Synthesis and evaluation of [(1R)-1-amino-2-(2,5-difluorophenyl)ethyl]cyclohexanes and 4-[(1R)-1-amino-2-(2,5-difluorophenyl)ethyl]piperidines as DPP-4 inhibitors

A series of 4-amino cyclohexanes and 4-substituted piperidines were prepared and evaluated for inhibition of DPP-4. Analog 20q displayed both good DPP-4 potency and selectivity against other proteases, while derivative 20k displayed long half life and modest oral bioavailability in rat. The most potent analog, 3-(5-aminocarbonylpyridyl piperidine 53j, displayed excellent DPP-4 activity with good selectivity versus other proline enzymes.     

Compounds from Kadsura angustifolia with anti-HIV activity

Four new cycloartane triterpenoids, angustific acid A (1), angustific acid B (2), angustifodilactone A (3) and angustifodilactone B (4) were isolated from the branches of Kadsura angustifolia together with six known compounds, micranoic acid B (5), nigranoic acid (6), schisandrin (7), schisantherin D (8), interiotherin B (9), schisantherin B (10). Their structures were established on the basis of extensive spectroscopic data analyses and comparison with spectroscopic data reported. Compound 1, characterized by the presence of a C-16/C-17, C-20/C-21 conjugated diene and a C-1/C-7 ester bridge formed in rings A and B, provided a novel structural skeleton for 3,4-secocycloartane triterpenoid derivatives. In addition, the anti-HIV activities of these compounds were determined in infected C8166 cells, and it was found that angustific acid A (1) exhibited the most potent anti-HIV activity with an EC₅₀ value of 6.1 μg/mL and a therapeutic index of more than 32.8.     

Tetra-acylated cyanidin 3-sophoroside-5-glucosides from the flowers of Iberis umbellata L. (Cruciferae)

The structures of 11 acylated cyanidin 3-sophoroside-5-glucosides (pigments 1-11), isolated from the flowers of Iberis umbellata cultivars (Cruciferae), were elucidated by chemical and spectroscopic methods. Pigments 1-11 were acylated with malonic acid, p-coumaric acid, ferulic acid, sinapic acid and/or glucosylhydroxycinnamic acids.Pigments 1-11 were classified into four groups by the substitution patterns of the linear acylated residues at the 3-position of the cyanidin. In the first group, pigments 1-3 were determined to be cyanidin 3-O-[2-O-(2-O-(acyl)-β-glucopyranosyl)-6-O-(trans-p-coumaroyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside], in which the acyl moiety varied with none for pigment 1, ferulic acid for pigment 2 and sinapic acid for pigment 3. In the second one, pigments 4-6 were cyanidin 3-O-[2-O-(2-O-(acyl)-β-glucopyranosyl)-6-O-(4-O-(β-glucopyranosyl)-trans-p-coumaroyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside], in which the acyl moiety varied with none for pigment 4, ferulic acid for pigment 5 and sinapic acid for pigment 6. In the third one, pigments 7-9 were cyanidin 3-O-[2-O-(2-O-(acyl)-β-glucopyranosyl)-6-O-(4-O-(6-O-(trans-feruloyl)-β-glucopyranosyl)-trans-p-coumaroyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside], in which the acyl moiety varied with none for pigment 7, ferulic acid for pigment 8, and sinapic acid for pigment 9. In the last one, pigments 10 and 11 were cyanidin 3-O-[2-O-(2-O-(acyl)-β-glucopyranosyl)-6-O-(4-O-(6-O-(4-O-(β-glucopyranosyl)-trans-feruloyl)-β-glucopyranosyl)-trans-p-coumaroyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside], in which acyl moieties were none for pigment 10 and ferulic acid for pigment 11.The distribution of these pigments was examined in the flowers of four cultivars of I. umbellata by HPLC analysis. Pigment 1 acylated with one molecule of p-coumaric acid was dominantly observed in purple-violet cultivars. On the other hand, pigments (9 and 11) acylated with three molecules of hydroxycinnamic acids were observed in lilac (purple-violet) cultivars as major anthocyanins. The bluing effect and stability on these anthocyanin colors were discussed in relation to the molecular number of hydroxycinnamic acids in these anthocyanin molecules.     

