超声辅助热水提取对铁皮石斛水溶性多糖得率和结构的影响

Effects of ultrasonic-assisted hot water extraction on the yield and structure of water soluble polysaccharides from Dendrobium officinale

为建立铁皮石斛水溶性多糖超声辅助热水提取法,本文比较了常温和热水提取体系中超声辅助提取对‘圣兰8号’铁皮石斛(Dendrobium officinale)水溶性多糖得率及其分子结构的影响。结果表明:超声辅助提取显著提高了铁皮石斛水溶性多糖得率,并使提取时间从2 h缩短至3 min;超声辅助-热水提取(95～100℃)可进一步提高得率,其中500 W超声3 min的效果最佳。凝胶渗透色谱结果显示,超声辅助提取的多糖多分散度显著增高。‘圣兰8号’铁皮石斛水溶性多糖由甘露糖、葡萄糖、半乳糖、阿拉伯糖、鼠李糖、木糖、葡萄糖醛酸和半乳糖醛酸组成,提取方法对多糖红外光谱和单糖组成无明显影响。铁皮石斛水溶性多糖具有刚果红结合能力,超声辅助提取不改变其与刚果红的结合特性。将500 W超声辅助-热水提取方法应用于13个铁皮石斛品种水溶性多糖的提取,发现茎中水溶性多糖质量分数在69.40～130.10 g/kg之间(按鲜质量计),叶片中则在15.30～34.10 g/kg之间(按鲜质量计),品种间存在较大差异。

Dendrobium officinale is an edible medicinal plant with polysaccharides as its important bioactive components. This study investigated the effects of ultrasonic-assisted extraction on the yield of D. officinale 'Shenglan No. 8'water soluble polysaccharides as well as the influence to the molecular structure. The results showed that ultrasonic-assisted methods significantly increased the yield of polysaccharides and shortened the extraction time from 2 h to 3 min. The highest extraction efficiency was obtained in the ultrasonic-assisted hot water synergetic extraction (500 W, 95-100 ℃, 3 min). The results of gel permeation chromatography (GPC) showed that the D. officinale polysaccharides through ultrasonic-assisted extraction were with higher polydispersity (PDI). The water soluble polysaccharides from D. officinale'Shenglan No. 8'were composed of mannose, glucose, galactose, arabinose, rhamnose, xylose, glucuronic acid and galacturonic acid. No significant difference was observed on the infrared spectrum and monosaccharide composition among the different extraction methods. The D. officinale polysaccharides had certain congo red-binding ability, which was not affected by the ultrasonic treatments. The optimum extract parameters (500 W, 95-100 ℃, 3 min) was applied in the comparison of polysaccharide content among 13 cultivars. The polysaccharide content varied among the cultivars and tissues, with a range of 69.40-130.10 g/kg fresh mass in the stem, and a range of 15.30-34.10 g/kg fresh mass in the leaf.