Effects of bile salts on propranolol distribution into liposomes studied by capillary electrophoresis

High-purity 1,2-dimyristoyl-sn-glycero-3-phosphocholine: synthesis and emulsifying performance evaluation

Introduction

1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC) is a promising emulsifier for bioactive delivery systems, but its industrial applications are limited by the lack of cost-effective and scalable synthetic routes. The purpose of this study was to economically produce high-purity DMPC by replacing commonly used column chromatography methods and to evaluate the emulsifying performance.

Methods

DMPC was synthesized from sn-glycero-3-phosphocholine using Steglich esterification followed by sequential recrystallization from ethyl acetate and acetone. The structure of DMPC was identified and its purity was confirmed using various spectroscopy and chromatography techniques. The emulsifying performance was evaluated by examining the effects of storage on the properties of o/w emulsions prepared using soybean oil with (i) soy PC, (ii) soy PC + DMPC (1:1, w/w), and (iii) DMPC as emulsifiers.

Results

The chemical impurities formed during the synthesis of DMPC was removed, and its final purity was 96%, and the melt transition temperature was 37.6°C. No visible difference between the three emulsions (soy PC, soy PC+DMPC, and DMPC) was observed during two-week storage, and the DMPC-based emulsion was more stable than soy PC emulsion, showing smaller particle size distribution during 6 months.

Discussion

The highly pure DMPC was synthesized by an economical method, and DMPC-based emulsions demonstrated physicochemical stable, highlighting its potential for food and pharmaceutical industry-related applications. Our findings suggest that DMPC holds promise as an emulsifier with broad applications in the food industry.

Magnetic targeting of lornoxicam/SPION bilosomes loaded in a thermosensitive in situ hydrogel system for the management of osteoarthritis: Optimization, in vitro, ex vivo, and in vivo studies in rat model via modulation of RANKL/OPG

Osteoarthritis is a bone and joint condition characterized pathologically by articular cartilage degenerative damage and can develop into a devastating and permanently disabling disorder. This investigation aimed to formulate the anti-inflammatory drug lornoxicam (LOR) into bile salt-enriched vesicles loaded in an in situ forming hydrogel as a potential local treatment of osteoarthritis. This was achieved by formulating LOR-loaded bilosomes that are also loaded with superparamagnetic iron oxide nanoparticles (SPIONs) for intra-muscular (IM) administration to improve joint targeting and localization by applying an external magnet to the joint. A 31.22 full factorial design was employed to develop the bilosomal dispersions and the optimized formula including SPION (LSB) was loaded into a thermosensitive hydrogel. Moreover, in vivo evaluation revealed that the IM administration of LSB combined with the application of an external magnet to the joint reversed carrageen-induced suppression in motor activity and osteoprotegerin by significantly reducing the elevations in mitogen-activated protein kinases, extracellular signal-regulated kinase, and receptor activator of nuclear factor kappa beta/osteoprotegerin expressions. In addition, the histopathological evaluation of knee joint tissues showed a remarkable improvement in the injured joint tissues. The results proved that the developed LSB could be a promising IM drug delivery system for osteoarthritis management.

The novel lactoferrin and DHA-codelivered liposomes with different membrane structures: Fabrication, in vitro infant digestion, and suckling pig intestinal organoid absorption

Inspired by membrane structure of breast milk and infant formula fat globules, four liposomes with different particle size (large and small) and compositions (Single phospholipids contained phosphatidylcholine, complex phospholipids contained phosphatidylcholine, phosphatidylethanolamine and sphingomyelin) were fabricated to deliver lactoferrin and DHA. In vitro infant semi-dynamic digestive behavior and absorption in intestinal organoids of liposomes were investigated. Liposomal structures were negligible changed during semi-dynamic gastric digestion while damaged in intestine. Liposomal degradation rate was primarily influenced by particle size, and complex phospholipids accelerated DHA hydrolysis. The release rate of DHA (91.7 ± 1.3 %) in small-sized liposomes (0.181 ± 0.001 μm) was higher than free DHA (unencapsulated, 64.6 ± 3.4 %). Complex phospholipids liposomal digesta exhibited higher transport efficiency (3.4-fold for fatty acids and 2.0-fold for amino acids) and better organoid growth than digesta of bare nutrients. This study provided new insights into membrane structure-functionality relationship of liposomes and may aid in the development of novel infant nutrient carriers.

