Longgu ("dragon bone," Ryu-kotsu, Fossilia Ossis Mastodi, or Os Draconis) is the only fossil crude drug listed in the Japanese Pharmacopoeia. All longgu in the current Japanese market is imported from China, where its resources are being depleted. Therefore, effective countermeasures are urgently needed to prevent resource depletion. One possible solution is the development of a substitute made from bones of contemporary animals that are closely related to the original animal source of the current longgu. However, no research has been conducted on the original animal source of longgu, except for a report on the longgu specimens present in the Shosoin Repository. Taxonomic examination was performed on the fossil specimens related to longgu which are owned by the Museum of Osaka University, Japan. In total, 20,939 fossil fragments were examined, of which 20,886 were mammalian fossils, and 246 of these fossils were classified into nine families. The longgu specimens from the Japanese market belonged to a relatively smaller variety of taxa than those from the Chinese market. Despite the variety of taxa in longgu, medical doctors using Kampo preparations with longgu have not reported any problems due to the presence of impurities in the original animal source. These results suggest that the effect of longgu is independent of its origin as long as it is closely related to the origin of the current longgu. Thus, despite the considerable effects of fossilization, our results could help in developing an optimal substitute for longgu.

Longgu (Fossilia Ossis Mastodi) is a non-botanical crude drug, defined as "the ossified bone of large mammal" in the Japanese Pharmacopoeia sixteenth edition (JP16). It is a non-reproducible drug and is now facing the threat of exhaustion. To solve this problem, we aimed to clarify the role of longgu in Kampo prescriptions, which has not yet been scientifically ascertained. In this study, we focused on decoction of Keishikaryukotsuboreito (KRB). The profile of inorganic and organic components in the extract was analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and gas chromatography flame ionization detection (GC/FID), respectively. Twenty-five elements were detected by ICP-MS in KRB and longgu-free KRB (KB) decoctions. However, 23 elements were detected in unadultrated longgu (R) decoctions, and their total amount was 30 times lower than those of the KRB and KB decoctions were. No organic compounds were detected in R decoctions by GC/FID, though many were detected in KRB and KB decoctions. KRB decoctions were distinguished from KB decoctions by multivariate analysis. The only difference in the crude drugs was the presence of longgu, and therefore the difference in the profiles was attributed to the effect of longgu. Longgu was submitted to terahertz (THz) wave spectrometry after the decocting process. The THz spectra indicated that longgu adsorbed compounds during the KRB decoction. These results suggested that longgu not only releases its components, but also adsorbs ingredients from other crude drugs during decoction.

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. 1 H magic angle spinning NMR (1 H-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 1 H-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.