Preparation of Juglans nigra L. husk extracts by applying an ultrasonic-assisted extraction method and process optimization of minerals extraction using response surface methodology

Abstract

The aims of this research were preparation of Juglans nigra husk extracts by employing an ultrasonic-assisted extraction method and process optimization of minerals extraction using response surface methodology. Extracts from J. nigra L. fresh husk were prepared using ethanol (70%, v/v) as a solvent, at different extraction temperatures: 15, 30 and 40 °C, and extraction times: 5, 15, 30, 60 and 80 min. The content of minerals in ethanol extracts was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The response surface methodology (RSM) was developed to evaluate the effect of two extraction factors as well as to optimize the extraction variables for each mineral individually. The RSM models pointed out 40 °C temperature and extraction time in the range 77–80 min as optimal conditions for extraction of macro- and micro-elements. Results of RSM optimization showed the relative order of maximum obtained yield of macro-elements: K>P>S>Ca>Mg and maximum yield of micro-elements was Si>Zn>Sr>Cu.