well-known terflavin A and punicalagin from C. incanus leaves were isolated. Their structures, including the gallagyl, flavogallonyl, valoneoyl, and hexahydroxydiphenoyl acyl groups, were revealed by spectroscopic evidence (HR-ESI-MS, 1D and 2D-NMR).