梯度醇沉兰州百合多糖结构及降血糖活性分析

Analysis of the structure and hypoglycemic activity of gradient alcoholic precipitation of Lanzhou lily polysaccharides

摘要:

以兰州百合为原料，采用热水提取和不同体积分数乙醇（30%，50%，70%，80% ）醇沉得到4种兰州百合多糖，分别记为BLP-30、BLP-50、BLP-70和BLP-80。测定BLP-30、BLP-50、BLP-70和BLP-80中可溶性总糖质量分数、蛋白质量分数、糖醛酸质量分数、紫外吸收光谱、单糖组成、相对分子质量等结构表征，运用相关性分析比较多糖对α-淀粉酶和α-葡萄糖苷酶的抑制能力与结构表征的相关性。结果表明，4种兰州百合多糖均不含或含有极少量糖醛酸和蛋白，可溶性总糖质量分数最高的为BLP-80的30.96%。4种多糖为混合多糖，均由甘露糖、葡萄糖和少量半乳糖组成，相对分子质量从BLP-30-1的645 kDa逐渐减小至BLP-70-4的2.45 kDa。其中BLP-30和BLP-50为葡聚糖，BLP-70为半乳甘露葡聚糖，BLP-80为甘露葡聚糖，BLP-30甘露糖、葡萄糖、半乳糖摩尔分数分别为10.18%、88.67%、1.15%；BLP-50甘露糖、葡萄糖、半乳糖摩尔分数分别为2.49%、97.02%、0.49%；BLP-70甘露糖、葡萄糖、半乳糖摩尔分数分别为26.94%、68.21%、4.85； BLP-80甘露糖和葡萄糖摩尔分数分别为41.56%和58.44%，不含半乳糖。4种多糖均具有一定的体外降血糖活性，且呈量效关系，4种多糖对α-淀粉酶和α-葡萄糖苷酶的抑制能力强弱顺序分别为BLP-70＞BLP-80＞BLP-30＞BLP-50和BLP-50＞BLP-70＞BLP-80＞BLP-30。相关性分析显示，4种多糖对α-淀粉酶的抑制能力与甘露糖和半乳糖的摩尔分数呈正相关（P＜0.05），多糖对α-淀粉酶的抑制能力与葡萄糖的摩尔分数呈负相关（P＜0.05）；多糖对α-葡萄糖苷酶的抑制能力与可溶性总糖质量分数、糖醛酸质量分数、甘露糖摩尔分数呈负相关（P＜0.05），多糖对α-葡萄糖苷酶的抑制能力与葡萄糖摩尔分数呈正相关（P＜0.05）。4种兰州百合多糖中BLP-70的体外降血糖活性更强，推测兰州百合多糖的相对分子质量在2~3 kDa之间，甘露糖与葡萄糖物质的量比在n（甘露糖）：n（葡萄糖）=1：2.5之间更有利于兰州百合多糖发挥体外降血糖活性。

Abstract:

Four polysaccharides were obtained by hot water extraction and alcoholic precipitation with different volume fractions of ethanol (30%, 50%, 70% and 80%), and were recorded as BLP-30, BLP-50, BLP-70 and BLP-80 respectively. The structural characterization of the polysaccharides, such as mass fraction of soluble total sugars, protein amount, mass fraction of glyoxylate, UV absorption spectra, monosaccharide composition and relative molecular masses, were determined and correlation analysis was applied to compare the inhibition ability of the polysaccharides against α-amylase and α-glucosidase with the structural characterization. The structural characterisation of total soluble sugars mass fraction, protein quantity fraction, glyoxylate mass fraction, UV absorption spectra, monosaccharide composition and relative molecular mass in BLP-30, BLP-50, BLP-70 and BLP-80 were determined and correlation analysis was applied to compare the inhibition ability of polysaccharides against α-amylase and α-glucosidase with the structural characterisation. The results showed that all four Lanzhou lily polysaccharides contained no or very small amounts of glyoxalate and protein, and the highest total soluble sugar mass fraction was 30.96% for BLP-80. The four polysaccharides are mixed polysaccharides, all consisting of mannose, glucose and a small amount of galactose, with a gradual decrease in relative molecular mass from 645 kDa for BLP-30-1 to 2.45 kDa for BLP-70-4. BLP-30 and BLP-50 are glucans, BLP-70 is galactomannan glucans and BLP-80 is mannoglucan glucans, 0.49%; BLP-70 mannose, glucose and galactose molar fractions were 26.94%, 68.21% and 4.85, respectively; BLP-80 mannose and glucose molar fractions were 41.56% and 58.44%, respectively, without galactose. All the four polysaccharides had certain in vitro hypoglycemic activity and showed a quantitative-effect relationship. The four polysaccharides inhibited α-amylase and α-glucosidase in the following order: BLP-70 > BLP-80 > BLP-30 > BLP-50 and BLP-50 > BLP-70 > BLP-80 > BLP-30, respectively. Correlation analysis showed that the inhibitory ability of the four polysaccharides on α-amylase was positively correlated with the molar fraction of mannose and galactose (P< 0.05), and the inhibitory ability of the polysaccharides on α-amylase was negatively correlated with the molar fraction of glucose (P< 0.05); the inhibitory ability of the polysaccharides on α-glucosidase was negatively correlated with the mass fraction of total soluble sugars, the mass fraction of glyoxylate, and the molar fraction of mannose (P< 0.05), and the inhibitory ability of polysaccharides on α-glucosidase was positively correlated with the molar fraction of glucose (P< 0.05). The in vitro hypoglycaemic activity of BLP-70 was stronger among the four species of Lily of Lanzhou polysaccharides. It is assumed that the relative molecular mass of Lily of Lanzhou polysaccharides is between 2 and 3 kDa, and that the ratio of mannose to glucose is between n (mannose):n (glucose) = 1:2.5, which is more conducive to the in vitro hypoglycaemic activity of Lily of Lanzhou polysaccharides.