Reversed‐phase high‐performance liquid chromatography (RP‐HPLC) determination of lipophilicity of furocoumarins: Relationship with DNA interaction

Self-Emulsifying Formulations to Increase the Oral Bioavailability of 4,6,4′-Trimethylangelicin as a Possible Treatment for Cystic Fibrosis

4,6,4′-trimethylangelicin (TMA) is a promising pharmacological option for the treatment of cystic fibrosis (CF) due to its triple-acting behavior toward the function of the CF transmembrane conductance regulator. It is a poorly water-soluble drug, and thus it is a candidate for developing a self-emulsifying formulation (SEDDS). This study aimed to develop a SEDDS to improve the oral bioavailability of TMA. Excipients were selected on the basis of solubility studies. Polyoxyl-35 castor oil (Cremophor® EL) was proposed as surfactant, diethylene glycol-monoethyl ether (Transcutol® HP) as cosolvent, and a mixture of long-chainmono-,di-, and triglycerides (Maisine® CC) or medium-chain triglycerides (LabrafacTM lipophile) as oil phases. Different mixtures were prepared and characterized by measuring the emulsification time, drop size, and polydispersity index to identify the most promising formulation. Two formulations containing 50% surfactant (w/w), 40% cosolvent (w/w), and 10% oil (w/w) (Maisine® CC or LabrafacTM lipophile) were selected. The results showed that both formulations were able to self-emulsify, producing nanoemulsions with a drop size range of 20–25 nm, and in vivo pharmacokinetic studies demonstrated that they were able to significantly increase the oral bioavailability of TMA. In conclusion, SEEDS are useful tools to ameliorate the pharmacokinetic profile of TMA and could represent a strategy to improve the therapeutic management of CF.

Synthesis and evaluation of a set of 4-phenylpiperidines and 4-phenylpiperazines as D2 receptor ligands and the discovery of the dopaminergic stabilizer 4-[3-(methylsulfonyl)phenyl]-1-propylpiperidine (huntexil, pridopidine, ACR16)

Modification of the partial dopamine type 2 receptor (D(2)) agonist 3-(1-benzylpiperidin-4-yl)phenol (9a) generated a series of novel functional D(2) antagonists with fast-off kinetic properties. A representative of this series, pridopidine (4-[3-(methylsulfonyl)phenyl]-1-propylpiperidine; ACR16, 12b), bound competitively with low affinity to D(2) in vitro, without displaying properties essential for interaction with D(2) in the inactive state, thereby allowing receptors to rapidly regain responsiveness. In vivo, neurochemical effects of 12b were similar to those of D(2) antagonists, and in a model of locomotor hyperactivity, 12b dose-dependently reduced activity. In contrast to classic D(2) antagonists, 12b increased spontaneous locomotor activity in partly habituated animals. The "agonist-like" kinetic profile of 12b, combined with its lack of intrinsic activity, induces a functional state-dependent D(2) antagonism that can vary with local, real-time dopamine concentration fluctuations around distinct receptor populations. These properties may contribute to its unique "dopaminergic stabilizer" characteristics, differentiating 12b from D(2) antagonists and partial D(2) agonists.

Differentiation and apoptosis in UVA-irradiated cells treated with furocoumarin derivatives

In this review we summarize the structure and biological effects of linear and angular psoralens. These compounds exhibit interesting biological effects on the cell cycle, apoptosis and differentiation. These molecules should be considered promising drugs in the therapy of several diseases, including psoriasis, mycosis fungoides and cancer. Also, preclinical data demonstrate a possible use of these molecules for the treatment of beta-thalassemia and other hematological disorders.

Structure−Activity Relationship Study on N-(1,2,3,4-Tetrahydronaphthalen-1-yl)-4-aryl-1-piperazinehexanamides, a Class of 5-HT7 Receptor Agents. 2