Itaconic acid derivatives and diketopiperazine from the marine-derived fungus Aspergillus aculeatus CRI322-03

Three metabolites, pre-aurantiamine (1), (−)-9-hydroxyhexylitaconic acid (4) and (−)-9-hydroxyhexylitaconic acid-4-methyl ester (5), together with two known compounds, paraherquamide E (6) and secalonic acid D (7), were isolated from the marine-derived fungus, Aspergillus aculeatus.     

Determination of the hydroxycinnamate profile of 12 members of the Asteraceae family

The hydroxycinnamates of the leaves of 12 plants of the Astreraceae family, Achillea millefolium, Arnica montana, Artemesia dracunculus, Cichorium intybus, Cnicus benedictus, Cynara scolymus, Echinops humilis, Inula helenium, Lactuca sativa, Petasites hybridus, Solidago virgaurea, and Tanacetum parthenium were investigated qualitatively by LC-MSⁿ. Thirty-nine chlorogenic acids were detected and all characterized to regioisomeric level on the basis of their fragmentation pattern in the tandem MS spectra, most of them for the first time from these sources with two of them previously not reported in nature. Both chlorogenic acids based on trans and cis-cinnamic acid substituents were identified. Assignment to the level of individual regioisomers was possible for seven caffeoylquinic acids (1-7), 11 dicaffeoylquinic acids (17-27), six feruloylquinic acids (9-14), two p-coumaroylquinic acids (15-16), two caffeoyl-feruloylquinic acids (28 and 29), four caffeoyl-p-coumaroylquinic acids (30-33), three dicaffeoyl-succinoylquinic acids (34-36), two dicaffeoyl-methoxyoxaloylquinic acids (37 and 38), and one tricaffeoylquinic acid (39). Furthermore, one caffeoylshikimic acid (40), one caffeoyltartaric acid (41), three dicaffeoyltartaric acids (42-44), and three caffeoyl-feruloyltartaric acids (45-47) were detected and shown to possess characteristic tandem MS spectra and were tentatively assigned on the basis of their retention time and previously developed hierarchical keys.     

Steroidal glycosides from the marine sponge Pandaros acanthifolium

The chemical composition of the Caribbean sponge Pandaros acanthifolium was investigated and led to the isolation of seven new steroidal glycosides namely pandarosides A-D (1, 3, 4 and 6) along with the three methyl esters of pandarosides A, C, and D (2, 5 and 7). Their structures were characterized as 3β-[β-glucopyranosyl-(1→2)-β-glucopyranosyloxyuronic acid]-16-hydroxy-5α,14β-poriferast-16-ene-15,23-dione (1) and its methyl ester (2), 3β-[β-glucopyranosyloxyuronic acid]-16-hydroxy-5α,14β-poriferast-16-ene-15,23-dione (3), 3β-[β-glucopyranosyl-(1→2)-β-glucopyranosyloxyuronic acid]-16-hydroxy-5α,14β-cholest-16-ene-15,23-dione (4) and its methyl ester (5), 3β-(β-glucopyranosyloxyuronic acid)-16-hydroxy-5α,14β-cholest-16-ene-15,23-dione (6) and its methyl ester (7) on the basis of detailed spectroscopic analyses, including 2D NMR and HRESIMS studies. Pandarosides A-D and their methyl esters (1-7) are all characterized by a rare 2-hydroxycyclopentenone D-ring with a 14β configuration. The absolute configuration of the aglycon part of pandaroside A (1) was assigned by comparison between experimental and TDDFT calculated circular dichroism spectra on the more stable conformer.     

(25S)-Cholesten-26-oic acid derivatives from an Indonesian soft coral Minabea sp.

(25S)-3-Oxocholesta-1,4-dien-26-oic acid (1) and a new (25S)-18-acetoxy-3-oxocholesta-1,4-dien-26-oic acid (2) were isolated from a soft coral Minabea sp. (cf. aldersladei) collected in North Sulawesi, Indonesia, together with two known cholic-acid-type compounds, 3-oxochol-1,4-dien-24-oic acid (3) and 3-oxochol-4-en-24-oic acid (4). The structures of these compounds were determined on the basis of their spectroscopic data. The absolute stereochemistry at C-25 of 2 was determined by comparative ¹H NMR study using chiral anisotropic reagents [(S)- and (R)-phenylglycine methyl esters]. This is the first to report compound 1 as a natural product.     

