Lipophilicity and its relationship with passive drug permeation

The trip of a drug inside the body: From a lipid-based nanocarrier to a target cell

To date, enormous investigations have been conducted to enhance medicines' target-oriented delivery to improve their therapeutic index. In this regard, lipid-based carrier system might have been regarded as prime delivery systems that are very close to the naturally cell-derived vesicles used for biomolecular communication among cells from occasionally remote tissues. Upon examination of the literature, we found a chasm between groups of investigations in drug pharmaceutics and thought that maybe holistic research could provide better information with respect to drug delivery inside the body, especially when they are going to be injected directly into the bloodstream for systemic distribution. While a collection of older research in most cases dealt with the determination of drug partition coefficient between the aqueous and cell membrane compartments, the link has been overlooked in newer investigations that were mostly focused on drug formulation optimization and their association with particle biodistribution. This gap in the literature motivated us to present the current opinion paper, in which drug physicochemical properties like drug lipophilicity/hydrophilicity is considered as an important element in designing drug-carrying liposomes or micelles. How a hypothetical high throughput cell-embedded chromatographic technique might help to investigate a nanocarrier tissue distribution and to design 'multi-epitope grafted lipid-based drug carrier systems' are discussed. Whenever we would need support for our opinions, we have provided analogy from hydrophobic biomolecules like cholesterol, steroid hormones, and sex hormones and encouraged readers to consider our principle hypothesis: If these molecules could reach their targets far away from the site of production, then a large list of hydrophobic drugs could be delivered to their targets using the same principles.

An investigation of the acute central nervous system effects of n-decane

Acute central nervous system (CNS) depression is the most sensitive toxicological effect associated with aliphatic hydrocarbon exposure. No observed effect levels for the CNS effects of aliphatic constituents decrease with increasing carbon number to C10 (Lammers et al., 2011; McKee et al., 2011), whereas constituents with carbon numbers > C10 do not produce CNS effects at maximally attainable vapor concentrations (Nilsen et al., 1988). Accordingly, as n-decane appeared to be the "worst case" for acute CNS effects among aliphatic hydrocarbon solvent constituents, experimental studies were conducted to more precisely define the no effect level. Rats were exposed for 8 h to n-decane, either constantly at 3000 mg/m³ or at higher levels using a discontinuous exposure protocol to assess the influence of fluctuating exposures. Neurobehavioral testing methods including visual discrimination performance and motor activity were used to assess performance, and concentrations of n-decane in blood and brain were measured to obtain pharmacokinetic data. No statistically significant differences were observed in the neurobehavioral tests, establishing 3000 mg/m³ as the no effect level for CNS effects in rats. These data support the recommended guidance value of 1050 mg/m³ for C9-C15 aliphatic hydrocarbons for use in calculating occupational exposure levels for complex hydrocarbon solvents and provide empirical evidence that advice from the ACGIH^® that within a working day there should be no more than 3 fluctuations, not longer than 15 min and not exceeding 3 times the Threshold Limit Value (TLV^®), is reasonable for this group of substances.

Solubility Models for the Recovery of Rosmarinic Acid from Orthosiphon Aristatus Extract Using Solid Phase Extraction

Hildebrand and Hansen solubility parameters, and log P value are widely used to determine the solubility of polymers in solvents. The models were used to explain the recovery of phytochemical, rosmarinic acid from Orthosiphon aristatus extract in C18 solid phase extraction (SPE) using the eluent consisting of ethyl acetate and chloroform in the decreasing polarity of solvent system. The experimental recovery of rosmarinic acid appeared to be well explained by the Hansen solubility model. The small difference in the Hansen solubility parameters, particularly for dispersion and hydrogen bonding forces, results in a higher polar solvent system for high rosmarinic acid recovery. The results found that the Hansen solubility model fitted well to the recovery of rosmarinic acid from crude extract with high coefficient of determination (R2 > 0.8), low standard error (4.4%), and p < 0.05. Hildebrand solubility is likely to be the second fit model, whereas log P has poor R2 < 0.7 and higher standard error (7.3%). The Hansen solubility model describes the interaction of solute–solvent in three dimensions (dispersion, polar, and hydrogen bonding forces) which can accurately explain the recovery of rosmarinic acid. Therefore, Hansen solubility can be used to predict the recovery of rosmarinic acid from O. aristatus extract using SPE.

Antiproliferative Activity of Pt(IV) Conjugates Containing the Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) Ketoprofen and Naproxen †

Cisplatin and several non-steroidal anti-inflammatory drugs (NSAIDs) have been proven to act synergistically or at least additively on several tumor cell lines. Dual-action cisplatin-based Pt(IV) combos containing ketoprofen and naproxen offer good antiproliferative performance on a panel of human tumor cell lines, including a malignant pleural mesothelioma (MPM) one, a very chemoresistant tumor. The main reason of the increased activity relies on the enhanced lipophilicity of these Pt(IV) conjugates that in turn promotes increased cellular accumulation. A quick Pt(IV)→Pt(II) reduction generates the active cisplatin metabolite. The NSAID adjuvant action seems to be almost independent from cyclooxygenase-2 (COX-2) expression in the tumor cells under investigation (lung A-549, colon HT-29, HCT 116, SW480, ovarian A2780, and biphasic MPM MSTO-211H), but it seems to rely (at least in part) on the activation of the NSAID activated gene, NAG-1 (a member of the transforming growth factor beta, TGF-β, superfamily), which has been suggested to be involved in NSAID antiproliferative activity.

Chloroacetamide derivatives as a promising topical treatment for fungal skin infections

The aim of this study was to evaluate the antifungal potential of 11 chloroacetamide derivatives and derivative incorporated into a film-forming system (FFS) as a potential alternative for the topical treatment of superficial and skin mycoses. The minimum inhibitory concentration (MIC) evaluation followed Clinical and Laboratory Standards Institute protocols M27-A3 (Candida) and M28-A2 (dermatophytes). Compounds 2, 3, and 4 were the most effective against Candida species (MIC range: 25-50 µg/mL) and dermatophytes (MIC range: 3.12-50 µg/mL). Compound 2 maintained its antifungal activity when incorporated in a FFS, with MIC values equivalent to the free compound. In addition, the compound does not act through complexation with ergosterol, suggesting that it may act on other targets of the fungal cell membrane. Chloroacetamide derivatives presented anti-Candida and anti-dermatophytic effectiveness. The FFS containing compound 2 has shown to be superior to traditional topical treatment of superficial and cutaneous fungal infections. It was found that these new chemical entities, with their applicability, are an excellent alternative to the topical treatment of fungal skin infections.

