College of Life Sciences, Key Laboratory of Specialty Agri-Product Quality and Hazard Controlling Technology of Zhejiang Province, China Jiliang University, Hangzhou, Zhejiang Province, 310018, P.R. China.
Int J Med Mushrooms. 2023;25(6):55-73. doi: 10.1615/IntJMedMushrooms.2023048271.
The cell wall of Auricularia auricula fruit bodies is extremely tough, making it difficult to dissolve the melanin using the traditional preparation method. To investigate the efficient preparation of melanin and its resistance to oxidative stress, this paper first used ultrasound-assisted alkaline cellulase to optimize the optimal wall-breaking parameters through a Box-Behnken design based on a single-factor experiment. After optimization, the yield of melanin from A. auricula reached 3.201 ± 0.018%. Then, different types and different proportions of deep eutectic solvents (DES) were used for further extraction. When choline chloride and urea were selected and the ratio was 1:2, the melanin yield was up to 25.99% ± 2.36%. Scanning electron microscope (SEM) images showed that the melanin was amorphous mass with no crystal structure. X-ray photoelectron spectroscopy (XPS) analysis revealed that the melanin was mainly composed of C (5.38%), O (15.69%) and N (30.29%), as was the typical composition of eumelanin. The melanin had a concentration-dependent relationship with both ABTS+ and hydroxyl radical scavenging ability; at the concentration of 0.5 mg/mL, it significantly prolonged Caenorhabditis elegans survival under hydrogen peroxide and methyl viologen stress and increased the glutathione level and enzyme (total superoxide dismutase and catalase) activities in vivo compared with the negative control (P < 0.05), indicating that the melanin enhances oxidative stress resistance in C. elegans.
银耳子实体的细胞壁非常坚韧，用传统的制备方法很难溶解黑色素。为了研究黑色素的有效制备及其抗氧化应激能力，本文首先采用超声辅助碱性纤维素酶，通过单因素实验的基础上，利用 Box-Behnken 设计优化了最佳破壁参数。优化后，银耳黑色素的产率达到 3.201 ± 0.018%。然后，进一步使用不同类型和不同比例的深共熔溶剂（DES）进行提取。当选择氯化胆碱和尿素，且比例为 1:2 时，黑色素的产率高达 25.99% ± 2.36%。扫描电子显微镜（SEM）图像显示，黑色素为无定形块状，无晶体结构。X 射线光电子能谱（XPS）分析表明，黑色素主要由 C（5.38%）、O（15.69%）和 N（30.29%）组成，这是真黑色素的典型组成。黑色素对 ABTS+和羟基自由基清除能力均具有浓度依赖性；在 0.5mg/mL 浓度下，与阴性对照相比，它显著延长了秀丽隐杆线虫在过氧化氢和甲基紫精胁迫下的存活时间，并增加了体内谷胱甘肽水平和酶（总超氧化物歧化酶和过氧化氢酶）活性（P < 0.05），表明黑色素增强了秀丽隐杆线虫的抗氧化应激能力。
