Macrocarpal C isolated from Eucalyptus globulus inhibits dipeptidyl peptidase 4 in an aggregated form.

Dipeptidyl peptidase 4 (DPP-4) inhibitors are used for the treatment of type-2 diabetes mellitus. Various synthetic inhibitors have been developed to date, and plants containing natural DPP-4 inhibitors have also been identified. Here, 13 plant samples were tested for their DPP-4 inhibitory activity. Macrocarpals A-C were isolated from Eucalyptus globulus through activity-guided fractionation and shown to be DPP-4 inhibitors. Of these, macrocarpal C showed the highest inhibitory activity, demonstrating an inhibition curve characterised by a pronounced increase in activity within a narrow concentration range. Evaluation of macrocarpal C solution by turbidity, nuclear magnetic resonance spectroscopy and mass spectrometry indicated its aggregation, which may explain the characteristics of the inhibition curve. These findings will be valuable for further study of potential small molecule DPP-4 inhibitors.

Isolation and lipolytic activity of eurycomanone and its epoxy derivative from Eurycoma longifolia.

Eurycomanone (1) and 13ß,21-epoxyeurycomanone (2) were isolated from Eurycoma longifolia for studies of lipolytic activity. Compound 1 enhanced lipolysis in adipocytes with an EC50 of 14.6µM, while its epoxy derivate, compound 2, had a stronger activity with an EC50 of 8.6µM. Based on molecular mechanistic study using several specific inhibitors to lipolytic signaling pathways, it was found that PKA inhibitor totally diminished the lipolytic activity of 1 and 2. Further immunoblotting analysis confirmed the activation of phosphorylated PKA by both 1 and 2. With the growing need to develop new anti-obesity agents, eurycomanone and its epoxy derivate can be used as promising lead compounds to target lipid catabolism.

Iriomoteolides-9a and 11a: two new odd-numbered macrolides from the marine dinoflagellate Amphidinium species.

Iriomoteolides-9a (1) and 11a (2), new 15- and 19-membered macrolides, respectively, have been isolated from the marine dinoflagellate Amphidinium species (strain KCA09052). Compounds 1 and 2 were obtained from the extracts of the algal cells inoculated in the PES and TKF seawater medium, respectively. The structures of 1 and 2 were assigned on the basis of detailed NMR analyses. Compounds 1 and 2 exhibited cytotoxic activity against human cervix adenocarcinoma HeLa cells.

Iriomoteolides-10a and 12a, Cytotoxic Macrolides from Marine Dinoflagellate Amphidinium Species.

Two new macrolides, iriomoteolides-10a (1) and -12a (2), have been isolated from a marine dinoflagellate Amphidinium sp. (KCA09053 strain), and their structures were elucidated on the basis of a detailed two dimensional (2D)-NMR analysis. Compound 1 is a novel 21-membered Amphidinium macrolide, which contains one tetrahydrofuran ring, two ketone carbonyls, two hydroxyl groups, and six one-carbon branches. Compound 2 is a new 12-membered macrolide related to amphidinolide Q. Compound 1 exhibited cytotoxic activity against human cervix adenocarcinoma HeLa and murine hepatocellular carcinoma MH134 cells.

Amphirionin-2, a novel linear polyketide with potent cytotoxic activity from a marine dinoflagellate Amphidinium species.

A novel linear polyketide, amphirionin-2 (1), with two unique hexahydrofuro[3,2-b]furan moieties has been isolated from the cultivated algal cells of a benthic dinoflagellate Amphidinium sp. (strain KCA09051). The structure was elucidated on the basis of detailed analyses of 2D NMR data, and the absolute configuration of C-5 was determined by using modified Mosher's method. Amphirionin-2 (1) exhibited potent cytotoxic activity against human colon carcinoma Caco-2 cells and human lung adenocarcinoma A549 cells.

Amphirionin-4 with potent proliferation-promoting activity on bone marrow stromal cells from a marine dinoflagellate amphidinium species.