Synthesis of [I]iodoDPA-713: A new probe for imaging inflammation

[¹²⁵I]IodoDPA-713 [¹²⁵I]1, which targets the translocator protein (TSPO, 18 kDa), was synthesized in seven steps from methyl-4-methoxybenzoate as a tool for quantification of inflammation in preclinical models. Preliminary in vitro autoradiography and in vivo small animal imaging were performed using [¹²⁵I]1 in a neurotoxicant-treated rat and in a murine model of lung inflammation, respectively. The radiochemical yield of [¹²⁵I]1 was 44 ± 6% with a specific radioactivity of 51.8 GBq/μmol (1400 mCi/μmol) and >99% radiochemical purity. Preliminary studies showed that [¹²⁵I]1 demonstrated increased specific binding to TSPO in a neurotoxicant-treated rat and increased radiopharmaceutical uptake in the lungs of an experimental inflammation model of lung inflammation. Compound [¹²⁵I]1 is a new, convenient probe for preclinical studies of TSPO activity.     

Synthesis, structure-activity relationship of novel substituted 4H-chromen-1,2,3,4-tetrahydropyrimidine-5-carboxylates as potential anti-mycobacterial and anticancer agents

Series of 4H-chromen-1,2,3,4-tetrahydropyrimidine-5-carboxylate derivatives 7a-7zb, 8a-8d and 9a-9d were synthesized and screened for their in vitro anti-mycobacterial activity against Mycobacterium tuberculosis H₃₇Rv (MTB) and cytotoxicity against three human cancer cell lines including A549, SK-N-SH and HeLa. The results indicate that six compounds are more potent and 7za is most effective anti-mycobacterial derivative compared to the standard drugs Ethambutol and Ciprofloxacin. However, 12 compounds exhibited cytotoxicity against human neuroblastoma cell line; amongst them the compound 7v is most effective compared to the standard drug Doxorubicin. This is the first report assigning in vitro anti-mycobacterial, anticancer and structure-activity relationship for this new class of 4H-chromen-1,2,3,4-tetrahydropyrimidine-5-carboxylates.     

Synthesis, modification, and evaluation of (R)-de-O-methyllasiodiplodin and analogs as nonsteroidal antagonists of mineralocorticoid receptor

Macrolide (R)-de-O-methyllasiodiplodin (1), discovered to be a potent nonsteroidal antagonist of the mineralocorticoid receptor (MR), was synthesized via an efficient method and evaluated for MR antagonistic activity together with its analogs. Among all the tested compounds, compounds 18a, 18b and 18c, exhibited more potent antagonistic activity against MR with IC₅₀ values ranging from 0.58 to 1.11 μM. Generally, it was obviously demonstrated that acetylation at phenolic hydroxyl groups and the ring size in analogs of 1 were very important for MR antagonist activity.     

Philadelphicalactones C and D and other cytotoxic compounds from Physalis philadelphica

Two new withanolides, philadelphicalactone C (1) and philadelphicalactone D (4), along with the known withaphysacarpin (3), ixocarpanolide (5), philadelphicalactone A (6), and ixocarpalactone A (7) were isolated from the aerial parts of Physalis philadelphica Lam. Structures of these compounds were determined by spectroscopic analyses and that of philadelphicalactone C (1) was confirmed by X-ray crystallographic analysis. Evaluation of the cytotoxic activity of all isolates and the derivative 2 against a panel of human cancer cell lines indicated a potent activity of compounds 2, 3, 6, and 7.     

Toxic polyketides produced by Fusarium sp., an endophytic fungus isolated from Melia azedarach

A new isocoumarin derivative named fusariumin (1), together with two known related resorcylic acid lactones aigialomycin D (2) and pochonin N (3), has been isolated from the cultures of Fusarium sp. LN-10, an endophytic fungus originated from the leaves of Melia azedarach. Their structures were established on the basis of extensive spectroscopic analyzes including 1D- and 2D- NMR (¹H-¹H COSY, HSQC, HMBC, and NOESY) experiments. Compounds 1-3 displayed significant growth inhibitory activity against the brine shrimp (Artemia salina).     

