Byoung Wook Choi

The radical scavenging effects of stilbene glucosides fromPolygonum multiflorum

The extract of the root ofPolygonum multiflorum exhibited a significant antioxidant activity assessed by the DPPH radical scavenging activityin vitro. The bioassay-guided fractionation of the extract yielded a stilbene glucoside, (E)-2,3,5,4′-tetrahydroxystilbene-2-0-²-d-glucopyra-noside (1) as an active constituent responsible for the antioxidant property. Compound1 demonstrated a moderate DPPH radical scavenging activity (IC50, 40 μM), while the corresponding deglucosylated stilbene 2 exhibited a much higher activity (IC50, 0.38 μM).

Cholinesterase inhibitory activity of two farnesylacetone derivatives from the brown alga Sargassum sagamianum

Two known farnesylacetone derivatives (1 and 2) were isolated from the Korean brown algaSargassum sagamianum off Jeju Island, Korea. Compounds1 and2 were identified as (5E,10Z)-6,10,14-trimethylpentadeca-5,10-dien-2,12-dione and (5E,9E,13E)-6,10,4-trimethyl-pentadeca-5,9,13-trien-2,12-dione, respectively, by comparison with the literature data. Compounds1 and2 showed moderate acetylcholinesterase and butyrylcholinesterase inhibitory activities with IC50 values of 65.0~48.0 and 34.0~23.0 μM, respectively.

Monoglycerides from the brown alga Sargassum sagamianum: Isolation, synthesis, and biological activity.

Polyunsaturated fatty acid-derived monoglycerides were characterized from the marine brown alga Sargassum sagamianum, collected from Jeju Island, Korea. A new compound of this structural class was isolated and determined to be 1-octadecatetraenoyl glycerol, by combined spectroscopic methods. Based on the structures and bioactivity of these compounds, a series of monoglycerides were synthesized using glycerol and various fatty acids. Several compounds exhibited moderate to significant inhibition of phospholipase A(2) and cyclooxygenase-2.

Genetic organization of the biosynthetic gene cluster for the indolocarbazole K-252a in Nonomuraea longicatena JCM 11136

Indolocarbazole metabolite K-252a is a natural product that was previously reported as a potent protein kinase C inhibitor with in vitro and in vivo potency. From a biosynthetic viewpoint, this compound possesses structurally interesting features such as an unusual furanosyl sugar moiety, which are absent in the well-studied staurosporine and rebeccamycin. A cosmid library from genomic DNA of Nonomuraea longicatena JCM 11136 was constructed and screened for the presence of genes to be involved in the biosynthesis of indolocarbazole K-252a. Using as a probe an internal fragment of vioB, a Chromobacterium violaceum gene encoding a multifunctional enzyme that catalyzes tryptophan decarboxylation and condensation reaction in violacein biosynthesis, we isolated a DNA region that directed the biosynthesis of K-252a when introduced into the heterologous expression host Streptomyces albus. Sequence analysis of 45xa0kb revealed genes for indolocarbazole core formation, glycosylation, and sugar methylation, as well as a regulatory gene and two resistance/secretion genes. The cloned genes should help to elucidate the molecular basis for indolocarbazole biosynthesis and generate new indolocarbazole analogues by genetic engineering.

Selective vasodilatation effect of sargahydroquinoic acid, an active constituent of Sargassum micracanthum, on the basilar arteries of rabbits.

Sargahydroquinoic acid (2), a major active constituent of Sargassum micracanthum collected from the coast of the East Sea in Korea, showed a selective vasodilatation effect on the basilar arteries of rabbits. Therefore, treatment with sargahydroquinoic acid may selectively accelerate cerebral blood flow through dilatation of the basilar artery without lowering systemic blood pressure.

A New antioxidant monoterpene glycoside, α-benzoyloxypaeoniflorin fromPaeonia suffruticosa

Abstractα-Benzoyloxypaeoniflorin (1), a new antioxidant monoterpene α-glycoside anomer was isolated fromPaeonia suffruticosa along with known compounds, β-benzoyloxypaeoniflorin (2), paeonolide, paeoniflorin and mudanpioside H. The structure of1 has been determined by comparing spectral data with those of β-benzoyloxypaeoniflorin(2). Compound1 exhibited moderately potent radical scavenging activity on DPPH radical.

