黄蜀葵茎叶多糖的乙酰化修饰及其免疫调节活性研究

Acetylated Modification of Polysaccharides from Stems and Leaves of Abelmoschus Manihot and Its Immunoregulatory Activity

目的应用乙酰化修饰方法与技术进行黄蜀葵茎叶多糖的结构修饰,并评价其体外免疫调节活性,以期为黄蜀葵茎叶废弃物的资源化利用提供思路和科学依据。方法采用水提醇沉法及DEAE-52离子交换法制备黄蜀葵茎叶粗多糖(SLAMP)和中性多糖(SLAMP-a),应用乙酸酐法制备3种乙酰化修饰产物(SLAMP-a1、SLAMP-a2、SLAMP-a3),且通过化学组成分析、柱前衍生HPLC法以及红外光谱法对多糖结构进行初步鉴定;此外,通过考察SLAMP-a及其3种乙酰化修饰产物对脾淋巴细胞体外增殖及RAW264.7释放NO的影响,评价四种多糖的免疫调节活性。结果 SLAMP-a总糖含量为99.76%,无体外免疫调节活性;3种修饰产物中,只有SLAMP-a1具有显著的刺激脾细胞增殖作用及激活RAW264.7产生NO。SLAMP-a1总糖含量为82.50%,取代度为0.62,主要由葡萄糖组成,且含有少量的甘露糖、半乳糖及阿拉伯糖。结论黄蜀葵茎叶多糖SLAMP-a经乙酰化修饰后,可显著提高体外免疫调节活性,SLAMP-a1有望开发成免疫调节剂,且乙酰化修饰方法与技术可作为黄蜀葵茎叶多糖资源化利用的有效途径。

OBJECTIVE Acetylated modification was applied to modify the structure of polysaccharide from stems and leaves of Abelrnoschus manihot, and the in vitro immunoregulatory activity of polysaccharides were evaluated, which was expected to provide the scientific evidence for the resource utilization of A. manihot disused parts. METHODS The crude polysaccharide （SLAMP） was obtained by water extraction and alcohol precipitation, and neutral polysaccharide （SLAMP-a） was further prepared by DEAE-52 ion exchange column. Acetic anhydride was used as acetylating agent to synthesize three acetylated derivatives （SLAMP-al, SLAMP-a2 and SLAMP-a3）. Their structures were preliminarily identified by chemical composition analysis, pre-column derivatization HPLC method and IR spectrum. In addition, in vitro immunoregulatory activity of SLAMP -a and three acetylated derivatives was evaluated by splenocyte proliferation together with its effects on NO production of RAW264.7. RESULTS SLAMP-a showed little immunomodulatory activity and the total sugar content was 99.76 % ; Among the three derivatives, only SLAMP-al could significantly stimulate the proliferation of spleen cells and activate RAW264.7 to product NO. SLAMP-al mainly contained glucose with a few of mannose, galactose and arabinose, and the total sugar and DS was 82.50M and 0.62 respectively. CONCLUSION In vitro immunomodulatory activity of polysaccharide SLAMP-a from stems and leaves of A. rnanihot is significantly enhanced by acetylation and SLAMP-al possesses the potential to develop as immunoregulatory agents. The acetylation modification is an effective way for resource utilization of polysaccharide from the disused stems and leaves of A. manihot.