Two antibacterial and PPARα/γ-agonistic unsaturated keto fatty acids from a coral-associated actinomycete of the genus Micrococcus.

A pair of geometrically isomeric unsaturated keto fatty acids, (6E,8Z)- and (6E,8E)-5-oxo-6,8-tetradecadienoic acids (1 and 2), were isolated from the culture broth of an actinomycete of the genus Micrococcus, which was associated with a stony coral, Catalaphyllia sp. Their chemical structures were elucidated by spectroscopic analysis including NMR and MS, with special assistance of spin system simulation studies for the assignment of an E geometry at C8 in 2. As metabolites of microbes, compounds 1 and 2 are unprecedented in terms of bearing a 2,4-dienone system. Both 1 and 2 showed antibacterial activity against the plant pathogen Rhizobium radiobacter and the fish pathogen Tenacibaculum maritimum, with a contrasting preference that 1 is more effective to the former strain while 2 is so to the latter. In addition, compounds 1 and 2 displayed agonistic activity against peroxisome proliferator-activated receptors (PPARs) with an isoform specificity towards PPARα and PPARγ.

Isolation, Identification, and Synthesis of a New Prenylated Cinnamic Acid Derivative from Brazilian Green Propolis and Simultaneous Quantification of Bioactive Components by LC-MS/MS.

A new cinnamic acid derivative, (E)-3-[4-hydroxy-3-((E)-3-formyl-2-butenyl)phenyl]-2- propenoic acid (20) has been isolated from the ethanol extract of Brazilian green propolis along with three known cinnamic acid derivatives, 3,4-dihydroxy-5-prenyl-(E)-cinnamic acid (4), capillartemisin A (6), and 2,2-dimethylchromene-6-(E)-propenoic acid (8), and a flavonoid, dihydrokaempferide (16) by liquid-liquid participation, a series of column chromatography and preparative HPLC. Their structures have been determined by spectroscopic analyses and chemical synthesis of compound 20. The simultaneous quantification of 20 constituents, including 10 cinnamic acid derivatives, 7 flavonoids, and 3 caffeoylquinic acid derivatives, has also been developed and validated using LC-MS/MS. The new compound 20 was shown to activate PPAR α but not PPAR ß or γ.

Cassane-type diterpenoids from Caesalpinia echinata (Leguminosae) and their NF-κB signaling inhibition activities.

Fourteen cassane-type diterpenoids, echinalides H-U, were isolated from the stem of Caesalpinia echinata Lam. (Leguminosae). The structures of the echinalides were elucidated by spectroscopic investigation, including 2D NMR spectroscopic analysis. The structures of echinalide H and echinalide T were further confirmed by single-crystal X-ray diffraction. The absolute configurations of echinalides H, I, J and K were determined by CD spectroscopy. Additionally, the absolute configurations of echinalide L and M were determined by chemical conversion from echinalide H. These compounds were evaluated for inhibitory activity against nuclear factor κB (NF-κB). Echinalide M showed the most potent inhibitory activity (47±11% at 5µM) toward NF-κB-responsive gene expression.

Hikiamides A-C, Cyclic Pentadepsipeptides from Fusarium sp. TAMA 456.

Three new cyclic pentadepsipeptides, hikiamides A-C (1-3), were isolated from the culture extract of Fusarium sp. TAMA 456. The structures were determined by spectroscopic analysis using NMR and MS, and the absolute configurations were established by using Marfey's method and chiral HPLC analysis. Hikiamides induced the differentiation of murine ST-13 preadipocytes into mature adipocytes at 2 µM and adiponectin mRNA expression (5- to 13-fold higher than control). They also induced PPAR-γ-dependent gene expression at a concentration from 0.63 to 10 µM in a gene reporter assay.

Structural design and synthesis of arylalkynyl amide-type peroxisome proliferator-activated receptor γ (PPARγ)-selective antagonists based on the helix12-folding inhibition hypothesis.

