Chemical Characterization of Pseudognaphalium obtusifolium by Gas Chromatography - Mass Spectrometry (GC-MS) to Assess Potential Therapeutic Phytochemicals and Toxicological Concerns Using Simulated Use Conditions
Master of Science
Sarah Rutan, PhD
Jason Flora, PhD
Maryanne Collinson, PhD
Julio Alvarez, PhD
Scott Gronert, PhD
Matthew Halquist, PhD
Chemical Characterization of Pseudognaphalium obtusifolium by Gas Chromatography – Mass Spectrometry (GC-MS) to Assess Potential Therapeutic Phytochemicals and Toxicological Concerns Using Simulated Use Conditions
By Regina Ballentine
Virginia Commonwealth University, 2019
Director: Sarah C. Rutan, Professor, Department of Chemistry
Currently, there is an increasing demand for natural therapies and herbal products to treat various ailments. It is generally believed that natural therapies have fewer side-effects than traditional western medicine; however, they are often used in different strengths and formulations without consistency of the levels of target compounds or knowledge about toxicity. Due to this growing trend, a comprehensive chemical evaluation of plants used for medicinal purposes is necessary.
Pseudognaphalium obtusifolium is a plant that has been used historically by Native Americans as an herbal medicine. It is a flowering plant belonging to the Asteraceae family indigenous to the Eastern United States. There are documented accounts of the Native Americans using the herb therapeutically. Reportedly, they used the plant to prepare tea and as filler for bedding. Additionally, they smoked the plant material.
To date, there has been little research published on the chemical composition of this plant. Thus, the objective of this work was to conduct a chemical survey of P. obtusifolium using methodologies that would simulate the three historical routes of administration (tea, bedding material, and smoke inhalation).
To determine the types of compounds that may be found in the plant, initial experiments using pressurized solvent extraction (PSE) with an ethanolic solvent were performed followed by analysis using gas chromatography – mass spectrometry (GC-MS) in scan mode. This extraction technique enabled a broad range of compounds to be identified.
For the analysis of the tea, the leaves and the flowers were ground and analyzed separately. The “tea” simulation was then performed using a water extraction which was then back extracted into dichloromethane for GC-MS analysis in Selected Ion Monitoring (SIM) mode. Seventeen target compounds (terpenes, terpinoids, flavanoids, etc.) were quantified using this method.
A bedding material simulation was performed using headspace solid phase micro-extraction (HS-SPME) to collect the volatile and/or semi-volatile components of the headspace. The compounds collected on the SPME fiber were then analyzed by GC-MS in scan and SIM modes to qualitatively and quantitatively determine the types of chemical compounds (most of which were terpenes) that may be off-gassed from bedding material. This analysis compared levels of compounds in two different crop years and four terpene compounds were quantified.
To simulate smoking of the plant material, the leaves and flowers were fashioned into smoking articles. Sample collection was performed by a smoking machine and smoke condensate was collected. The smoke condensate was then analyzed by GC-MS in scan mode. As combustion and pyrolysis of plant material are known to produce toxic products, specific potentially harmful compounds were investigated and quantified.
This chemical analysis of P. obtusifolium identified target compounds that can be found in the three simulated usage forms. Identification of these compounds gives insight on why the Native Americans may have used P. obtusifolium as an herbal medicine. Among the detected compounds, there were many unknowns. Elucidating these unknown compounds will be important in the effort to understand the full chemical profile of this plant.
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