I. Applications of quantitation of stable isotopic tracers by fast atom bombardment mass spectrometry. II. Structure elucidation of a series of acetogenins by mass spectrometry

Ya-Mei Liu, Purdue University

Abstract

Part I. Isotopic tracers have played a major role in developing our present understanding of the distribution and movement of essential metals in living system. Most investigations have used radioactive isotopic tracers because they are easily quantified in biological materials. Although stable isotopes could also be used as tracers, they have not been used extensively because they are difficult to quantify with high accuracy. We have developed a method which uses a conventional high resolution mass spectrometer equipped with a fast atom bombardment source to quantify stable isotopic tracers of calcium and magnesium with high accuracy. This method has been used to determine intestinal absorption of calcium and magnesium by nine low birthweight infants. In addition, the endogenous fecal calcium excretion had been determined with this method. Part II. Tetrahydrofuranoid acetogenins are a new class of higher plant compounds that are characteristic of the plant family Annonaceae. Because these long-chain polyketide derivatives are showing a number of promising biological activities, there is considerable interest in isolating and characterizing these acetogenins. A variety of mass spectral methods were used to establish the structures of a series of acetogenins, including EI and CI mass spectra, exact masses, and MS/MS. Because of their low volatility and thermal instability, EI mass spectra of the acetogenins usually have few peaks which can be directly related to the original structure. As a result, this investigation has made extensive use of trimethylsilyl (h$\sb{3}$ and d$\sb{3}$) and acetyl (h$\sb{3}$ and d$\sb{3}$) derivatives. The EI mass spectra of the trimethylsilyl derivatives have numerous fragment peaks which are diagnostic of molecular structure.

Degree

Ph.D.

Advisors

Smith, Purdue University.

Subject Area

Analytical chemistry

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