Formulation and in vitro evaluation of niacin-loaded nanoparticles to reduce prostaglandin mediated vasodilatory flushing

OBJECTIVE

Niacin, activating G-protein coupled receptor (GPR) 109A, stimulates release of vasodilatory prostaglandins (PGs) such as PGE2 which can elicit niacin-associated flushing side effects. Poly-lactic-co-glycolic acid (PLGA) and poly-lactic acid (PLA) are used in nanoparticle (NP) drug delivery to reduce adverse effects and modulate drug release. Our study evaluated the in vitro effects of niacin-loaded PLGA or PLA-NPs on PGE2 expression in whole human blood as a model for niacin-induced flushing.

MATERIALS AND METHODS

NPs were formulated using a solvent evaporation process and characterized by size, polydispersity, zeta potential, drug entrapment, morphology, and drug release. NP in vitro effects on PGE2 release were measured via ELISA analysis.

RESULTS

PLGA-NPs demonstrated the lowest NP size (66.7 ± 0.21 nm) with the highest zeta potential and percent drug entrapment (42.00 ± 1.62 mV and 69.09 ± 0.29%, respectively) when compared to PLA-NPs (130.4 ± 0.66 nm, 27.96 ± 0.18 mV, 69.63 ± 0.03 %, respectively). In vitro release studies showed that PLGA-NPs underwent significant reductions in cumulative drug release when compared to PLA-NPs (p < 0.05). Furthermore, when compared to plain niacin, PLGA-NPs significantly reduced in vitro PGE2 release (p < 0.05).

CONCLUSIONS

These results support the use of PLGA-NPs as a novel method of delivery for reducing niacin-associated flushing.

Synthesis and anti-hypertensive effects of the twin drug of nicotinic acid and quercetin tetramethyl ether

A novel twin drug consisting of nicotinic acid (VB3) and quercetin tetramethyl ether (QTME) has been synthesized as an antihypertensive in a total yield of 79.2% through methylation, hydrolysis, acylation and esterification starting from rutin. The structures of synthesized compounds were elucidated by 1H-NMR, 13C-NMR and elemental analysis. The anti-hypertensive effects of an oral daily dose (15 mg/kg) of the synthesized compounds in spontaneously hypertensive (SHR) rats and normotensive Wistar Kyoto (WKY) rats were analysed. The data demonstrate that the twin drug VB3-QTME both reduces the elevated blood pressure and prolongs the action time in SHR rats without effect on WKY rats. However, definitive evidence of a precise mechanism of action by which VB3-QTME might decrease blood pressure remains elusive. Based on the results, the therapeutic potential of this twin drug is discussed.

Synthesis, characterization, crystal structure and DFT studies on 3-(1H-benzo[d][1,2,3]triazol-1-yl)-1-oxo-1-m-tolylpropan-2-yl-nicotinate

3-(1H-Benzo[d][1,2,3]triazol-1-yl)-1-oxo-1-m-tolylpropan-2-yl-nicotinate (BOTN) has been synthesized and characterized by elemental analysis, IR, UV-vis and fluorescence spectroscopy. Its crystal structure has also been determined by X-ray single crystal diffraction. For BOTN, density functional theory (DFT) calculations of the structure and vibrational frequencies have been performed at B3LYP/6-311G** level. The comparisons between the experimental vibrational frequencies and the predicted data show that B3LYP/6-311G** method can simulate the IR of BOTN on the whole. Based on the vibration analysis, thermodynamic properties of BOTN have been calculated. The correlative equations between the thermodynamic properties and the temperatures have also been listed. The experimental UV-vis spectra present two peaks and theoretical UV-vis spectra obtained by TD-DFT method exhibit three peaks. The comparison between them suggests that the B3LYP/6-311G** method can only approximately simulate the UV-vis spectra of BOTN. The fluorescence determination reveals two emission bands at 423 and 489 nm, respectively.

Synthesis of (aryloxyacetylamino)-isonicotinic/nicotinic acid analogues as potent hypoxia-inducible factor (HIF)-1α inhibitors

We report a new series of HIF-1alpha inhibitors which were obtained through structural modifications of previously reported lead 1. The in vitro inhibitory potencies of newly synthesized compounds were evaluated against hypoxia-induced HIF-1 activation using cell-based reporter assay in three human cancer cell lines including SK-Hep-1, Hep3B, and AGS cells. Several compounds displayed significant inhibitory activity in all the three tested cell lines. In particular, analogue 17 displayed potent inhibition of hypoxia-induced accumulation of HIF-1alpha protein in Hep3B cell line, in addition to the dose-dependent inhibition of HIF-1 target genes VEGF and EPO.

A practical synthesis of 2-((1H-pyrrolo[2,3-b]pyridine-4-yl)methylamino)-5- fluoronicotinic acid

A practical synthesis of a key pharmaceutical intermediate, 2-[(1H-pyrrolo[2,3-b]pyridine-4-yl)methylamino]-5-fluoronicotinic acid (1), is described. To introduce the aminomethyl moiety of 2 via a palladium-catalyzed cyanation/reduction sequence, a regioselective chlorination of 7-azaindole via the N-oxide was developed. A highly selective monodechlorination of 2,6-dichloro-5-fluoronicotinic acid was discovered to afford the nicotinic acid 3. The two building blocks 2 and 3 were then coupled to complete the preparation of 1.

