WILEY AWARD ADDRESS

Monday, September 22, 2008, 1:00 p.m. – 1:30 p.m.

Innovations in Mass Spectrometry: Advancing Research in Natural Products

Professor Richard B. van Breemen, Ph.D. Winner of the 2008 Harvey Wiley Award Professor of Medicinal Chemistry and Pharmacognosy University of Illinois at Chicago College of Pharmacy

Until the development of liquid chromatography-mass spectrometry (LC-MS), natural product studies using chromatography and mass spectrometry were limited to volatile and thermally stable compounds that could be analyzed using GC-MS. As the ionization technology advanced, isolated non-volatile compounds could be analyzed using mass spectrometers equipped with desorption ionization techniques such as fast atom bombardment, laser desorption or field desorption. When direct liquid introduction methods such as continuous-flow fast atom bombardment mass spectrometry were introduced, mixtures of natural products such as botanical extracts containing carotenoids and chlorophylls could be analyzed for the first time using LC-MS. By the early 1990s, LC-MS using electrospray and atmospheric pressure chemical ionization eclipsed all previous LC-MS techniques. These innovations have enabled biomedical mass spectrometrists to characterize and measure natural products belonging to virtually any chemical class - even those present in complex mixtures and matrices.

Today, accurate mass measurements of molecular ion species provide information that enables the determination of the elemental compositions of natural products. In addition, tandem mass spectrometry (MS-MS) studies produce structurally significant fragment ions that facilitate compound identification, and hyphenated methods based on LC-MS-MS are being used for the quantitative analysis of natural products in complex mixtures. After becoming a standard tool for the quantitative analysis of pharmaceutical agents for the purpose of quality control or in support of clinical trials, LC-MS-MS is now used for the standardization of botanical dietary supplements and in support of clinical trials of the safety and efficacy of botanical dietary supplements and isolated natural products. For example, LC-MS-MS assays were developed for the quantitative analysis of isoflavones and triterpene glycosides in extracts of red clover (Trifolium pratense L.) and black cohosh (Cimicifuga racemosa L. Nutt.) at the UIC/NIH Botanical Center for Dietary Supplements Research. Then, these standardized extracts were used to measure isolflavones and triterpene glycosides in blood and urine samples obtained during phase I pharmacokinetics studies and phase II clinical trials of the safety and efficacy of these botanical dietary supplements in the relief of hot flashes in menopausal women.

For the discovery of pharmacologically active compounds, LC-MS screening assays have been developed which facilitate the rapid isolation and identification of the active natural products in complex extracts. As an example, ultrafiltration LC-MS was developed and is being used at the UIC/NIH Botanical Center for Dietary Supplements Research for the discovery of estrogenic natural products in botanical dietary supplements used by menopausal women. Additional LC-MS screening assays based on targets such as RXR, cyclooxygenase-2, and Keap1 are being used to screen extracts of marine bacteria and botanicals for cancer chemoprevention agents. After pharmacologically active compounds are identified, LC-MS and LC-MS-MS may be used to facilitate in vitro, in vivo and clinical trials of pharmacokinetics, bioavailability, metabolism, and toxicity. As an example of safety testing, an LC-MS-MS assay has been developed to screen natural products for metabolic activation to electrophilic intermediates that can alkylate proteins and DNA and potentially cause toxicity.

As a result of technological developments in mass spectrometry over the last 20 years, highly selective and sensitive assays based on LC-MS and LC-MS-MS now enable the determination of mass, elemental composition, and structural features that facilitate the rapid identification of natural products in complex biological matrices such as plant or bacterial extracts. Screening assays based on LC-MS accelerate the discovery of pharmacologically active compounds from natural product sources. Quantitative assays based on LC-MS-MS are being used to support the chemical standardization of botanical dietary supplements. Finally, LC-MS-MS assays are being used to expedite studies of the safety and efficacy of pharmacologically active compounds in both preclinical and clinical studies.

ABOUT DR. VAN BREEMEN

Professor Richard van Breemen received his Ph.D. in Pharmacology from the Johns Hopkins University in Baltimore, Maryland, in 1985, and a B.A. in chemistry from Oberlin College in Oberlin, Ohio, in 1980. From 1985-1986, he carried out postdoctoral research in the Middle Atlantic Mass Spectrometry Facility at the Johns Hopkins University School of Medicine, which is a regional shared instrumentation facility supported by the National Science Foundation. After establishing a mass spectrometry facility for biotechnology research as assistant professor of chemistry at North Carolina State University, Professor van Breemen joined the University of Illinois College of Pharmacy in 1994 as associate professor of medicinal chemistry. Since 2000, he has been professor of medicinal chemistry at the University of Illinois. He is the co-director of the UIC/NIH Center for Botanical Dietary Supplements Research which was founded in 1999 and is also the Faculty Director of the Mass Spectrometry Laboratory of the UIC Research Resources Center which is a campus-wide shared instrumentation facility.

The research of Professor van Breemen concerns the application of liquid chromatography-tandem mass spectrometry to the discovery and development of botanical natural products as cancer chemoprevention agents and the investigation of botanical dietary supplements as alternatives to traditional estrogen replacement therapy. In the area of drug discovery, he is the co-inventor of pulsed ultrafiltration mass spectrometry, which is a technique for screening mixtures of compounds such as botanical extracts for potential new therapeutic agents. In addition to the discovery of pharmacologically active compounds, applications of pulsed ultrafiltration liquid chromatography-tandem mass spectrometry include the investigation of the metabolism, bioavailability, and toxicity of these lead compounds. His research is funded primarily by the National Institutes of Health including the National Cancer Institute, the Office of Dietary Supplements, the National Center for Complementary and Alternative Medicine, and the National Institute of General Medical Sciences.

Professor van Breemen is author or co-author of more than 200 scientific papers and two patents. Since 1997, he has been Editor-in-Chief of the journal Combinatorial Chemistry & High Throughput Screening (see http://www.bentham.org/ccht/). In addition, he is on the Editorial Board of Biomedical Chromatography. At scientific conferences, he has been recognized with awards for outstanding papers by the International Society for the Study of Xenobiotics and the American Oil Chemists Society. In 1995, he was named by the Editors of Spectroscopy as one of 19 “Bright Young Stars” in the field of analytical spectroscopy. Finally, he is the recipient of the University Scholar faculty award from the University of Illinois.