The extraction optimization, characterization, and adjuvant therapeutic effects on colorectal cancer of a pectin polysaccharide (CBP-4a) obtained from Cibotium barometz.

Colorectal cancer (CRC) is the third most common cancer worldwide. 5-fluorouracil (5-FU) is a first-line chemotherapeutic drug for the treatment of CRC; however, its selectivity is poor, it has serious side effects, and its long-term use is prone to drug resistance. In this study, the ultrasonic-assisted cellulase method was used to extract polysaccharides from Cibotium barometz. Under the optimum extraction conditions, the highest polysaccharide extraction rate reached 14.34 ± 0.41 %, and the crude polysaccharide of C. barometz (CBP) was extracted under these conditions. Furthermore, an acidic homogeneous polysaccharide (CBP-4a) with a molecular weight of 99.77 kDa was isolated and purified from CBP. Structural analysis showed that CBP-4a was a novel pectin polysaccharide with a main chain composed of homogalacturonan (HG) and rhamnogalacturonan-I (RG-I) domains. In vitro experiments indicated that CBP-4a could significantly enhance the sensitivity of HCT15 and CT26.WT cells to 5-FU in a non-cytotoxic manner; it could also enhance the S-phase arrest of the cell cycle, migration inhibition, ROS accumulation and apoptosis induced by 5-FU. In vivo experiments showed that the combination of CBP-4a and 5-FU significantly inhibited tumor growth in mice compared with 5-FU alone. This study expands the medicinal range of C. barometz and provides a scientific basis and theoretical support for the development of polysaccharide drugs for the adjuvant treatment of CRC.