Research Paper Volume 14, Issue 23 pp 9466—9483

Figure 4. Natural products, tannic acid and chlorophyllin, were able to decrease mammosphere formation. We tested the effects of more natural compounds, such as tannic acid and chlorophyllin copper salt. (A) Tannic acid is a type of polyphenol. Interestingly, it is effective in inhibiting CSC propagation, at concentrations >10 μM; its IC50 is 25 μM. (B) Chlorophyllin is a derivative of chlorophyll which significantly decreases the mammosphere number starting at a concentration of 50 μM and reduces propagation by > 90% at a concentration of 100 μM. Bar graphs are shown as the mean ± SEM; t-test, two-tailed test. ***p < 0.001, ****p < 0.0001. Chemical formulae are indicated.