Background: Two species of ginger were used in Thai traditional medicine as Zingiber officinale Roscoe and Zingiber ligulatum Roxb.
Objective: To investigate for identification two types of ginger by morphological and microscopic characters, DNA profiles, and determination of 6-gingerol content by HPLC.
Material and Method: Fresh rhizomes of two gingers, their ages more than one year were collected from 12 sources in 4 parts of Thailand. The fresh leaves were also collected for studying DNA profile by amplified fragment length polymorphism (AFLP) method.
Results: The morphological characters of two types of gingers were almost corresponded to AFLP patterns and they were identified as Z. officinale Rocs. and Z. ligulatum Roxb. Microscopic examinations of dried rhizomes from the both species showed the same pattern. By means of HPLC and TLC methods, 6-gingerol content was found only in Z. officanale in range of 2.58-17.04% but disappeared in Z. ligulatum.
Conclusion: Determination of 6-gingerol content by HPLC or TLC pattern can be used to identified two types of ginger used in Thai Traditional Medicine.

Keywords: Zingiber officinale, Zingiber ligulatum, DNA mapping, 6-gingerol