Hyoung-Geun Kim

Glycosyl glycerides from the aerial parts of Malva verticillata and their chemopreventive effects

A new glycosyl glyceride (5) along with twelve known ones (1-4 and 6-13) including two sulfoquinovosyl glycerides (1 and 2) were isolated from the aerial parts of Malva verticillata. Based on several spectroscopic methods, compound 5 was identified to be (2S)-1-O-β-d-galactopyranosyl-3-O-isostearoyl glyceride, and named malvaglycolipid A. Compounds 1 and 2 contained a unique sugar, (6-deoxy-6-sulfo)-α-d-glucopyranose, which very rarely occurs in natural sources. This is the first report for the isolation of compounds 1 and 2 from natural sources and the structure determination using NMR experiment. It was also of note that no glycosyl glyceride has previously been isolated from the family of Malvaeae. Most glycosyl glycerides showed cytotoxicity to HepG2, AGS, HCT-15, and A549 human cancer cells. Especially, compounds 1, 2, and 11 exhibited significant cytotoxicity to AGS cells, with IC50 values of 33.7 ± 0.64 μM, 11.1 ± 0.07 μM, and 10.6 ± 0.10 μM, respectively. The n-BuOH fraction and compounds 1, 2, and 11 increased the number of apoptotic cells in the Tali assay and had a significant effect on the levels of proteins related to apoptosis including PARP, caspase-3, Bcl-2, Bax, and β-actin.

Isolation and Quantification of Ginsenoside Rh23, a New Anti-Melanogenic Compound from the Leaves of Panax ginseng

A new ginsenoside, named ginsenoside Rh23 (1), and 20-O-β-d-glucopyranosyl-3β,6α,12β,20β,25-pentahydroxydammar-23-ene (2) were isolated from the leaves of hydroponic Panax ginseng. Compounds were isolated by various column chromatography and their structures were determined based on spectroscopic methods, including high resolution quadrupole/time of flight mass spectrometry (HR-QTOF/MS), nuclear magnetic resonance (NMR) spectroscopy, and infrared (IR) spectroscopy. To determine anti-melanogenic activity, the change in the melanin content in melan-a cells treated with identified compounds was tested. Additionally, we investigated the melanin inhibitory effects of ginsenoside Rh23 on pigmentation in a zebrafish in vivo model. Compound 1 inhibited potent melanogenesis in melan-a cells with 37.0% melanogenesis inhibition at 80 µM and also presented inhibition on the body pigmentation in zebrafish model. Although compound 2 showed slightly lower inhibitory activity than compound 1, it also showed significantly decreased melanogenesis in melan-a cell and in zebrafish model. These results indicated that compounds isolated from hydroponic P. ginseng may be used as new skin whitening compound through the in vitro and in vivo systems. Furthermore, this study demonstrated the utility of MS-based compound 1 for the quantitative analysis. Ginsenoside Rh23 (1) was found at a level of 0.31 mg/g in leaves of hydroponic P. ginseng.

Flavonoid 8-O-Glucuronides from the Aerial Parts of Malva verticillata and Their Recovery Effects on Alloxan-Induced Pancreatic Islets in Zebrafish

Malva verticillata (Cluster mallow), a leafy vegetable that has been popular in East Asia for a long time, has also been used in herbal teas and medicines. The aqueous fraction of the aerial parts of Malva verticillata, exhibiting a very high quantity of flavonoids compared to the EtOAc and n-BuOH fractions, exhibited significant recovery effects on pancreatic islets damaged by alloxan in zebrafish larvae. Thus, the bioactive components responsible for this anti-diabetic activity were investigated. A new flavonoid glucuronide (1) and five known flavonoids were isolated from the aqueous fraction. Based on several spectroscopic methods, compound 1 was identified to be nortangeretin-8-O-β-d-glucuronide, and was named malvaflavone A. The A-ring of compound 1 had a 5,6,7,8-tetrahydroxy moiety, which rarely occurs in plant systems. Also 8-O-glucuronide attached to the flavonoid moiety was rarely occurred in plant system. Compounds 1, 3, 4, and 6 significantly improved the pancreatic islet size in zebrafish at 0.1 μM, and compounds 1 and 6 were found to block β-cell K+ channels in experiments with diazoxide. In ABTS, ORAC, and SOD assays, compounds 1–5 exhibited high anti-oxidant activities compared with quercetin and BHA (positive controls), indicating that the 8-O-glucuronide attached to the flavonoid moiety is a key structure for the expression of anti-oxidant activity. This is the first report of the isolation of compounds 1–6 from M. verticillata as well evaluated for anti-diabetic and anti-oxidant ativities.

