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)-α-D-galacturonan, while the branch principally consisted of (1 → 5)-α-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 IC values of 5.55, 4.35 and 3.52 mg mL after 24, 48 and 72 h, and 5.33, 3.63 and 2.97 mg mL 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.