Chung Sub Kim

Colibactin is a complex secondary metabolite produced by some genotoxic gut <i>Escherichia coli</i> strains. The presence of colibactin-producing bacteria correlates with the frequency and severity of colorectal cancer in humans. However, because colibactin has not been isolated or structurally characterized, studying the physiological effects of colibactin-producing bacteria in the human gut has been difficult. We used a combination of genetics, isotope labeling, tandem mass spectrometry, and c

<i>Escherichia coli</i> is a common inhabitant of the human microbiota and a beacon model organism in biology. However, an understanding of its signaling systems that regulate population-level phenotypes known as quorum sensing remain incomplete. Here, we define the structure and biosynthesis of autoinducer-3 (AI-3), a metabolite of previously unknown structure involved in the pathogenesis of enterohemorrhagic <i>E. coli</i> (EHEC). We demonstrate that novel AI-3 analogs are derived from threoni

Four biflavonoid glycosides, balsamisides A-D (1-4), and nine known compounds (5-13) were obtained from the white petals of Impatiens balsamina. The 2D structures of the purified phytochemicals were established using conventional NMR techniques in addition to the new long-range HSQMBC NMR experiment. Acid hydrolysis followed by experimental and quantum-mechanics-based ECD data analysis permitted full configurational assignment of the purified metabolites. Compounds 1-13 were assessed for their p

Eleven new abietane-type diterpenes, holophyllins D-N (1-11), and 17 known analogues (12-28), were isolated from a MeOH extract of the trunk of Abies holophylla. The chemical structures of 1-11 were determined through spectroscopic data analysis, including NMR ((1)H and (13)C NMR, DEPT, (1)H-(1)H COSY, HMQC, HMBC, and NOESY) and HRFABMS methods. All isolated compounds (1-28) were evaluated for their cytotoxicity against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-116), for thei

Chaenomeles sinensis has been consumed traditionally for the treatment of throat diseases, diarrhea, inflammatory diseases, and dry beriberi. Repeated chromatography of the CHCl₃-soluble fraction from the 80% MeOH extract of C. sinensis twigs led to the isolation of three new triterpenoids, sinenic acid A (1), 3β-O-cis-feruloyl-2α,19α-dihydroxyurs-12-en-28-oic acid (2), and 3β-O-cis-caffeoylbetulin (3), together with 20 analogues. The chemical structures of 1-3 were determined using d

Six new lignans (1-6) were isolated from the trunk of Abies holophylla MAXIM, together with 11 known lignans (7-17). The structures of 1-7 were elucidated by spectroscopic methods, acid hydrolysis, and use of the modified Mosher's method. The effects of the isolates on nerve growth factor induction in a C6 rat glioma cell line were evaluated. Compounds 6, 7, and 13 showed significant induction of nerve growth factor secretion at concentrations of 10 μM. Compounds 1, 5, 6, and 16 showed moderate

Phytochemical investigation of the twigs of Chaenomeles sinensis led to the isolation and identification of six new lignan glycosides, chaenomiside A-F (1-6), along with five known ones (7-11). Their chemical structures were determined by spectroscopic methods, including NMR, MS, ECD, and GC/MS analyses. All the isolated compounds (1-11) were tested for their inhibitory effects on nitric oxide (NO) production in lipopolysaccharide-activated murine microglial cells and the secretion of nerve grow

In the course of our continuing search for bioactive constituents of Korean medicinal plants, we isolated five new oxylipins, chaenomic acid A-E (1-5), and six known ones (6-11) from the twigs of Chaenomeles sinensis. The structures of the new compounds (1-5) were determined by spectroscopic methods, including 1D and 2D NMR ((1)H and (13)C NMR, (1)H-(1)H COSY, HMQC, HMBC, and NOESY), olefin cross-metathesis, and LC/MS analysis. The known compounds (6-11) were identified by comparison of their sp

Three new diterpenoids (1-3) and three new triterpenoids (4-6) were isolated from the trunk of Abies holophylla together with 19 known terpenoids. The chemical structures of 1-6 were determined through NMR and MS data analyses. Also, the structural assignments of some of these compounds were verified and elucidated utilizing computational methods coupled with a statistical procedure (CP3, DP4, and DP4+). All the isolated compounds were evaluated for their cytotoxicity against four human cancer c

Three new diterpenoids, 18-formyloxy-8 β-hydroxysandaracopimar-15-ene (1), 15(R)-N-butoxypinusolidic acid (2), and 15,16-dihydro-15,16-dimethoxylambertianic acid (3), along with twelve known compounds (4-15) were isolated from MeOH extracts of leaves of Thuja orientalis L. The structures of the three new compounds were elucidated on the basis of spectroscopic analyses, including extensive 2D-NMR data. The absolute stereochemistry of compound 2 was clarified by a CD spectroscopic study. The isola

Brown algae comprise up to 2000 species with wide dissemination in temperate zones. A comprehensive untargeted metabolic profiling guided by molecular networking of three uninvestigated Red-Sea-derived brown algae, namely <i>Sirophysalis trinodis</i>, <i>Polycladia myrica</i>, and <i>Turbinaria triquetra</i>, led to the identification of over 115 metabolites categorized as glycerolipids, fatty acids, sterol lipids, sphingolipids, and phospholipids. The three algae exhibited low-to-moderate antio

As a part of an ongoing search for bioactive constituents from Korean medicinal plants, the phytochemical investigations of the twigs of Salix glandulosa afforded 12 new phenolic glycosides (1-12) and a known analogue (13). The structures of 1-13 were characterized by a combination of NMR methods ((1)H and (13)C NMR, (1)H-(1)H COSY, HMQC, and HMBC), chemical hydrolysis, and GC/MS. The absolute configuration of 13 [(1R,2S)-2-hydroxycyclohexyl-2'-O-trans-p-coumaroyl-β-d-glucopyranoside] was determ