Heating or ginger extract reduces the content of Pinellia ternata lectin in the raphides of Pinellia tuber.

Pinellia tuber, the dried tuber of Pinellia ternata, causes a very strong acridity sensation in the oral and laryngopharynx mucosa when taken orally in its unprocessed form. In traditional Chinese medicine (TCM), this sensation has been called "toxicity", and Pinellia tuber must be processed using ginger extract, licorice, or alum. In Japanese traditional Kampo medicine, since "toxicity" can be eliminated by decocting, it should not be processed. However, little is known about the mechanism underlying the "detoxification" of Pinellia tubers. In this study, we produced murine antiserum using recombinant P. ternata lectin (PTL), developed an immuno-fluorescence staining method for PTL in the needle-shaped crystals (raphides) that were prepared by petroleum ether extraction (PEX) from Pinellia tuber, and elucidated the mechanism of the processing of Pinellia tuber using heat or ginger extract. After heating the raphides in water, the amount of PTL contained in the raphides was significantly reduced by the immunostaining, although the shape of the raphides was not changed. Incubating raphides with dried ginger extract also significantly reduced the amount of PTL in the raphides in a concentration-dependent manner. By the activity-guided fractionation of ginger extract, the active ingredients in the ginger extract were oxalic acid, tartaric acid, malic acid, and citric acid. Among these four organic acids, oxalic acid mainly contributed to the effect of dried ginger extract by its content in ginger extract and its activity. These results exhibit scientific evidences for the traditional theories of processing to "detoxify" Pinellia tuber in TCM and Kampo medicine.

Historical Study for the Differences of Processing of Pinellia ternata Tuber Between China and Japan.

Pinellia Tuber (the dried tuber of Pinellia ternata (Thunb.) Makino [Araceae]) (PT) is a crude drug used in traditional Chinese medicine (TCM) and Japanese Kampo medicine. PT is subjected to additional processing before use in TCM because of its toxic, while the processing has not been used in Kampo medicine. The aim of this study is to clarify the reason why the differences about the processing of PT between TCM and Kampo medicine have been appeared. We investigated successive literatures published in China and in Japan from the Han dynasty to the modern age. The descriptions about the processing of PT in China had appeared since the Later Han dynasty as washing, and after that, various processing methods have been recorded, such as boiling, steaming, making cakes, and fermenting to prepare PT malt (PTM) with various drug additives. The objective of the processing for PT was not only to remove its toxicity but to change drug properties, and several kinds of processed PT had been developed to treat different types of "phlegm" in the Ming dynasty. The current Chinese Pharmacopoeia recommends the use of processed PT to avoid the toxicity, and registers unprocessed PT as well as three kinds of processed PT except for PTM which had been deleted in 2015 edition. These processing methods for PT have been established in the Qing dynasty. The oldest description in Japan was appeared in 1363, and the processing methods had been influenced by the literatures in the Song dynasty. After that, the processed PT in Japan had mainly been PTM until the 18th century. In 1738, Shuan Kagawa wrote that PT should not be processed because its pharmacological effects disappeared and the toxicity of PT disappeared by preparing its decoction without processing. Then, the processing of PT has been unpopular, and the Japanese Pharmacopoeia has registered PT since 1939 without any processing. Compared to TCM, Japanese Kampo medicine has tended to avoid ideologism based on traditional knowledge and to adopt positivism. This policy has reflected the differences in the processing of PT between Kampo medicine and TCM.

The acrid raphides in tuberous root of Pinellia ternata have lipophilic character and are specifically denatured by ginger extract.

Unprocessed dried tuberous root of Pinellia ternata (Pinellia Tuber) has been used as a component of traditional Japanese Kampo medicine, while this crude drug is usually used after processing with Ginger in traditional Chinese medicine (TCM). It is known that the raphides contained in unprocessed Pinellia Tuber can induce severe acrid irritation of the oral and laryngopharynx mucosa when it is boiled insufficiently. However, the mechanism of the inducing irritation by the raphides nor that of the detoxification by heat or processing with Ginger have been left unclear, mainly because of the difficulties in the extraction and the purification of the raphides and in the assays of acridity. In this study, we developed an easy protocol that can be used to collect raphides from unprocessed Pinellia Tuber and an assay protocol that can be used to evaluate the acridity of the raphides in vitro. The raphides of Pinellia Tuber were discovered to have a lipophilic character and to be collected easily by the extraction using petroleum ether. It was also found that the denaturation of the raphides could be assayed by the dispersity of them in petroleum ether layer of the water/petroleum ether partition, and the acridity of the raphides was found to be in correlation with the assayed denaturation. The raphides were denatured by heat, methanol, or Ginger extract and the denaturing activity of Ginger on raphides was found to be attributable to its lipophilic and thermostable components, which may explain the meaning of the processing of Pinellia Tuber with Ginger in TCM, and may lead to the development of an easier and safer protocol to administer Pinellia Tuber. In addition, it was found that rinsing the mouth with salad oil can effectively relieve irritation of the oral mucosa caused by unprocessed Pinellia Tuber, probably due to the lipophilicity of the raphides.