Microwave-Assisted Extraction of Condensed Tannins from Branches of Prunus spinosa L.: Response Surface Modeling and Optimization

The present study was conducted in order to investigate the parameters influencing the extraction of condensed tannins from branches of Prunus spinosa L. as a source of biomass, using a two-level factorial design. The extraction of condensed tannins was performed using microwave assisted-extraction (MAE)-a green technique to produce concentrated and pure extracts. Experimental tests were run to establish the effects of independent variables on the extraction of condensed tannins (expressed as catechin and epicatechin), which were quantified using high-performance thin-layer chromatography-densitometry. Four process variables were evaluated: ethanolic solvent concentration (% v/v) (30, 70), liquid-to-solid ratio (mL/g) (6:1, 10:1), extraction time (min) (2, 5) and microwave power (W) (400, 600). The significant influencing parameters were liquid-to-solid ratio and solvent concentration. The maximum content of condensed tannins (3.4 mg g(-1) catechin and 3.45 mg g(-1) epicatechin) was obtained using 70% v/v ethanol, 10:1 liquid-to-solid ratio, 5 min of extraction time and 600 W microwave power. MAE is beneficial for increasing the amounts of the targeted compounds.