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Research Interest:

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Research Interest:
My research interests consist in the synthesis of natural and semi-synthetic products in order to study their biological activity. Currently, my laboratory group is working with the preparation of some unsaturated fatty acids to study their antibacterial, anticancer, and anti-topoisomerase activities. One of the special features that make my research group a competitive one is that they develop organic synthetic skills and also they are able to perform antimicrobial and anti-topoisomerase bioassays. In this sense, my students learn skills that prepare them for entering to graduate/medicine school, employment in the pharmaceutical, and contract synthesis industries.

Research Project 1:
Collaborators: Dr. Néstor M. Carballeira, University of Puerto Rico-Río Piedras Campus and Dr. José W. Rodríguez, Universidad Central del Caribe School of Medicine
Treatment of microbial infections has been problematic during the past years because the current drugs are losing their effectiveness, since microbes are acquiring resistance towards these treatments. Despite the fact that many compounds are being evaluated as antimicrobial agents, there is an urgency to develop new treatments in order to replace those which have lost effectiveness. For example, recently it was reported that novel synthesized diynoic fatty acids were antifungal against several strains of Candida albicans and Cryptococcus neoformans. Other studies have shown that unsaturated fatty acids were antimicrobial against susceptible- and methicillin-resistant S. aureus. Although there are several studies that explain that the fatty acid biosynthesis is a target for the antimicrobial activity of unsaturated fatty acids, just one report associated the antimicrobial activity of fatty acids with the DNA topoisomerase. For this reason, this research is intended to formally study the antimicrobial properties of commercially available and newly synthesized unsaturated fatty acids and how these properties are associated with the inhibition of the microbial topoisomerase II. In order to perform this study, two specifics aims were delineated. In specific aim 1, the antimicrobial activity of unsaturated fatty acids was evaluated using both the Kirby-Bauer and microdilution susceptibility tests. The Kirby-Bauer test used fatty acid-impregnated disks in order to test whether Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus saprophyticus, and Bacillus cereus are susceptible to specific fatty acid, while the microdilution susceptibility test used several dilutions of fatty acids in order to determine their minimal concentration that inhibit or kill the above-mentioned microbes. In specific aim 2, we are planning to study the effect of several antimicrobial fatty acids on the inhibition of E. coli topoisomerase II.

Research Project 2:
Collaborators: Dr. Néstor M. Carballeira, University of Puerto Rico-Río Piedras Campus and Dr. José W. Rodríguez, Universidad Central del Caribe School of Medicine
The antimicrobial properties of unsaturated fatty acids have been studied for many years with the goal of identifying new antibacterial treatments. Unsaturated fatty acids are mainly found in microorganisms, algae, and plants, where they act as a chemical defense against microorganisms. According to the literature, the antimicrobial properties of straight-chain unsaturated fatty acids are influenced by the chain length, positions of cis-double bonds, and degrees of unsaturation. For example, it had been reported that the antimicrobial properties of 2-alkynoic acids against Gram-positive and Gram-negative bacteria is influenced by the chain length. Among 2-alkynoic fatty acids reported in the literature, 2-hexadecynoic acid is the most interesting alkynoic fatty acid due to its antifungal, cytotoxic, and antimicrobial properties. In 2006, it was reported that 2-hexadecynoic acid was antimycobacterial against M. tuberculosis H37Rv. Literature had reported that the antimycobaterial properties of 2-hexadecynoic acid are due to the inhibition of the enoyl-ACP reductase (mycobacterial FabI), an important molecular target for the mycobacterial fatty acid synthesis. Although it is well known that fatty acid synthesis is a target for antibacterial activity of unsaturated fatty acids, further research needs to be done in order to find other molecular targets, e.g., DNA topoisomerases. DNA topoisomerases are nuclear enzymes that catalyze the breaking and rejoining of DNA strands and that are involved in generating the necessary topological and conformational changes in DNA. These changes are essential for several cellular processes such as replication, recombination, and transcription. In addition to their normal cellular functions, DNA topoisomerases are known to be important molecular targets for some antibacterial drugs. In order to gain further knowledge about the biological properties of 2-hexadecynoic acid, we performed the total synthesis of 2-hexadecynoic acid, evaluated its antibacterial and cytotoxic properties, and evaluated its inhibitory activity against human topoisomerase I. Our preliminary results revealed that 2-hexadecynoic acid was antibacterial against the Gram-positive Staphylococcus aureus, Staphylococcus saprophyticus, and Bacillus cereus at concentrations that ranges from 15.6 to 31.25µg/mL. Also, the cytotoxicity of 2-hexadecynoic acid against peripheral blood mononuclear cells (PBMC) was evaluated and we found that this fatty acid was cytotoxic against PBMC at 250 µg/mL. These results suggest that 2-hexadecynoic acid is more selective against bacterial cells than human cells. Moreover, we found that 2-hexadecynoic acid was inhibitory against human DNA topoisomerase I implying that the antibacterial activity of this fatty acid against Gram-positive bacteria could be a result, at least in part, responsible of the inhibitory activity of the acid against topoisomerases.

