Preparation of oligomeric phenolic compounds (DHPs) from coniferin and syringin and characterization of their anticancer properties

Abstract

Lignin precursors of coniferin and syringin were synthesized and used to prepare guaiacyl-type and guaiacyl-syringyl-type oligomeric compounds (designated here as dehydrogenation polymers DHP-G, DHP-GS) via bulk method. The carbon 13 nuclear magnetic resonance spectroscopy (13C-NMR) spectra indicated that both DHPs contained typical lignin substructures. The DHPs were extracted sequentially with petroleum ether, ether, ethanol, and acetone to obtain eight fractions (F11 to F14 and F21 to F24). The 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) experimental results showed that the growth of cervical cancer cells was inhibited by the two ether-soluble fractions F12 and F22, with semi-inhibitory concentration (IC50) values of 81.60 ± 9.30 and 103.24 ± 14.09 μg/mL, respectively. The bioactive compounds in F12 and F22 were separated by a preparative chromatography method. Ten bioactive compounds (G1 to G5 and GS1 to GS5) were obtained. Mass spectroscopy analysis revealed the following chemical structures: G1, β-5 G-type dimer; G2, (β-5)(β-5) G-type trimer; GS1, β-5 GS-type dimer; and GS2, (β-O-4)(β-5) GS-type trimer. The compounds had inhibitory effects on cervical cancer cells. The syringyl aromatic ring decreased the anticancer activity of DHP, and the β-O-4 linkages did not contribute to the anticancer activity. It was also found that the carboxyl groups contributed to the anticancer activity of DHP.