Tae Hyung Won

Beta-carboline alkaloids derived from the ascidian Synoicum sp.

Six β-carboline alkaloids (1-6) of the eudistomin Y class were isolated from the Korean ascidian Synoicum sp. These compounds were chemically converted to a known compound, eudistomin Y(1) (7) and six new derivatives, designated eudistomins Y(8)-Y(13) (8-13). Several of these natural and synthetic compounds exhibited moderate to significant antimicrobial activity, weak cytotoxic activity, and inhibitory activities toward sortase A, isocitrate lyase, and Na(+)/K(+)-ATPase. Structure-activity relationships were also deduced.

Brominated aromatic furanones and related esters from the ascidian Synoicum sp.

Nine new compounds, tris-aromatic furanones (1, 2, 3a, 3b, and 4) and related bis-aromatic diesters (5a, 5b, 6a, and 6b), are described from the ascidian Synoicum sp. collected off the coast of Chuja-do, Korea. The structures of these compounds, designated as cadiolides E and G-I (1-4) and synoilides A and B (5 and 6), were determined by extensive spectroscopic analyses. The absolute configuration at the asymmetric center of cadiolide G (2) was assigned by ECD analysis. Of these new compounds, cadiolide I and the synoilides possess unprecedented carbon skeletons. Several of these compounds exhibited significant inhibition against diverse bacterial strains as well as moderate inhibition against the enzymes sortase A, isocitrate lyase, and Na(+)/K(+)-ATPase.

New Benzoxazine Secondary Metabolites from an Arctic Actinomycete

Two new secondary metabolites, arcticoside (1) and C-1027 chromophore-V (2), were isolated along with C-1027 chromophore-III and fijiolides A and B (3–5) from a culture of an Arctic marine actinomycete Streptomyces strain. The chemical structures of 1 and 2 were elucidated through NMR, mass, UV, and IR spectroscopy. The hexose moieties in 1 were determined to be d-glucose from a combination of acid hydrolysis, derivatization, and gas chromatographic analyses. Arcticoside (1) and C-1027 chromophore-V (2), which have a benzoxazine ring, inhibited Candida albicans isocitrate lyase. Chromophore-V (2) exhibited significant cytotoxicity against breast carcinoma MDA-MB231 cells and colorectal carcinoma cells (line HCT-116), with IC50 values of 0.9 and 2.7 μM, respectively.

Bioactive Metabolites from the Fruits of Psoralea corylifolia

Twenty-four metabolites, including seven new compounds (1-7), were isolated from the dried fruits of Psoralea corylifolia. On the basis of combined spectroscopic and chemical analysis, the new compounds were determined to be six flavonoids (1-6) and a meroterpenoid (7). The absolute configurations of the natural products obtained, including the previously undetermined 16 and 17, were assigned by several methods, such as NOE spectroscopy, optical rotation, and CD spectroscopy. Several of these compounds exhibited moderate inhibitory activity toward Staphylococcus mutans-derived SrtA (2, 6, and 16) and significant stimulation of SIRT1 activity (2, 3, and 15).

Inhibition of Candida albicans isocitrate lyase activity by cadiolides and synoilides from the ascidian Synoicum sp.

Tris-aromatic furanones (1-4) and related bis-aromatic diesters (5 and 6) isolated from the dark red ascidian Synoicum sp., were evaluated for their inhibitory activities toward Candida albicans isocitrate lyase (ICL). These studies led to the identification of compounds 1, 3, and 4 as potent ICL inhibitors, with IC50 values of 7.62, 17.16, and 10.36 μM, respectively. Growth phenotype of ICL deletion mutants and Northern blot analysis data indicated that compound 1 inhibits the ICL expression in C. albicans under C2 carbon utilizing condition.