Toxicokinetics of Deltamethrin: Dosage Dependency, Vehicle Effects, and Low-Dose Age-Equivalent Dosimetry in Rats

There is increasing concern that infants and children may be at increased risk of neurological effects of pyrethroids, the most widely used class of insecticide. The objectives of this investigation were to (1) characterize the dose-dependent toxicokinetics (TK) of deltamethrin (DLM) for exposures ranging from environmentally relevant to acutely toxic; (2) determine the influence of an aqueous versus oil vehicle on oral absorption and bioavailability; and (3) determine whether DLM exhibits low-dose, age-equivalent internal dosimetry. Serial arterial plasma samples were obtained for 72 h from adult, male Sprague Dawley rats given 0.05-5.0 mg DLM/kg as an oral bolus in corn oil (CO). DLM exhibited linear, absorption rate-limited TK. Increases in maximum plasma concentration (Cmax) and AUC∘∞ were directly proportional to the dose. Oral bioavailability was quite limited. The vehicle and its volume had modest effect on the rate and extent of systemic absorption in adult rats. Postnatal day (PND) 15, 21, and 90 (adult) rats received 0.10, 0.25, or 0.50 mg DLM/kg orally in CO and were sacrificed periodically for plasma, brain, and liver collection. Age-dependent differences between PND 15 and 90 plasma Cmax and AUC∘24 values progressively diminished as the dose decreased, but there was a lack of low dose age equivalence in these brain and liver dosimeters. Other maturational factors may account for the lack of the low-dose age equivalence in brain and liver. This investigation provides support for the premise that the relatively low metabolic capacity of immature subjects may be adequate to effectively eliminate trace amounts of DLM and other pyrethroids from the plasma.

Identification of peptidomimetics as novel chemical probes modulating fibroblast growth factor 14 (FGF14) and voltage-gated sodium channel 1.6 (Nav1.6) protein-protein interactions

The voltage-gated sodium (Nav) channel is the molecular determinant of action potential in neurons. Protein-protein interactions (PPI) between the intracellular Nav1.6 C-tail and its regulatory protein fibroblast growth factor 14 (FGF14) provide an ideal and largely untapped opportunity for development of neurochemical probes. Based on a previously identified peptide FLPK, mapped to the FGF14:FGF14 PPI interface, we have designed and synthesized a series of peptidomimetics with the intent of increasing clogP values and improving cell permeability relative to the parental lead peptide. In-cell screening using the split-luciferase complementation (LCA) assay identified ZL0177 (13) as the most potent inhibitor of the FGF14:Nav1.6 channel complex assembly with an apparent IC₅₀ of 11 μM. Whole-cell patch-clamp recordings demonstrated that ZL0177 significantly reduced Nav1.6-mediated transient current density and induced a depolarizing shift of the channel voltage-dependence of activation. Docking studies revealed strong interactions between ZL0177 and Nav1.6, mediated by hydrogen bonds, cation-π interactions and hydrophobic contacts. All together these results suggest that ZL0177 retains some key features of FGF14-dependent modulation of Nav1.6 currents. Overall, ZL0177 provides a chemical scaffold for developing Nav channel modulators as pharmacological probes with therapeutic potential of interest for a broad range of CNS and PNS disorders.

Discovery of Orally Bioavailable and Liver-Targeted Hypoxia-Inducible Factor Prolyl Hydroxylase (HIF-PHD) Inhibitors for the Treatment of Anemia

We report herein the design and synthesis of a series of orally active, liver-targeted hypoxia-inducible factor prolyl hydroxylase (HIF-PHD) inhibitors for the treatment of anemia. In order to mitigate the concerns for potential systemic side effects, we pursued liver-targeted HIF-PHD inhibitors relying on uptake via organic anion transporting polypeptides (OATPs). Starting from a systemic HIF-PHD inhibitor (1), medicinal chemistry efforts directed toward reducing permeability and, at the same time, maintaining oral absorption led to the synthesis of an array of structurally diverse hydroxypyridone analogues. Compound 28a was chosen for further profiling, because of its excellent in vitro profile and liver selectivity. This compound significantly increased hemoglobin levels in rats, following chronic QD oral administration, and displayed selectivity over systemic effects.

Cannabinoid Receptor 2 Signalling Bias Elicited by 2,4,6-Trisubstituted 1,3,5-Triazines

Cannabinoid receptor 2 (CB2) is predominantly distributed in immune tissues and cells and is a promising therapeutic target for modulating inflammation. In this study we designed and synthesised a series of 2,4,6-trisubstituted 1,3,5-triazines with piperazinylalkyl or 1,2-diethoxyethane (PEG2) chains as CB2 agonists, all of which were predicted to be considerably more polar than typical cannabinoid ligands. In this series, we found that triazines containing an adamantanyl group were conducive to CB2 binding whereas those with a cyclopentyl group were not. Although the covalent attachment of a PEG2 linker to the adamantyl triazines resulted in a decrease in binding affinity, some of the ligands produced very interesting hCB2 signalling profiles. Six compounds with notable hCB2 orthosteric binding were functionally characterised in three pathways; internalisation, cyclic adenosine monophosphate (cAMP) and ERK phosphorylation (pERK). These were predominantly confirmed to be hCB2 agonists, and upon comparison to a reference ligand (CP 55,940), four compounds exhibited signalling bias. Triazines 14 (UOSD017) and 15 were biased towards internalisation over cAMP and pERK, and 7 was biased away from pERK activation relative to cAMP and internalisation. Intriguingly, the triazine with an amino-PEG2-piperazinyl linker (13 [UOSD008]) was identified to be a mixed agonist/inverse agonist, exhibiting apparent neutral antagonism in the internalisation pathway, transient inverse agonism in the cAMP pathway and weak partial agonism in the pERK pathway. Both the cAMP and pERK signalling were pertussis toxin (PTX) sensitive, implying that 13 is acting as both a weak agonist and inverse agonist at CB2 via Gαi/o. Compound 10 (UOSD015) acted as a balanced high intrinsic efficacy agonist with the potential to produce greater hCB2-mediated efficacy than reference ligand CP 55,940. As 10 includes a Boc-protected PEG2 moiety it is also a promising candidate for further modification, for example with a secondary reporter or fluorophore. The highest affinity compound in this set of relatively polar hCB2 ligands was compound 16, which acted as a slightly partial balanced agonist in comparison with CP 55,940. The ligands characterised here may therefore exhibit unique functional properties in vivo and have the potential to be valuable in the future development of CB2-directed therapeutics.

