Abstract: Aim To investigate the plant origin and the identity of the red substance on the surface of Hong Dangshen, a unique medicinal material for diarrhea in Hong Kong. Methods The HPLC fingerprints and 5S rRNA gene spacer sequences of Hong Dangshen were obtained and compared with those of genuine species of Radix Codonopsis. The X-ray diffraction spectrum of the red substance was analyzed and compared with that of Halloysitum Rubrum. Results Hong Dangshen showed very similar HPLC fingerprints to the Codonopsis species and the highest similarity to Codonopsis pilosula var. modesta in terms of 5S rRNA gene spacer sequences. The X-ray diffraction spectrum of the red substance was consistent with that of Halloysitum Rubrum. Conclusion The source plant of Hong Dangshen was suggested to be Codonopsis pilosula var. modesta, one of the genuine original plants of Radix Codonopsis (Dangshen) in the China Pharmacopoeia (2005 edition). The red substance on the surface of Hong Dangshen was indicated to be Halloysitum Rubrum, a traditional medicinal mineral for chronic diarrhea. Our data suggest that Hong Dangshen is derived from the roots of Codonopsis pilosula var. modesta which has been processed with Halloysitum Rubrum, and the name is suggested to be Radix Codonopsis Praeparata Halloysita Rubra.

Key words: Radix Codonopsis Praeparata Halloysita Rubra, Radix Codonopsis Praeparata Halloysita Rubra, Codonopsis pilosula var. modesta, Codonopsis pilosula var. modesta, HPLC, HPLC, 5S rRNA gene spacer, 5S rRNA gene spacer, X-ray, X-ray, Halloysitum Rubrum, Halloysitum Rubrum, lobetyolin, lobetyolin