Tangeretin (5,6,7,8,4′-pentamethoxyflavone, TAN), a natural polymethoxyflavone (PMF) present in citrus fruits, is reported to have several biological functions. Our previous studies show that demethylation at the C5 group of PMFs resulted in more potent anti-cancer property. In this study, we prepared an acetylated TAN (5-ATAN) with an acetyl group at C5 position to replace 5-methyl group of tangeretin and compared the anti-proliferative activities of TAN, 5-demethyl TAN (5-DTAN) and 5-ATAN. We found that all the PMFs caused significant cytotoxicity effect in human colon cancer HCT116 and HT-29 cells. Treatment of HCT116 cells with TAN, 5-DTAN and 5-ATAN resulted in G2/M phase cell cycle arrest while 5-DTAN and 5-ATAN also triggered apoptosis but not TAN. Cleavage of caspase-3 and increased p53 protein expression observed in 5-DTAN and 5-ATAN-treated HCT116 cells suggested the apoptosis-dependent mechanism. Moreover, 5-ATAN exhibited a more effective anti-proliferative and apoptosis-inducing effect than 5-DTAN in HT-29 cells. Interestingly, cell cycle arrest at S and G2/M phase were found in 5-ATAN treated HT-29 cells whereas 5-DTAN only caused G2/M phase arrest. These results suggest that 5-DTAN and 5-ATAN could be effective anti-cancer agents.
Sludge from biological wastewater treatment procedures was treated using microwave heating pyrolysis to reduce the environmental impact of a chemical plant. In this study, major elements, trace elements, PAHs and nitro-PAHs in raw sludge, and pyrolysis residues were investigated. The contents of major element from raw sludge were carbon 46.7 ± 5.9%, hydrogen 5.80 ± 0.58%, nitrogen 6.81 ± 0.59%, and sulfur 1.34 ± 0.27%. Trace elemental concentrations including Zn, Mn, Cr, Cd, As, and Sn were 0.410 ± 0.050, 0.338 ± 0.008, 0.063 ± 0.006, 0.019 ± 0.001, 0.004 ± 0.001, and 0.003 ± 0.002 mg/g, respectively. For various pyrolysis temperatures, Ca, Fe, Sr, Cr, and Sn contents remained at almost the same level as those in raw sludge. Results indicated that these elements did not easily volatilize. The content of 16 PAH species was about 4.78 μg/g in the raw sludge and 23-65 μg/g for pyrolysis residues associated with various temperatures. The content of ten nitro-PAHs was about 58 ng/g for the raw sludge and 141-744 ng/g for pyrolysis residues. The total nitro-PAH content was highest at 600 °C and then decreased when the temperature was over 600 °C. Total nitro-PAH content was about 247 ng/g at 800 °C.
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