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CHOI RESEARCH GROUP

Research in the Choi group is focused on the discovery of unique natural products from sediment-dervied or biomass-associated microorganisms from terrestrial or marine environments and medicinal plants.

We do SCUBA dive for the underwater sample collection and take trails for terrestrial sample collection. Currently, we have over 2,000 microbial samples (bacteria, fungi and cyanobacteria) in the lab. Several of them were found as unreported microorganisms and we reported four bacterial strains (a bacterial strain in new family, and three in new species). Also, diverse research samples were provided by collaborators.

Collection Sites

  Korean peninsula

  Kosrae, Federated States of Micronesia

  Quinapondan, The Philippines

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Collaborators - Research Samples

  Deep-sea sediments (KMOU)

  Antarctic lichens (KOPRI)

  Genetically modified crops (KAERI)

  Marine cyanobacteria (SIO)

The main research focus of Choi lab is on the discovery of unique natural products in microbial culture extracts and medicinal plant extracts. In order for the fast de-replication, we have used LC-MS system (Agilent single MS) and in-house UV spectra library along with several chemical databases (AntiMarin, NpAtlas, and SciFinder). Also, we actively used molecular networking techniques.

The chemical constituents with structural novelty have been isolated with diverse chromatographic techniques (open column chromatography, thin layer chromatography, medium pressure LC, high performance LC, and centrifugal partition chromatography). The structures of purified compounds were determined with spectroscopic data analyses including 1D NMR (1H and 13C), 2D NMR (COSY, HSQC, HMBC, NOESY, ROESY, TOCSY, HETLOC, and HSQMBC), MS (HR-FABMS, HR-ESIMS), MS2 (HR-ESI-MS2 in combination with molecular networking), electronic circular dichroism (ECD), and specific rotation.

Particularly, the lab is specialized for the absolute configuration analysis of novel natural products. The absolute configuration analysis is achieved by spectroscopic data analysis method, chemical derivatization method or computer-assisted calculation method.

Spectroscopic Data Analysis 

  NOE/ROE

  J-based Configurational Analysis 

Chemical Derivatization

  C3 Marfey's method

  Advanced Mosher's method

  PGME, olefin metathesis

  Hydrolysis, Ozonolysis

  Oxidation/ Reduction

Computer-assisted Calculation

  SPARTAN, GAUSSIAN

  ECD Spectra

  NMR Chemical Shifts (DP4+)

  Coupling Constants (J-DP4)

  Specific Rotation

We have in-house anti-bacterial and anti-fungal assays as well as beta-secretase assays. More detail pharmacological activity evaluation has been accomplished by collaboration with diverse research groups.

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 - Cancer, Angiogenesis

 - Premenstrual syndrome, Wound healing

 - Vascular inflammation, Sepsis, PM-induced pulmonary damage

 - Allergy, Inflammation

 - Osteoporosis, Rheumatoid Arthritis

 - Neurodegeneration, Neuroprotection

 - Biofilm formation, Tuberculosis

Natural products are useful for the chemotaxonomy of living organisms. Our group have key instruments for metabolite profiling such as UPLC, LCMS and NMR. The data analyses are performed with several data processing platforms (MS2 data with feature-based molecular networking on GNPS platform and NMR data with Chenomx, and multi-variable analysis with SIMCA).

RESEARCH INTERESTS

Discovery of New Natural Products Sources

Structure Elucidation of Natural Products

Discovery of Bioactive Natural Products 

Mass Spectrometry-based Metabolomics Study 

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