Deciphering a novel polysaccharide from Keemun black tea: structural elucidation and anti-colorectal cancer exploration.

Background: Keemun black tea (KBT) is one of the three major black teas in the world, which is famous for unique Keemun aroma and various health-promoting benefits. However, the structural characteristics and anti-tumor effects of the principal active polysaccharides in KBT have not been explored.

Results: In the present study, a novel homogeneous polysaccharide (KBPW1) with high anti-tumor activity was isolated from KBT by an activity-oriented sequential isolation procedure. Structure characterization determined that the molecular weight of KBPW1 was 3.8 × 10³ Da, predominantly composed of glucose, arabinose and galactose with a molar ratio of 6.36, 2.62 and 1.02. The backbone of KBPW1 was primarily comprised of →4)-β-D-Glcp-(1→, β-D-Glcp-(1→, α-L-Araf-(1→, →3,5)-β-L-Araf-(1→ and →3)-β-D-Galp-(1→, and its branches were mainly consisted of →4,6)-β-D-Glcp-(1→, →6)-β-D-Glcp-(1→ and →5)-α-L-Araf-(1→). In vitro and in vivo anti-tumor activity evaluation experiments showed that KBPW1 remarkably induced apoptosis of colorectal cancer cells CT-26 and effectively inhibited cell proliferation, migration, invasion and colony formation. Moreover, KBPW1 reduced the expression levels of C-myc, vimentin and Notch1 proteins. Mechanistically, KBPW1 inhibits tumor angiogenesis, metastasis and growth by blocking the Notch signaling and down-regulating apoptosis-related proteins expression.

Conclusion: The findings obtained in the present study suggest that KBPW1 is a potential natural therapeutic agent for colorectal cancer. © 2025 Society of Chemical Industry.