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

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