Isolation and Characterization of an Antiproliferative Compound in the Herbal Anticancer Remedy Essiac
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Essiac is a popular herbal tea with purported anticancer effects. Despite these claims, previous studies on Essiac have yielded contradictory results, with some reports showing increased proliferation and others showing decreased proliferation of cancerous and transformed cells in the presence of Essiac. We report that whole Essiac tea inhibits the in vitro proliferation of transformed Chinese hamster ovary (CHO) cells, as measured by a 5-carboxyfluoroscein diacetate acetoxymethyl ester cell viability assay. The antiproliferative effect is lessened when the CHO cells are engineered to overexpress the Myc oncoprotein, suggesting that Myc does not sensitize cells to Essiac-induced death. Upon liquid-liquid extraction with chloroform, acidic aqueous Essiac fractions displayed antiproliferative effects, while neutral, basic, and chloroform fractions showed either no effect or mild proliferative effects. We propose that contradictory findings from previous studies resulted from differential sensitivity in the tested cell lines to the various proliferative and antiproliferative compounds within Essiac, which cannot be deduced when whole Essiac is applied. Furthermore, our investigations suggest that Essiac contains an antiproliferative compound that becomes charged and protonated between pH 5 and 4, suggesting that it may be a large, aromatic amine. Future work in isolating this compound could provide a possible anticancer agent and help explain the paradoxical effects of Essiac on cancer cells.