Antitumor activity of a polysaccharide from longan seed on lung cancer cell line A549 in vitro and in vivo.

In this study, a water-soluble longan seed polysaccharide (WLSP), with a molecular weight of 57 kDa, was isolated from longan seed. Gas chromatography (GC) analysis showed that WLSP was composed mainly of rhamnose (Rha), mannose (Man), arabinose (Ara), galactose (Gal), and glucose (Glc), with molar ratios of 2.4:1.5:2.3:5.6:6.5. The result in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that WLSP showed a dose-dependent antiproliferative effect on the proliferation of A549 human lung cancer cells, which is consistent with the amount of lactate dehydrogenase (LDH) release from A549 cells. Prompted by this antiproliferative effect, we further examined its antiproliferative mechanism and in vivo anticancer effect. Our results showed that WLSP had the ability to cause cell cycle arrest in G1 phase, activation of caspases 3 and 9, and cleavage of poly[ADP (ribose)] polymerase (PARP) in A549 cells. The result of this in vivo study showed that WLSP could suppress the growth of xenograft A549 tumors and induce apoptosis. Taken together, these results indicate that WLSP exert an anticancer effect in vitro and in vivo and may be useful for the prevention of lung tumorigenesis.