ABSTRACT
Grape processing by-products (particularly grape pomace) are known to contain high amounts of phenolic compounds. To improve the extraction of phenols from this by-product, it is necessary to develop a method and set and model optimal conditions for their extraction. By applying the design of experiments (DoE) approach, optimal experimental factors of Ultrasound-assisted extraction (USAE) were determined to obtain grape pomace extracts with a satisfactory yield of phenols anthocyanins, as well as extracts with high antioxidant capacity using reagents approved in the food industry. Initial method optimization covered two experimental factors: solvent concentration and the weight ratio of the sample and solvent using fixed USAE conditions from literature. For the final method optimization, the three investigated experimental factors were: pH value, the temperature of extraction, and extraction time. The optimal experimental conditions for the development of the method were 55% ethanol, sample/solvent ratio 1:40, pH 4.5, T 55 °C, and 30 min. Depending on the primary goal of the extraction process (the antioxidant activity, total phenolic content, content of individual phenols, or content of individual anthocyanins), these parameters can easily be modified to obtain the desired recovery. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-021-05317-9.
ABSTRACT
Resveratrol was recognized as the major factor responsible for the beneficial properties of red wine. Several resveratrol-based dietary supplements are available, but their efficacy has not been sufficiently tested. This study was designed to examine the effect of resveratrol supplementation, using a commercially available product, on the metabolic status of experimental animals with induced hyperlipidemia or type 2 diabetes mellitus (T2DM). Hyperlipidemia was induced by feeding the rats a standard pellet diet supplemented with cholesterol. T2DM was induced by adding 10% fructose to drinking water and streptozotocin. Treatment with resveratrol-based supplement improved glycemic control in diabetic animals and significantly decreased serum low-density-lipoprotein (LDL) and triglyceride levels, concurrently increasing the high-density-lipoprotein (HDL) levels in animals with hyperlipidemia. Resveratrol-treated animals had improved tolerance to glucose loading. Supplementation did not induce alterations in parameters of liver and renal function. Findings indicate that commercial resveratrol supplement improves metabolic control in rats with induced hyperlipidemia and T2DM.
