Key Laboratory of New Animal Drug Project of Gansu Province, Key Laboratory of Veterinary Pharmaceutical Development of Ministry of Agriculture, Lanzhou Institute of Husbandry and Pharmaceutical Sciences, Chinese Academy of Agricultural Sciences, Lanzhou 730050, China.
College of Food Science and Engineering of Gansu Agricultural University, Lanzhou 730070, China.
Ultrason Sonochem. 2017 Sep;38:246-255. doi: 10.1016/j.ultsonch.2017.03.021. Epub 2017 Mar 10.
In this study, we aimed to optimize the extraction of polysaccharides from the leaves of Rhododendron aganniphum and investigate its rheological properties and antioxidant activity. After optimizing the operating parameters using a Box-Behnken design (BBD), the results showed that the optimal ultrasound-assisted extraction conditions were as follows: extraction temperature, 55°C; liquid-solid ratio, 25:1; extraction time, 2.2h; and ultrasound treatment power, 200W. The optimized experimental yield of polysaccharides by ultrasound-assisted extraction (PUAE) was 9.428%, higher than that obtained by hot water extraction (PHWE) for 12h at the same liquid-solid ratio and extraction temperature. In the in vitro antioxidant activity tests, PUAE had higher positive radical scavenging activity for hydroxyl, superoxide and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals than PHWE. However, PUAE and PHWE solutions had similar intermolecular interactions in the steady-shear flow and dynamic viscoelasticity tests, resulting in similar macroscopic behaviour. With respect to the apparent viscosity, storage modulus (G') and loss modulus (G″) of PUAE were lower at the same shear rate or angular frequency. All PUAE solutions exhibited non-Newtonian shear-thinning pseudoplastic behaviour that was accurately described by the Carreau model but was better fit by the power-law model at high shear rates (≥1/s), which demonstrated that the variation in the apparent viscosity dependence was greater at higher concentrations and shear rates. The G' and G″ of the solutions increased as the experimental frequency increased from 0.05 to 500rad/s under all experimental concentrations, and the modulus crossover point decreased gradually with increasing PUAE concentration. The above results demonstrated that the ultrasound-assisted extraction methods gave a higher yield of polysaccharides from the leaves of R. aganniphum with a shorter extraction time than the hot water extraction method, which could affect the apparent viscosity and dynamic viscoelasticity. PUAE presented good radical scavenging activity for DPPH, superoxide and hydroxyl radicals in vitro and could be used as a natural antioxidant in the food and medical industries.
在这项研究中，我们旨在优化从宽钟杜鹃叶中提取多糖的方法，并研究其流变性质和抗氧化活性。通过 Box-Behnken 设计（BBD）优化操作参数后，结果表明，超声辅助提取的最佳条件为：提取温度 55°C，液固比 25:1，提取时间 2.2h，超声处理功率 200W。超声辅助提取（PUAE）优化实验多糖得率为 9.428%，高于相同液固比和提取温度下热水提取（PHWE）12h 的得率。在体外抗氧化活性测试中，PUAE 对羟基自由基、超氧自由基和 1,1-二苯基-2-苦基肼基（DPPH）自由基的正自由基清除活性均高于 PHWE。然而，在稳态剪切流和动态粘弹性测试中，PUAE 和 PHWE 溶液具有相似的分子间相互作用，导致宏观行为相似。就表观粘度而言，在相同剪切速率或角频率下，PUAE 的储能模量（G'）和损耗模量（G″）较低。所有 PUAE 溶液均表现出非牛顿剪切稀化假塑性行为，该行为可以通过 Carreau 模型准确描述，但在较高剪切速率（≥1/s）下，幂律模型拟合得更好，这表明在较高浓度和剪切速率下，表观粘度的变化更大。在所有实验浓度下，当实验频率从 0.05 增加到 500rad/s 时，溶液的 G'和 G″均增加，并且随着 PUAE 浓度的增加，模量交叉点逐渐降低。上述结果表明，与热水提取方法相比，超声辅助提取方法从宽钟杜鹃叶中提取多糖的产率更高，提取时间更短，这可能会影响表观粘度和动态粘弹性。PUAE 对 DPPH、超氧自由基和羟基自由基具有良好的体外清除自由基活性，可作为食品和医药工业中的天然抗氧化剂。
