Antiproliferation of melanoma cells by polysaccharide isolated from Zizyphus jujuba

Objective: Zizyphus jujuba, a traditional Chinese herb rich in functional components such as polysaccharide, has been widely consumed in Asian countries. The objective of this study was to determine the antiproliferation effect of melanoma cells as affected by deproteinized polysaccharide (DPP) isolated from Z jujuba. Methods: Deproteinized polysaccharide was obtained through boiling water extraction, ethanol precipitation, deproteinization, and dialysis, and the molecular weight of DPP was determined by high-performance gel-filtration chromatography. Melanoma cell viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, the cell cycle was analyzed by flow cytometry, the formation of apoptotic bodies was observed under a fluorescence microscope at 450 nm, and caspase-3 and caspase-9 were measured by an assay kit. Results: Deproteinized polysaccharide was composed of two fractions with average molecular weights of 143 108 and 67 633 Da. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test showed that the antiproliferation effect of DPP on melanoma cells followed a dose- and time-dependent course. The 50% inhibitory concentration of DPP in inhibiting melanoma cell growth was 3.99 +/- 0.10 mg/mL after 24-h treatment but decreased significantly to 3.36 +/- 0.14 mg/mL after 48 h. The cell cycle assay revealed melanoma cells to be arrested in G2/M phase. Moreover, with DPP treatment, the apoptotic bodies were generated, accompanied by an increase in caspase-3 and caspase-9 activity. Conclusions: This outcome suggested that DPP may be used as a potential anti-skin cancer agent for further in vivo and clinical trial experiments. (C) 2012 Elsevier Inc. All rights reserved.