Bile Acids and Their Derivatives as Potential Modifiers of Drug Release and Pharmacokinetic Profiles

Bile acids have received considerable interest in the drug delivery research due to their peculiar physicochemical properties and biocompatibility. The main advantage of bile acids as drug absorption enhancers is their ability to act as both drug solubilizing and permeation-modifying agents. Therefore, bile acids may improve bioavailability of drugs whose absorption-limiting factors include either poor aqueous solubility or low membrane permeability. Besides, bile acids may withstand the gastrointestinal impediments and aid in the transporter-mediated absorption of physically complexed or chemically conjugated drug molecules. These biomolecules may increase the drug bioavailability also at submicellar levels by increasing the solubility and dissolution rate of non-polar drugs or through the partition into the membrane and increase of membrane fluidity and permeability. Most bile acid-induced effects are mediated by the nuclear receptors that activate transcriptional networks, which then affect the expression of a number of target genes, including those for membrane transport proteins, affecting the bioavailability of a number of drugs. Besides micellar solubilization, there are many other types of interactions between bile acids and drug molecules, which can influence the drug transport across the biological membranes. Most common drug-bile salt interaction is ion-pairing and the formed complexes may have either higher or lower polarity compared to the drug molecule itself. Furthermore, the hydroxyl and carboxyl groups of bile acids can be utilized for the covalent conjugation of drugs, which changes their physicochemical and pharmacokinetic properties. Bile acids can be utilized in the formulation of conventional dosage forms, but also of novel micellar, vesicular and polymer-based therapeutic systems. The availability of bile acids, along with their simple derivatization procedures, turn them into attractive building blocks for the design of novel pharmaceutical formulations and systems for the delivery of drugs, biomolecules and vaccines. Although toxic properties of hydrophobic bile acids have been described, their side effects are mostly produced when present in supraphysiological concentrations. Besides, minor structural modifications of natural bile acids may lead to the creation of bile acid derivatives with the reduced toxicity and preserved absorption-enhancing activity.

Bile Acids and Their Derivatives as Potential Modifiers of Drug Release and Pharmacokinetic Profiles

Bile acids have received considerable interest in the drug delivery research due to their peculiar physicochemical properties and biocompatibility. The main advantage of bile acids as drug absorption enhancers is their ability to act as both drug solubilizing and permeation-modifying agents. Therefore, bile acids may improve bioavailability of drugs whose absorption-limiting factors include either poor aqueous solubility or low membrane permeability. Besides, bile acids may withstand the gastrointestinal impediments and aid in the transporter-mediated absorption of physically complexed or chemically conjugated drug molecules. These biomolecules may increase the drug bioavailability also at submicellar levels by increasing the solubility and dissolution rate of non-polar drugs or through the partition into the membrane and increase of membrane fluidity and permeability. Most bile acid-induced effects are mediated by the nuclear receptors that activate transcriptional networks, which then affect the expression of a number of target genes, including those for membrane transport proteins, affecting the bioavailability of a number of drugs. Besides micellar solubilization, there are many other types of interactions between bile acids and drug molecules, which can influence the drug transport across the biological membranes. Most common drug-bile salt interaction is ion-pairing and the formed complexes may have either higher or lower polarity compared to the drug molecule itself. Furthermore, the hydroxyl and carboxyl groups of bile acids can be utilized for the covalent conjugation of drugs, which changes their physicochemical and pharmacokinetic properties. Bile acids can be utilized in the formulation of conventional dosage forms, but also of novel micellar, vesicular and polymer-based therapeutic systems. The availability of bile acids, along with their simple derivatization procedures, turn them into attractive building blocks for the design of novel pharmaceutical formulations and systems for the delivery of drugs, biomolecules and vaccines. Although toxic properties of hydrophobic bile acids have been described, their side effects are mostly produced when present in supraphysiological concentrations. Besides, minor structural modifications of natural bile acids may lead to the creation of bile acid derivatives with the reduced toxicity and preserved absorption-enhancing activity.

Nanoemulsion as a Platform for Iontophoretic Delivery of Lipophilic Drugs in Skin Tumors

Lipophilic drugs do not usually benefit from iontophoresis mainly because they do not solubilize in aqueous formulations suitable for the application of electric current. To explore the influence of iontophoresis on penetration of these drugs, a cationic nanoemulsion was developed to solubilize zinc phthalocyanine (ZnPc), a promising drug for the treatment of skin cancer. To verify the influence of particle size on iontophoresis, an emulsion of nanoemulsion-like composition was also developed. The formulations were characterized and cutaneous and tumor penetration studies were performed in vitro and in vivo, respectively. With particles of about 200 nm, the nanoemulsion solubilized 2.5-fold more ZnPc than the 13-µm emulsion. At the same concentration of ZnPc, in vitro passive penetration studies showed that the nanoemulsion increased, after 1 h of treatment, by almost 4 times the penetration of ZnPc into the viable layers of the skin when compared to the emulsion, whereas iontophoresis of nanoemulsion resulted in a 16-fold increase in ZnPc penetration in only 30 min. An in vivo study in a murine model of melanoma showed that ZnPc reached the tumor after iontophoresis of the nanoemulsion. Therefore, iontophoresis of nanoemulsions appears to be a promising strategy for the topical treatment of tumors with lipophilic drugs.

