Manufacture of wood-cement boards VIII: Cement-hardening inhibitory compounds of keyaki (Japanese zelkova, Zelkova serrata)

To isolate and identify the cement-hardening inhibitory components of keyaki (Japanese zelkova, Zelkova serrata Makino), methanol extractives containing inhibitory components were fractionated by successive organic solvent extraction and column chromatography, and the inhibition of these fractions was determined. Spectroscopic analysis of one isolated compound identified it to be keyakinin with the C-glucoside structure of a flavonol. According to the inhibitory indices, the compound was found to be the main cement-hardening inhibitory component of keyaki. Extraction of keyaki with hot water or a blend of keyaki with up to 30% hinoki as a suitable species diminished the cement-hardening inhibition of wood-cement board to a great extent, suggesting that such treatments are economical countermeasures to this inhibition.