Electronic Theses and Dissertations


Jing Li

Date of Award


Document Type


Degree Name

Ph.D. in Pharmaceutical Sciences

First Advisor

Ikhlas A. Khan

Second Advisor

Marc Slattery

Third Advisor

Jordan K. Zjawiony

Relational Format



During the last decade, the use of herbal medicine has expanded globally and gained popularity. With the tremendous expansion in the use of herbal medicine worldwide, safety and efficacy as well as quality control of herbal medicines have become more and more issues of concern for both health authorities and the public. Although herbal medicine has been in use for hundreds to thousands years, very limited science-based data exist to explicit its chemical constituents, pharmacological activities and toxicity. Therefore, lack of scientific evidence for herbal medicine usage elicits the need for systematic studies of herbal medicine, including phytochemical, analytical, and biological investigation.

Two projects are included in the dissertation. The first one is the “Science Based Authentication of Dietary Supplements - Studies of Scutellaria Species on the Chemical Constituents, Analytical Method, and Biological Activities”. The second project is the “Phytochemical Investigation of Pfaffia paniculata Kuntze”. American skullcap (Scutellaria lateriflora L.), belonging to the family Labiatae, is native to North America and was used as a tonic, tranquilizing, and antispasmodic remedies. Since 1989 safety concerns about American skullcap were raised due to the reports of hepatotoxic reactions after skullcap-containing preparations were ingested. Therefore, this plant was listed in the FDA Poisonous Plant Database and has been classified as an “Herb of Undefined Safety”. Meanwhile, it was reported to be adulterated with germander, e.g. Teucrium chamaedry, and T. canadense, which is a group of plants with hepatotoxicity. Very few studies have been previously reported associated with the quality control, toxicity investigation, and pharmacological activities of this herbal medicine as well as compounds isolated from it. The primary objective of this project is to explore the chemical constituents of American skullcap, which will be used as reference markers to develop a validated chemical fingerprinting method for the differentiation of it from its adulterant, germander. From the MeOH extract of the aerial parts of this plant sixteen compounds, including three minor coumarins in which two are new, six flavonoids, four triterpenes, two steroids, and one fatty acid were isolated and characterized. In order to compare the similarity of chemical components between American skullcap and Chinese skullcap (S. baicalensis), also to obtain more marker compounds, the chemical components of Chinese skullcap, which is the most often used herb medicine in this genus, were also studied and seventeen flavonoids have been isolated. Based on the chemical constituents, a simple HPLC-PDA fingerprinting method was developed, which can be used to authenticate S. lateriflora species, to distinguish it from its potential adulterants, to compare the chemical profiles of related species in this genus, and to assess the quality of commercial products claiming to contain S. lateriflora. In the present study three classes of compounds, including eleven flavonoids isolated from two Scutellaria species mentioned above and two phenylpropanoids, as well as one diterpene isolated from T. canadense, were used as markers simultaneously to provide comprehensive analysis for the above mentioned purposes. As part of the efforts of this project, a HPLC/ESI-MSn method was established which alloa fast characterization of thirteen flavonoids and one stilbene derivative from American skullcap without time-consuming isolation of compounds even if reference compounds are not available. The biological activities of the two skullcap extracts and thirteen flavonoids isolated from them were evaluated on a panel of bioassays, including cytotoxicity, antioxidant, anti-inflammatory, estrogenic activity and activations on peroxisome proliferator-activated receptor-alpha and -gamma (PARP and PPARγ). Neither skullcap extracts nor pure compounds tested shocytotoxicity against a panel of mammalian normal and solid tumor cell lines at the tested concentrations. During the investigation of chemical constituents of American skullcap no neoclerodane diterpenes, which are responsible for the hepatotoxicity in germander (Kouzi et al., 1994), were found. Taken together, these evidences suggest that the reports of hepatotoxic reactions on American skullcap might very likely be due to its adulterant germander. In the present bioassay study, the most significant finding was the identification of PPARs activation of skullcap extracts as well as several characteristic flavonoids, such as baicalein, baicalin, wogonin, and chrysin etc. that provides some information on possible new application of skullcap, especially American skullcap, for the treatment of diabetic-related diseases. Also the potent activity of these flavonoids on PPARs suggests the potential of these flavonoids as leads for PPARα and PPARγ agonists.

P. paniculata Kuntze, belonging to the family Amaranthaceae, is a large, rambling, shrubby ground vine with an intricate, deep, and extensive root system. It is the most employed species in commercial preparations in Brazil as “Brazilian ginseng” and has been commonly used for three centuries with the same indications as American and Asian ginseng. More than fifty preparations, which contained or were produced from plant P. paniculata are available on USA market, but no analytical method(s) existed to assess the quality of P. paniculata raw materials, and the products claiming to contain P. paniculata. In order to develop an appropriate validated quantitative analytical method for the quality control of this plant material and dosage form the detailed phytochemical investigation of P. paniculata was carried out. Two new nortriterpenoids pfaffine A and B, one new compound pfaffine C, along with eleven known compounds were isolated and identified from the roots of this plant. These compounds will be used as markers for quality control of raw materials of P. paniculata as well as products claiming to contain this species.





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