Purification and characterization a polysaccharide from Hedyotis diffusa and its apoptosis inducing activity toward human lung cancer cell line A549.

In this study, we first isolated and purified a homogeneous polysaccharide (HDP) from Hedyotis diffusa. Its molecular weight was estimated to be about 89 kDa and GC analysis identified that it was composed of glucose, galactose, and mannose in a molar ratio of 2.0:1.0:1.0. Treatment with HDP (25, 100, and 200 μg/ml) resulted in growth inhibitory effect on A549 cells by inducing apoptosis. Moreover, induction of apoptosis by HDP was accompanied with the release of cytochrome c from mitochondria into the cytosol prior to the activation of caspase-9 and -3 in A549 cells. Also, a higher ratio of Bax/Bcl-2 proteins was observed in A549 cells followed by HDP treatment. Additionally, in vivo study showed that HDP (50 and 100 mg/kg) could suppress the growth of A549 subcutaneous xenograft tumors. Taken together, these results indicated that the HDP exerted an anticancer effect in vitro and in vivo and may be useful as a potent antitumor agent for the prevention of lung cancer.