Multifunctional Activity of Polyphenolic Compounds Associated with a Potential for Alzheimer's Disease Therapy from Ecklonia cava

Five polyphenols were isolated and purified from a brown alga Ecklonia cava. These compounds showed diverse biological activities such as antioxidative, antiinflammatory, and enzyme inhibitory activities. This led us to investigate the potential of these compounds as Alzheimers disease drugs. All of the compounds showed moderate acetylcholinesterase inhibitory activity in a micromolar range (IC50 from 16.0 to 96.3u2009μM). For butyrylcholinesterase, a new target for the treatment of Alzheimers disease, phlorofucofuroeckol‐A (PFF‐A), showed a particularly potent inhibitory activity (IC50 0.95u2009μM), which is over 100‐fold greater than for acetylcholinesterase. These compounds inhibited glycogen synthase kinase 3 beta, which is related to the formation of hyperphosphorylated tau and generation Aβ. Bieckol and PFF‐A inhibited amyloid precursor protein biosynthesis. PFF‐A also showed very strong β‐secretase inhibitory activity with IC50 of submicromole. These results render these compounds as interesting potential drug candidates for Alzheimers disease. Copyright

Anti-HIV-1 efficacy of extracts from medicinal plants

The anti-HIV-1 activities of butanol, hexane, chloroform and water extracts from four widely used folk medicinal plants (Sophora flavescens, Tulipa edulis, Herba ephedra, and Pachyma hoelen Rumph) were evaluated in this study. The hexane extract of Pachyma hoelen Rumph, PH-4, showed effective inhibition against HIV-1. The 50% effective concentration (EC50) of PH-4 was 37.3 μg/ml in the p24 antigen assay and 36.8% in the HIV-1 recombinant RT activity test (at 200 μg/ml). In addition, the PH-4 showed the protective effect on the infected MT-4 cells, with a 58.2% rate of protection. The 50% cytotoxic concentration (CC50) of PH-4 was 100.6 μg/ml. These results suggest that PH-4 from Pachyma hoelen Rumph might be the candidate for the chemotherapy agent against HIV-1 infection with further study.

Inhibitory effect of imperatorin on insulin-like growth factor-1-induced sebum production in human sebocytes cultured in vitro

AIMSnAcne is a common skin disease that originates in the sebaceous gland. The pathogenesis of acne is very complex, involving the increase of sebum production and perifollicular inflammation. In this study, we screened the anti-lipogenic material and demonstrated its effect using cultured human sebocytes.nnnMAIN METHODSnNormal human sebocytes were cultured by explanting the sebaceous glands. To evaluate the anti-lipogenic effect, sebocytes were treated with test materials and (14)C-acetate incorporation assay was performed.nnnKEY FINDINGSnTo screen the anti-lipogenic materials, we tested the effect of many herbal plant extracts. We found that Angelica dahurica extract inhibited the insulin-like growth factor-1 (IGF-1)-induced sebum production in terms of squalene synthesis in sebocytes. Furthermore, imperatorin isolated from A. dahurica showed remarkable inhibitory effect on squalene production as well as squalene synthase promoter activity. To investigate the putative action mechanism, we tested the effect of imperatorin on intracellular signaling. The results showed that imperatorin inhibited IGF-1-induced phosphorylation of Akt. In addition, imperatorin significantly down-regulated PPAR-γ and SREBP-1, the important transcription factors for lipid synthesis.nnnSIGNIFICANCEnThese results suggest that imperatorin has a potential for reducing sebum production in sebocytes, and can be applicable for acne treatment.

Isolation of Diacyl Glycerol Acyl Transferase (DGAT) Inhibitors from Pachydictyon coriaceum

The pharmacological inhibition of acyl CoA:diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) has emerged as a target for the treatment of obesity and type 2 diabetes. Chromatographic analysis of the brown alga, Pachydictyon coriaceum, led to the isolation of diterpene dictyol E and hydroxyisocrenulatin. Pharmacological assay of these compounds demonstrated DGAT inhibitory activity with IC50 values of 46.0u2009μm and 23.3u2009μm, respectively. Copyright