Polyoxyethylene glycol ethers of fatty alcohols used in cloud point extraction of Viola tricolor: Polyphenols solubilization, antioxidant activity studies and molecular dynamic simulations

The following paper proposes a modern method of obtaining an extract from Viola tricolor L. with a high rutin content and enhanced antioxidant activity. Conventional isolation of active substances from plant raw material is high-cost, elaborate and often harmful to the environment. The ultrasonic assistance micelle-mediated extraction method (UAMME) and the cloud-point extraction/separation technique are interesting alternatives. This work discusses the relationship between salt concentration and the cloud-point extraction (CPE) yield. The molecular dynamic simulations investigated the impact of hydrocarbon chain length and the ratio of oxyethylene/oxypropylene units of model surfactants on the interactions between extraction system components. Micellar extract from the Viola tricolor was obtained using C9-11 Pareth-5 at 1 wt/vol% and subsequently concentrated by CPE with the addition of NaCl in concentrations from 5% to 30%. For comparison, water and ethanol extracts were also prepared. Antioxidant properties, polyphenols and flavonoid contents were measured for all samples. The HPLC method was used to determine the rutin concentration. The simulation part of the study confirmed the dependence of bioflavonoid solubilization efficiency on the surfactant structure. The determined descriptors allowed for finding the optimal structure of the model surfactants and gave a hint for their application to obtain extracts with high concentrations of antioxidants.