Formation of a Bile Salt-Drug Hydrogel to Predict Human Intestinal Absorption

The unique character of bile salts to self-assemble into hydrogels in the presence of halide salts was exploited in this work to facilitate the prediction of human intestinal absorption (%HIA) for a set of 25 compounds. This was achieved by firstly incorporating each compound separately within the process of gel formation to create a series of gel-drug membranes. Scanning electron microscopy analysis of the freeze-dried samples of the blank bile salt hydrogels and drug-loaded bile salt hydrogels indicated a unique microstructure made of a network of intertwined fibrils. Drug-loaded sodium deoxycholate hydrogels were then utilized as the donor phase to study permeability using flow-through and static diffusion cells. The resulting values of the release-permeability coefficient (K_p) were then analyzed, along with other molecular descriptors, for the %HIA using multiple linear regression. Overall, when comparing predicted values (using the systems presented in this study) with known literature values, it can be seen that both methods (i.e., using static and flow-through cells) had good predictability with R²_PRED values of 79.8% and 79.7%, respectively. This study therefore proposes a novel, accurate, and precise way to predict HIA for compounds of pharmaceutical interest using a simple in vitro permeation system. It is important to develop alternatives to the current methods used in prediction of HIA, which are expensive and time-consuming or include the use of animals. Therefore, the proposed method in this study being economic and time-saving provides superiority over these current methods and suggests the possibility of its use as an alternate to such methods for prediction of HIA.

The active compounds derived from Psoralea corylifolia for photochemotherapy against psoriasis-like lesions: The relationship between structure and percutaneous absorption

8‑Methoxypsoralen (8-MOP) in combination with ultraviolet A (PUVA) is a photochemotherapy for management of psoriasis. 8-MOP is a natural compound from Psoralea corylifolia. The present work was undertaken to evaluate the percutaneous absorption of five compounds derived from P. corylifolia, and to further explore the inhibitory effect on psoriasis-like lesions generated by imiquimod stimulation in a mouse model. 8-MOP, psoralen, isopsoralen, psoralidin, and bakuchiol were comparatively tested for in vitro skin permeation, keratinocyte apoptosis, and in vivo antipsoriatic potency. The pig ear skin deposition of 8-MOP, isopsoralen, and bakuchiol at an equimolar dose was 0.47, 0.58, and 0.50 nmol/mg, respectively, which was comparable and higher than that of psoralen (0.25 nmol/mg) and psoralidin (0.14 nmol/mg). Psoralidin and bakuchiol were absorbed into the skin without further penetration across the skin. Besides experimental data of physicochemical properties, the hydrogen bond number, total polarity surface, and stratum corneum lipid docking calculated could explain the correlation of the penetrant structure with the skin permeability. The antiproliferative activity against keratinocytes was stronger for 8-MOP and isopsoralen than the others. Topical application of PUVA by using 8-MOP and isopsoralen on imiquimod-induced plaque significantly reduced transepidermal water loss from 55 to 33 and 38 g/m²/h, respectively. The epidermal thickening elicited by imiquimod (117 μm) was decreased to 62 and 26 μm by 8-MOP and isopsoralen application. IL-6 expression in psoriasiform skin was downregulated by isopsoralen but not 8-MOP. Isopsoralen may be a potential candidate for PUVA therapy.

Synthesis and antitumoral activity of novel analogues monastrol-fatty acids against glioma cells

Monastrol is a small cell-permeable heterocyclic molecule that is recognized as an inhibitor of mitotic kinesin Eg5. Heterocyclic-fatty acid derivatives are a new class of compounds with a broad range of biological activities. This work describes a comparative study of the in vitro antitumoral activity of a series of new long-chain monastrol analogues against rat glioblastoma cells. The novel analogues C6-substituted monastrol and oxo-monastrol were synthesized via Biginelli multicomponent condensation of fatty β-ketoester in good yields using a simple approach catalyzed by nontoxic and free-metal sulfamic acid. Following synthesis, their in vitro antitumoral activities were investigated. Notably, all analogues tested were active against rat glioblastoma cells. Superior activity was observed by analogues derived from palmitic and stearic fatty acid chains; these compounds were the most potent molecules, showing 13-fold higher potency than monastrol with IC50 values of 5.11 and 6.85 μM, respectively. These compounds could provide promising new lead derivatives for more potent antitumor drugs.

Synthesis of proline derived benzenesulfonamides: A potent anti-Trypanosoma brucei gambiense agent

Thousands of death in Africa and other developing nations are still attributed to trypanosomiasis. Excessive sleep has been associated with increased inflammation. We report herein, the synthesis, antitrypanosomal and anti-inflammatory activities of eight new carboxamide derivatives bearing substituted benzenesulfonamides. The base promoted reactions of l-proline and L-4-hydroxyproline with substituted benzenesulfonyl chlorides gave the benzenesulfonamides (11a-h) in excellent yields. Boric acid mediated amidation of the benzenesulfonamides (11a-h) and p-aminobenzoic acid (12) gave the new carboxamides (13a-h) in excellent yields. The new carboxamides were tested for their antitrypanosomal and anti-inflammatory activities against Trypanosome brucei gambiense and inhibition of carrageenan-induced rat paw edema. Compound 13f was the most potent antitrypanosomal agent with an IC50 value of 2 nM as against 5 nM for melarsoprol; whereas compound 13a was the most potent anti-inflammatory agent with percentage inhibition of carrageenan-induced rat paw edema of 58, 60, 67 and 84% after 0.5 h, 1 h, 2 h and 3 h administration respectively. The structure-activity relationship study revealed that substitution at the para position in the benzenesulfonamide ring increased both the antitrypanosomal and anti-inflammatory activities. The 4-hydroxyprolines (13a-d) showed higher anti-inflammatory activity than the prolines (13e-h). In contrast, the prolines (13e-h) had higher antitrypanosomal activities than the 4-hydroxyprolines. The link between excessive sleep and inflammation makes the report of this class of compounds possessing both antitrypanosomal and anti-inflammatory activity worthwhile. The pharmacokinetic studies showed that the compounds would not pose oral bioavailability, transport and permeability problems.