Peroxisome proliferator-activated receptor γ (PPARγ) antagonists are candidates for treatment of type 2 diabetes, obesity and osteoporosis. However, few rational design strategies are currently available. Here, we utilized the helix12 (H12)-folding inhibition hypothesis, in combination with our previously determined X-ray crystal structure of PPARγ agonist MEKT-21 (6) complexed with the PPARγ ligand-binding domain, to design and develop a potent phenylalkynyl amide-type PPARγ antagonist 9i, focusing initially on pinpoint structural modification of the propanoic acid moiety of 6. Since 9i retained very weak, but distinct, PPARγ agonist activity, we next modified the distal benzene ring of 9i, aiming to delete the residual PPARγ agonist activity while retaining the antagonist activity. Introduction of a chlorine atom at the 2-position of the distal benzene ring afforded 9p, which exhibited potent, PPARγ-selective full antagonist activity without detectable agonist activity. We found that 9p stabilized the corepressor-PPARγ complex and suppressed basal PPARγ activity. This compound showed anti-adipogenesis activity at the cellular level. This agonist-antagonist switching concept based on the H12-folding inhibition hypothesis should also be applicable for designing other classes of PPARγ full antagonists.

Hesperetin glucuronides induce adipocyte differentiation via activation and expression of peroxisome proliferator-activated receptor-γ.

In previous reports, hesperidin, a flavonoid glucoside from citrus fruit, is hydrolyzed to hesperetin, an aglycone of hesperidin, and converted to the hesperetin glucuronides (H7-OG and H3'-OG) in vivo and depresses blood glucose levels. But there are no reports on the activity of hesperetin glucuronides. To determine the activity of hesperetin glucuronides, H7-OG and H3'-OG were synthesized and peroxisome proliferator-activated receptor-γ (PPARγ) agonist activity was observed at 250 µM. These glucuronides accelerated the differentiation of 3T3-L1 cells into adipocytes at 10 µM. Furthermore, H7-OG showed additive effects in reporter gene assays and caused noncompetitive reactions in time-resolved fluorescence resonance energy transfer assays with a thiazolidinedione derivative. Our results indicated that hesperetin glucuronides activated PPARγ, accelerated adipocyte differentiation.

Molecular dynamics study-guided identification of cyclic amine structures as novel hydrophobic tail components of hPPARγ agonists.

We previously reported that a α-benzylphenylpropanoic acid-type hPPARγ-selective agonist with a piperidine ring as the hydrophobic tail part (3) exhibited sub-micromolar-order hPPARγ agonistic activity. In order to enhance the activity, we planned to carry out structural development based on information obtained from the X-ray crystal structure of hPPARγ ligand binding domain (LBD) complexed with 3. However, the shape and/or nature of the binding pocket surrounding the piperidine ring of 3 could not be precisely delineated because the structure of the omega loop of the LBD was poorly defined. Therefore, we constructed and inserted a plausible omega loop by means of molecular dynamics simulation. We then used the reconstructed LBD structure to design new mono-, bi- and tricyclic amine-bearing compounds that might be expected to show greater binding affinity for the LBD. Here, we describe synthesis and evaluation of α-benzylphenylpropanoic acid derivatives 8. As expected, most of the newly synthesized compounds exhibited more potent hPPARγ agonistic activity and greater hPPARγ binding affinity than 3. Some of these compounds also showed comparable aqueous solubility to 3.

Nocapyrones: α- and γ-pyrones from a marine-derived Nocardiopsis sp.

One new α-pyrone (nocapyrone R (1)), and three known γ-pyrones (nocapyrones B, H and L (2-4)) were isolated from the culture extract of a Nocardiopsis strain collected from marine sediment. Structures of these compounds were determined on the basis of spectroscopic data including NMR and MS. γ-Pyrones 2-4 were found to induce adiponectin production in murine ST-13 preadipocyte cells but the α-pyrone 1 had no activity. The absolute configuration of the anteiso-methyl branching in 4 was determined by HPLC comparison of a degraded product of 4 with standard samples as a 2:3 enantiomeric mixture of (R)- and (S)-isomers.

Potent protein glycation inhibition of plantagoside in Plantago major seeds.

Plantagoside (5,7,4',5'-tetrahydroxyflavanone-3'-O-glucoside) and its aglycone (5,7,3',4',5'-pentahydroxyflavanone), isolated from a 50% ethanol extract of Plantago major seeds (Plantaginaceae), were established to be potent inhibitors of the Maillard reaction. These compounds also inhibited the formation of advanced glycation end products in proteins in physiological conditions and inhibited protein cross-linking glycation. These results indicate that P. major seeds have potential therapeutic applications in the prevention of diabetic complications.

Mechanism of peroxisome proliferator-activated receptor gamma (PPARγ) transactivation by hesperetin glucuronides is distinct from that by a thiazolidine-2,4-dione agent.

