“The very first step towards success in any occupation is to become interested in it.“Sir William Osler (1849 – 1919)
Pioneers in Natural Product Mass Spectrometry
Natural products have been the focus of the van Breemen laboratory for decades. Our laboratory was among the first worldwide to measure carotenoids using LC-MS and LC-MS/MS, and and introduced innovative ionization techniques to carotenoid analysis including fast atom bombardment, electrospray and atmospheric pressure chemical ionization. In support of our clinical studies of botanical safety and efficacy, our laboratory has developed, validated and applied many LC-MS/MS assays to the quantitative analysis of natural products in human serum and tissues. For example, we have measured lycopene from tomatoes in human serum and prostate tissue, we have measured xanthohumol and 8-prenylnaringenin from hops in human serum and breast tissue, and we have measured red clover isoflavones, black cohosh triterpene glycosides, and licorice flavanones in human serum.
Still at the forefront of natural product analysis, we are actively exploring how ion mobility mass spectrometry can separate natural product mixtures for tandem mass spectrometric characterization. As an alternative to liquid chromatography-mass spectrometry (HPLC-MS and UHPLC-MS), ion mobility-MS can separate natural products in the gas phase in just milliseconds compared with minutes for chromatography. Examples of our natural product research using ion mobility-MS includes separations of cis- and trans-carotenoids like β-carotene and lycopene, and separations of procyanidins from cocoa and cranberry.
Inventors of Affinity Selection-Mass Spectrometry
Noteworthy among the innovations in natural products research, drug discovery and mass spectrometry in the van Breemen laboratory are the inventions of the Affinity Selection-Mass Spectrometry (AS-MS) techniques of pulsed ultrafiltration-mass spectrometry (PUF-MS) and magnetic microbead affinity selection screening (MagMASS). These are pioneering approaches to identify ligands for therapeutically important receptors beginning with complex mixtures such as botanical extracts or combinatorial libraries. To put the impact of PUF-MS and MagMASS for natural product drug discovery in perspective, one can accomplish in a few days using these affinity selection-mass spectrometry techniques what would take a team of researchers several months or more to complete using bioassay-guided fractionation (still the standard approach in most natural product laboratories). In addition, these AS-MS approaches offer the unique ability to discover ligands that bind allosterically and cooperatively to sites other than the active site. This provides an opportunity to find pairs of ligands that bind simultaneously and synergistically to the same pharmacological target. After identifying natural product ligands to important therapeutic targets, the van Breemen laboratory then uses mass spectrometry to explore the human absorption, metabolism and safety of these potential therapeutic agents in vitro and in vivo. Note that AS-MS is rapidly being adopted by the pharmaceutical industry as a faster, less expensive and more effective tool for high-throughput screening of combinatorial libraries.
Prevention of Diseases of Aging: Neurological Disease and Cancer Chemoprevention
Since the 1990s, the van Breemen laboratory has been actively involved in the discovery and development of natural products for the prevention of diseases of aging. We have also utilized mass spectrometry to measure biomarkers in serum, urine and tissues that indicate risk or progression of cancer and neurological diseases like Alzheimer’s disease, multiple sclerosis and Parkinson’s disease. For example, we have carried out clinical trials to investigate how lycopene (the red carotenoid in the tomato) might prevent prostate cancer in men. In all of our clinical studies, we have developed and applied mass spectrometry to measure markers of oxidative stress and biomarkers of disease. For example, we routinely measure oxidative stress markers such as 8-oxo-deoxyguanosine as an indicator of DNA damage, and 8-iso-PGF2α as a biomarker of lipid peroxidation. For neurological degenerative diseases, we use mass spectrometry to measure glycosphingolipids like psychosine, sulfatides, and aggregation disease proteins like β-amyloid and tau. We also use our affinity selection-mass spectrometry drug discovery technology to discover new natural products that can help prevent cancer and neurodegeneration.
Safety of Natural Products: Drug-Botanical Interactions
To ensure the safe use of dietary supplements, especially botanical dietary supplements, the van Breemen laboratory is investigating their potential for drug interactions. We are studying standardized extracts of botanicals for possible inhibition or induction of drug metabolizing enzymes and drug transporters. To ensure reproducibility, these extracts are botanically authenticated and both chemically and biologically standardized. Our approach utilizes in vitro assays of enzyme and transporter inhibition and induction (using human liver and intestinal microsomes, cell monolayer models of intestinal transport, and mass spectrometry) as well as human clinical trials to verify the clinical relevance of our preclinical predictive models. In humans, we are evaluating the potential for botanical dietary supplements to cause pharmacokinetic drug interactions; in other words, we are determining whether the simultaneous use of therapeutic drugs and dietary supplements can change the length of time and concentration of drugs in the human body. Currently, we are carrying out three clinical trials involving hops, red clover and licorice, which are popular dietary supplements used by menopausal women to control menopausal hot flashes as alternatives to hormone therapy.
“An ion for your thought?”
Richard van Breemen
Professor of Medicinal Chemistry
Department of Pharmaceutical Sciences
College of Pharmacy
305 Linus Pauling Science Center
Corvallis, Oregon, USA, 97331