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Extraction, purification, and characterization of polysaccharides from marine algae Gracilaria lemaneiformis with anti-tumor activity

Fulin Shi, Xiaolin Yan, Kit-Leong Cheong, Yang Liu
Process biochemistry 2018 v.73 pp. 197-203
Gracilaria, adjuvants, algae, ammonium sulfate, antineoplastic activity, cell proliferation, chemical structure, ethanol, galactose, human cell lines, molecular weight, polysaccharides, purification methods, response surface methodology, temperature, ultrasonics
Recently, rapid and effective extraction and purification methods have attracted considerable interest as alternative approaches to conventional methods. In this study, ultrasonic-microwave-assisted extraction (UMAE) was used to extract Gracilaria lemaneiformis polysaccharides, and the response surface methodology was used to determine the optimum extraction conditions. Subsequently, an aqueous two-phase system (ATPS) was applied to the purification of crude polysaccharides. The chemical structure and anti-tumor activities of three fractions of purified G. lemaneiformis polysaccharides were also investigated. We found that the optimal condition for UMAE was 50 W of ultrasonic power, 31.7 min, 87°C and at a solid-to-water ratio of 1.0:60.7 of extraction temperature. The extraction yield of polysaccharides reached 34.8% under optimum UMAE conditions. The crude polysaccharides were successfully partitioned in the intermediate phase with a recovery rate of 81.1% in an ethanol/ammonium sulfate system. After being fractionated by a DEAE Sephadex A-50 column, three polysaccharide fractions (GLP1, GLP2, and GLP3) were obtained, accounting for 14.3%, 65.2% and 20.6%, respectively. GLP1, GLP2 and GLP3 were mainly composed of galactose with molecular weights of 5.5 kDa, 85 kDa and 82 kDa, respectively. Those polysaccharides exhibited inhibition activity on MCF-7, HepG-2, and Hela cell proliferation in vitro, and GLP-3 exhibited the highest anti-tumor activities. These results indicated that UMAE and ATPS are rapid, efficient, and environmentally-friendly extraction and purification methods for marine algal polysaccharides. These G. lemaneiformis polysaccharides could potentially be used as anti-cancer adjuvants in conjunction with pharmaceutical therapies.