Cytotoxicity of seven bisphenol analogues compared to bisphenol A and relationships with membrane affinity data

Bisphenol A (BPA) is a chemical used in numerous industrial applications. Due to its well ascertained toxicity as endocrine disruptor, industries have started to replace it with other bisphenols whose alleged greater safety is scarcely supported by literature studies. In this study, the toxicity of seven BPA analogues was evaluated using both in silico and in vitro techniques, as compared to BPA toxicity. Furthermore, their affinity indexes for phospholipids (i.e. phospholipophilicity) were determined by immobilized artificial membrane liquid chromatography (IAM-LC) and possible relationships with in vitro toxic activity were also investigated. The results on four different cell cultures yielded similar ranking of toxicity for the bisphenols considered, with IC₅₀ values confirming their poor acute toxicity. As compared to BPA, bisphenol AF, bisphenol B, bisphenol M, and bisphenol A diglycidyl ether resulted more toxic, while bisphenol S, bisphenol F and bisphenol E were found as the less toxic congeners. These results are partly consistent with the scale of phospholipid affinity showing that toxicity increases at increasing membrane affinity. Therefore, phospholipophilicity determination can be assumed as a useful preliminary tool to select less toxic congeners to surrogate BPA in industrial applications.

Lipophilicity of New Anticancer 1,6- and 3,6-diazaphenothiazines by of Use RP TLC and Different Computational Methods

The lipophilicity of new two series of anticancer active 10-substituted 1,6- and 3,6-diazaphenothiazines has been investigated using reversed-phase thin-layer chromatography. Their lipophilicity (RM0 and log PTLC) was determined with mixtures of acetone and Tris buffer as mobile phases. The relative lipophilicity parameter RM0 and specific hydrophobic surface area b were significantly intercorrelated showing congeneric classes of diazaphenothiazines. The parameter RM0 was transformed into parameter log PTLC by use of the calibration curve. The parameter log PTLC was compared with computationally calculated lipophilic parameters log Pcalcd. The lipophilicity was discussed with the structure elements and was correlated with molecular descriptors, ADME properties and in vitro anticancer activities.

A Family of Rhodium Complexes with Selective Toxicity toward Mismatch Repair-Deficient Cancers

Rhodium metalloinsertors are a unique set of metal complexes that bind specifically to DNA base pair mismatches in vitro and kill mismatch repair (MMR)-deficient cells at lower concentrations than their MMR-proficient counterparts. A family of metalloinsertors containing rhodium-oxygen ligand coordination, termed "Rh-O" metalloinsertors, has been prepared and shown to have a significant increase in both overall potency and selectivity toward MMR-deficient cells regardless of structural changes in the ancillary ligands. Here we describe DNA-binding and cellular studies with the second generation of Rh-O metalloinsertors in which an ancillary ligand is varied in both steric bulk and lipophilicity. These complexes, of the form [Rh(L)(chrysi)(PPO)]²⁺, all include the O-containing PPO ligand (PPO = 2-(pyridine-2-yl)propan-2-ol) and the aromatic inserting ligand chrysi (5,6-chrysene quinone diimine) but differ in the identity of their ancillary ligand L, where L is a phenanthroline or bipyridyl derivative. The Rh-O metalloinsertors in this family all show micromolar binding affinities for a 29-mer DNA hairpin containing a single CC mismatch. The complexes display comparable lipophilic tendencies and p K_a values of 8.1-9.1 for dissociation of an imine proton on the chrysi ligand. In cellular proliferation and cytotoxicity assays with MMR-deficient cells (HCT116O) and MMR-proficient cells (HCT116N), the complexes containing the phenanthroline-derived ligands show highly selective cytotoxic preference for the MMR-deficient cells at nanomolar concentrations. Using mass spectral analyses, it is shown that the complexes are taken into cells through a passive mechanism and exhibit low accumulation in mitochondria, an off-target organelle that, when targeted by parent metalloinsertors, can lead to nonselective cytotoxicity. Overall, these Rh-O metalloinsertors have distinct and improved behavior compared to previous generations of parent metalloinsertors, making them ideal candidates for further therapeutic assessment.

The cluster [Re6Se8I6]3- penetrates biological membranes: drug-like properties for CNS tumor treatment and diagnosis

Tumorigenic cell lines are more susceptible to [Re₆Se₈I₆]^3- cluster-induced death than normal cells, becoming a novel candidate for cancer treatment. Still, the feasibility of using this type of molecules in human patients remains unclear and further pharmacokinetics analysis is needed. Using coupled plasma optical emission spectroscopy, we determined the Re-cluster tissue content in injected mice, as a biodistribution measurement. Our results show that the Re-cluster successfully reaches different tissues, accumulating mainly in heart and liver. In order to dissect the mechanism underlying cluster biodistribution, we used three different experimental approaches. First, we evaluate the degree of lipophilicity by determining the octanol/water partition coefficient. The cluster mostly remained in the octanol fraction, with a coefficient of 1.86 ± 0.02, which indicates it could potentially cross cell membranes. Then, we measured the biological membrane penetration through a parallel artificial membrane permeability assays (PAMPA) assay. The Re-cluster crosses the artificial membrane, with a coefficient of 122 nm/s that is considered highly permeable. To evaluate a potential application of the Re-cluster in central nervous system (CNS) tumors, we analyzed the cluster's brain penetration by exposing cultured blood-brain-barrier (BBB) cells to increasing concentrations of the cluster. The Re-cluster effectively penetrates the BBB, reaching nearly 30% of the brain side after 24 h. Thus, our results indicate that the Re-cluster penetrates biological membranes reaching different target organs-most probably due to its lipophilic properties-becoming a promising anti-cancer drug with high potential for CNS cancer's diagnosis and treatment.

