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

OBJECTIVE Acetylated modification was applied to modify the structure of polysaccharide from stems and leaves of Abelmoschus 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-a1， 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-a1 could significantly stimulate the proliferation of spleen cells and activate RAW264.7 to product NO. SLAMP-a1 mainly contained glucose with a few of mannose， galactose and arabinose， and the total sugar and DS was 82.50% and 0.62 respectively. CONCLUSION In vitro immunomodulatory activity of polysaccharide SLAMP-a from stems and leaves of A. manihot is significantly enhanced by acetylation and SLAMP-a1 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.