To find new plant-derived antitumor drugs, hydrolysate and fractions of poplar were analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for their inhibitory effect against liver cancer HepG-2 cells. Strong cytotoxicity of hydrolysate was revealed at processing temperature of 180 °C or above. The hydrolysate formed at 180 °C was sequentially extracted using organic solvent to obtain five fractions, and only the diethyl ether-soluble fraction (FDe) showed specific cytotoxicity. The eluted fraction of acetone/n-hexane (F1) was further isolated by column chromatography separation from the FDe fraction at a yield of 70%, and could severely decrease cell viability. LC-MS chromatography indicated that 5-hydroxymethyl furfural, ρ-hydroxybenzoic acid and syringaldehyde were the main compounds in the F1 fraction. Furthermore, the results of flow cytometry, Western blotting, and polymerase chain reaction indicated that syringaldehyde could tightly control the growth and metabolism of HepG-2 cells. The findings could move forward the value-added applications of lignocellulosic hydrolysate on traditional medicines.
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