A Rationally Designed Multifunctional Antibiotic for the Treatment of Drug-Resistant Acne

Acne is a multifactorial skin disease, underpinned by colonization of Propionibacterium acnes and inflammation. The emergence of resistant P. acnes strains has affected the current acne treatment algorithm. This setback served as an impetus for rationally designing a library of next-generation antibiotics that exhibit a bactericidal effect on resistant P. acnes and exert an immunomodulatory function to reduce inflammation. In silico screening showed that one of the molecules, VCD-004, exhibits improved mode of binding to bacterial DNA gyrase. VCD-004 shows high potency against clinical isolates of resistant P. acnes and excellent efficacy in vivo. Furthermore, VCD-004 exhibits a superior mutant prevention index, suggesting that it impedes the development of resistance better than clindamycin. Additionally, it shows optimal skin penetration and has a potent anti-inflammatory effect via reduction of proinflammatory cytokines (IL-6) independent of its antibacterial action. VCD-004 affects P. acnes-induced nuclear accumulation of NF-κB in THP-1 cells. The in vitro viability of human keratinocytes in the presence of VCD-004 indicates a desirable therapeutic window for topical use. Such rationally designed bactericidal and immunomodulatory dual pharmacophore-based lipophilic molecule(s) can emerge as the next-generation topical therapy for acne with underlying resistant P. acnes etiology.

Screening therapeutics according to their uptake across the blood-brain barrier: A high throughput method based on immobilized artificial membrane liquid chromatography-diode-array-detection coupled to electrospray-time-of-flight mass spectrometry

The Blood-Brain Barrier (BBB) plays an essential role in protecting the brain tissues against possible injurious substances. In the present work, 79 neutral, basic, acidic and amphoteric structurally unrelated analytes were considered and their chromatographic retention coefficients on immobilized artificial membrane (IAM) stationary phase were determined employing a mass spectrometry (MS)-compatible buffer based on ammonium acetate. Their BBB passage predictive strength was evaluated and the statistical models based on IAM indexes and in silico physico-chemical descriptors showed solid statistics (r² (n - 1) = 0.78). The predictive strength of the indexes achieved by the MS-compatible method was comparable to that achieved by employing the more "biomimetic" Dulbecco's phosphate buffered saline, even if some differences in the elution order were observed. The method was transferred to the MS, employing a diode-array-detection coupled to an electrospray ionization source and a time-of-flight analyzer. This setup allowed the simultaneous analysis of up to eight analytes, yielding a remarkable acceleration of the analysis time.

Accessing lipophilicity of drugs with biomimetic models: A comparative study using liposomes and micelles

Lipophilicity is a physicochemical property of crucial importance in drug discovery and drug design. Biomimetic models, such as liposomes and micelles, constitute a valuable tool for the assessment of lipophilicity through the determination of partition coefficients (log K_p). However, the lack of standardization hampers the judgment about which model or method has the best and broadest passive drug permeation predictive capacity. This work provides a comparative analysis between the methodologies based on biomimetic models to determine the partition coefficient (log K_p). For that purpose, a set of reference substances preconized by the Organization for Economic Cooperation and Development (OECD) guidelines was used. The biomimetic models employed were liposomes and micelles composed by 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC) and hexadecylphosphocholine (HePC), respectively. Both lipids were used as representative phospholipids of natural membranes. The partition coefficients between biomimetic models and aqueous phases were determined by derivative spectroscopy at physiological conditions (37 °C and pH 7.4). The partition coefficients obtained using biomimetic models are quite different and more reliable than the ones obtained using an octanol/water system. Comparing the performance of the two biomimetic models, micelles revealed to be suitable only for substances with high molar absorption coefficient and log K_p > 3, but in general liposomes are the best model for accessing lipophilicity of drugs. Furthermore, a comparison between experimental data and the partition coefficients determined by the computational method COSMOmic is also provided and discussed. As a final summarizing result, a decision tree is provided in order to guide the selection of a tool for assessing the lipophilicity of drugs.

Synthesis and Bioactivity of Reduced Chalcones Containing Sulfonamide Side Chains

The effect on the bioactivity of antibacterial sulfonamide drugs against malaria and tuberculosis via an increase of the lipid solubility groups by condensation with a reduced chalcone was investigated. Sulfonamide derivatives (8a-8d) were obtained via a 1,3-diarylpropane scaffold, prepared by reduction of the relevant chalcones, followed by the addition of a sulfonamide moiety via the Mannich and the Mannich exchange reactions. The ClogP values indicated that the lipophilicities of 8a-8d and intermediate reduced chalcones and N-alkylated reduced chalcones (5a-7a) were much higher than those of the sulfonamides (1a-1c). The N-alkylated reduced chalcone derivatives 6 and 7 exhibited the highest antimalarial (Plasmodium falciparum (NF54 strain)) activity. Addition of the sulfonamide group weakened the activity, even though some ClogP values were higher, while 1a-1c showed no activity. The reduced chalcones 5a and 5 showed potent growth inhibition of Mycobacterium tuberculosis (H37Rv strain), but the sulfonamide derivatives 8a and 8d showed no or insignificant activity (0 and 14%, respectively) against M. tuberculosis, despite high ClogP values. Thus, the possible increase in bioactivity expected from an increase in ClogP values (lipophilicity) might be counteracted by the higher molecular weight of the studied analogues.

Elucidating the Skin Delivery of Aglycone and Glycoside Flavonoids: How the Structures Affect Cutaneous Absorption

Flavonoids are bioactive phytochemicals that exhibit protective potential against cutaneous inflammation and photoaging. We selected eight flavonoid aglycones or glycosides to elucidate the chemistry behind their skin absorption capability through experimental and computational approaches. The skin delivery was conducted using nude mouse and pig skins mounted on an in vitro Franz cell assembly. The anti-inflammatory activity was examined using the O₂^•– and elastase inhibition in activated human neutrophils. In the equivalent dose (6 mM) application on nude mouse skin, the skin deposition of naringenin and kaempferol was 0.37 and 0.11 nM/mg, respectively, which was higher than that of the other flavonoids. Both penetrants were beneficial for targeted cutaneous therapy due to their minimal diffusion across the skin. The absorption was generally greater for topically applied aglycones than glycosides. Although naringenin could be classified as a hydrophilic flavonoid, the flexibility of the chiral center in the C ring of this flavanone could lead to better skin transport than the flavonols and flavones with a planar structure. An optimized hydrophilic and lipophilic balance of the flavonoid structure was important for governing the cutaneous delivery. The hydrogen bond acceptor and stratum corneum lipid docking estimated by molecular modeling showed some relationships with the skin deposition. The interaction with cholesteryl sulfate could be a factor for predicting the cutaneous absorption of aglycone flavonoids (correlation coefficient = 0.97). Baicalin (3 µM) showed the highest activity against oxidative burst with an O₂^•– inhibition percentage of 77%. Although naringenin displayed an inhibition efficiency of only 20%, this compound still demonstrated an impressive therapeutic index because of the high absorption. Our data are advantageous to providing the information on the structure–permeation relationship for topically applied flavonoids.