Solid-phase synthesis of a small library of 3-phenylthio-3-nicotinyl propionic acid derivatives acting as antagonists of the integrin αVβ3

We describe the synthesis of a series of low molecular weight inhibitors of the alphavbeta3 integrin obtained by modifying a high-throughput screening hit with micromolar activity. A solid phase synthesis to prepare 3-phenylthio-3-nicotinyl propionic acid derivatives, exemplified by 13c, was set up. Compounds with nanomolar activity in the biochemical assay and able to efficiently inhibit cell adhesion mediated by vitronectin have been obtained.

Synthesis and Structure of a Water-Soluble Hexanuclear Silver(I) Nicotinate Cluster Comprised of a “Cyclohexane-Chair”-Type of Framework, Showing Effective Antibacterial and Antifungal Activities: Use of “Sparse Matrix” Techniques for Growing Crystals of Water-Soluble Inorganic Complexes

The synthesis of a water-soluble anionic silver 2-mercaptonicotinate complex having effective antibacterial and antifungal properties is described. Its structure has been confirmed to be a hexameric cluster by an X-ray diffraction analysis of a mixed Na(+)/Tris(+) salt (Tris(+) = tris(hydroxymethyl)methylammonium cation). The [Ag(mna)](6)(6-) cluster has a Ag(6)S(6) core and an overall shape of twisted hexagonal cylinder with six sulfur atoms and six silver atoms alternating on a puckered drum-like surface. Each Ag atom is trigonally coordinated by one N and two S ligands. The overall [Ag(mna)](6)(6-).4Na(+).2[(HOCH(2))(3)CNH(3)](+).10H(2)O complex has a layered appearance in the crystal packing diagram, with a [Ag(mna)](6)(-) cluster layer alternating with a solvent layer consisting of sodium atoms, Tris buffer cations, and water molecules. The structure is almost identical to that of a neutral [Ag(Hmna)](6) complex reported earlier. The neutral and charged complexes are both known to possess antimicrobial activities, and some biological properties of these and related compounds are briefly discussed in this paper.

Three-dimensional open frameworks based on cobalt(II) and nickel(II) m-pyridinecarboxylates

Three-dimensional open frameworks [Co2(nicotinate)4(mu-H2O)]-CH3CH2OH-H2O, 1, and [Ni2(nicotinate)4(mu-H2O)]-CH3CH2OH-H2O, 2, were obtained by hydro(solvo)thermal reactions between 3-cyanopyridine and cobalt(II) nitrate and nickel(II) perchlorate, respectively. Both 1 and 2 exhibit complicated 3-D structures based on [M2(nicotinate)4(mu-H2O)] (M = Co or Ni) building blocks and possess open channels that are occupied by removable solvent molecules. 3-D open frameworks [M2L4(mu-H2O)]-HL-(H2O)x (where M = Co, x = 2, 3, and M = Ni, x = 1, 4, and L = trans-3-(3-pyridyl)acrylate) were similarly prepared with trans-3-(3-pyridyl)acrylic acid in place of 3-cyanopyridine. Compounds 3 and 4 are isostructural and exhibit network topologies similar to that of 1 with open channels occupied by disordered trans-3-(3-pyridyl)acrylic acid and water guest molecules. Crystal data for 1: triclinic space group Ponebar, a = 10.534(1) A, b = 11.907(1) A, c = 14.046(1) A, alpha = 106.645(1) degrees, beta = 101.977(1) degrees, gamma = 112.078(1) degrees, and Z = 4. Crystal data for 2: tetragonal space group P4/ncc, a = 20.089(1) A, c = 14.016(1) A, and Z = 4. Crystal data for 3: monoclinic space group C2/c, a = 14.082(2) A, b = 15.278(2) A, c = 18.537(2) A, beta = 105.360(2) degrees, and Z = 2. Crystal data for 4: monoclinic space group C2/c, a = 14.082(1) A, b = 15.250(1) A, c = 18.606(1) A, beta = 106.747(1) degrees, and Z = 2.

Preparation of trifluoromethylpyridine libraries

S-Alkylation followed by heterocyclization of trifluoromethyl-3-cyano-2(1H)-pyridinethiones was used for preparation of libraries of S-alkyl trifluoromethylpyridines and thieno[2,3-b]pyridines. The S-alkylation (in water--DMF mixtures) was successful for all 18 alkylating agents employed (yields typically > 50%). S-Alkyl derivatives were further converted to corresponding thieno[2,3-b]pyridines via heterocyclization in base conditions (yields > 65%). Structures of new compounds were elucidated by a combination of IR and 1H NMR spectroscopy and elemental analysis and were confirmed by means of single-crystal X-ray diffraction analysis.

