A new method has been proposed for enhancing extraction yield of rutin from Sophora japonica, in which a novel ultrasonic extraction system has been developed to perform the determination of optimum ultrasonic frequency by a two-step procedure. This study has systematically investigated the influence of a continuous frequency range of 20-92 kHz on rutin yields. The effects of different operating conditions on rutin yields have also been studied in detail such as solvent concentration, solvent to solid ratio, ultrasound power, temperature and particle size. A higher extraction yield was obtained at the ultrasonic frequency of 60-62 kHz which was little affected under other extraction conditions. Comparative studies between existing methods and the present method were done to verify the effectiveness of this method. Results indicated that the new extraction method gave a higher extraction yield compared with existing ultrasound-assisted extraction (UAE) and soxhlet extraction (SE). Thus, the potential use of this method may be promising for extraction of natural materials on an industrial scale in the future.

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Highlights Flavonoids was extracted from peanut shells using an ultrasound-assisted process. Ultrasound used as intensification tool with highest flavonoids yield of 9.263 mg/g. UAE gave higher yield as compared with that of SE and HRE. Phenomenological model was fitted for kinetic modelling and it’s validation. Comparison of two models have been introduced to describe the extraction kinetic of flavonoids.