Advanced Mass Spectrometry Techniques and Computational Tools for the Chemical Characterization of Botanicals.
Friday, August 2, 2024 9am
About this Event
2100 SW Campus Way, Corvallis, OR 97331
a Chem Dept Thesis Defense ft: MD Nure Alam (Maier Group)
With the growing interest in dietary supplements, including botanicals, safety and quality control of herbal preparations have become important concerns. Traditionally, only one or a few marker compounds or pharmacologically active constituents have been used for evaluating authenticity and quality of botanical supplements. However, botanical preparations are chemically diverse multi-component mixtures, and the chemical composition can vary based on plant origins, harvest seasons, drying and preparation processes. Thus, to ensure quality and chemical consistency of botanical supplements a move to comprehensive characterization of the phytochemical constituents of botanical preparation is needed.
In this dissertation, analytical methods based on chromatography and advanced mass spectrometry techniques in conjunction with computational tools were developed and applied to detect, characterize, and quantify phytochemical constituents in two medicinal plants, Centella asiatica (L.) Urb. (CA) and Withania somnifera (L.) Dunal. (WS). Both plants are known for their purported antioxidant properties, improvement of cognitive function and use to ameliorate anxiety, depression and sleep disorders. The phytochemical constituents of these plants are complex and require robust analytical techniques to provide accurate characterization. Composition of the phytochemicals of both plants were explored using liquid chromatography tandem mass spectrometry (LC-MS/MS)-based metabolomics approach. LC-MS/MS based metabolomics is a molecular fingerprinting method for acquiring global profiles of small molecule constituents of complex mixtures including plant extracts.
Major phytochemical of C. asiatica are isoprenoid derivatives, which includes sesquiterpenes, pentacyclic triterpenoids and saponins, and phenylpropanoid derivatives, such as caffeoylquinic acids, and flavonoids. W. somnifera phytochemicals are steroidal lactones (withanolides and withanosides), alkaloids, withanamides, and phenolic compounds. Depending on origin and preparation, plants and derived extracts have distinct chemical compositions which are related to bioactive properties. Accurate characterization of each set of phytochemicals is critical to outline comprehensive bioactivity principles. The complete study is divided into three distinct chapters as described below:
Chapter 3: “Chemical profiling of Centella asiatica greenhouse-grown cultivars by high resolution mass spectrometry” describes the phytochemical-level investigation of four different cultivars of C. asiatica, grown and harvested at different times of the year in a greenhouse-controlled environment. Data reduction and clustering techniques were explored for determining distinction and diversity of cultivars. Innovative computational tools were introduced for studying differentiation of twelve neuroactive compounds during vegetative propagation for the cultivars.
Chapter 4: “Development of a characterization and identification strategy of phytochemicals from Withania somnifera (WS, Ashwagandha) plant materials by LC-HRMS/MS” provides the annotation of different compounds detected from methanolic extracts of root and leaf. The scope and limitations of MS-based metabolomics approach are discussed.
Chapter 5: “Development and application of a mass spectrometry-based assay for screening of electrophilic natural product in botanical extracts” investigates electrophilic compounds in W. somnifera root and leaf. This study provides proof of principle for drug discovery research with the promise of selective detection of bioactive natural products based on their distinct chemical reactivity.
Briefly, this research provides a platform to explore the diversity of phytochemicals in two medicinal plants: W. somnifera and C. asiatica using liquid chromatography tandem mass spectrometry (LC-MS/MS) based metabolomics approach. It provides a standard guideline to characterize known compounds in addition to identification of unknowns and is limited to secondary metabolites. The strategic method of investigation of phytochemical compositions and levels in different species and parts related to cultivation, sample preparation, instrumentation, and computations are transferable to medicinal plants grown in controlled environment.
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