A linear polyketide, amphirionin-4 (1), has been isolated from cultivated algal cells of the marine dinoflagellate Amphidinium species. The structure was elucidated on the basis of detailed analyses of 1D and 2D NMR data, and the absolute configurations of C-4 and C-8 were determined using the modified Mosher's method. Amphirionin-4 (1) exhibited extremely potent proliferation-promoting activity on murine bone marrow stromal ST-2 cells (950% promotion) at a concentration of 0.1 ng/mL.

Observation of glycolytic metabolites in tumor cell lysate by using hyperpolarization of deuterated glucose.

Hyperpolarization of stable isotope-labeled substrates and subsequent NMR measurement of the metabolic reactions allow for direct tracking of cellular reactions in vitro and in vivo. Here, we report the hyperpolarization of (13)C6-glucose-d7 and evaluate its use as probes to observe glucose flux in cells. We measured the lifetime of the polarized signal governed by the spin-lattice relaxation time T1. (13)C6-Glucose-d7 exhibited a T1 that was over ten times as long as that of (13)C6-glucose, and metabolic NMR studies of hyperpolarized (13)C6-glucose-d7 using tumor cell lysate led to observation of the resonances due to phosphorylated fluctofuranoses generated through aerobic glycolysis.

Hydroxylamine enhances glucose uptake in C2C12 skeletal muscle cells through the activation of insulin receptor substrate 1.

Diabetes mellitus is a global disease, and the number of patients with it is increasing. Of various agents for treatment, those that directly act on muscle are currently attracting attention because muscle is one of the main tissues in the human body, and its metabolism is decreased in type II diabetes. In this study, we found that hydroxylamine (HA) enhances glucose uptake in C2C12 myotubes. Analysis of HA's mechanism revealed the involvement of IRS1, PI3K and Akt that is related to the insulin signaling pathway. Further investigation about the activation mechanism of insulin receptor or IRS1 by HA may provide a way to develop a novel anti-diabetic agent alternating to insulin.

Identification of hydroxychavicol and its dimers, the lipase inhibitors contained in the Indonesian spice, Eugenia polyantha.

Inhibition of pancreatic lipase is effective for a prevention of obesity. Eugenia polyantha is a tropical tree whose leaves are known as a spice and also as an ingredient for Jamu, the traditional medicine of Indonesia. We found inhibitory activity against pancreatic lipase in the extract of E. polyantha leaves. Purification of the active principals resulted in isolation of hydroxychavicol, and two structurally new dimers. All of the isolated compounds showed inhibitory activity against the porcine pancreatic lipase and high content of hydroxychavicol (1.83 wt.%) indicated this compound to be responsible for the majority of inhibitory activity of E. polyantha extract. Furthermore, hydroxychavicol is reported to possess anti-carcinogenic, anti-oxidant, anti-microbial and anti-inflammatory activity which is related to traditional usage of this plant. These results offer this plant as an attractive material for treating various health problems including obesity.

Iriomoteolide-3a, a cytotoxic 15-membered macrolide from a marine dinoflagellate amphidinium species.

A 15-membered macrolide, iriomoteolide-3a (1), with an allyl epoxide has been isolated from a marine benthic dinoflagellate Amphidinium sp. (strain HYA024), and the structure was assigned by detailed analyses of 2D NMR data. Relative and absolute configurations were elucidated on the basis of conformational studies of 1 and its acetonide (2) and modified Mosher's method of 1, respectively. Iriomoteolide-3a (1) and the acetonide (2) exhibited potently cytotoxic activity against antitumor cells.

Inhibitory effects of 5,6,7-trihydroxyflavones on tyrosinase.

Baicalein (1), 6-hydroxyapigenin (6), 6-hydroxygalangin (13) and 6-hydroxy-kaempferol (14), which are naturally occurring flavonoids from a set of 14 hydroxy-flavones tested, exhibited high inhibitory effects on tyrosinase with respect to L-DOPA, while each of the 5,6,7-trihydroxyflavones 1, 6, 13 or 14 acted as a cofactor to monophenolase. Moreover, 6-hydroxykaempferol (14) showed the highest activity and was a competitive inhibitor of tyrosinase compared to L-DOPA. 5,6,7-Trihydroxyflavones 1, 6, 13 or 14 showed also high antioxidant activities. Hence, we conclude that the 5,6,7-trihydroxy-flavones are useful as good depigmentation agents with inhibitory effects in addition to their antioxidant properties.