Asperphenins A and B, Lipopeptidyl Benzophenones from a Marine-Derived Aspergillus sp. Fungus

Asperphenins A (1) and B (2), novel diastereomeric lipopeptidyl benzophenone metabolites, were isolated from a marine-derived Aspergillus sp. fungus. On the basis of the results of combined spectroscopic analyses, the structures of these compounds were determined to be linear assemblies of three motifs: a hydroxy fatty acid, a tripeptide, and a trihydroxybenzophenone. The absolute configurations were assigned using chemical modifications and electronic circular dichroism (ECD) calculations. The novel compounds exhibited significant cytotoxicity on diverse cancer cells.

New Cyclic Cystine Bridged Peptides from the Sponge Suberites waedoensis

Two new peptides, chujamides A (1) and B (2), were isolated from the marine sponge Suberites waedoensis, which was collected from Korean waters. Based upon the results of the combined spectroscopic analyses, the structures of these compounds were determined to be proline-riched and cyclic cystine bridged dodeca- and undecapeptides. The absolute configurations of all amino acid residues were determined to be l by advanced Marfey’s analysis. The new compounds exhibited weak cytotoxicities against A549 and K562 cell-lines, and compound 2 also demonstrated moderate inhibitory activity against Na+/K+-ATPase.

Simultaneous analysis of furfural metabolites from Rehmanniae radix preparata by HPLC-DAD–ESI-MS

A method based on HPLC with diode array detector (DAD) and electrospray ionisation mass spectrometry (ESI-MS) was established for the simultaneous determination of 5-HMF and its derivatives, including a new 5-HMF derivative, in Rehmanniae radix preparata. Validation parameters, such as linearity, limit of detection, limit of quantification, recovery, accuracy, and precision, were successfully obtained. In addition, the efficiencies of diverse extraction methods were compared for the development of a standard analytical method. The verified method was successfully applied to the quantitative determination of four representative metabolites in eighteen R. radix preparata samples from Korea and China. Additionally, the increase in the amount of 5-HMF derivatives was monitored during the processing of three dried R. radix samples. The results showed that a newly isolated diglycosylated 5-HMF derivative, 5-(α-D-galactopyranosyl-(1→6)-α-D-galactopyranosyloxymethyl)-2-furancarboxaldehyde, appeared in concentrations comparable to that of 5-HMF, suggesting its potential to serve as a marker compound in R. radix preparata.

Simultaneous analysis of bioactive metabolites from Ziziphus jujuba by HPLC-DAD-ELSD-MS/MS

A high-performance liquid chromatography (HPLC) with diode array detector (DAD), evaporative light scattering detector (ELSD) and electrospray ionization mass spectrometry (ESI-MS) was established for the simultaneous determination of nine representative metabolites of the alkaloid, flavonoid and triterpenoid classes from Ziziphus jujuba var. spinosa. The optimal chromatographic conditions were obtained on an ODS column and the mobile phase was composed of water and methanol with 0.1% formic acid using a gradient elution system. Using the developed methods, all of the validation parameters were successfully obtained. In addition, effectiveness of diverse extraction methods was compared to each other for the development of standard analytic method. The verified method was successfully applied to the quantitative determination of representative metabolites in commercial samples of Z. jujuba and Z. mauritiana from different markets in Korea, China and Myanmar. The analytical results showed that the contents of the nine analytes vary significantly with sources and species, thus demonstrating its potential for the detection of this plant.

Manzamine Alkaloids from an Acanthostrongylophora sp. Sponge

Five new manzamine alkaloids (1-5) and new salt forms of two known manzamines (6 and 7), along with seven known compounds (8-14) of the same structural class, were isolated from an Indonesian Acanthostrongylophora sp. sponge. On the basis of the results of combined spectroscopic analyses, the structure of kepulauamine A (1) was determined to possess an unprecedented pyrrolizine moiety, while others were functional group variants of known manzamines. These compounds exhibited weak cytotoxicity, moderate antibacterial activity, and mild inhibition against the enzyme isocitrate lyase.