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The NCI Drug Discovery program relies on a steady supply of compounds for screening, and pure bioactive lead drug compounds have to be supplied to research labs. The Natural Products Support Group processes all of the higher plant, marine organism and fungal specimen acquisitions made by the NCI to get them into a form suitable for biological evaluation. From each specimen both an organic solvent soluble and an aqueous soluble extract is prepared by methods given on the NPSG homepage. At present the library of crude natural products extracts consists of ~160,000 unique materials, with that number constantly increasing at the rate of ~8,000 per year. All natural products extracts are placed into 96 well microtiter plate format for use in the screening laboratories. There are ~1,750 platemaps, each plate containing 88 different substances. As microtiter plates are consumed in screening, the library is continually replenished. About 30,000 microtiter plates per year are produced in both 96 well and 384 well formats. The process for determining whether the toxic component present in a crude natural product extract, found to be of interest in a screen, is a known compound or something new, is termed dereplication. Dereplication of toxic extracts is carried out by HPLC chromatography of crude extract, with the eluate from the column passing through four detectors: Evaporative Laser Light Scattering, fluorescence, diode array and API mass spectrometers, while ~95% of the flow is collected into microtiter plate format. The microtiter plate is bioassayed to determine which wells contain the component of interest. Often, through combination of the physical and biological data, and computer literature searches, compound identity can be determined. The analytical information collected from each crude extract becomes a part of the NCI archives. When some larger quantity of the compound is required for research use, the NPSG will devise a scaled up method for isolation, and will produce from a few milligrams, to kilograms, of the compound for NCI researchers. Examples of these projects can be found on the NPSG homepage. Credentials Mr. McCloud is a graduate of The Ohio State University, and did graduate studies in the Department of Biochemistry at North Carolina State University under the direction of professors F.H. Smith and S.B. Tove. During military service he spent two years in the Department of Virus Diseases at Walter Reed Army Institute of Research (WRAIR) working in the areas of viral epidemiology and vaccine development under Drs. J.M. Dalrymple and W.E. Brandt. Natural Products Chemistry experience was gained as a member of the scientific staff in the Department of Medicinal Chemistry, School of Pharmacy at Purdue University, working for Dr. J. M. Cassady, whose major research interest was in discovery of new anticancer compounds from higher plant sources. Mr. McCloud has been at the Frederick facility since 1986, where he established the Natural Products Extraction Lab, and support facilities. His professional interest, aside from discovering novel bioactive natural products, is in development of new chromatographic materials and techniques. He is a member of the American Society of Pharmacognosy and a participant in the Washington Area Chromatography Discussion group and the Laboratory Robotics Interest Group. Recent Publications NCBI PubMed listing of publications by Thomas McCloud Stephen AG, Worthy KM, Towler E, Mikovits JA, Sei S, Roberts P,
Yang QE, Akee RK, Klausmeyer P, McCloud TG, Henderson L, Rein A,
Covell DG, Currens M, Shoemaker RH, Fisher RJ. Identification of
HIV-1 nucleocapsid protein: nucleic acid antagonists with cellular
anti-HIV activity. Biochem Biophys Res Commun. 2002 Sep 6;296(5):1228-37. Simon, J.E., Jato, J.C., Thomas, D.W., Symonds, P., Alkire, B.H., McCloud, T. C., Cragg, G.M., Morales, M.R., Foster, P.F., Miller, J.S., Gereau, R.E., (1996) "Investigations on Ancistrocladus korupensis: A Promising Source of Michellamine B from Cameroon", J. Soc. Economic Botany Beutler, J.A., Alvarado-Lindner, A.B. and McCloud, T.G.: Further studies
on phorbol ester bioactivity in the Euphorbiaceae. Annals of the Missouri
Botanical Garden 83:530-533, 1996. McCloud, T.G., Britt, J.R., Cartner, L.K., Pearl, K.C., Majadly, F.D., Muschik, G.M., Klueh, P.A., Cragg, G.M., Thomas, D.W., Jato, J.G., Simon, J.E.: Quantitation of the Anti-HIV Alkaloids Michellamine A & B by HPLC. Phytochemical Analysis 8: 120 - 123, 1997. McCloud, T.G., Burns, M.P., Majadly, F.D., Muschik, G.M., Miller, D.A., Poole, K.K., Roach, J.M., Ross, J.T., Lebherz,W.B., III: Production of Brefeldin-A. Jol. of Industrial Microbiology 15: 5-9, 1995. Chan, K.C., Majadly, F., McCloud, T.G., Muschik, G.M., Issaq, H.J. and Snader, K.M.: Micellar electrokinetic chromatography of the anti-human immunodeficiency virus (HIV) agent michellamine B with absorption and laser-induced fluorescence detection. Electrophoresis 15: 1310-1315, 1994. Beutler, J.A., McKee, T.C., Fuller, R.W., Tischler, M., Cardellina, J.H.,II, McCloud, T.G., Snader, K.M. and Boyd, M.R.: Frequent occurrence of HIV-inhibitory sulfated polysaccharides in marine invertebrates. Antiviral Chem.& Chemotherapy 3: 167-172, 1993. Schaufelberger, D.E., McCloud, T.G. and Beutler, J.A.: Laser-light-scattering detection for high-speed countercurrent chromatography. J. Chromatogr. 538(1): 87-90, 1991. Beutler, J.A., Alvarado, A.B., Schaufelberger, D.E., Andrews, P. and McCloud, T.G.: Dereplication of phorbol bioactives: Lyngbya majuscula and Croton cuneatus. J. Nat.Prod. 53: 867-874, 1990. Witherup, K.M., Look, S.A., Stasko, M.W., McCloud, T.G., Issaq, H.J., Muschik, G.M.: High Performance liquid chromatographic separation of taxol and related compounds from Taxus brevifolia. J. Liq. Chromatogr. 12(11), 2117-32,1989. Stasko, M.W., Witherup, K.M., Ghiorzi, T.J., McCloud, T.G., Look, S., Muschik, G.M., Issaq, H.J.: Multimodal thin layer chromatographic separation of taxol and related compounds from Taxus brevifolia. J. Liq. Chromatogr. 12(11), 2133- 43, 1989. Beutler, J.A., Alvarado, A.B., McCloud, T.G. and Cragg,G.M.: Distribution of phorbol ester bioactivity in the Euphorbiaceae. Phytotherapy Res. 3: 188-192, 1989. McCloud, T.G., Klausmeyer, P, Newman, D.J: Dereplication of Penicillium Bioactives Using Multidector HPLC and Bioactivity Profiles . Presented at the American Society of Pharmacognosy Annual Meeting July 22-26, 2000, Seattle, WA. |
