<p>Abstract</p> <p>Background</p> <p>Ovarian 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.</p> <p>Methods</p> <p>The leaves of a plant endemic to Australia, <it>Calomeria amaranthoides</it>, were extracted and then fractionated by column chromatography. <it>In vitro </it>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.</p> <p><it>In vivo </it>cytotoxicity was tested on ascites, developed in the abdomen of nude mice after inoculation with human OVCAR<sub>3 </sub>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.</p> <p>Results</p> <p>Two compounds were isolated by chromatographic fractionation and identified by <sup>1</sup>H-NMR, <sup>13</sup>C-NMR and mass spectrometry analyses, EPD, an α-methylene sesquiterpene lactone of the eremophilanolide subtype, and EPA, an α-methylene carboxylic acid.</p> <p>Cytotoxicity of EPD for normal fibroblasts at all time points IC<sub>50 </sub>was greater than 10 μg/mL, whereas, for OVCAR<sub>3 </sub>cells at 48 hours IC<sub>50 </sub>was 5.3 μg/mL (95% confidence interval 4.3 to 6.5 μg/mL).</p> <p>Both, 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.</p> <p>Changes 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.</p> <p>Conclusions</p> <p>For the first time both crude plant extract from <it>Calomeria amaranthoides </it>and EPD have been shown to have potent anti-cancer effects against ovarian cancer.</p