Antineoplastic unsaturated fatty acids from Fijian macroalgae

Phytochemical analysis of Fijian populations of the green alga Tydemania expeditionis led to the isolation of two unsaturated fatty acids, 3(ζ)-hydroxy-octadeca-4(E),6(Z),15(Z)-trienoic acid (1) and 3(ζ)-hydroxy-hexadeca-4(E),6(Z)-dienoic acid (2), along with the known 3(ζ)-hydroxy-octadeca-4(E),6(Z)-dienoic acid (4). Investigations of the red alga Hydrolithon reinboldii led to identification of a glycolipid, lithonoside (3), and five known compounds, 15-tricosenoic acid, hexacosa-5,9-dienoic methyl ester, β-sitosterol, 10(S)-hydroxypheophytin A, and 10(R)-hydroxypheophytin A. The structures of 1-3 were elucidated by spectroscopic methods (1D and 2D NMR spectroscopy and ESI-MS). Compounds 1, 2, and 4, containing conjugated double bonds, demonstrated moderate inhibitory activity against a panel of tumor cell lines (including breast, colon, lung, prostate and ovarian cells) with IC₅₀ values ranging from 1.3 to 14.4 μM. The similar cell selectivity patterns of these three compounds suggest that they might act by a common, but unknown, mechanism of action.     

New furin inhibitors based on weakly basic amidinohydrazones

A novel series of amidinohydrazone-derived furin inhibitors was prepared; the most potent compounds 17 and 21 inhibit furin with K_i values of 0.46 and 0.59 μM, respectively. In contrast to inhibitor 17, which still contains a guanidino residue, compound 21 possesses only weakly basic amidinohydrazone groups.     

Anti-inflammatory activity of constituents from Glechoma hederacea var. longituba

Rosmarinic acid, its analogues, and a phenolic compound were obtained from G. hederacea var. longituba. There were two new compounds, methyl isoferuloyl-7-(3,4-dihydroxyphenyl) lactate (1) and benzyl-4′-hydroxy-benzoyl-3′-O-β-d-glucopyranoside (4), and four known compounds (2, 3, 5 and 6). The structures of these compounds were determined on the basis of spectroscopic methods. Each compound was tested by NF-κB luciferase assay and three rosmarinic acid analogues inhibited NF-κB production and the induction of COX-2 and iNOS mRNA in HepG2 cells.     

Iridoids from Gentiana loureirii

Iridoid glycosides, 2′,3′,6′-tri-O-acetyl-4′-O-trans-p-(O-β-d-glucopyranosyl)coumaroyl-7-ketologanin (1), 2′-O-caffeoylloganic acid (2), 2′-O-p-hydroxybenzoylloganic acid (3), 2′-O-trans-p-coumaroylloganic acid (4), and 2′-O-cis-p-coumaroylloganic acid (5), were isolated from whole plants of Gentiana loureirii along with six known iridoids, 7-ketologanin (6), loganin (7), loganic acid (8), sweroside, boonein, and isoboonein, and three other known compounds. Their structures were elucidated by spectroscopic means and chemical correlations. The isolated iridoids were evaluated for antibacterial and antioxidant activities, but were either inactive or very weakly active.     

Alternative conformations of the x region of human protein disulphide-isomerase modulate exposure of the substrate binding b' domain

