Development and validation of ultrasound-assisted solid-liquid extraction of phenolic compounds from waste spent coffee grounds

•Spent coffee grounds (SCG) are a valuable source of phenolic compounds.•First time phenolic compounds were recovered from SCG by USLE method.•Influence of extraction parameters over the extraction yield was studied using BBD.•Ultrasound acts unswervingly on the SCG to release phytochemicals.•Optimum condition for maximum extraction of phenolic compounds was determined. In this current work, Box-Behnken statistical experimental design (BBD) was adopted to evaluate and optimize USLE (ultrasound-assisted solid-liquid extraction) of phytochemicals from spent coffee grounds. Factors employed in this study are ultrasonic power, temperature, time and solid-liquid (SL) ratio. Individual and interactive effect of independent variables over the extraction yield was depicted through mathematical models, which are generated from the experimental data. Determined optimum process conditions are 244W of ultrasonic power, 40°C of temperature, 34min of time and 1:17g/ml of SL ratio. The predicted values were in correlation with experimental values with 95% confidence level, under the determined optimal conditions. This indicates the significance of selected method for USLE of phytochemicals from SCG.