Here we report the synthesis of N-(1,2,3,4-tetrahydronaphthalen-1-yl)-4-aryl-1-piperazinealkylamides 16-29 that were designed to elucidate both structure-affinity and -activity relationships for the 5-HT7 receptor, by targeting the substituent in 2-position of the aryl linked to the piperazine ring. The affinities of 16-29 for 5-HT7, 5-HT1A, 5-HT2A, and D2 receptors were assessed by radioligand binding assays. The intrinsic activities at the 5-HT7 receptor of the most potent compounds were determined. A series of substituents covering a wide range of electronic, steric, and polar properties was evaluated, revealing a key role on 5-HT7 receptor affinity and intrinsic activity. Certain lipophilic substituents (SCH3, CH(CH3)2, N(CH3)2, CH3, Ph) led to high-affinity agonists, whereas OH and NHCH3 substituents switched intrinsic activity toward antagonism. 4-[2-(1-Methylethyl)phenyl]-N-(1,2,3,4-tetrahydronaphthalen-1-yl)-1-piperazinehexanamide (19), 4-(2-diphenyl)-N-(1,2,3,4-tetrahydronaphthalen-1-yl)-1-piperazinehexanamide (21), and 4-(2-dimethylaminophenyl)-N-(1,2,3,4-tetrahydronaphthalen-1-yl)-1-piperazinehexanamide (22) were identified as potent 5-HT7 receptor agonists (Ki = 0.13-1.1 nM, EC50 = 0.90-1.77 microM), showing selectivity over 5-HT1A, 5-HT2A, and D2 receptors.

Effect of Ring Methylation on the Photophysical, Photochemical and Photobiological Properties of cis-Dichlorobis(1,10-Phenanthroline)Rhodium(III)Chloride†

Methylated analogues of cis-dichlorobis(1,10-phenanthroline)rhodium(III)chloride (BISPHEN) have been prepared in order to increase the hydrophobicity of the parent compound, and thus create octahedral rhodium (III) complexes suitable for use as anticancer and antiviral agents that can be photoactivated. The parent complex has been shown in earlier work to be unable to cross through cell membranes. Octamethylation, as in the case of cis-dichlorobis(3,4,7,8-tetramethyl-1,10-phenanthroline)rhodium(III)chloride (OCTBP), provides enough hydrophobicity to be taken up by KB tumor cells. It also provides a higher level of ground-state association with double-stranded DNA and increases the quantum efficiency of photoaquation by greater than 10-fold, relative to BISPHEN. OCTBP forms covalent bonds to deoxyguanosine when irradiated with the nucleoside, as has been seen with the parent complex. Irradiation of OCTBP in the presence of the KB or M109 tumor cell lines using narrow-band UVB (lambda = 311 nm) irradiation initiates a considerable amount of phototoxicity. There is evidence that OCTBP acts as a prodrug (i.e. after passing through the cell membrane the metal complex is photolyzed to cis-chloro aquo OCTBP, which may be the active phototoxic agent). OCTBP and the tetramethyl analogue cis-dichlorobis(4,7-dimethyl-1,10-phenanthroline)rhodium(III)chloride (47TMBP) also show photoaquation upon excitation with visible light (lambda > 500 nm), and indeed, some phototoxicity of KB cells is observed at these wavelengths as well. This is attributed to direct population of photoactive triplet-excited states. These results, together with our earlier studies of cis-dichloro[dipyrido(3,2-a: 2',3'-c)phenazine (1,10-phenanthroline)rhodium(III)chloride (DPPZPHEN) demonstrate that such octahedral rhodium complexes are viable "photo-cisplatin" reagents.

Mechanism of action of 4-hydroxymethyl-1,6,8-trimethylfuro[2,3-h]quinolin-2(1H)-one, a very active angular furocoumarin-like sensitizer

The molecular structure of 1,4,6,8-tetramethylfuro[2,3-h]quinolin-2(1H)-one (FQ), a recent furocoumarin-like photosensitizer, has been modified with the aim of reducing its strong genotoxicity, by replacing the methyl group at 4 position with a hydroxymethyl one, and so obtaining 4-hydroxymethyl-1,6,8-trimethylfuro[2,3-h]quinolin-2(1H)-one (HOFQ). This modification gave rise to a strong reduction of lipophilicity and dark interaction with DNA. The formation of monoadducts (MA) was deeply affected, whereas the induction of bifunctional adducts between DNA and proteins (DPC(L>0)) was replaced by an efficient production of DNA-protein cross-links at zero length (DPC(L=0)), probably via guanine damage. Because of its angular molecular structure, HOFQ does not form interstrand cross-links (ISC): therefore, DPC(L=0) and MA represent the main lesions induced by HOFQ in DNA. In comparison with FQ (which induces MA and DPC(L>0)) and 8-methoxypsoralen (8-MOP) (MA, ISC, DPC(L>0)), HOFQ seems to be a more selective agent. In fact, contrary to FQ and 8-MOP, HOFQ, together with a noticeable antiproliferative activity, shows low levels of point mutations in bacteria and of clastogenic effects in mammalian cells. HOFQ is also an efficient apoptosis inducer, especially in comparison with 8-MOP, when tested at equitoxic experimental conditions; this property might be correlated with the complete HOFQ inability of inducing skin erythemas, a well-known side effect of classic furocoumarin photosensitization.

