超声波-微波联合辅助提取澳洲坚果青皮多糖工艺优化及其抗氧化活性

研究分析了澳洲坚果不同果实部位的多糖提取率。以澳洲坚果青皮为原料，采用超声波-微波联合辅助法提取多糖，运用单因素实验与正交实验考察了微波功率、提取时间、料液比、超声温度4个因素对多糖提取率的影响，研究其最优提取条件。以VC为对照，通过测定澳洲坚果青皮多糖清除1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl，DPPH）、羟基自由基的能力与还原力评价其抗氧化活性。结果表明：澳洲坚果不同果实部位中，青皮的多糖提取率最高。澳洲坚果青皮多糖超声波-微波联合辅助提取工艺中各因素对提取率的影响力排序为提取时间>料液比>超声温度>微波功率，且其均达到了极显著水平（P＜0.01），最佳提取工艺条件为：提取时间90 min、超声温度65 ℃、料液比1:25（g/mL）、微波功率400 W，在此条件下提取率达到1.96%。澳洲坚果青皮多糖的抗氧化活性与质量浓度呈良好的极显著正相关（P＜0.01），相关系数R分别为0.9707、0.9813、0.9912，具有较强的DPPH、羟基自由基清除能力和较高的还原力，其半抑制浓度（half maximal inhibitory concentration，IC50）分别为38.55、20.38、41.51 μg/mL，相同浓度下略低于VC。研究结果为澳洲坚果青皮的综合利用和青皮多糖产品的进一步开发提供一定的理论依据。

Process Optimization of Ultrasonic/microwave-assisted Extraction and Antioxidant Activity of Polysaccharide from Macadamia Green Husk

The yield of polysaccharides from macadamia green husk, shell and kernel were conducted, respectively. The extraction of polysaccharide from macadamia green husk by ultrasonic/microwave-assisted extraction was optimized using one-factor and orthogonal array design methods, the effects of microwave power, extraction time, solid-to-liquid ratio and ultrasonic temperature on the yield were explored. The scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals, and reducing power were investigated by comparing with vitamin C as control. Results showed that the yield of polysaccharides from macadamia green husk was the highest in the different parts of Macadamia nut fruit. Extraction time, solid-to-liquid ratio, ultrasonic temperature and microwave power all had highly significant effects on extraction yield (P<0.01), and these factors could be ranked in decreasing order of significance: extraction time, solid-to-liquid ratio, ultrasonic temperature and microwave power. The optimal extraction conditions were determined as follows: extraction time, 90 min; ultrasonic temperature, 65 ℃; solid-to-liquid ratio, 1:25 (g/mL); microwave power, 400 W. Under these conditions, the yield of polysaccharide from macadamia green husk was up to 1.96%. Macadamia green husk polysaccharide showed concentration dependent antioxidant activities (P<0.01), their correlation coefficients were 0.9707, 0.9813 and 0.9912, respectively, and had strong scavenging capacities against DPPH and hydroxyl radicals and reducing power with half maximal inhibitory concentration (IC50) of 38.55, 20.38 and 41.51 μg/mL, respectively, which were better than vitamin C at the same concentration. The results could provide some theoretical reference for the comprehensive utilization of macadamia green husk and the further development of macadamia green husk polysaccharide products.