Transition in Longgu Surface Associated with Decoction Process of Keishikaryukotsuboreito

We aim to attain the sustainable use of longgu and have investigated the significance of longgu in Keishikaryukotsuboreito (KRB) decoction. We have already reported that longgu alters compound profiles in KRB decoction and hypothesized that it does so by adsorbing foreign organic compounds into its superficial pores. In the present study, we focused on the adsorbability of organic materials onto longgu surface as the cause of component profile alteration. We analyzed the physical changes in longgu through the decoction process by measuring the adsorbed water on longgu surface. 1H magic angle spinning NMR (1H-MASNMR) spectroscopic analysis revealed that raw longgu (R-raw) as well as decocted longgu [whether single (R-r) or KRB (R-krb) decoction] adsorbed water. However, the amount of adsorbed water in R-krb was smaller than that in R-raw and R-r. The nitrogen adsorption isotherms of longgu samples indicated that longgu was macroporous. The Brunauer–Emmett–Teller (BET) surface area of R-krb was smaller than that of R-raw and R-r. Further, thermogravimetric analysis of longgu samples showed that R-krb adsorbed matter that R-raw and R-r did not adsorb. The above findings and the 1H-MASNMR analysis of heated longgu samples suggested that longgu adsorbed organic compounds into the pores. We considered that longgu adsorbed organic compounds during KRB decoction into its superficial pores through the decoction process.