Chun Whan Choi

Antiproliferative effects of saponins from the roots of Platycodon grandiflorum on cultured human tumor cells.

Three new triterpenoid saponins, platyconic acid B lactone (1), deapio-platyconic acid B lactone (2), and deapio-platycodin D(2) (3), together with 17 known triterpenoid saponins, were isolated from a root extract of Platycodon grandiflorum. The structures of 1-3 were determined on the basis of spectroscopic data interpretation and chemical transformation. Saponins with a platycodigenin or polygalacic acid unit as a sapogenin demonstrated significant inhibitory effects on the proliferation of a small panel of cultured human tumor cells.

In Vitro BACE-1 Inhibitory Activity of Resveratrol Oligomers from the Seed Extract of Paeonia lactiflora

A new resveratrol oligomer (1) together with eight related components (2- 9) were isolated from the seed extract of Paeonia lactiflora (Paeoniaceae) as active principles responsible for the inhibition of beta-site APP-cleaving enzyme 1 (BACE-1) in vitro. The chemical structure of 1 was established as (-)-7a,8a- CIS- ε-viniferin with the aid of spectroscopic analyses including NOESY experiments. All isolated resveratrol oligomers (1- 9) demonstrated significant inhibition on baculovirus-expressed BACE-1 in a dose-dependent manner, which was assessed by the FRET assay using Rh-EVNLDAEFK as a substrate in vitro.

Galbanic Acid, a Cytotoxic Sesquiterpene from the Gum Resin of Ferula asafoetida, Blocks Protein Farnesyltransferase

Farnesylation of the activated RAS oncogene product by protein farnesyltransferase (FTase) is a critical step for its oncogenic function. Bioassay-guided purification of Ferula asafoetida (Umbelliferae) extract led to the isolation of the coumarin-derived sesquiterpene galbanic acid (1) as an active principal for FTase inhibitory activity, together with the four structurally related sesquiterpenes karatavicinol (2), umbelliprenin (3), farnesiferol B (4), and farnesiferol C (5). The 50 % inhibitory concentration (IC (50)) of 1 against FTase in an enzyme-based assay was calculated as 2.5 µM. Compound 1 also demonstrated potent inhibition of the proliferation of oncogenic RAS-transformed NIH3T3/Hras-F in a dose-dependent manner. The IC (50) value of 1 on the proliferation of oncogenic RAS-transformed NIH3T3/Hras-F cells was calculated as 16.2 µM, whereas its IC (50) value on control vector-transfected normal RAS-containing NIH3T3/ZIPneo cells was 58.5 µM.

Isolation of xanthones from adventitious roots of St. John’s Wort (Hypericum perforatum L.) and their antioxidant and cytotoxic activities

In this phytochemical study, 5 xanthones, 1,3,5,6-tetrahydroxyxanthone [1], 1,5,6-trihydroxy-3-methoxyxanthone [2], ferrxanthone [3], brasilixanthone B [4], and neolancerin [5] were isolated from adventitious roots of St. John’s wort (Hypericum perforatum L.). Compound 1–5 were evaluated for antioxidant activities using the intracellular reactive oxygen species (ROS) radical scavenging 2′,7′-dichlorfluorescein-diacetate (DCFDA) assay and for cytotoxic activity against the HL-60 human promyelocytic leukemia cells. Among them, compound 1–4 exhibited scavenging activity with inhibition values of 27.4–33.2% at 10 μM; compound 1, 2, and 4 reduced the viability of HL-60 cells significantly, with IC50 values of 31.5, 28.9, and 27.7 μM, respectively.

Diarylheptanoid glycosides from Tacca plantaginea and their effects on NF-κB activation and PPAR transcriptional activity.

In the screening search for NF-κB inhibitory and PPAR transactivational agents from medicinal plants, a methanol extract of the whole plant of Tacca plantaginea and its aqueous fraction showed the significant activities. Bioassay-guided fractionation combined with repeated chromatographic separation of the aqueous fraction of the methanol extract of T. plantaginea resulted in the isolation of two new diarylheptanoid glycosides, plantagineosides A (1) and B (2), an unusual new cyclic diarylheptanoid glycoside, plantagineoside C (3), and three known compounds (4-6). Their structures were determined by extensive spectroscopic and chemical methods. Compounds 3-6 significantly inhibited TNFα-induced NF-κB transcriptional activity in HepG2 cells in a dose-dependent manner, with IC(50) values ranging from 0.9 to 9.4 μM. Compounds 1-6 significantly activated the transcriptional activity of PPARs in a dose-dependent manner, with EC(50) values ranging from 0.30 to 10.4 μM. In addition, the transactivational effects of compounds 1-6 were evaluated on three individual PPAR subtypes, including PPARα, γ, and β(δ). Compounds 1-6 significantly enhanced the transcriptional activity of PPARβ(δ), with EC(50) values in a range of 11.0-30.1 μM. These data provide the rationale for using T. plantaginea and its components for the prevention and treatment of inflammatory and metabolic diseases.