Isolation, structural characterization, and anti-lung cancer evaluation of fucoidan isolated from the brown seaweed <i>Turbinaria decurrens</i>

Fucoidan is a naturally occurring sulphate-containing polysaccharide and a major active compound in Turbinaria decurrens, a brown seaweed commonly found in the Indian Ocean. Cancer, particularly lung cancer, poses a huge health burden in terms of incidence and mortality in India and globally. This study used a hot water extraction method. The seaweed extract was cleared by ethanol precipitation, further characterized, and its efficacy tested against lung cancer in vitro. The isolated compound was purified with ion-exchange chromatography, 13C solid-state nuclear magnetic resonance (NMR), attenuated total reflection infrared (ATR-IR), and Fourier transform infrared spectroscopy (FTIR). The antioxidant properties of fucoidan are known but there are few reports about oxidative stress-mediated lung cancer relevant to Turbinaria decurrens. The purified compound was tested against the lung cancer A549 cell line in vitro, and an IC50 concentration of purified fucoidan did not show any cytotoxicity in normal human embryonic kidney (HEK293) cells. The results showed the promising antioxidant potential of fucoidan. Mechanistically, fucoidan-induced cell cycle arrest in the S-M phase in a dose- and time-dependent manner. Fucoidan was able to induce mitochondrial membrane damage in A549 cells. Acridine AO/EB dual staining combined with western blotting revealed that fucoidan has the potential to inhibit anti-apoptotic Bcl-2 protein and significantly (p < 0.05) increased pro-apoptotic protein expression in A549 human lung cancer cells.