Psoralen derivatives and longwave ultraviolet irradiation are active in vitro against human melanoma cell line

Cutaneous malignant melanoma is a very serious form of skin cancer that arises from melanocytes. Currently there is no effective treatment for metastatic melanoma so intense clinical trials are evaluating new drugs for this human malignancy. Psoralens are a group of compounds that bind to DNA in rapidly dividing cells and with ultraviolet light in the A band (UVA) cause DNA crosslinking, thereby preventing cellular division. They are used in the treatment of psoriasis and cutaneous T-cell lymphoma among other skin and blood diseases. We have investigated the cytotoxic potential of three psoralen derivatives plus UVA exposure (PUVA) on a established cell line of human melanoma. Cells were treated with different concentrations of 8-methoxypsoralen (8-MOP), 4,5',8-trimethylpsoralen (TMP) and 7-methylpyridopsoralen (MPP), for 1 h and after exposure to UVA light (0.3 J/cm(2)) were allowed to recover over a 24-72 h period. Viability was assessed by the microculture 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay. Cisplatin, one of the most important drugs in the chemotherapy of melanoma, was included for comparative studies. All the psoralen derivatives tested were markedly cytotoxic in a dose and post-exposure-time dependent manner. The IC(50) values for 72 h of post-exposure time were as follows: MPP=0.05+/-0.01, TMP=0.13+/-0.003 and 8-MOP=10.79+/-1.85 micromol/L. Regardless of the limitations of the in vitro model, our results suggested that the lower IC(50) values of TMP and MPP might be of clinical importance.

Disposition of 4,6,4'-trimethylangelicin in mice maintained in the dark and after UVA irradiation

The disposition of the furocoumarin 4,6,4'-trimethylangelicin (4,6,4'-TMA) was studied in mice. After oral administration of (3)H 4,6,4'-TMA, radioactivity measured in serum shows fast absorption and slow elimination. Serum protein binding is higher as compared to 8-methoxypsoralen (8-MOP), currently used in photochemotherapy (PUVA) and linearly declines from 30 min to 6 h after administration. Distribution in the various organs was similar to that of 8-MOP and was relatively uninfluenced by UVA radiation, required for the biological effects of 4,6,4'-TMA. Mice eliminate (3)H 4,6,4'-TMA mostly through the urine, but also through the faeces. Two metabolites were identified in the urine and serum of the treated mice, one of which proved to be a derivative of 4,6,4'-TMA, formed by hydrogenation of the double 4',5' bond of the furocoumarin nucleus.

Hydrophobicity parameters determined by reversed-phase liquid chromatography. XV: optimal conditions for prediction of log P(oct) by using RP-HPLC procedures

The use of log k derived from reversed phase (RP)-HPLC retention times provides a convenient method for estimating log P(oct) values (P(oct): 1-octanol/water partition coefficient). In order to establish optimal HPLC conditions, the difference between chromatographic (C18 modified column and aqueous methanol eluents) and bulk solvent systems was examined by use of a batch-like equilibration with octane/aqueous methanol. Comparison of values for log P(O/M-W) (log P for the Octane/MeOH-Water partitioning system) and log k measured for monosubstituted pyrazines at different methanol concentrations, showed closest correlation (r, 0.94) with 50% aqueous methanol; and importantly, under these conditions, log k shows even better correlation (r, 0.99) with log P(oct). Effects of residual silanols on HPLC retention with C18 stationary phases were examined. The results show that, in the presence of a small quantity of accessible silanols, the use of 50% aqueous methanol (M50) as eluent yields values of log k directly proportional to log P(oct) in accord with our earlier proposal that use of log k(M50) provides a convenient means for rapid estimation and prediction of log P(oct).