Optimisation of ultrasound assisted extraction of phenolic compounds from Sparganii rhizoma with response surface methodology

► Ultrasound-assisted extraction was used for the phenolic compounds extraction from sparganii rhizome. ► Response surface methodology was used to optimise the process variables. ► Six phenolic compounds were identified by comparing relative retention times and UV–Vis spectra with those of reference standards. ► Ultrasound-assisted extraction has a strong potential as a method for the extraction of phenolic compounds from this material. The present study reports on the extraction of phenolic compounds from sparganii rhizome. Box–Behnken Design (BBD), a widely used form of response surface methodology (RSM), was used to investigate the effect of process variables on the ultrasound-assisted extraction (UAE). Three independent variables including ethanol concentration (%), extraction time (min) and solvent-to-material ratio (mL/g) were studied. The results showed that the optimal UAE condition was obtained with an ethanol concentration of 75.3%, an extraction time of 40min and a solvent-to-material ratio of 19.21mL/g for total phenols, and an ethanol concentration of 80%, an extraction time of 33.54min and solvent-to-material ratio of 22.72mL/g for combination of ρ-hydroxybenzaldehyde, ρ-coumaric acid, vanillic acid, ferulic acid, rutin and kaempferol. The experimental values under optimal conditions were in good consistent with the predicted values, which suggested UAE is more efficient process as compared to solvent extraction.