The Anticancer Effect And Mechanism Of Xanthones From Gentianopsis Paludosa Ma

Cancer is normally a disease of failing to control the cell growth and proliferation, which accounts for almost one-fifth of deaths in China and causes the death of 100 to 350 out of every 100,000 people each year worldwide. Cancer therapy has been an attracting research topic in all of worldwide.Gentianopsis paludosa Ma (Gentianaceae) is an annual herb and widely distributed in China, India, Nepal, Bhutan and Sikkim. As a Chinese traditional medicine, this plant has been commonly used in Tibet Province of China as a folk medicine. At the same time, it was extensively used for clinical treatment of conjunctivitis, hepatitis, nephritis, gastroenteritis. In recent years, with the further pharmacological investigation of Gentianopsis paludosa Ma, a lot of new pharmacologica effects were detected.In this study, the anticancer potentials of four xanthones (Compound 1~4) from Gentianopsis paludosa Ma were evaluated. Cytotoxicity of the four xanthones was tested on HepG2 cells and HL-60 cells by Sulforhodamine B (SRB) assay. Clonogenic survival assay, trypan blue exclusion method, AO/EB staining and DNA fragmentation assay were conducted to investigate the effect on growth inhibition and apoptosis in the two cell lines in vitro. At the same time, structure-activity relationships (SARs) of the xanthones were investigated. The results showed that the xanthones had significant cytotoxicity and inhibition of proliferation in both HepG2 cells and HL-60 cells and could induce apoptosis in these two cell lines. The cytotoxic activity tendency of the four xanthones was compound 3 >compound 2 >compound 4 >compound 1 in HepG2 cells and compound 2 >compound 3 >compound 4 >compound 1 in HL-60 cells. SARs indicated that the methoxy group had more cytotoxic contribution than hydroxyl group at site C-8 in structural scaffold of xanthone. The glycosidea at site C-1 may aggravate the stereospecific blockade of compound 4 and reduced its cytotoxic activity.In addition, the anticancer mechanism of Compound 2 was researched in this study. When the cells treated with lower concentrations of xanthone 1 (12.4 to 74.4μM), significant proliferation inhibition was detected by cell viability assay and morphological analyses in a time- and dose-dependent manner, and conspicuous G1 and G2/M cell cycle arrest were observed by flow cytometric analysis. However, when the cells treated with higher doses of xanthone 1 (82.7 to 330.8μM), significant apoptosis was observed by double sequential AO/EB staining, DNA fragmentation assay and flow cytometric analysis. In addition, conspicuous DNA damage was detected by comet assay. In short, all the results showed that xanthone 1 had a significant cytotoxic effect and could induce proliferation inhibition and apoptosis in HL-60 cells in a time- and dose-dependent manner. It was possible that xanthone 1 could induce DNA damage in HL-60 cells, which resulted in G1 phase arrest at the lower concentrations and G2/M phase arrest at the higher concentrations, thus inhibiting the cell proliferation, and irreparable DNA damage at the higher concentrations might be responsible for the occurrence of apoptosis.