Structural feature and antitumor activity of a N-acetylglucosamine containing polysaccharide from Ganoderma sinense

Ganoderma sinense is a precious traditional Chinese medicine to improve health and treat numerous diseases with a time-honored history. Herein, the antitumor activities of crude polysaccharides (GS50, GS70, GS90, and GSB) derived from the water or alkali extracts of G. sinense were investigated in a 4T1 tumor-bearing Balb/c mouse model. The results demonstrated that GS70 exhibited a notable suppression of tumor growth and induced apoptosis through the PI3K/AKT pathway. A polysaccharide GSP70-2 (6.4 kDa) was separated from GS70, consisting of glucose, mannose, and N-acetylglucosamine in a molar ratio of 4.4:6.1:1.0. Methylation analysis, partial acid hydrolysis, and nuclear magnetic resonance spectroscopy results revealed that the backbone of GSP70-2 was composed of →3)-β-D-Glcp-(1→, →6)-α-D-Manp-(1→, and →4)-α-D-Manp-(1→, and the side chain was substituted at O-3 or O-4 of →6)-β/α-D-Manp-(1→ and O-6 of →3)-α-D-Glcp-(1→. GSP70-2 exhibited a pronounced inhibitory effect on the proliferation of 4T1 cells, suggesting that GSP70-2 was one of the bioactive components in GS70. In addition, GSP70-2 could promote the apoptosis of 4T1 cells by reducing the mitochondrial membrane potential and regulating genes related to cell apoptosis. Consequently, the above results suggested that GSP70-2 could be developed as a potential option for treating breast cancer.