Synergistic effects of thiols and amines on antiradical efficiency of protocatechuic acid.

DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity of protocatechuic acid and its structural analogues (methyl protocatechuate, 3',4'-dihydroxyacetophenone, 3,4-dihydroxybenzaldehyde, and 3,4-dihydroxybenzonitrile) were examined in aprotic and protic solvents. In aprotic acetonitrile, all test compounds scavenged two radicals. In protic methanol, however, these compounds rapidly scavenged five radicals except for protocatechuic acid, which consumed only two radicals. The result indicated that higher radical scavenging activity in methanol than in acetonitrile was due to a nucleophilic addition of the methanol molecule on the oxidized quinones, which led to a regeneration of catechol structures. To investigate the importance of the nucleophilic addition on the quinones for the high radical scavenging activity, DPPH radical scavenging activity of protocatechuic acid and its analogues was examined in the presence of a variety of nucleophiles. The addition of a strong nucleophile such as a cysteine derivative significantly increased the radical scavenging equivalence. Furthermore, thiol adducts at C-2 and C-2,5 of protocatechuic acid and its analogues were isolated from the reaction mixtures. These results strongly suggest that the quinone of protocatechuic acid and its analogues undergo a nucleophilic attack at C-2 to yield 2-substituted-3,4-diols. Then, a regenerated catechol moiety of adducts scavenge two additional radicals by reoxidation into quinones, which undergo the second nucleophilic attack at the C-5. This mechanism demonstrates a possibility of synergistic effects of various nucleophiles on the radical scavenging ability of plant polyphenols containing a 3,4-dihydroxy substructure like protocatechuic acid and its analogues.

Activin A induces phosphorylation of Smad2 but not complex formation of Smad2 with Smad4 in human colon cancer cell line HT-29.

Western blotting coupled with immunoprecipitation showed that activin A treatment induced phosphorylation of Smad2 but not complex formation of Smad2/4 in human colon cancer-derived HT-29 cells. Because HT-29 cells expressed neither Smad4 mRNA nor Smad4 protein, it is suggested that deletion of Smad4 leads to a defect of formation of Smad2/4 complex upon activin A stimulation in HT-29 cells.

Polyphenols from some foodstuffs as inhibitors of ovalbumin permeation through caco-2 cell monolayers.

Some spices showed high inhibitory activity against ovalbumin permeation through Caco-2 cell monolayers. Pimentol from allspice, rosmarinic acid and luteolin-7-O-beta-glucuronide from thyme, quercetin-3-O-beta-glucuronide from coriander and rutin from tarragon were identified as the active principles. A structure-activity relationship study among the active isolates and their related compounds indicated that the presence of a catechol structure played an important role in the inhibitory activity of each compound.

Antitumor activity of palmitic acid found as a selective cytotoxic substance in a marine red alga.

In a previous report, we discussed an extract from a marine red alga, Amphiroa zonata, which shows selective cytotoxic activity to human leukemic cells, but no cytotoxicity to normal human dermal fibroblast (HDF) cells in vitro. In this study, we identified palmitic acid, a selective cytotoxic substance from the marine algal extract, and investigated its biological activities. At concentrations ranging from 12.5 to 50 micrograms/ml, palmitic acid shows selective cytotoxicity to human leukemic cells, but no cytotoxicity to normal HDF cells. Furthermore, palmitic acid induces apoptosis in the human leukemic cell line MOLT-4 at 50 micrograms/ml. Palmitic acid also shows in vivo antitumor activity in mice. One molecular target of palmitic acid in tumor cells is DNA topoisomerase I, however, interestingly, it does not affect DNA topoisomerase II, suggesting that palmitic acid may be a lead compound of anticancer drugs.