Anticancer Potential of New Zealand Surf Clam Extracts
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The field of nutraceuticals, functional foods, and chemo-preventive compounds in the treatment/control of cancer is experiencing an increased awareness in both scientific and public domains. This study stems from my earlier work on the antioxidative properties associated with New Zealand surf clam extracts. In this thesis, I have evaluated and presented the cytotoxic activities of extracts from three New Zealand surf clam species: Diamond Shell (Crassula aequilatera), Storm shell (Mactra murchisoni), and Tua Tua (Paphies donacina). These were tested against seven cancer cell lines: A549, Hep G2, MIA PaCa-2, MCF-7, PC-3, SiHa, and WiDr. Clams were either heat processed (blanched and oven dried) or cold processed (frozen and freeze-dried) prior to extraction. These were extracted in distilled water and absolute ethanol in series. A portion of the ethanolic extracts was further fractioned into two parts using petroleum ether (pe) or ethyl acetate (ea). A cell viability study using the MTT assay was then performed to screen for the most potent fractions and concentrations. Cell viability was deterred in all cell lines at the three-day time point, to varying degrees. Then, cells underwent an apoptosis assay, which revealed that apoptosis was indeed induced in NZ surf clam extract-treated cancer cells. The apoptosis observed was confirmed by measuring the caspase-3 and -7 activities in the treated cells. High caspase activities were observed in all treated cells. Furthermore, a cell cycle analysis was carried out, to investigate cell cycle arrest. Cell cycle arrest was observed in the G2/M- and S- phases in most cases. The differences in biochemical components and cytotoxic effects of extracts from the two methods of preparation - heat processing and cold processing, indicate that heat treatments of extracts are associated with lower cytotoxic activities, mainly cell proliferation inhibition, induction of apoptosis, and concomitant caspase-3/7 activities. This study is the first comprehensive report on the cytotoxic properties of the three tested New Zealand surf clams’ extracts. My results build on my previous work on the clam’s antioxidant properties, and propose its role in health-related applications, such as a bioactive food constituent. The promising compounds found in this study can also now be isolated and employed in possible synergetic combination with traditional chemotherapy against cancer.