Hee Cheol Kang

Cytotoxic and Neuroprotective Biflavonoids from the Fruit of Rhus parviflora

Six biflavonoids, succedaneaflavanone (1), mesuaferrone B (2), rhusflavanone (3), rhusflavone (4), agathisflavone (5), and cupressuflavone (6), were isolated from the fruits of Rhus parviflora. The chemical structures of the compounds were determined based on NMR, fast atom bombardment mass spectrometry, and IR. Biflavonoid compounds were evaluated for cytotoxicity against human cancer cell lines, including human colon carcinoma (HCT-116), human breast carcinoma (MCF-7), and human cervical carcinoma (HeLa). Biflavonoids 2, 3, and 5 showed significant cytotoxicity with IC50 values of 17.25 μM (mesuaferrone B against HCT-116), 17.50 μM (rhusflavone against MCF-7), and 15.20 μM (agathisflavone against HeLa). Compound 5 showed inhibition of β-secretase activity at a 10 μM concentration. Compound 6 showed inhibition of cyclin-dependent kinases (CDK2 and CDK5) with IC50 values of 18.58 and 9.29 μM, respectively.

New diarylpropanoids from Lindera glauca Bl. heartwood

Abstract From the heartwood of Lindera glauca Blume three new diarylpropanoids have been isolated and identified, which were named lindeglaucol, lindeglaucone, and lindeglaucoside A. Chipped heartwood was extracted repeatedly with 80% aqueous methanol (MeOH) at room temperature, and the concentrated methanolic extract was successively partitioned with ethyl acetate (EtOAc), n-butanol, and H2O. From the EtOAc fraction, three new diarylpropanoids and a known chalconoid were isolated through repeated column chromatography with silica gel, octadecyl silica gel, and Sephadex LH-20. The chemical structures of the compounds were elucidated by interpretation of extensive spectroscopic data such as nuclear magnetic resonance, fast atom bombardment mass spectroscopy, and infrared. In addition, a known chalconoid, cilicicone B, was isolated for the first time from the heartwood of L. glauca.

Flavonoid glycosides from the fruit of Rhus parviflora and inhibition of cyclin dependent kinases by hyperin

Chrysoeriol-7-O-β-d-glucopyranoside (1), luteolin-7-O-β-d-glucopyranoside (2), quercetin-3-O-β-d-glucopyranoside (3), quercetin-3-O-β-d-galactopyranoside (4), and quercetin-3-O-α-l-rhamnopyranoside (5) were isolated for the first time from the fruits of Rhus parviflora. The chemical structures of the compounds were determined using nuclear magnetic resonance, fast atom bombardment mass spectrometry, and infrared spectroscopy. Compound 4 (hyperin) inhibited cyclin dependent kinases (CDK2 and CDK5) in vitro with IC50 values of 21.02 and 10.28 μM, respectively.

Flavonoids from Lindera glauca Blume as low-density lipoprotein oxidation inhibitors

In order to identify antioxidant flavonoids from Lindera glauca Blume, we performed phytochemical analysis of L. glauca Blume heartwood and isolated eight flavonoids – lindeglaucol (1), lindeglaucone (2), cilicicone B (3), tamarixetin 3-O-α-L-rhamnoside (4), procyanidin A2 (5), cinnamtannin B1 (6), cinnamtannin D1 (7), and procyanidin A1 (8) – through repeated column chromatography over silica gel (SiO2), octadecyl silica gel (ODS) and Sephadex LH-20. The chemical structures of compounds 1–8 were elucidated from spectroscopic data (NMR, IR and MS). The low-density lipoprotein oxidation inhibitory activities of the isolated compounds were evaluated in vitro by using the thiobarbituric acid reactive substances assay. Compounds 5–8 exhibited high inhibition activity, comparable to the positive control butyl hydroxyl toluene. Compounds 2 and 3 were slightly less active, while 1 and 4 expressed low activity.

Triterpenoids from Fragaria ananassa calyx and their inhibitory effects on melanogenesis in B16-F10 mouse melanoma cells.

Column chromatographic technology was applied to isolate six purified ursane triterpenoids from the calyx of Fragaria ananassa and they were identified on the basis of spectroscopic methods to be ursolic acid (1), pomolic acid (2), 2-oxo-pomolic acid (3), 3-O-acetyl pomolic acid (4), fupenzic acid (5) and euscaphic acid (6). This is the first study in which these compounds have been isolated from the calyx of F. ananassa. Compared to a well-known inhibitor, α-arbutin, compounds 2–6 showed a significant decrease in intracellular melanin content in B16-F10 cells, and in culture media melanin.