Potential of liposomes and lipid membranes for the separation of β-blockers by capillary electromigration and liquid chromatographic techniques

β-Blockers belong to a frequently used class of drugs primarily used to treat heart and circulatory conditions. Here we describe the use of lipid vesicles and liposomes as cell membrane biomimicking models in capillary electromigration (CE) and liquid chromatography (LC) techniques for the investigation of interactions between lipid membranes and β-blockers. In addition to liposomes, the use of commercial intravenous lipid emulsions, and their interactions with β-blockers are also discussed. Different CE and LC instrumental techniques designed for these purposes are introduced. Other methodologies for studying interactions between β-blockers and lipid membranes are also briefly discussed, and the different methodologies are compared. The aim is to give the reader a good overview on the status of the use of liposomes and lipids in CE and LC for studying β-blocker interactions.

Structural Changes in Liposomal Vesicles in Association with Sodium Taurodeoxycholate

Liposomes composed of soy lecithin (SL) have been studied widely for drug delivery applications. The stability and elasticity of liposomal vesicles are improved by incorporating additives, including edge activators. In this study, we report the effect of sodium taurodeoxycholate (STDC, a bile salt) upon the microstructural characteristics of SL vesicles. Liposomes, prepared by the thin film hydration method, were characterized by dynamic light scattering (DLS), small-angle neutron scattering (SANS), electron microscopy, and rheological techniques. We noticed a reduction in the size of vesicles with the incremental addition of STDC. Initial changes in the size of spherical vesicles were ascribed to the edge-activating action of STDC (0.05 to 0.17 µM). At higher concentrations (0.23 to 0.27 µM), these vesicles transformed into cylindrical structures. Morphological transitions at higher STDC concentrations would have occurred due to its hydrophobic interaction with SL molecules in the bilayer. This was ascertained from nuclear magnetic resonance observations. Whereas shape transitions underscored the deformability of vesicles in the presence of STDC, the consistency of bilayer thickness ruled out any dissociative effect. It was interesting to notice that SL-STDC mixed structures could survive high thermal stress, electrolyte addition, and dilution.

Pitavastatin-loaded bilosomes for oral treatment of hepatocellular carcinoma: a repurposing approach

Albeit its established efficacy as an anti-hyperlipidemic agent, pitavastatin (PIT) has been shown to have other various therapeutic effects. One of these effects is the anti-cancer activity against hepatocellular carcinoma (HCC). This effect has been evaluated in this study for the first time via its oral delivery loaded in bilosomes both in vitro in hepatocellular carcinoma (HCC) cell line; HepG2 and in vivo in an Ehrlich ascites carcinoma (EAC) model. Moreover, the impact of surface modification of bilosomes with lactoferrin (LF) as an active targeting ligand for HCC was investigated. Bilosomes were prepared by thin-film hydration and different molar phospholipid to bile salt ratios were used to optimize the bilosomal formulation. The molar phospholipid to bile salt ratio was adjusted to 4:1 at pH 7.4. LF-coated bilosomes possessed a particle size, PDI, entrapment efficiency, and zeta potential of 112.28 nm ± 6.35, 0.229 ± 0.06, 90.56% ± 3.22, and −7.86 mV ± 1.13, respectively. LF-coated bilosomes also increased permeation of PIT when tested on Caco-2 cells by 3.1-folds (compared to uncoated ones or free PIT solution). It also improved the cytotoxicity of HepG2 spheroids 44-folds more than PIT-free solution. RT-PCR analysis showed that LF-coated PIT-loaded bilosomes caused an improvement (2-fold increase) in the apoptotic potential of PIT mediated by caspase-3. In conclusion, the optimized LF-coated PIT-loaded bilosomes were cytotoxic to HCC with improved hepatocytes permeation and cellular uptake. Thus, the proposed formula could be a promising treatment for HCC.

