Effect of mirabilitum in formularization: Change of prolyl endopeptidase inhibitory activity and of constituents using the preparation method of Tokaku-joki-to (Persia and Rhubarb combination)

To clarify the effect of Mirabilitum in formularization, change of prolyl e ndopeptidase inhibitory activity and of constituents using the preparation method of a Kampo formula Tokaku-joki-to (Persia and Rhubarb combination) w as examined by the liquid chromatography-mass spectroscopy (LC-MS) method, Mirabilitum under boiling condition caused qualitative and quantitative cha nge of the constituents through hydrolysis which caused a change of its act ivity. This was considered to be the main reason the classical Chinese medi cal book "Shang han Lun" specified that Mirabilitum should be added at a la ter stage of decoction.