UPLC-QTOF/MS-Based Metabolomics Applied for the Quality Evaluation of Four Processed Panax ginseng Products

In the food industry and herbal markets, it is critical to control the quality of processed Panax ginseng products. In this study, ultra-performance liquid chromatography coupled to quadrupole time of flight mass spectrometry (UPLC-QTOF/MS)-based metabolomics was applied for the quality evaluation of white ginseng (WG), tae-geuk ginseng (TG), red ginseng (RG), and black ginseng (BG). Diverse metabolites including ginsenosides were profiled by UPLC-QTOF/MS, and the datasets of WG, TG, RG, and BG were then subjected to multivariate analyses. In principal component analysis (PCA), four processed ginseng products were well-differentiated, and several ginsenosides were identified as major components of each product. S-plot also characterized the metabolic changes between two processed ginseng products, and the major ginsenosides of each product were found as follows: WG (M-Rb1, M-Rb2, M-Rc, Re, Rg1), TG (Rb2, Rc, Rd, Re, Rg1), RG (Rb1, Rb2, Rc, Rd, Re, Rg1), and BG (Rd, Rk1, Rg5, Rg3). Furthermore, the quantitative contents of ginsenosides were evaluated from the four processed ginseng products. Finally, it was indicated that the proposed metabolomics approach was useful for the quality evaluation and control of processed ginseng products.

New Lignans from the Flower of Forsythia koreana and Their Suppression Effect on VCAM-1 Expression in MOVAS Cells

Six lignans including two new lignans were obtained as the principal components of the Forsythia koreana flowers via silica gel (SiO2), octadecyl SiO2 (ODS) as well as Sephadex LH‐20 column chromatography. In addition to two new lignans, named koreanaside A ((7R,8S,7′R,8′S)‐7,7′‐diepoxy‐5′‐hydroxy‐3,3′‐dimethoxylignan 4‐O‐β‐d‐glucopyranoside) and koreanaside B ((7R,8S,7′S,8′R)‐7,9′‐epoxy‐9,5′,7′‐trihydroxy‐3,3′‐dimethoxylignan 4‐O‐β‐d‐glucopyranoside), four known lignans were identified to be (+)‐phylligenin, (−)‐epipinoresinol, pinoresinol, and tinosposide A. The structures and absolute configurations of koreanasides A and B were established by means of analysis of spectroscopic data (NMR, IR, FAB‐MS, and CD), whereas the structures of known lignans were identified by comparison their NMR and MS values with those in the reported literature. Their chemical structures including configuration were established by means of analysis of spectroscopic data (NMR, IR, FAB‐MS, and CD) but also comparison of their NMR and MS values with those in the reported literature. This is the first article for isolation of six lignans of F. koreana flowers. Koreanasides A and B showed high radical scavenging activity with oxygen radical absorbance capacity (ORAC) values of 0.97 ± 0.01 and 1.02 ± 0.01, respectively. Koreanaside A also prohibited expressing VCAM‐1 in MOVAS cells with 80.5% at 25 mg/mL.

New Iridoid from the Stems of Viburnum erosum

A new iridoid (1) was isolated from the stems of Viburnum erosum along with two known iridoids, 7-O-tigloylsecologanolic acid (2) and 7-ketologanin (3). The chemical structure of the compounds was established based on NMR, IR, and MS spectroscopic data.