Determination of Scientific Name of Bitter “Qust”: an Important Controversial Plant Source in the Iranian Medicinal Plants Market for Neurological Complications

Background and objectives: Traditional medicine could provide a hopeful area of research to mitigate the suffering of patients. “Qust” is one of the medicinal plants that are mentioned in Persian Medicine (PM) for treatment of neurological diseases. There is diversity within the scientific name of “Qust” in different references. Some have introduced Saussurea costus (Falc.) Lipsch. (Asteraceae), while others have presented Costus speciosus (J. Koenig) Sm. (Costaceae) as “Qust”. Since “Qust” is not endemic in Iran, there is difficulty to access to the whole plant for its identification. Hence, this study has aimed to identify available bitter “Qust” which is composed of roots of the plant in the Iranian market. Methods: Macroscopic characters and microscopic properties of powders and transverse sections of specimens with essential oil analysis of the Indian and one of the Iran herbal market samples using chromatography-mass spectrometry (GC-MS) were investigated for identification of bitter “Qust”. Results: Microscopic evaluation showed presence of secretory cavities and their specific size, narrow radial rows of conducting tissue alternating with broad medullary rays in the secondary phloem and xylem, presence of inulin, absence of starch and calcium oxalate crystals in the bitter “Qust” particles. Further, positive response was observed to S. costus identifying test. In the analysis of essential oils, active components of S. costus, such as dehydrocostus lactone, were identified in the examined essential oils. Conclusion: According to the results, it could be concluded that bitter “Qust” in Iran herbal market most probably is S. costus.