Elucidation of the fine structure and anti-breast tumor activity of a glucomannan from the pseudobulbs of Pleione bulbocodioides.

Pseudobulbs of Pleione bulbocodioides have been used as traditional Chinese medicine for a long time to treat cancers through decoction with water. However, as its main water-soluble ingredient, the structure of polysaccharide has not been elucidated yet. To obtain its polysaccharide with antitumor activity, a series of isolation, structural identification and antitumor evaluation experiments were performed. As a result, a newly discovered glucomannan, named PBP, was isolated and purified from the pseudobulbs of P. bulbocodioides. The molecular weight of PBP is 1.11 × 10 Da. Its monosaccharide composition comprises mannose and glucose at a molar ratio of 5:3. The fine structure of PBP was confirmed as a linear glucomannan backbone primarily comprising repeating →4)-β-d-Glc-(1 → 4)-β-d-Man-(1 → 4)-β-d-Glc-(1 → 4)-β-d-Man-(1 → 4)-β-d-Glc-(1 → 4)-β-d-Man-(1→4)-β-d-Man-(1 → 4)-β-d-Man-(1 → via a combination of analytical techniques and enzymolysis methods. PBP effectively inhibited the growth of 4T1 tumors with low toxicity in vivo. Furthermore, a noteworthy augmentation in the expression levels of CD4+ and CD8+ T cells suggested the existence of an elevated immune response. In summary, a new glucomannan with anti-breast tumor activity was obtained, which has the potential to contribute to breast cancer therapy.