Hesperidin, a flavanone glycoside present abundantly in citrus fruits, is predominantly metabolized to hesperetin-7-O-ß-D-glucuronide (H7-OG) and hesperetin-3'-O-ß-D-glucuronide (H3'-OG), which exhibit partial agonistic activity towards peroxisome proliferator-activated receptor gamma (PPARγ). Here, in order to understand the mechanism(s) of action of PPARγ transactivation elicited by hesperetin glucuronides, we compared the transactivation activities of PPARγ (ligand-binding domain (LBD)) mutants by hesperetin glucuronides and troglitazone, a thiazolidine-2,4-dione class PPARγ full agonist. The assay results indicated that the mechanisms of activation of PPARγ by hesperetin glucuronides and by troglitazone are distinct, probably due to a difference in the binding sites of these compounds on the PPARγ LBD. Flavanone-class PPARγ partial agonists, luteolin and hesperetin glucuronides, showed similar activation profiles of the PPARγ LBD mutants, even though they have different side chain functionalities.

New cassane-type diterpenoids of Caesalpinia echinata (Leguminosae) exhibiting NF-κB inhibitory activities.

Seven new cassane-type diterpenoids, echinalides A-G (1-7), were isolated from the stem of Caesalpinia echinata LAM. (Leguminosae). The structures were established on the basis of their chemical properties and spectroscopic evidence, including two dimensional (2D)-NMR analysis. These compounds were assessed for inhibitory activity against nuclear factor κB (NF-κB). Echinalides C and D, in particular, significantly inhibited NF-κB-responsive reporter gene expression at 5.0 µM, an effect almost equivalent to that of parthenolide, a known potent inhibitor of NF-κB.

γ-Mangostin from Garcinia mangostana pericarps as a dual agonist that activates Both PPARα and PPARδ.

We tested the peroxisome proliferator-activated receptor (PPAR)δ agonistic activity of a Garcinia mangostana pericarp extract to develop a treatment for the metabolic syndrome, and demonstrated γ-mangostin to be an active compound on the basis of a luciferase reporter gene assay. γ-Mangostin induced the expression of the uncoupling protein-3 (UCP-3) gene which is related to energy expenditure and fat metabolism in L6 cells. We showed that γ-mangostin is a dual agonist that activates both PPARδ and PPARα. γ-Mangostin also induced the expression of acyl-CoA synthase and carnitine palmitoyl-transferase 1A genes in HepG2 cells. These results suggest the potential of γ-mangostin as a preventive agent of the metabolic syndrome.

Culcitiolides E-J, six new eremophilane-type sesquiterpene derivatives from Senecio culcitioides.

Culcitiolides E-J (1-6), six new eremophilane-type sesquiterpenes, were isolated from the stem of Senecio culcitioides SCH. BIP. (Asteraceae). The structures were determined by detailed NMR spectral analysis. The inhibitory activities of these compounds against nuclear factor κB (NF-κB)-dependent gene expression were assessed. Culcitiolides E, H, and I potently inhibited NF-κB-induced gene expression at 20 µM.

Culcitiolides A-D, four new eremophilane-type sesquiterpene derivatives from Senecio culcitioides.

Four new eremophilane-type sesquiterpenes, culcitiolides A-D, were isolated from the stem of Senecio culcitioides Sch. Bip (Asteraceae). Their structures were established by detailed 2D NMR spectroscopic and single-crystal X-ray experiments. These compounds were assessed for inhibitory activity against nuclear factor kappaB (NF-kappaB). Culcitiolides C and D at 20 microM showed 97 and 100% inhibition of NF-kappaB activity, respectively.

Norlichexanthone isolated from fungus P16 promotes the secretion and expression of adiponectin in cultured ST-13 adipocytes.

