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...taken from the ecosystem of the bryozoa Bugula neritina. Ulmic acid is loosely defined group of molecules that are the alcohol extracts of naturally occurring organic matter. The FT-ICR analysis focuses on carbon compounds [C.sub.16]-[C.sub.24] and [C.sub.35]. [C.sub.35] is examined by FT-ICR because its structure may represent the bryophan ring, the central structural feature in all bryostatins.
Keywords: Ulmic acid, FT-ICR, MALDI-TOF-MS, bryostatin
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INTRODUCTION
Humic substances (HS) are the product of plant and animal decay and are ubiquitous in nature (1, 2, 3). Divided by chemical and physical characteristics, HS are separated into categories called humic acid (HA), fulvic acid (FA), and humin. Both HA and FA belong to the water-soluble class of compounds. This loosely defined group of molecular species can include sugars, lignin, peptides and proteins, antibiotics (i.e., lactams and tetracyclins), carbohydrates (and cyclitols), lipids, nucleic acids and component units, terpenoids including retinoids and steroids, tetrapyrroles and related compounds. Some of these compounds have a low water solubility and subsequently aggregate in the aqueous phase (4, 5). Ulmic acid is defined as the alcohol-based extract of naturally-occurring organic matter (NOM). There exists little research in the literature on ulmic acid or its chemical composition. Marine natural products (MNP) are typically large organic compounds with low water solubility. Many MNPs are thought to exist in the local ecosystem or produced by bacteria that have a symbiotic relationship with the host organism. Original work in this lab with NOM focused on fundamental physical and chemical characteristics such as studying aggregate sizes and natural chlorination processes (2-5). Recently NOMs have been studied to better understand ecosystems that contain organisms that produce marine natural products. Extracting solvents used to remove MNPs from their host organism have traditionally been methanol, ethanol, or methanol/chloroform.
FT-ICR analysis of molecular samples exhibits mass accuracy and resolution (6). It has been successfully applied to the analysis of Suwannee River humic acid (7) and led to the assignment of thousands of empirical formulas for the HA standard obtained from the International Humic Substance Society located at the Georgia Institute of Technology (Atlanta, GA). HA has a very low solubility in alcohols due to the large number of carboxylate groups. MALDI-TOF-MS is widely used for high-mass nonvolatile molecular species that include sugars, peptides, and proteins. In this lab, FT-ICR and MALDI-MS have recently been incorporated in studies involving the marine natural products bryostatin and ET743 (8-12).
Little is known about the actual production of a marine natural product by a bacterial species. Do the bacteria use enzymes to link together a series of small molecules (i.e., ethanol, acetate) through a complex synthesis to form a large structure such as bryostatin? Does it simply take a single large molecule that is ubiquitous in the environment and perform a few simple steps to reach the final product? Are there any obvious precursors in the host organism's ecosystem? There is no single set of experiments that can completely define the marine geochemistry of an ecosystem and outline the synthesis of a complex molecule. However, systematic data gathering can help scientists define the basic chemical conditions in which the bacterial species resides. In generating the data tables presented here, there is a hope to provide other scientists with a glimpse into the organic constituents present in the Bugula neritina ecosystem that are extracted with methanol. Figure 1 presents a possible scheme for either the degradation or synthesis of bryostatin involving smaller organic species. For the degradation one would start at the top of the schematic and follow the route down, and in a synthesis one would start at the bottom and move up. A number of schemes have been developed in which the weakest bonds or reactive centers are considered in order to discover potential precursors identified in the extract.
[FIGURE 1 OMITTED]
In searching for a potential precursor both here and in past mass spectrometry-based studies,...
NOTE: All illustrations and photos
have been removed from this article.
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