Optimization of ultrasound-assisted extraction of antioxidant phenolics from Capparis spinosa flower buds and LC–MS analysis

The proposed mathematical model allowed to predict total polyphenols (TP) yields and antioxidant activity (AA) of the extracts in a wide range of experimental conditions: time ( t ) (0–240 min), ultrasound power ( US ) (0–100 W), ethanol concentration ( S ) (0–50% ethanol in water) and temperature ( T ) (20–60 °C). Optimization for TP predicted that the best results was obtained at T = 60 °C, S = 50% ethanol, US = 100 W and t = 240 min which was 39.96 mg GAE/g dm. Simulations were made also for the antioxidant activity; optimization predicted that highest antioxidant activity should be obtained at T = + 1, S = + 1, US = + 0.1 at 240 min, corresponding to 116.1 µmol TE/g dm. Both experimental and model results showed that presence of ethanol in the solvent enhanced incredibly the extraction productivity. Temperature effect was positive, but less pronounced. In addition, the phenolic profile of Capparis spinosa (caper) extracts was investigated by liquid chromatograph coupled to mass spectrometer (LC-DAD-ESI–MS). The quercetin-3-rutinoside was the major flavonoid in C. Spinosa flower buds extract, followed by quercetine rhamnoside and kaempferol rhamnoside.