College of Life Science and Technology, Heilongjiang Bayi Agricultural Univ., Daqing, 163319, P.R. China.
Academy of State Administration of Grain, Beijing, 100037, P.R. China.
J Food Sci. 2018 Jul;83(7):1948-1955. doi: 10.1111/1750-3841.14148. Epub 2018 Jun 25.
Rice bran polysaccharides (RBPSs) are the major active constituents of rice bran (RB). In this study, we utilized intracellular enzymes from Grifola frondosa to modify RBPSs, which were extracted from RB using ultrasound. To enhance the effect on natural killer (NK) cell cytotoxicity of modified polysaccharides (mRBPSs) generated from RBPSs, an orthogonal test (L [3] ) was employed to optimize the modification conditions. Based on the results of a single-factor test, the enzyme to polysaccharide ratio, reaction temperature, reaction pH, and reaction time were the main factors affecting mRBPSs-enhanced NK-cell cytotoxicity. The best conditions were determined to be an enzyme to polysaccharide ratio of 1:5, a reaction temperature of 40 °C, a reaction pH of 4, and a reaction time of 4 hr. By optimizing the conditions, the NK-cell cytotoxicity induced by mRBPSs was the highest, increasing by 12.01% ± 0.08%. Gas chromatographic analysis revealed that mRBPSs consists of rhamnose, arabinose, xylose, mannose, glucose, and galactose at a molar ratio of 7:21:6:5:53:48, which was 8:13:8:5:44:44 before modification. High-performance liquid chromatography results indicated molecular weights for the RBPSs of approximately 10 Da, which decreased to 10 to 10 Da after modification. Antioxidant activity tests revealed high capacity of mRBPSs for scavenging 1,1-diphenyl-2-picrylhydrazyl radicals and hydroxyl free radicals at 1.0 mg/mL.
Rice bran polysaccharides (RBPSs) contain compounds with many biological activities. However, these polysaccharides difficult to absorb due to high molecular weights and unexposed active sites, which are the main factors that limit their use in functional foods. The results of this study demonstrate that modification of RBPSs using intracellular enzymes from an edible fungus alters the molecular weights and monosaccharide composition of RBPSs. In addition, immune and antioxidant activities of RBPSs were increased. The findings provide a new and beneficial application for rice bran.
米糠多糖（RBPSs）是米糠（RB）的主要活性成分。在这项研究中，我们利用糙皮侧耳（Grifola frondosa）的细胞内酶来修饰从米糠中用超声提取的 RBPSs。为了增强修饰多糖（mRBPSs）对自然杀伤（NK）细胞细胞毒性的作用，我们采用正交试验（L [3] ）来优化修饰条件。基于单因素试验的结果，酶与多糖的比例、反应温度、反应 pH 和反应时间是影响 mRBPSs 增强 NK 细胞细胞毒性的主要因素。最佳条件确定为酶与多糖的比例为 1:5、反应温度为 40°C、反应 pH 为 4 和反应时间为 4 小时。通过优化条件，mRBPSs 诱导的 NK 细胞细胞毒性最高，增加了 12.01%±0.08%。气相色谱分析表明，mRBPSs 由鼠李糖、阿拉伯糖、木糖、甘露糖、葡萄糖和半乳糖组成，摩尔比为 7:21:6:5:53:48，修饰前为 8:13:8:5:44:44。高效液相色谱结果表明，RBPSs 的分子量约为 10 Da，修饰后降低至 10 至 10 Da。抗氧化活性测试表明，mRBPSs 在 1.0 mg/mL 时对 1,1-二苯基-2-苦基肼自由基和羟基自由基的清除能力很强。
米糠多糖（RBPSs）含有多种具有生物活性的化合物。然而，由于这些多糖的分子量高且暴露的活性位点少，导致它们难以吸收，这是限制其在功能性食品中应用的主要因素。本研究结果表明，使用食用真菌的细胞内酶修饰 RBPSs 会改变 RBPSs 的分子量和单糖组成。此外，RBPSs 的免疫和抗氧化活性也得到了提高。研究结果为米糠提供了一种新的有益应用。
