目的 从香菇子实体中分离纯化得到精制香菇多糖，并对其结构和体外抗肿瘤活性进行研究。方法 采用碱提-醇沉法提取香菇粗多糖，并通过脱色、超滤分离纯化得到精制香菇多糖，命名为LNT₂。苯酚-硫酸法测定总糖量，高效凝胶色谱法测定相对分子质量，紫外光谱检测蛋白质和核酸，旋光度实验测定比旋光度。综合运用酸水解、高碘酸氧化、甲基化等化学分析法和傅里叶红外光谱、核磁共振光谱等光谱分析法对LNT₂的化学结构进行分析；通过刚果红实验对LNT₂的糖链构象进行考察；采用四甲偶氮唑盐（MTT）比色法测定LNT₂对小鼠肝腹水瘤H₂₂细胞增殖的抑制率。结果 经测定香菇多糖LNT₂为均一组分多糖，其相对分子质量（M_W）为1.852×10⁵、含糖量为94.99%，比旋光度为+8.03°；紫外光谱显示LNT₂在280和260 nm处无吸收峰。综合化学分析和光谱分析推出LNT₂为β构型的葡聚糖，其主链由1-3连接的葡聚糖组成，分支点位于糖的6位，侧链由末端葡萄糖残基组成；刚果红实验表明LNT₂分子在较低浓度NaOH溶液中呈三螺旋构象。体外抗肿瘤实验表明LNT₂能显著抑制小鼠肝腹水瘤H₂₂细胞的增殖，且呈量效依赖性。结论 精制香菇多糖LNT₂为均一相对分子质量的多糖组分，其结构为β构型1-3连接葡聚糖；初步表明LNT₂为三股螺旋结构，且具有一定的抗肿瘤活性，为其进一步的开发利用奠定了一定的基础。

Objective To purify the lentinan from sporophore of Lentinus edodes and to study the structure and antitumor activity in vitro of lentinan. Methods A refined lentinan, named LNT₂, was isolated from the sporophore of L. edodes by alkali extraction and alcohol precipitation, and further purified by hydrogen peroxide decoloration and ultrafiltration. The molecular weight and sugar content of LNT₂ were measured by HPLC and phenol-sulfuric acid method, respectively. UV was used to detect the protein and nucleic acid in LNT₂, and specific rotation was detected. The chemical structure of LNT₂ was determined by acid hydrolysis, periodate oxidation, methylation analysis, Fourier infrared spectrum, and NMR experiments. The chain conformation of LNT₂ was evaluated by Congo-red test. The inhibitory effect of LNT₂ on H₂₂ tumor cells growth was evaluated using MTT assay. Results The molecular weight, sugar content, and [α]_D²⁰ value of LNT₂ were estimated to be 185 200, 94.99%, and +8.03°, respectively. UV spectrum showed that there were no peaks at 280 and 260 nm. Chemical and spectroscopic analyses illustrated that LNT₂ had a backbone chain of β-(1→3)-linked glucopyranosyl residues and had branches of single glucosyl stubs at C-6 of terminal glucose sugar residues. Congo-red test revealed that LNT₂ exhibited a triple helix comformation in low concentration of NaOH solution. Results of the antitumor activity in vitro demonstrated that LNT₂ could exhibit the strong effect against the growth of H₂₂ tumor cells and showed a dose-dependent manner. Conclusion LNT₂ is composed of β-(1→3)-linked glucan and has a triple helix comformation. Moreover, LNT₂ could present the certain antitumor activities in vitro. Our study lays a solid foundation for the development and utilization of LNT₂.

国家自然科学基金资助项目（81373300）