Development of Geraniol-Loaded Liposomal Nanoformulations against Salmonella Colonization in the Pig Gut

Salmonella is a global health threat, with pig production being one of the main sources of human salmonellosis. The current study investigated the antivirulence properties of geraniol for inhibiting the in vitro colonization of Salmonella. The minimum inhibitory (MIC) and bactericidal concentrations (MBC) of geraniol against Salmonella typhimurium followed by the sub-MIC of geraniol were determined. Results provided clear evidence that geraniol at 1/8 MIC can be used as an effective, non-toxic antivirulence compound to inhibit virulence factors (motility, adhesion, and invasiveness) affecting the colonization of S. typhimurium on IPEC-J2 cells. Additionally, the findings signified that microfluidics is an emerging technology suitable for the preparation of stable liposomes with a small size (<200 nm) and high encapsulation efficiency (EE) of up to 92.53%, which can act as effective carriers of geraniol into the pig gastrointestinal tract (GIT), targeting Salmonella, preventing colonization, and thus increasing the safety of the food supply chain.

Bile Acid Detection Techniques and Bile Acid-Related Diseases

Bile acid is a derivative of cholinergic acid (steroidal parent nucleus) that plays an important role in digestion, absorption, and metabolism. In recent years, bile acids have been identified as signaling molecules that regulate self-metabolism, lipid metabolism, energy balance, and glucose metabolism. The detection of fine changes in bile acids caused by metabolism, disease, or individual differences has become a research hotspot. At present, there are many related techniques, such as enzyme analysis, immunoassays, and chromatography, that are used for bile acid detection. These methods have been applied in clinical practice and laboratory research to varying degrees. However, mainstream detection technology is constantly updated and replaced with the passage of time, proffering new detection technologies. Previously, gas chromatography (GS) and gas chromatography-mass spectrometry (GC-MS) were the most commonly used for bile acid detection. In recent years, high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) has developed rapidly and has gradually become the mainstream bile acid sample separation and detection technology. In this review, the basic principles, development and progress of technology, applicability, advantages, and disadvantages of various detection techniques are discussed and the changes in bile acids caused by related diseases are summarized.

The influence of the gut microbiota on the bioavailability of oral drugs

Due to its safety, convenience, low cost and good compliance, oral administration attracts lots of attention. However, the efficacy of many oral drugs is limited to their unsatisfactory bioavailability in the gastrointestinal tract. One of the critical and most overlooked factors is the symbiotic gut microbiota that can modulate the bioavailability of oral drugs by participating in the biotransformation of oral drugs, influencing the drug transport process and altering some gastrointestinal properties. In this review, we summarized the existing research investigating the possible relationship between the gut microbiota and the bioavailability of oral drugs, which may provide great ideas and useful instructions for the design of novel drug delivery systems or the achievement of personalized medicine.

An Update on Pharmaceutical Strategies for Oral Delivery of Therapeutic Peptides and Proteins in Adults and Pediatrics

While each route of therapeutic drug delivery has its own advantages and limitations, oral delivery is often favored because it offers convenient painless administration, sustained delivery, prolonged shelf life, and often lower manufacturing cost. Its limitations include mucus and epithelial cell barriers in the gastrointestinal (GI) tract that can block access of larger molecules including Therapeutic protein or peptide-based drugs (TPPs), resulting in reduced bioavailability. This review describes these barriers and discusses different strategies used to modify TPPs to enhance their oral bioavailability and/or to increase their absorption. Some seek to stabilize the TTPs to prevent their degradation by proteolytic enzymes in the GI tract by administering them together with protease inhibitors, while others modify TPPs with mucoadhesive polymers like polyethylene glycol (PEG) to allow them to interact with the mucus layer, thereby delaying their clearance. The further barrier provided by the epithelial cell membrane can be overcome by the addition of a cell-penetrating peptide (CPP) and the use of a carrier molecule such as a liposome, microsphere, or nanosphere to transport the TPP-CPP chimera. Enteric coatings have also been used to help TPPs reach the small intestine. Key efficacious TPP formulations that have been approved for clinical use will be discussed.