Protein disulphide isomerase (PDI) is a key multi-domain protein folding catalyst in the endoplasmic reticulum. The b’ domain of PDI is essential for the non-covalent binding of incompletely folded protein substrates. Earlier, we defined the substrate binding site in the b’ domain of human PDI by modelling and mutagenesis studies. Here, we show by fluorescence and NMR that recombinant human PDI b’x (comprising the b’ domain and the subsequent x linker region) can assume at least two different conformations in solution. We have screened mutants in the b’x region to identify mutations that favour one of these conformers in recombinant b'x, and isolated and characterised examples of both types. We have crystallised one mutant of b’x (I272A mutation) in which one conformer is stabilized, and determined its crystal structure to a resolution of 2.2 Å. This structure shows that the b’ domain has the typical thioredoxin fold and that the x region can interact with the b’ domain by ”capping” a hydrophobic site on the b’ domain. This site is most likely the substrate binding site and hence such capping will inhibit substrate binding. All of the mutations we previously reported to inhibit substrate binding shift the equilibrium towards the capped conformer. Hence, these mutations act by altering the natural equilibrium and decreasing the accessibility of the substrate binding site. Furthermore, we have confirmed that the corresponding structural transition occurs in the wild type full-length PDI. A cross-comparison of our data with that for other PDI-family members, Pdi1p and ERp44, suggests that the x region of PDI can adopt alternative conformations during the functional cycle of PDI action and that these are linked to the ability of PDI to interact with folding substrates.     

Bioactive saponins from Microsechium helleri and Sicyos bulbosus

Eleven oleanane-type saponins (1-11) have been isolated from Microsechium helleri and Sicyos bulbosus roots and were evaluated for their antifeedant, nematicidal and phytotoxic activities. Saponins {3-O-β-d-glucopyranosyl (1 → 3)-β-d-glucopyranosyl-2β,3β,16α,23-tetrahydroxyolean-12-en-28-oic acid 28-O-α-l-rhamnopyranosyl-(1 → 3)-β-d-xylopyranosyl-(1 → 4)-[β-d-xylopyranosyl-(1 → 3)]-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranoside} (1), and {3-O-β-d-glucopyranosyl-2β,3β,16α,23-tetrahydroxyolean-12-en-28-oic acid 28-O-α-l-rhamnopyranosyl-(1 → 3)-β-d-xylopyranosyl-(1 → 4)-[β-d-xylopyranosyl-(1 → 3)]-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranoside} (2) were also isolated from M. helleri roots together with the two known compounds 3 and 4. Seven known structurally related saponins (5-11) were isolated from S. bulbosus roots. The structures of these compounds were established as bayogenin and polygalacic glycosides using one- and two-dimensional NMR spectroscopy and mass spectrometry. Compounds 7, 10, bayogenin (12) and polygalacic acid (13) showed significant (p < 0.05) postingestive effects on Spodoptera littoralis larvae, compounds 5-11 and 12 showed variable nematicidal effects on Meloydogyne javanica and all tested saponins had variable phytotoxic effects on several plant species (Lycopersicum esculentum, Lolium perenne and Lactuca sativa). These are promising results in the search for natural pesticides from the Cucurbitaceae family.     

Phenolic compounds and rare polyhydroxylated triterpenoid saponins from Eryngium yuccifolium

Phytochemical investigation on the whole plant of Eryngium yuccifolium resulted in the isolation and identification of three phenolic compounds (1-3) and 12 polyhydroxylated triterpenoid saponins, named eryngiosides A-L (4-15), together with four known compounds kaempferol-3-O-(2,6-di-O-trans-p-coumaroyl)-β-d-glucopyranoside (16), caffeic acid (17), 21β-angeloyloxy-3β-[β-d-glucopyranosyl-(1→2)]-[β-d-xylopyranosyl-(1→3)]-β-d-glucuronopyranosyloxyolean-12-ene-15α,16α,22α,28-tetrol (18), and saniculasaponin III (19). This study reports the isolation of these compounds and their structural elucidation by extensive spectroscopic analyses and chemical degradation.     

Eudistomidins H-K, new β-carboline alkaloids from the Okinawan marine tunicate Eudistoma glaucus

Four new β-carboline alkaloids, eudistomidins H-K (1-4), were isolated from an Okinawan marine tunicate Eudistoma glaucus and the structures of 1-4 were elucidated on the basis of spectroscopic data. Eudistomidins H (1) and I (2) were new β-carboline alkaloids possessing a unique fused-tetracyclic ring system consisting of a tetrahydro β-carboline ring and a hexahydropyrimidine ring. Eudistomidin J (3) showed relatively potent cytotoxicity against murine leukemia cells P388 and L1210, and human epidermoid carcinoma cells KB in vitro.