Abstract
An ultrasound-assisted extraction (UAE) method was developed for the efficient extraction of natural antioxidants from the flowers of Jatropha integerrima. Four independent variables, including ethanol concentration, solvent/material ratio, ultrasound irradiation time and temperature were studied by single factor experiments. Then, the central composite rotatable design and response surface methodology were employed to investigate the effect of three key parameters (ethanol concentration, solvent/material ratio, and ultrasound irradiation time) on the antioxidant activities of the flower extracts. The optimal extraction conditions were an ethanol concentration of 59.6%, solvent/material ratio of 50:1, ultrasound irradiation time of 7 min, and ultrasound irradiation temperature of 40 °C. Under these conditions, the optimized experimental value was 1103.38 ± 16.11 µmol Trolox/g dry weight (DW), which was in accordance with the predicted value (1105.49 µmol Trolox/g DW). Furthermore, the antioxidant activities of flower extracts obtained by UAE were compared with those produced by the traditional maceration and Soxhlet extraction methods, and UAE resulted in higher antioxidant activities after a shorter time at a lower temperature. The results obtained are helpful for the full utilization of Jatropha integerrima, and also indicate that ultrasound-assisted extraction is an efficient method for the extraction of natural antioxidants from plant materials.
Highlights
Antioxidants play an important role in preventing or slowing down autoxidation in biological systems and food, and have attracted much attention [1]
The results indicate that natural antioxidants from Jatropha integerrima reached an equilibrium of desorption and solubility at 40 ̋ C, and some thermally unstable antioxidants from the flowers could be decomposed at higher temperature [21,30]
According to the single factor experiment results, an ethanol concentration of 50% (v/v), solvent/material ratio of 40:1, and ultrasound irrdiation time of 15 min were chosen as the central condition of the central composite experiment design, and the effects of three independent variables on the dependent variable (TEAC value) at five levels were investigated
Summary
Antioxidants play an important role in preventing or slowing down autoxidation in biological systems and food, and have attracted much attention [1]. Naturally-occurring antioxidants in plants like flavonoids and phenolic acids are an important part of the human diet, and are of considerable interest due to their capacity for scavenging free radicals like superoxide anion radical and hydroxyl radical, which can cause several diseases, such as cancer, arteriosclerosis, autoimmune and neurodegenerative syndromes [2,3,4,5,6]. Natural antioxidants from herbs and spices could preserve the quality of food products from chemical oxidation and lipid rancidity as more safety and healthy additives compared with synthetic ones [1,6,7]. Evaluation, extraction, separation and purification of natural antioxidants are very important. Effective extraction of antioxidants from plant materials is very helpful for full utilization of natural resources.
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