Lipophilicity assessement in drug discovery: Experimental and theoretical methods applied to xanthone derivatives

For the last several years, searching of new xanthone derivatives (XDs) with potential pharmacological activities has remained one of the main areas of interest of our group. The optimization of biological activity and drug-like properties of hits and leads is crucial at early stage of the drug discovery pipeline. Lipophilicity is one of the most important drug-like properties having a great impact in both pharmacokinetics and pharmacodynamics processes. In this work, we describe the lipophilicity of a small library of bioactive XDs, previously synthesized by our group, using different methods: computational, vortex-assisted liquid-liquid microextraction coupled with high-performance liquid chromatography (VALLME-HPLC), reversed-phase high-performance thin layer chromatography (RP-HPTLC), reversed-phase high-performance liquid chromatography (RP-HPLC), and biomembrane model by the partition between micelles and aqueous phase. The different results obtained by the used methods were compared and discussed. The methodologies and data gathered in this study will expand the investigation of lipophilicity of XDs, an important class of compounds in medicinal chemistry.

Biophysical Properties and Antiviral Activities of Measles Fusion Protein Derived Peptide Conjugated with 25-Hydroxycholesterol

Measles virus (MV) infection is re-emerging, despite the availability of an effective vaccine. The mechanism of MV entry into a target cell relies on coordinated action between the MV hemagglutinin (H) receptor binding protein and the fusion envelope glycoprotein (F) which mediates fusion between the viral and cell membranes. Peptides derived from the C-terminal heptad repeat (HRC) of F can interfere with this process, blocking MV infection. As previously described, biophysical properties of HRC-derived peptides modulate their antiviral potency. In this work, we characterized a MV peptide fusion inhibitor conjugated to 25-hydroxycholesterol (25HC), a cholesterol derivative with intrinsic antiviral activity, and evaluated its interaction with membrane model systems and human blood cells. The peptide (MV.

Group-Based Optimization of Potent and Cell-Active Inhibitors of the von Hippel-Lindau (VHL) E3 Ubiquitin Ligase: Structure-Activity Relationships Leading to the Chemical Probe (2S,4R)-1-((S)-2-(1-Cyanocyclopropanecarboxamido)-3,3-dimethylbutanoyl)-4-hydroxy-N-(4-(4-methylthiazol-5-yl)benzyl)pyrrolidine-2-carboxamide (VH298)

The von Hippel–Lindau tumor suppressor protein is the substrate binding subunit of the VHL E3 ubiquitin ligase, which targets hydroxylated α subunit of hypoxia inducible factors (HIFs) for ubiquitination and subsequent proteasomal degradation. VHL is a potential target for treating anemia and ischemic diseases, motivating the development of inhibitors of the VHL:HIF-α protein–protein interaction. Additionally, bifunctional proteolysis targeting chimeras (PROTACs) containing a VHL ligand can hijack the E3 ligase activity to induce degradation of target proteins. We report the structure-guided design and group-based optimization of a series of VHL inhibitors with low nanomolar potencies and improved cellular permeability. Structure–activity relationships led to the discovery of potent inhibitors 10 and chemical probe VH298, with dissociation constants <100 nM, which induced marked HIF-1α intracellular stabilization. Our study provides new chemical tools to probe the VHL-HIF pathways and new VHL ligands for next-generation PROTACs.

Anticancer potential of aminomethylidene-diazinanes I. Synthesis of arylaminomethylidene of diazinetriones and its cytotoxic effects tested in glioblastoma cells

Diazinane and aryl moieties with vinylamine linkers were synthesized to investigate the importance of their structural variations as potential anti-glioblastoma agents. Structural variations incorporated on to the diazinane moiety included oxa and thio derivatives, each with a variety of nitrogen-bound substituents. The size and shape of the aromatic moiety was varied, with the final variation introducing two carbonyl groups, yielding a substituted anthraquinone. Readily available diazinanes and aryl amines were used asan advantageous foundation. Several parameters were calculated whilst engineering these compounds, including: ClogP, molecular polarizability, polar surface area, minimal molecular projected area, and pK_a. In addition, a simple and efficient procedure was developed to synthesize these compounds. It was demonstrated that a vinylamine with 1,3-diazinane-2,4,6-trione and 1-anthraquinone moiety is the most promising drug candidate causing almost 70% of LN229 tumor cell death at 1µg/ml. In addition, its molecular polarizability, polar surface area and minimal molecular projected area indicate a possible potential of this molecule for crossing BBB.

A Simple, Robust and Efficient Computational Method for n-Octanol/Water Partition Coefficients of Substituted Aromatic Drugs

In this paper, multiple linear regression (MLR) was used to build quantitative structure property relationship (QSPR) of n-octanol-water partition coefficient (logP_o/w) of 195 substituted aromatic drugs. The molecular descriptors were calculated for each compound by the VLifeMDS. By applying genetic algorithm/multiple linear regressions (GA/MLR) the most relevant descriptors were selected to build a QSPR model. The robustness of the model was characterized by the statistical validation and applicability domain (AD). The prediction results from MLR are in good agreement with the experimental values. The R² and Q²_LOO for MLR are 0.9433, 0.9341. The AD of the model was analyzed based on the Williams plot. The effects of different selected descriptors are described.