Adiponectin, an adipose-derived protein, shows insulin-sensitizing, anti-diabetic and anti-atherogenic activities, which implies that the protein represents a potential target to improve lifestyle-related diseases like type 2 diabetes. Based on our hypothesis that agents that cause adipocyte differentiation could also act as adiponectin secretion enhancers, we screened butanol extracts of 96 fungus culture extracts for their differentiation-inducing activity in ST-13 preadipocytes. We found that the butanol extract of a fungus P16 culture extract possessed such an activity, and isolated norlichexanthone as an active compound through activity-guided fractionation. Oil red O staining showed that norlichexanthone induced adipogenesis in ST-13 cells. Its differentiation-inducing activity was supported by the observation that norlichexanthone dose-dependently increased the mRNA expression of fatty acid-binding protein and peroxisome proliferator activated receptor γ (PPARγ), markers of adipocyte differentiation. Western blot analysis demonstrated that the compound enhanced the secretion of adiponectin protein in a dose-dependent manner. An increase in mRNA expression of adiponectin was also observed in the norlichexanthone-treated ST-13 cells. Actinomycin D treatment blocked the enhancement of adiponectin mRNA expression by norlichexanthone, suggesting that it is the result of increased transcription. A luciferase reporter assay indicated that norlichexanthone was unlikely to be an agonist of PPARγ, implying that its action of mechanism might differ from those of thiazolidinediones which upregulate adiponectin expression via activation of PPARγ. These findings suggest the possibility that norlichexanthone has the potential to treat and/or prevent lifestyle-related diseases, including metabolic syndrome, type 2 diabetes, atherosclerosis and cardiovascular diseases.

Efficacy of dibenzoylmethane derivatives in protecting against endoplasmic reticulum stress and inhibiting nuclear factor kappa B on dextran sulfate sodium induced colitis in mice.

We recently reported that some dibenzoylmethane (DBM) derivatives have a protective effect against endoplasmic reticulum (ER) stress and inhibit nuclear factor kappa B (NF-κB). The aim of this study was to evaluate the effect of DBM derivatives against dextran sulfate sodium (DSS)-induced colitis in mice. The DBM derivatives used in this study were 4,4'-dibromodibenzoylmethane that protects against ER stress, and, 4,4'-dichlorodibenzoylmethane that protects against ER stress and inhibits NF-κB. In each group, the presence of faecal occult blood, the disease activity index score (DAI score) and intestinal length were examined. Both of the DBM derivatives with protective effects against ER stress significantly improved occult bleeding of the colitis induced by DSS. The 4,4'-dichlorodibenzoylmethane significantly reduced the DAI score and inhibited the shortening of colon length, but the 4,4'-dibromodibenzoylmethane did not. These findings suggest that both the protective effect against ER stress and inhibitory effect on NF-κB are needed in the treatment of DSS-induced colitis. Therefore, the effect of 4,4'-dichlorodibenzoylmethane maybe beneficial in the therapeutic regulation of ulcerative colitis.

Comparative study on determination of antioxidant and membrane activities of propofol and its related compounds.

Certain anesthetics have been suggested to protect against the pathological states associated with oxidative stress. We compared the antioxidant and membrane activities of propofol (2,6-diisopropylphenol) and its related compounds to address the structure-activity relationship especially in a lipid membrane phase. They were studied for the effects on 1,1-diphenyl-2-picrylhydrazyl radicals, nitro blue tetrazolium reduction by superoxide anions and membrane lipid peroxidation by peroxynitrite, and also for the induced changes in membrane fluidity of liposomes. 2-Isopropylphenols scavenged free radicals with the potency being propofol>2,5-diisopropylphenol>2-isopropylphenol>2,4-diisopropylphenol, but not 3- and 4-isopropylphenols and 1,3- and 1,4-diisopropylbenzenes. The tested compounds showed no significant superoxide dismutase-like effects. Propofol inhibited membrane lipid peroxidation more intensively than 2,5-diisopropylphenol, 2,4-diisopropylphenol and 2-isopropylphenol. Despite structurally resembling antioxidant alpha-tocopherol, 2,6-dimethylphenol was less potent than propofol. Propofol produced 50% inhibition of the lipid peroxidation in unsaturated phosphatidylcholine liposomal membranes and cell-mimetic membranes at 4.0 and 10.1 microM, respectively. Propofol and 2-alkylphenolic compounds interacted with membranes to increase their fluidity with the potency correlating with lipid peroxidation inhibiting activity. The 2-isopropylphenol structure is a requisite for both lipid peroxidation inhibition and membrane fluidity modification. The structure-specific membrane interactivity appears to be one of possible antioxidant mechanisms for propofol.

Identification of nobiletin, a polymethoxyflavonoid, as an enhancer of adiponectin secretion.

Adiponectin, an adipocyte-derived protein with insulin-sensitizing, anti-diabetic and anti-atherogenic activities, is known to be induced during adipocyte differentiation. Nobiletin, a citrus polymethoxy flavonoid, was found to induce the differentiation of ST-13 preadipocytes into mature adipocytes and enhance the production of adiponectin protein at a concentration of 10 microM.