Physicochemical properties, in vitro release and skin permeation studies of a topical formulation of standardized pomegranate rind extract

The aim of the present study was to develop a stable formulation containing standardized pomegranate rind extracts (SPRE) for topical use in the treatment of dermal diseases. Ellagic acid (EA) as the major active constituent of SPRE (not less than 13%) was quantified by HPLC as an indicator for studies on the stability, in vitro drug release, and skin penetration/retention. The formulation prepared with polyethylene glycols (PEG 400 and PEG 4000) containing 5% SPRE has been found to be stable and provide a release rate of 36.6741±5.0072 μg/cm2/h that was best fitted to the zeroorder kinetic model. EA from SPRE did not penetrate the full-thickness rat skin but the skin retention of EA was determined to be 2.22±0.16 μg/cm2 with a total recovery of 95.14±5.51%. The results indicated that this 5% SPRE PEG ointment was of satisfactory physicochemical properties and worth further in vivo investigations.