Optimization of Antioxidant Flavonoids Extraction From <i>Helianthus annuus</i> L. Ray Florets for Cardioprotective Nutraceuticals

The aim of this study was to investigate the ultrasound-assisted extraction (UAE) of antioxidant flavonoids from sunflower (Helianthus annuus) ray florets through the optimization of the parameters (temperature, extraction ratio, and solvent concentration) using a response surface methodology (RSM), then to validate the model conducting wet-lab analyses, and finally, to characterize the optimized extracts for composition and in vitro cardioprotective potential. Within RSM, the parameters of UAE were optimized by maximization of the response variables yield of flavonoid extraction and Trolox equivalent antioxidant capacity. Two optimal solutions obtained in 73% ethanol, at 30:1 (v/w) extraction ratio and 80°C (extract 1') and in 77% ethanol, at 12:1 (v/w) extraction ratio and 40°C (extract 2') were validated. HPLC analysis revealed that rutin and myricetin were the main flavonoids in both optimized extracts and slightly higher amounts were quantified in extract 2'. In addition, extract 2' presented higher free radical scavenging activity and angiotensin-converting enzyme (ACE) inhibition than extract 1'. Both extracts were cytocompatible in an endothelial cell culture, in a wide range of concentrations (31.25-500 µg/mL) and stimulated the cell metabolism, after 24 h of cultivation. Optimized extract 2' containing flavonoids from sunflower ray florets with antioxidant properties and cardioprotective potential was also a solution of interest for the bioeconomy, due to less consuming extraction conditions. This extract could be recommended for further testing as a valuable ingredient of novel cardioprotective nutraceuticals.