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Research
We have been working in different fields of Organic Chemistry (chemistry of natural products, organic synthesis, NMR, and mass spectrometry).
Organic Synthesis
We have used organic synthesis as a way to obtain a wide range of potentially bioactive compounds. A wide range of organic compounds has been synthesized by our research group, such as dihydrobenzofuran neolignans [79, 82, 84, 88, 94, 95], and curcuminoids [89, 93].
Figure 1. Basic skeleton of dihydrobenzofuran neolignans (I) and monoketone curcuminoids (II).
Mass Spectrometry
In the last two decades, electrospray ionization mass spectrometry (ESI-MS) has made the analysis of non-volatile and high-molecular-weight compounds possible. However, because ESI is a soft ionization method, ions with low content of internal energy are produced with little or no fragmentation. For structure elucidation using ESI, tandem mass spectrometry (MS/MS) is usually employed. In MS/MS, precursors ions are selected and activated by different activation methods (most often, collision-induced dissociation, or CID), then producing fragment ions, which are separated in a second MS stage. One of the main focus of our group is the investigation of the gas-phase fragmentation reactions involved in ESI-CID-MS/MS. For this purpose, we have synergistically combined accurate-mass data, multiple-stage mass spectrometry (MSn), and thermochemical data estimated by Computational Chemistry. These studies are essential for understanding the effect of a substituent on the gas-phase fragmentation pathways and the data generated can be used for the identification of structurally-related compounds (e.g., in vivo or in vitro metabolites) without the need of isolation or even in de-replication of natural products using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS).
Scheme 1. The electrospray (ESI) ion source.
Scheme 2. The electrospray (ESI) ion source.
Besides investigating compounds we have synthesized in our lab [79, 94], our group also works in partnership with other groups, who have provided us with different synthetic and natural compounds [19, 26, 50, 73, 75, 83, 90, 94]. Therefore, if you have a series of compounds displaying similar structures, please, contact us to start a cooperative work.
Nuclear Magnetic Resonance
During the structure elucidation process, comparison of the 1H and 13C experimental data with those from literature is almost mandatory. However, many NMR data were reported between the '60s and '80s, with most of the multiplicities reported as "multiplets" and some ambiguous signal assignments. In this scenario, we have "only eventually" used bidimensional methods to unequivocally assign 1H and 13C data.
Figure 2. Unequivocal assignment of the dihydrobenzofuran neolignans 1H NMR data.
Chemistry of Natural Products
Our projects in this field have been restricted to plant-derived essential oils and the chemical constituents thereof. Essential oils are mixtures of volatile compounds extracted from plants, where they play an important ecological role (e.g., pollinizer attraction and chemical defense). We are interested in the extraction and evaluation of the antimicrobial, insecticidal and antiparasitic activities of these essential oils. Our efforts have been focused on the antimicrobial, antiparasitic, and insecticidal activity of essential oils.
Scheme 3: Basic steps of our studies on the chemical composition and biological activities of plant-derived essential oils.
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