Transfersomes: A Promising Nanoencapsulation Technique for Transdermal Drug Delivery

Transdermal delivery systems have gained much interest in recent years owing to their advantages compared to conventional oral and parenteral delivery systems. They are noninvasive and self-administered delivery systems that can improve patient compliance and provide a controlled release of the therapeutic agents. The greatest challenge of transdermal delivery systems is the barrier function of the skin's outermost layer. Molecules with molecular weights greater than 500 Da and ionized compounds generally do not pass through the skin. Therefore, only a limited number of drugs are capable of being administered by this route. Encapsulating the drugs in transfersomes are one of the potential approaches to overcome this problem. They have a bilayered structure that facilitates the encapsulation of lipophilic and hydrophilic, as well as amphiphilic, drug with higher permeation efficiencies compared to conventional liposomes. Transfersomes are elastic in nature, which can deform and squeeze themselves as an intact vesicle through narrow pores that are significantly smaller than its size. This review aims to describe the concept of transfersomes, the mechanism of action, different methods of preparation and characterization and factors affecting the properties of transfersomes, along with their recent applications in the transdermal administration of drugs.

Bilosomes as a novel carrier for the cutaneous delivery for dapsone as a potential treatment of acne: preparation, characterization and in vivo skin deposition assay

In our study, the potential of bilosomes as novel vesicular carrier for the cutaneous delivery of the sulphone compound, Dapsone, for topical treatment of acne was investigated. The effect of different formulation variables (type and concentration of bile salt, and molar ratio of Span 60:cholesterol) on the properties of DPS-loaded bilosomes was investigated using a full factorial design. Design Expert software was used for data analysis and optimization of DPS-loaded bilosomes. The optimized bilosomes, chosen on the basis of their superior properties giving maximum entrapment, in vitro release after different time intervals and RE% with minimum vesicle size. Results showed that the bilosome system prepared using Span^® 60: Cholesterol (5:1) and containing 0.25 M sodium deoxycholate as the bile salt was found to obey these criteria, with a desirability value of 0.637. Therefore, this system was chosen for further assessment for its morphological properties, zeta potential, thermal analysis using differential scanning calorimetry and X-ray diffractometry. Results revealed that the chosen bilosomes were spherical in shape with no aggregation, and contained DPS in a molecularly dispersed amorphous form. Finally, the capability of the optimized DPS-loaded bilosomes to deliver DPS through rat skin layers will be investigated and compared with that of DPS alcoholic solution. Results showed that the amounts of DPS retained in the skin treated with DPS-loaded bilosomes, and DPS alcoholic solution after 24 h were found to be 170.57 ± 55.12 and 120.24 ± 10.7 µg/mL, respectively, representing about 1.5-fold higher drug retained in the bilosomes-treated skin. Finally, the safety and the tolerability of the prepared bilosomes were assessed using histopathological examination, and revealed that the control untreated skin sections and skin sections treated with DPS-loaded bilosomes showed normal histological structures characterized by absence of defects or inflammation. Such results can be considered a good addition in the field of pharmaceutical drug delivery for effective topical therapy of acne.

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.

