Hyi-Seung Lee

Gageotetrins A-C, noncytotoxic antimicrobial linear lipopeptides from a marine bacterium Bacillus subtilis.

Gageotetrins A-C (1-3), a unique class of linear lipopeptides, consisting of di- and tetrapeptides and a new fatty acid were isolated from a Marine Bacillus subtilis. The structures of 1-3 were assigned by spectroscopic data and their absolute stereochemistries were ascertained by chemical derivatization. Compounds 1-3 displayed good antimicrobial activities with MIC values of 0.01-0.06 μM. However, these compounds failed to register any cytotoxicity (GI50 > 30 μg/ml) against human cancer cell lines.

Identification of bioactive metabolites against adenosine A1 receptor using NMR-based metabolomics

Marine sponges are relatively less explored for their chemical features but highly anticipated resource for bioactive compounds. In this paper we report the screening of marine sponges crude extracts for their potential to bind the adenosine A1 receptor. Many samples showed very promising activity and in order to identify the active components, a metabolomics-chemometrics approach is employed. Nuclear magnetic resonance spectroscopy is used for the metabolic profiling of the marine sponges and partial least squares (PLS) and orthogonal PLS (OPLS) algorithms are used to correlate the metabolomics with bioactivity data. Using several two dimensional-NMR techniques, the resonances responsible for the separation of high activity samples from the medium and low activity samples were identified as associated to metabolites like halisulfate 1, halisulfate 3–5, and suvanine (1–5), all belongs to sesterterpenes class. The reference compounds for these metabolites are also tested for the activity, which endorse the findings of the applied methodology.

Gageopeptins A and B, new inhibitors of zoospore motility of the phytopathogen Phytophthora capsici from a marine-derived bacterium Bacillus sp. 109GGC020

The motility of zoospores is critical in the disease cycles of the peronosporomycetes that cause devastating diseases in plants, fishes, vertebrates, and microbes. In the course of screening for secondary metabolites regulating the motility of zoospores of Phytophthora capsici, we discovered two new inhibitors from the ethyl acetate extract of the fermentation broth of a marine-derived strain Bacillus sp. 109GGC020. The structures of these novel metabolites were elucidated as new cyclic lipopeptides and named gageopeptins A (1) and B (2) by spectroscopic analyses including high resolution MS and extensive 1D and 2D NMR. The stereoconfigurations of 1 and 2 were assigned based on the chemical derivatization studies and reviews of the literature data. Although compounds 1 and 2 impaired the motility of zoospores of P. capsici in dose- and time-dependent manners, compound 1 (IC50 = 1 μg/ml) was an approximately 400-fold stronger motility inhibitor than 2 (IC50 = 400 μg/ml). Interestingly, the zoospores halted by compound 1 were subsequently lysed at higher concentrations (IC50 = 50 μg/ml). Compounds 1 and 2 were also tested against some bacteria and fungi by broth dilution assay, and exhibited moderate antibacterial and good antifungal activities.