铁皮石斛低温干燥抑制其水溶性多糖的聚合反应

Low-temperature Drying of Dendrobium officinale Inhibit Polymerization of Water-soluble Polysaccharides

本研究旨在探明干燥温度对铁皮石斛中多糖分子结构和抗氧化活性的影响。分别以新鲜铁皮石斛、以及60、100和140℃热风干燥铁皮石斛为实验材料,通过提取和纯化制备水溶性石斛多糖FDOP、60 DOP、100 DOP和140 DOP,然后对石斛多糖进行分子结构分析和抗氧化活性测定。FDOP和60 DOP的还原端含量分别为1.82%、1.70%。然而,100 DOP和140 DOP的还原端含量分别降低至1.42%、1.10%。各铁皮石斛多糖主要由甘露糖和葡萄糖组成,单糖摩尔比与干燥温度之间无明显的关联。随着干燥温度的升高,石斛多糖的分子量分布曲线向大分子量方向偏移。FDOP、60 DOP、100 DOP和140 DOP中分子量103~106 u的多糖组分质量比分别为70.68%、67.70%、62.24%和58.11%。在UV光谱的280 nm处,FDOP、60 DOP、100 DOP没有吸收峰,而140 DOP有吸收峰。分子量103~106 u的多糖组分、还原端较多的铁皮石斛多糖具有较大的自由基清除能力和还原力。在铁皮石斛干燥中,60℃的温度有利于抑制多糖的聚合反应,保持多糖的抗氧化活性。本研究为石斛功能食品的生产及利用提供了技术数据和理论依据。

The present study was carried out to investigate the effects of drying temperature on the molecular structure and antioxidant activity of the polysaccharides in Dendrobium officinale. Four types of water-soluble polysaccharides from D. officinale, i.e., FDOP, 60 DOP, 100 DOP and 140 DOP, were prepared through extraction and purification after hot air drying of fresh D. officinale, and D. officinale at 60 ℃, 100 ℃, 140 ℃, respectively. Molecular structure and antioxidant activity of the polysaccharides from D. officinale were analyzed. It was found that the contents of the reducing end were 1.82% and 1.70% for FDOP and 60 DOP, respectively, but decreased to 1.42% for 100 DOP and 1.10% for 140 DOP. Each D. officinale polysaccharide was composed mainly of mannose and glucose. No obvious correlation was found between drying temperature and the molar ratio of monosaccharides. As the drying temperature increased, the molecular weight distribution curve of D. officinale polysaccharides shifted towards high molecular weight. The mass ratios of the polysaccharide fractions within the molecular weight range of 103~106 u were 70.68%, 67.70%, 62.24% and 58.11%, respectively, for FDOP, 60 DOP, 100 DOP and 140 DOP. At 280 nm of the UV spectra, 140 DOP had an absorption peak whilst FDOP, 60 DOP and 100 DOP hadn’t. The polysaccharide constituents with the molecular weights in the range of 103~106 u and containing more reducing ends showed higher free radical scavenging ability and reducing power. During the drying of Dendrobium officinale, the drying temperature set at 60 ℃ facilitated the suppression of polymerization reaction while retaining the antioxidant activity of its polysaccharides. The present study provides technical data and theoretical basis for the production and utilization of D. officinale-containing functional foods.