Cytinus hypocistis (L.) L.: Optimised heat/ultrasound-assisted extraction of tannins by response surface methodology

Abstract Tannins are a class of phenolic compounds commonly found in plants and studied for their bioactive and inhibitory enzyme properties. Cytinus hypocistis (L.) L. is a wild edible parasitic plant whose biological properties have been correlated with its high tannin content. Thus, studying the extraction of tannins from C. hypocistis will give comprehensive clues to enhance the recovery of these high added-value bioactive compounds. The present work applied Response Surface Methodology (RSM) to optimise tannins extraction using Heat-Assisted (HAE) and Ultrasound-Assisted (UAE) methods. Two three-factor Rotatable Central Composite Designs were used to assess the linear, quadratic, and interaction effects of the independent variables on the target responses. The obtained results from both extraction systems revealed high ethanol percentages as the critical factor in increasing tannin content. The optimum global processing conditions predicted by the polynomial models were 95.1 min, 46.4 °C, and 74.3% ethanol for HAE; and 18.7 min, 327.4 W, and 69.3% ethanol for UAE. Following these conditions, 200 mg and 178 mg of total tannins per g of extract were recovered using HAE and UAE, correspondingly. Although HAE presented a higher final response, the UAE stood out as a time-saving technique.