Rapid large scale purification of ellagitannins from pomegranate husk, a by-product of the commercial juice industry

Pomegranate (Punica granatum L.)fruits are widely consumed fresh and in processed forms as juice, jams and wine. Pomegranate fruit husk/peel is a rich source of hydrolyzable tannins called ellagitannins (ETs). In the commercial pomegranate juice (PJ)industry, these ETs are extracted from the husk in significant quantities into the juice due to their hydrophilic properties. Pomegranate husk, a by-product of the PJ industry, is therefore an inexpensive and abundant source of ETs. Previous methods to isolate pomegranate ETs included labor intensive and time-consuming solid phase extractions by column chromatography (C-18, polyamides, cellulose, Sephadex Lipophilic LH-20, Diaion HP20)and/or use of specialized instruments such as preparative-high performance liquid chromatography (HPLC). We have used an Amberlite XAD-16 resin vacuum-aspirated column to rapidly purify an aqueous extract of pomegranate husk to afford total pomegranate tannins (TPT)in substantial yields (58-60 g TPT/kg husk; time <1 h). Using analytical HPLC and tandem LC-ES/MS, evaluation of TPT showed that it contains the major fruit husk ET, punicalagin