The Potential of Minor Ginsenosides Isolated from the Leaves of Panax ginseng as Inhibitors of Melanogenesis

Three minor ginsenosides, namely, ginsenoside Rh6 (1), vina-ginsenoside R4 (2) and vina-ginsenoside R13 (3), were isolated from the leaves of hydroponic Panax ginseng. The chemical structures were determined based on spectroscopic methods, including fast atom bombardment mass spectroscopy (FAB-MS), 1D-nuclear magnetic resonance (NMR), 2D-NMR, and, infrared (IR) spectroscopy. The melanogenic inhibitory activity of compounds 1, 2 and 3 was 23.9%, 27.8% and 35.2%, respectively, at a concentration of 80 µM. Likewise, the three compounds showed inhibitory activity on body pigmentation on a zebrafish model, which is commonly used as a model for biomedical or cosmetic research. These results from in vitro and in vivo systems suggest that the three aforementioned compounds isolated from Panax ginseng may have potential as new skin whitening compounds.

Fucosterols from Hizikia fusiformis and their proliferation activities on osteosarcoma-derived cell MG63

Four fucosterol derivatives were isolated from the ethyl acetate fraction of Hizikia fusiformis. The chemical structures of the sterols were elucidated as fucosterol (1), a mixture of 24R,28R- and 24S,28R-epoxy-24-ethylcholesterol at the ratio of 3 to 2 (2), and 24R-saringosterol (3), all of which exhibited proliferation activity on MG63 cells.

Constituents of Machilus thunbergii bark and inhibition of cyclin-dependent kinases (CDKs) by procyanidin B2

Stigmast-5-en-3β,7β-diol (1), stigmast-5-en-3β,7α-diol (2), (+)-isolariciresinol-9-O-β-d-xylopyranoside (3), procyanidin B2 (4), and epicatechin-(4β→8)-epicatechin-(4β→6)-epicatechin (5) were isolated for the first time from the bark of Machilus thunbergii. The chemical structures of the compounds were determined based on nuclear magnetic resonance, electronic ionization mass spectrometry, fast atom bombardment mass spectrometry, and IR. Compound 4 demonstrated inhibitory activity against cyclin-dependent kinases (CDK2, CDK4, and CDK5) in vitro with IC50 values 17.22, 1.08, and 0.26 μM, respectively.

A Study of the Whitening Activities of Magnolia obovata Bark Ethyl Acetate Fractions as Cosmetic Ingredient

EtOAc fractions of Magnolia obovata (M. obovata) Bark extracts were studied for the potential ingredient as a safe and effective whitening cosmetic material. The concentration of active substances honokiol was determined by HPLC. In vitro, the fractions reduced the extracellular and intracellular melanin contents in B16F10 cells in dose dependently and inhibited extracellular melanin secretion (IC50 = 11.05 μg/mL). The 12.5 μg/mL treatment of maximum concentration effectively inhibited up to about 60% to the amount of extracullular melanin. Also, the 12.5 μg/mL treatment of maximum concentration effectively inhibited up to about 59% to the amount of intracullular melanin (IC50 = 10.85 μg/mL). The IC50 value of α-arbutin used as a positive control was 59.99 μg/mL. So, EtOAc fractions of M. obovata Bark extracts showed whitening effect when compared with the non-treatment group. In case of in vivo study, Cosmetic cream with EtOAc fractions of M. obovata Bark extracts was approved by Ethics committee of KDRI (IRB number: KDRI-IRB-1537). As a result in progress for skin sensitization as well as assessment of skin irritation through repeated patch test, skin allergens was identified as non sensitizing agents. Also, cosmetic cream with EtOAc fractions of M. obovata Bark extracts showed significant topical whitening effect and reliable skin safety when compared with the non-treatment group. In conclusion, EtOAc fractions of M. obovata Bark extracts may be a useful cosmetic ingredient for effective skin whitening.

Phenylglycosides from the Stems of Spiraea prunifolia var. simpliciflora

One new phenylglycoside, 1-hydroxy-3,4,5-trimethoxyphenyl-1-O-[6′-O-(4″-carboxy-1″ ,3″ ,5″ - trihydroxy)phenyl]-β-D-glucopyranoside (1), along with eight known ones, isosalicin (2), vanilloloside (3), (4-hydroxy-3,5-dimethoxyphenyl)methyl-β-D-glucopyranoside (4), crenatin (5), hydrageifolin I (6), tachioside (7), isotachioside (8), and koaburside (9), were isolated from the stems of Spiraea prunifolia var. simpliciflora. The chemical structures of these compounds were identified on the basis of spectroscopic data such as NMR, FAB-MS, and IR. All these compounds were isolated from this plant for the first time.