Effect of drug amlodipine on the charged lipid bilayer cell membranes DMPS and DMPS + DMPC: a molecular dynamics simulation study

In this work, the effects of the anti-hypertensive drug amlodipine in native and PEGylated forms on the malfunctioning of negatively charged lipid bilayer cell membranes constructed from DMPS or DMPS + DMPC were studied by molecular dynamics simulation. The obtained results indicate that amlodipine alone aggregates and as a result its diffusion into the membrane is retarded. In addition, due to their large size aggregates of the drug can damage the cell, rupturing the cell membrane. It is shown that PEGylation of amlodipine prevents this aggregation and facilitates its diffusion into the lipid membrane. The interaction of the drug with negatively charged membranes in the presence of an aqueous solution of NaCl, as the medium, is investigated and its effects on the membrane are considered by evaluating the structural properties of the membrane such as area per lipid, thickness, lipid chain order and electrostatic potential difference between bulk solution and lipid bilayer surface. The effect of these parameters on the diffusion of the drug into the cell is critically examined and discussed.

Absorption-Enhancing Effects of Bile Salts

Bile salts are ionic amphiphilic compounds with a steroid skeleton. Among the most important physiological properties of bile salts are lipid transport by solubilization and transport of some drugs through hydrophobic barriers. Bile salts have been extensively studied to enhance transepithelial permeability for different marker molecules and drugs. They readily agglomerate at concentrations above their critical micelle concentration (CMC). The mechanism of absorption enhancement by bile salts appears to be complex. The aim of the present article was to review bile salt structure and their application as absorption enhancers and the probable mechanism for increasing permeation based on previous studies.

Niosomal carriers enhance oral bioavailability of carvedilol: effects of bile salt-enriched vesicles and carrier surface charge

Carvedilol (CRV) is an antihypertensive drug with both alpha and beta receptor blocking activity used to preclude angina and cardiac arrhythmias. To overcome the low, variable oral bioavailability of CRV, niosomal formulations were prepared and characterized: plain niosomes (without bile salts), bile salt-enriched niosomes (bilosomes containing various percentages of sodium cholate or sodium taurocholate), and charged niosomes (negative, containing dicetyl phosphate and positive, containing hexadecyl trimethyl ammonium bromide). All formulations were characterized in terms of encapsulation efficiency, size, zeta potential, release profile, stability, and morphology. Various formulations were administered orally to ten groups of Wistar rats (n=6 per group). The plasma levels of CRV were measured by a validated high-performance liquid chromatography (HPLC) method and pharmacokinetic properties of different formulations were characterized. Contribution of lymphatic transport to the oral bioavailability of niosomes was also investigated using a chylomicron flow-blocking approach. Of the bile salt-enriched vesicles examined, bilosomes containing 20% sodium cholate (F2) and 30% sodium taurocholate (F5) appeared to give the greatest enhancement of intestinal absorption. The relative bioavailability of F2 and F5 formulations to the suspension was estimated to be 1.84 and 1.64, respectively. With regard to charged niosomes, the peak plasma concentrations (C_max) of CRV for positively (F7) and negatively charged formulations (F10) were approximately 2.3- and 1.7-fold higher than after a suspension. Bioavailability studies also revealed a significant increase in extent of drug absorption from charged vesicles. Tissue histology revealed no signs of inflammation or damage. The study proved that the type and concentration of bile salts as well as carrier surface charge had great influences on oral bioavailability of niosomes. Blocking the lymphatic absorption pathway significantly reduced oral bioavailability of CRV niosomes. Overall twofold enhancement in bioavailability in comparison with drug suspension confers the potential of niosomes as suitable carriers for improved oral delivery of CRV.

Multifaceted applications of bile salts in pharmacy: an emphasis on nanomedicine

The human body has long provided pharmaceutical science with biomaterials of interesting applications. Bile salts (BSs) are biomaterials reminiscent of traditional surfactants with peculiar structure and self-assembled topologies. In the pharmaceutical field, BSs were employed on the basis of two different concepts. The first concept exploited BSs' metabolic and homeostatic functions in disease modulation, whereas the second one utilized BSs' potential to modify drug-delivery characteristics, which recently involved nanotechnology. This review is the first to gather major pharmaceutical applications of BSs from endogenous organotropism up to integration into nanomedicine, with a greater focus on the latter domain. Endogenous applications highlighted the role of BS in modulating hypercholesterolemia and cancer therapy in view of enterohepatic circulation. In addition, recent BS-integrated nanomedicines have been surveyed, chiefly size-tunable cholate nanoparticles, BS-lecithin mixed micelles, bilosomes, probilosomes, and surface-engineered bilosomes. A greater emphasis has been laid on nanosystems for vaccine and cancer therapy. The comparative advantages of BS-integrated nanomedicines over conventional nanocarriers have been noted. Paradoxical effects, current pitfalls, future perspectives, and opinions have also been outlined.