Synthesis of 1,2-diacyl-3-nicotinoyl glycerol derivatives and evaluation of their acute effects on plasma lipids in the rat

Nicotinic acid (CAS 59-67-6) is the only hypolipidemic agent whose activity has been shown both on atherosclerotic lesions and on long term mortality. Unfortunately, its use is hindered by the frequent occurrence ( > 70%) of adverse reactions (i.e. cutaneous rash, pruritus and, most significantly, flush). New prodrugs of nicotinic acid have been prepared by the use of diacylglycerol esters. In the rat, after acute oral administration of these products, a significant decrease of the free fatty acid plasma levels was obtained without the dramatic increase in nicotinic acid plasma levels observed after the oral administration of an equimolecular dose of nicotinic acid. The most interesting ester, S 16961 ((d,l)-1,2-dipalmitoyl-3-nicotinoyl glycerol, CAS 160555-46-4) is undergoing clinical trials.

Nicotinylidene derivatives for the structural elucidation of glycerol mono-ethers and mono-esters by gas chromatography/mass spectrometry

Nicotinylidene and methylnicotinylidene derivatives of representative glycerol ethers and glycerol esters were prepared by their reaction with pyridine-3-carboxaldehyde and 3-acetyl pyridine respectively. Each compound gave two sets of diastereoisomers which could be separated by gas-liquid chromatography. The extent of formation of the derivatives was nearly quantitative and chromatographic peak shape was good. The compounds producing both peaks gave similar spectra but with differences that were characteristic of the isomer. The derivatives fragmented in an analogous manner to that reported earlier for nicotinate derivatives of alcohols and picolinyl derivatives of carboxylic acids, with the production of a series of diagnostic ions formed by radical-induced cleavage of the chain following random hydrogen abstraction. Branched chain compounds, exemplified by glycerol ethers, gave spectra in which one of the ions diagnostic of the branch-point was missing. Unsaturated compounds, exemplified by the glycerol esters, gave characteristic mass spectra in which separation between ions representing formal cleavage at each side of the double bond enabled the position of this bond to be determined. In addition the spectra of unsaturated compounds contained two abundant ions whose formation could be rationalized by abstraction of the allylic hydrogen atoms. The nicotinylidene derivatives gave more diagnostic spectra than the methylnicotinylidene derivatives, whose spectra were complicated by the appearance of ions produced by loss of the methyl and pyridyl groups from the derivative. Both derivatives were superior to the nicotinate derivatives of these dihydroxy compounds in that only one pyridine residue was introduced on derivatization; this gave a lower molecular weight increment and allowed compounds with longer chains to be examined.(ABSTRACT TRUNCATED AT 250 WORDS)

N-succinimidyl 5-(trialkylstannyl)-3-pyridinecarboxylates: a new class of reagents for protein radioiodination

N-Succinimidyl 5-(trialkylstannyl)-3-pyridinecarboxylates (alkyl = Me, Bu) have been prepared and used as a precursor to label N-succinimidyl 5-[131I]iodo-3-pyridinecarboxylate (SIPC). SIPC was obtained in greater than 80% yield from either the methyl or butyl precursor with N-chlorosuccinimide and heating at 60-65 degrees C. Significantly lower yields were observed with tert-butyl hydroperoxide. After a 30-min incubation with [131I]SIPC at pH 8.5, goat IgG, an intact monoclonal antibody (MAb), and a MAb F(ab')2 fragment were labeled in 60-65% yield. Specific binding of the MAb and MAb fragment after SIPC labeling was identical with that observed with N-succinimidyl 3-iodobenzoate and higher than that reported previously for these MAbs after labeling by using the Iodogen method. When 5-[131I]iodonicotinic acid was injected into normal mice, thyroid uptake was less than 0.2% of the injected dose, reflecting the inertness of this compound to deiodination. Paired-label biodistribution studies indicate that for both the MAb and the F(ab')2 labeled by using SIPC, accumulation of activity in the thyroid and other tissues is comparable to that observed when these proteins were labeled by using N-succinimidyl 3-iodobenzoate. The results of this study suggest that SIPC may be a reagent for labeling MAbs with halogen nuclides.

Synthesis and properties of (4-13C)NAD+. Observation of its binding to yeast alcohol dehydrogenase by 13C-NMR spectroscopy

Starting from (13C)formic acid, acetone and cyanoacetamide samples of (4-13C)nicotinic acid and (4-13C)-nicotinamide were synthesised in an overall and additive yield of 11%. 1H-NMR and mass spectroscopy showed 90% enrichment of 13C in the expected position. NADase-catalysed exchange between thionicotinamide-adenine dinucleotide and (4-13C)nicotinamide furnished (4-13C)NAD+ which was purified, characterized and quantified by 1H-NMR and 13C-NMR spectroscopy and by enzymic assay. The 13C-NMR signal of (4-13C)beta-NAD+ (146.09 ppm) was broadened and shifted (147.83 ppm) upon binding to yeast alcohol dehydrogenase.