Background\r\nOvarian cancer remains the leading cause of death from gynaecological malignancy. More than 60% of the patients are presenting the disease in stage III or IV. In spite of combination of chemotherapy and surgery the prognosis stays poor for therapy regimen.\r\nMethods\r\nThe leaves of a plant endemic to Australia, Calomeria amaranthoides, were extracted and then fractionated by column chromatography. In vitro cytotoxicity tests were performed with fractions of the plant extract and later with an isolated compound on ovarian cancer cell lines, as well as normal fibroblasts at concentrations of 1-100 �µg/mL (crude extract) and 1-10 �µg/mL (compound). Cytotoxicity was measured after 24, 48 and 72 hours by using a non-fluorescent substrate, Alamar blue.\r\nIn vivo cytotoxicity was tested on ascites, developed in the abdomen of nude mice after inoculation with human OVCAR3 cells intraperitoneally. The rate of change in abdomen size for the mice was determined by linear regression and statistically evaluated for significance by the unpaired t test.\r\nResults\r\nTwo compounds were isolated by chromatographic fractionation and identified by 1H-NMR, 13C-NMR and mass spectrometry analyses, EPD, an a-methylene sesquiterpene lactone of the eremophilanolide subtype, and EPA, an a-methylene carboxylic acid.\r\nCytotoxicity of EPD for normal fibroblasts at all time points IC50 was greater than 10 �µg/mL, whereas, for OVCAR3 cells at 48 hours IC50 was 5.3 �µg/mL (95% confidence interval 4.3 to 6.5 �µg/mL).\r\nBoth, the crude plant extract as well as EPD killed the cancer cells at a final concentration of 10 �µg/mL and 5 �µg/mL respectively, while in normal cells only 20% cell killing effect was observed. EPA had no cytotoxic effects.\r\nChanges in abdomen size for control versus Cisplatin treated mice were significantly different, P = 0.023, as were control versus EPD treated mice, P = 0.025, whereas, EPD versus Cisplatin treated mice were not significantly different, P = 0.13.\r\nConclusions\r\nFor the first time both crude plant extract from Calomeria amaranthoides and EPD have been shown to have potent anti-cancer effects against ovarian cancer.
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