Extraction optimization of oleanolic and ursolic acids from pomegranate (Punica granatum L.) flowers

An ecofriendly ultrasonic-assisted extraction (UAE) technique was developed for rapid extraction of bioactive compounds oleanolic and ursolic acids from pomegranate flowers. Several different influential extraction parameters, such as ultrasonic power, extraction time, solvent type, aqueous ethanol concentration, loading ratio and extraction temperature, were investigated. The optimum extraction conditions were 90% ethanol solution as solvent, ultrasound power 150 W, the liquid:material ratio of 20:1 (v/w) and extraction for 50 min at 40 °C. Scanning electron microscopy showed that ultrasonic treatment resulted in a number of pits on cells of pomegranate flowers. Extracts obtained from 30 min of UAE showed higher antioxidant activity than those of other conventional methods. The UAE method was more efficient than classical methods included maceration, stirring extraction and heat reflux extraction.

► Oleanolic acid in pomegranate flowers were ultrasound-assisted extracted (UAE).
► Several different influential extraction parameters were studied.
► Extracts from UAE show higher antioxidant activity than those of other methods.
► Compared with the classical methods, UAE method was shown to be higher efficiency.