Optimisation of Extraction and Identification of Gallotannins from Sumac Leaves

The extraction of gallotannins from sumac leaves (Rhus coriaria L.) was studied and the best extraction conditions were found to be maceration of the ground leaves in water at 45°C for 60 min without agitation. A full-scale pilot extraction plant with four vessels was designed to simulate a counter-current procedure. Water was added always to the vessel containing the almost fully extracted sumac leaves. At 8 h intervals, the concentrated extract was collected and the spent material was discarded; fresh sumac leaves were then introduced into the system. The tannin content of the extracts were mainly measured by complexing them with a collagen protein matrix (hide-powder assay). The extract constituents were analysed using normal-phase high-performance liquid chromatography, where eight polygalloyl glucose components were identified. The higher the molecular weight of the extract components the greater its retention with the hide powder.