Comparison of Menthae Herba written with the same kanji characters () in Japan and China.

Menthae Herba is an herbal medicine whose name is written with the same kanji characters () in both the Japanese Pharmacopoeia, 18th Edition (JP) and in the Pharmacopoeia of the People's Republic of China (CP). However, the original plant are Mentha arvensis Linné var. piperascens Malinvaud in JP and Mentha haplocalyx Briq. in CP. To clarify the similarities and differences between Menthae Herba in Japan and that in China, morphological observations, essential oil component analysis, and DNA analysis were performed on marketed products of Menthae Herba in Japan and in China. The morphological observations based on the description of JP Menthae Herba showed that most of the samples matched the items listed in the description. Essential oil component analysis by gas chromatography-mass spectrometry showed that the amount of menthol varied among samples and that menthol was not always the principal compound in the oil. The original plant species was confirmed by DNA analysis of the rpl16 intron region in chloroplast DNA and all samples matched the sequence of M. canadensis. The results showed that Menthae Herba products distributed in both Japan and China contained M. canadensis, but they had different compositions of essential oil, with menthol-rich Menthae Herba being dominant in the Japanese market.