Wittig reaction (with ethylidene triphenylphosphorane) of oxo-hydroxy derivatives of 5β-cholanic acid: Hydrophobicity, haemolytic potential and capacity of derived ethylidene derivatives for solubilisation of cholesterol

Bile acid salts are biosurfactants which form mixed micelles with phospholipids in vertebrates. These mixed micelles are suitable for solubilisation of cholesterol. For therapeutic purposes some bile acid salts as sodium ursocholate are used. However, bile acid anions possess low capacity for solubilisation of cholesterol. Thus, synthesis of more hydrophobic and less membranotoxic bile acid derivatives is of the great interest. In this paper Wittig reaction between ethylidene triphenylphosphorane and different bile acids oxo derivatives is examined. Wittig reaction of bile acids has not been studied much. C12 oxo group is inert in this reaction. If Wittig reaction happens on C7 oxo group stereospecifically E ethylidene stereoisomer is obtained, while the same reaction on C3 oxo group leads to more reactive not sterospecific product. In this paper stereochemical course of investigated Wittig reactions is thoroughly analysed. Hydrophobicity of derived products is determined over the temperature (T) dependence on retention coefficients (k) in reversed phase high resolution chromatography. Using method of principle components on k=f(T) matrix it is found that values of first principle components best describe hydrophobicity of analysed bile acids, while the second principal component is responsible for their hydrophilicity. By in silico molecular descriptors: valence connectivity index of order 3 (X3v) and packing density index (PDI), linear regression equations are obtained that can be used to predict hydrophobicity (over retention coefficient) of bile acids that belong to set of more congeneric groups. Membranotoxicity is determined by haemolytic potential. Monoethylidene derivatives of bile acids (in the form of anions) have lower membranotoxicity than deoxycholic acids anion. Sodium salt of deoxycholic acid 7-ethylidene derivative has 11% greater capacity for solubilisation of cholesterol monohydrate than sodium salt of deoxycholic acid.

Transport of organic cationic drugs: effect of ion-pair formation with bile salts on the biliary excretion and pharmacokinetics

More than 40% of clinically used drugs are organic cations (OCs), which are positively charged at a physiologic pH, and recent reports have established that these drugs are substrates of membrane transporters. The transport of OCs via membrane transporters may play important roles in gastrointestinal absorption, distribution to target sites, and biliary and/or renal elimination of various OC drugs. Almost 40 years ago, a molecular weight (Mw) threshold of 200 was reported to exist in rats for monoquaternary ammonium (mono QA) compounds to be substantially (e.g., >10% of iv dose) excreted to bile. It is well known that some OCs interact with appropriate endogenous organic anions in the body (e.g., bile salts) to form lipophilic ion-pair complexes. The ion-pair formation may influence the affinity or binding of OCs to membrane transporters that are relevant to biliary excretion. In that sense, the association of the ion-pair formation with the existence of the Mw threshold appears to be worthy of examination. It assumes the ion-pair formation of high Mw mono QA compounds (i.e., >200) in the presence of bile salts in the liver, followed by accelerated transport of the ion-pair complexes via relevant bile canalicular transporter(s). In this article, therefore, the transport of OC drugs will be reviewed with a special focus on the ion-pair formation hypothesis. Such information will deepen the understanding of the pharmacokinetics of OC drugs as well as the physiological roles of endogenous bile salts in the detoxification or phase II metabolism of high Mw QA drugs.