Structural elucidation of an acidic polysaccharide from Citrus grandis 'Tomentosa' and its anti-proliferative effects on LOVO and SW620 cells

Citrus grandis 'Tomentosa' (CGT) which is a region-famous medicinal and edible plant contains plentiful bioactive polysaccharides, however, its chemical structures and specific bioactivities still need to be further explored. In the present study, an acidic polysaccharide (CGTP-AP) was extracted and purified from the pulps of CGT. The structure elucidation and anti-cancer activity of CGTP-AP were investigated. Structure characterization indicated that CGTP-AP was a homogeneous heteropolysaccharide composed of arabinose, galactose and galacturonic acid in a molar ratio of 2.45:1:2.77, with an average molecular weight of 2721.68 kDa. Partial acid hydrolysis, methylation and NMR spectrometry revealed that the backbone of CGTP-AP mainly composed of (1 -> 4)-alpha-D-galacturonan, while the branch principally consisted of (1 -> 5)-alpha-L-Araf. In addition, CGTP-AP exhibited effective anti-proliferation against colon cancer cells LOVO and SW620 cells in dose- and time-dependent manners, with IC50 values of 5.55, 4.35 and 3.52 mg mL(-1) after 24, 48 and 72 h, and 5.33, 3.63 and 2.97 mg mL(-1) after 24, 48 and 72 h, respectively. This study indicated that CGTP-AP might be utilized as a promising food supplement for the patients of colon disorders. (C) 2019 Elsevier B.V. All rights reserved.