Lipophilicity and biomimetic properties to support drug discovery

INTRODUCTION

Lipophilicity, expressed as the octanol-water partition coefficient, constitutes the most important property in drug action, influencing both pharmacokinetic and pharmacodynamics processes as well as drug toxicity. On the other hand, biomimetic properties defined as the retention outcome on HPLC columns containing a biological relevant agent, provide a considerable advance for rapid experimental - based estimation of ADME properties in early drug discovery stages. Areas covered: This review highlights the paramount importance of lipophilicity in almost all aspects of drug action and safety. It outlines problems brought about by high lipophilicity and provides an overview of the drug-like metrics which incorporate lower limits or ranges of logP. The fundamental factors governing lipophilicity are compared to those involved in phospholipophilicity, assessed by Immobilized Artificial Membrane Chromatography (IAM). Finally, the contribution of biomimetic properties to assess plasma protein binding is evaluated. Expert opinion: Lipophilicity and biomimetic properties have important distinct and overlapping roles in supporting the drug discovery process. Lipophilicity is unique in early drug design for library screening and for the identification of the most promising compounds to start with, while biomimetic properties are useful for the experimentally-based evaluation of ADME properties for the synthesized novel compounds, supporting the prioritization of drug candidates and guiding further synthesis.

Development and characterization of a 99m Tc-tricarbonyl-labelled estradiol derivative obtained by "Click Chemistry" with potential application in estrogen receptors imaging

Assessment of the presence of estrogen receptors in breast cancer is crucial for treatment planning. With the objective to develop a potential agent for estrogen receptors imaging, we present the development and characterization of a ^99m Tc-tricarbonyl-labelled estradiol derivative. Using ethinylestradiol as starting material, an estradiol derivative bearing a 1,4-disubstituted 1,2,3-triazole-containing tridentate ligand system was synthesized by "Click Chemistry" and fully characterized. Labelling with high yield and radiochemical purity was achieved through the formation of a ^99m Tc-tricarbonyl complex. The radiolabelled compound was stable, exhibited moderate binding to plasma protein (approximately 33%) and lipophilicity in the adequate range (logP 1.3 ± 0.1 at pH 7.4). Studies in MCF7 showed promising uptake values (approximately 2%). However, more than 50% of the activity is quickly released from the cell. Biodistribution experiments in normal rats confirmed the expected "in vivo" stability of the radiotracer but showed very high gastrointestinal and liver activity, which is inconvenient for in vivo applications. Taking into consideration the well-documented influence of the chelating system in the physicochemical and biological behaviour of technetium-labelled small biomolecules, research will be continued using the same pharmacophore but different complexation modalities of technetium.

Pterostilbene, a Methoxylated Resveratrol Derivative, Efficiently Eradicates Planktonic, Biofilm, and Intracellular MRSA by Topical Application

Pterostilbene is a methoxylated derivative of resveratrol originated from natural sources. We investigated the antibacterial activity of pterostilbene against drug-resistant Staphylococcus aureus and the feasibility of using it to treat cutaneous bacteria. The antimicrobial effect was evaluated using an in vitro culture model and an in vivo mouse model of cutaneous infection. The minimum inhibitory concentration (MIC) assay demonstrated a superior biocidal activity of pterostilbene compared to resveratrol (8~16-fold) against methicillin-resistant S. aureus (MRSA) and clinically isolated vancomycin-intermediate S. aureus (VISA). Pterostilbene was found to reduce MRSA biofilm thickness from 18 to 10 μm as detected by confocal microscopy. Pterostilbene showed minimal toxicity to THP-1 cells and was readily engulfed by the macrophages, facilitating the eradication of intracellular MRSA. Pterostilbene exhibited increased skin absorption over resveratrol by 6-fold. Topical pterostilbene application improved the abscess formation produced by MRSA by reducing the bacterial burden and ameliorating the skin architecture. The potent anti-MRSA capability of pterostilbene was related to bacterial membrane leakage, chaperone protein downregulation, and ribosomal protein upregulation. This mechanism of action was different from that of resveratrol according to proteomic analysis and molecular docking. Pterostilbene has the potential to serve as a novel class of topically applied agents for treating MRSA infection in the skin while demonstrating less toxicity to mammalian cells.

Predicting a Drug's Membrane Permeability: A Computational Model Validated With in Vitro Permeability Assay Data

Membrane permeability is a key property to consider during the drug design process, and particularly vital when dealing with small molecules that have intracellular targets as their efficacy highly depends on their ability to cross the membrane. In this work, we describe the use of umbrella sampling molecular dynamics (MD) computational modeling to comprehensively assess the passive permeability profile of a range of compounds through a lipid bilayer. The model was initially calibrated through in vitro validation studies employing a parallel artificial membrane permeability assay (PAMPA). The model was subsequently evaluated for its quantitative prediction of permeability profiles for a series of custom synthesized and closely related compounds. The results exhibited substantially improved agreement with the PAMPA data, relative to alternative existing methods. Our work introduces a computational model that underwent progressive molding and fine-tuning as a result of its synergistic collaboration with numerous in vitro PAMPA permeability assays. The presented computational model introduces itself as a useful, predictive tool for permeability prediction.

Vascular permeability in the RG2 glioma model can be mediated by macropinocytosis and be independent of the opening of the tight junction

This study evaluates the extravasation pathways of circulating macromolecules in a rat glioma model (RG2) which was observed by both magnetic resonance imaging using ultrasmall superparamagnetic iron oxide and electron microscopy. Although magnetic resonance imaging signal enhancement was observed as soon as 10 min after injection (9.4% 2 h after injection), electron microscopy showed that endothelial cells were still tightly sealed. However, circulating immunoglobulin G and ultrasmall superparamagnetic iron oxide were found in large membrane compartments of endothelial cells, in the basal lamina (7.4 ± 1.2 gold particles/µm² in the tumor versus 0.38 ± 0.17 in healthy tissue, p = 1.4.10^-5) and between tumoral cells. Altogether, this strongly suggests an active transport mediated by macropinocytosis. To challenge this transport mechanism, additional rats were treated with amiloride, an inhibitor of macropinocytosis, leading to a reduction of membrane protrusions (66%) and of macropinosomes. Amiloride however also opened tumoral tight junctions allowing a larger extravasation of ultrasmall superparamagnetic iron oxide (magnetic resonance imaging signal enhancement of 35.7% 2 h after injection). Altogether, these results suggest that ultrasmall superparamagnetic iron oxide and immunoglobulin G in the RG2 glioma model follow an active extravasation pathway mediated by a macropinocytosis process. Amiloride also appears as a potential strategy to facilitate the extravasation of chemotherapeutic drugs in glioma.