By Eric Brand

The botanical sources of Chinese medicinals in the Curcuma family are rather complex.  The medicinals Yu Jin, E Zhu, and Jiang Huang are derived from the roots and rhizomes of similar plants, and in many situations the same botanical species can be used for multiple medicinals, depending on the processing method and plant part used. 

The root of the plant Curcuma wenyujin is often used as Yu Jin, and the root of Curcuma longa, Curcuma kwangsiensis and Curcuma phaeocaulis are used as Yu Jin as well.  When Curcuma wenyujin is processed with pao zhi and sliced differently, it is known as E Zhu, and the rhizomes of Curcuma kwangsiensis and Curcuma phaeocaulis are regarded as E Zhu as well.  The rhizome of Curcuma longa is known as Jiang Huang, and the uncooked rhizome of Curcuma wenyujin is a form of Jiang Huang that is formally known as Pian Jiang Huang.  Pian Jiang Huang is the most commonly-used form of Jiang Huang in Eastern China, such as the region around Zhejiang and Shanghai. 

Pian Jiang Huang and standard Jiang Huang have been used interchangeably for years and they have only recently been separated into separate entries in the Chinese Pharmacopoeia.  The TCM actions ascribed to the two products are thus identical, but they have been separated into two entries because they are derived from different botanicals.  This is a somewhat similar situation to that of astragalus and hedysarum.  In new editions of the Chinese Pharmacopoeia, astragalus (Huang Qi) and hedysarum (Hong Qi) have separate entries to preserve their botanical distinction, but traditionally they were regarded as two forms of the same herb with regional variations in preference.  Thus, the precise botanical identity of medicinals such as Yu Jin, Jiang Huang, and E Zhu varies depending on region and the specific product form used.