Research Project 3:

Collaborators: Dr. Nawal Boukli, Universidad Central del Caribe School of Medicine, Néstor M. Carballeira, University of Puerto Rico-Río Piedras Campus and Dr. José W. Rodríguez, Universidad Central del Caribe School of Medicine
This research project addresses the evaluation of the antibacterial properties of unsaturated fatty acids. Our preliminary results reveal that palmitoleic acid and 2-hexadecynoic acid were potent antibacterial unsaturated fatty acids, and we suggest that the cis-double bond at C-9 and the triple bond at C-2 are fundamental for their antibacterial activity. Based on these preliminary results, we are proposing the synthesis of the novel (Z)-9-hexadecen-2-ynoic acid because we believe that the incorporation of both a cis-double bond at C-9 and a triple bond at C-2 in this compound will increase its antibacterial potency against non-pathogenic and pathogenic bacteria. In addition, we are interesting to further study the antibacterial properties of (5Z,9Z)-5,9-hexadecadienoic acid, a diunsaturated analog of palmitoleic acid, because the literature has reported that this fatty acid has both antibacterial and anti-topoisomerase I properties. In this research project we will use the novel proteomic approach to analyze the bacterial response to the treatment of palmitoleic acid and its analogues (Z)-9-hexadecen-2-ynoic acid and (5Z,9Z)-5,9-hexadecadienoic acid. We believe that the presence of the above-mentioned fatty acids will induce change in the bacterial protein expression that can be characterized by using proteomic approach. By using proteomics, we are expecting to identify/validate differentially expressed proteins that are associated with important processes for bacterial cell life. We hypothesize that palmitoleic acid and its analogues will effectively suppress the growth of both non-pathogenic and pathogenic bacteria by inhibiting the activity of molecular targets, such as topoisomerase II (DNA gyrase). For this reason, we will study, for first time, inhibitory activity of antibacterial fatty acids against DNA gyrase in order to determine whether or not the inhibition of this enzyme is associated with the antibacterial properties of these fatty acids. In addition, we will corroborate results from bacterial DNA gyrase inhibitory tests with proteomics in order to identify differentially expressed proteins associated with this enzyme. All of these studies will provide us with a better understanding about the mechanistic pathway that explains the antibacterial activity of palmitoleic acid and its analogues. Furthermore, these studies will allow the development of more effective and broadly acting antibacterial fatty acids. Results from this research project will provide the foundations for the development of potent antibacterial agents to address the antibiotic resistance problem. For each specific aim of this project, we will combine well established methods with new approaches, with alternative approaches available for the novel experiments. Current experiments would be continued to study the antibacterial properties of the analogue of palmitoleic acid, while the bacterial responses to these fatty acids and the inhibitory tests against DNA gyrase will be also done in the project.

Dr. Sanabria’s research members:

Ms. Camille Ríos (PR-LSAMP Fellow)
Ms. Coral Jiménez (PR-LSAMP Fellow)
Ms.Idializ Domínguez (PRAABRE-INBRE Fellow)
Mr. Luis López (PR-LSAMP Fellow)

Former research members:

Ms. Nadja Soto (PR-LSAMP Fellow)
Mr. Christopher Rivera (PR-LSAMP Fellow)
Mr. Javier Fraguela (PRAABRE-INBRE Fellow)

Ms. Idializ Domínguez (right) and Mr. Luis López (left) during their poster presentation at the PRAABRE-INBRE External Advisory Committee Meeting, celebrated in San Juan, PR

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February 5th, 2013 at 5:11 am

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