Ethylene Glycol-Linked Amino Acid Diester Prodrugs of Oleanolic Acid for PepT1-Mediated Transport: Synthesis, Intestinal Permeability and Pharmacokinetics

Scutellarein derivatives with histamine H3 receptor antagonism and cholinesterase inhibitory potency as multi target-directed ligands for possible Alzheimer's disease therapy

A series of scutellarein 7-l-amino acid carbamate-4'-cycloalkylamine propyl ether conjugates were designed and synthesized for the first time as multifunctional agents for Alzheimer's disease (AD) therapy. The designed compounds exhibited more balanced and effective multi-target potency. Among them, compound 11l, l-Valine carbamate derivative of scutellarein cycloheptylamine ether, exhibited the most potent inhibition of electric eel AChE enzymes and human AChE enzymes, with an IC50 values of 7.04 μM and 9.73 μM, respectively. Moreover, 11l exhibited more potent H3R antagonistic activities than clobenpropit, with an IC50 value of 1.09 nM. Compound 11l not only displayed excellent inhibition of self- and Cu2+-induced Aβ1-42 aggregation (95.48 % and 88.63 % inhibition, respectively) but also induced the disassembly of self- and Cu2+-induced Aβ fibrils (80.16 % and 89.30 % disaggregation, respectively). Moreover, 11l significantly reduced tau protein hyperphosphorylation induced by Aβ25-35. It exhibited effective antioxidant activity and neuroprotective potency, and inhibited RSL3-induced PC12 cell ferroptosis. Assays of hCMEC/D3 and hPepT1-MDCK cell line permeability indicated that 11l would have optimal blood-brain barrier permeability and intestinal absorption characteristics. In addition, in vivo studies revealed that compound 11l significantly attenuated learning and memory impairment in an AD mouse model. Finally, a pharmacokinetic characterization of 11l indicated favorable druggability and pharmacokinetic properties. Taken together, our results suggest that 11l is a potential candidate for AD treatment and merits further investigation.

Evaluating physiochemical properties of FDA-approved orally administered drugs

INTRODUCTION

Analyses of orally administered FDA-approved drugs from 1990 to 1993 enabled the identification of a set of physiochemical properties known as Lipinski's Rule of Five (Ro5). The original Ro5 and extended versions still remain the reference criteria for drug development programs. Since many bioactive compounds do not conform to the Ro5, we validated the relevance of and adherence to these rulesets in a contemporary cohort of FDA-approved drugs.

AREAS COVERED

The authors noted that a significant proportion of FDA-approved orally administered parent compounds from 2011 to 2022 deviate from the original Ro5 criteria (~38%) or the Ro5 with extensions (~53%). They then evaluated if a contemporary Ro5 criteria (cRo5) could be devised to better predict oral bioavailability. Furthermore, they discuss many case studies showcasing the need for and benefit of increasing the size of certain compounds and cover several evolving strategies for improving oral bioavailability.

EXPERT OPINION

Despite many revisions to the Ro5, the authors find that no single proposed physiochemical rule has universal concordance with absolute oral bioavailability. Innovations in drug delivery and formulation have dramatically expanded the range of physicochemical properties and the chemical diversity for oral administration.

Pentacyclic triterpene-amino acid derivatives induced apoptosis and autophagy in tumor cells, affected the JNK and PI3K/AKT/mTOR pathway

A series of pentacyclic triterpene-amino acid derivatives were synthesized and tested for anti-proliferative activity. The results showed that most of the target compounds had good anti-proliferative activity. 2c did not contain protecting groups and hydrochloride, had excellent cytotoxicity, so it had been selected for further study in the mechanism of action in T24 cells. The data from transcriptome sequencing indicated that 2c was found to be closely related to apoptosis and autophagy. Observation of fluorescence staining and analysis from flow cytometry demonstrated that 2c induced apoptosis and cause cell cycle arrest in S/G2 phase in T24 cells. Molecular mechanism studies exhibited that 2c induced apoptosis in the intrinsic and extrinsic pathways. 2c also induced cellular autophagy in T24 cells. Results from Western Blotting showed that 2c could activate JNK pathway and inhibit PI3K/AKT/mTOR pathway. In conclusion, 2c was deserved further investigation in the field of anti-tumor.

Design, synthesis and biological evaluation of new multi-target scutellarein hybrids for treatment of Alzheimer's disease

Scutellarein hybrids were designed, synthesized and evaluated as multifunctional therapeutic agents for the treatment of Alzheimer's disease (AD). Compounds 11a-i, containing a 2-hydroxymethyl-3,5,6-trimethylpyrazine fragment at the 7-position of scutellarein, were found to have balanced and effective multi-target potencies against AD. Among them, compound 11e exhibited the most potent inhibition of electric eel and human acetylcholinesterase enzymes with IC50 values of 6.72 ± 0.09 and 8.91 ± 0.08 μM, respectively. In addition, compound 11e displayed not only excellent inhibition of self- and Cu2+-induced Aβ1-42 aggregation (91.85% and 85.62%, respectively) but also induced disassembly of self- and Cu2+-induced Aβ fibrils (84.54% and 83.49% disaggregation, respectively). Moreover, 11e significantly reduced tau protein hyperphosphorylation induced by Aβ25-35, and also exhibited good inhibition of platelet aggregation. A neuroprotective assay demonstrated that pre-treatment of PC12 cells with 11e significantly decreased lactate dehydrogenase levels, increased cell viability, enhanced expression of relevant apoptotic proteins (Bcl-2, Bax and caspase-3) and inhibited RSL3-induced PC12 cell ferroptosis. Furthermore, hCMEC/D3 and hPepT1-MDCK cell line permeability assays indicated that 11e would have optimal blood-brain barrier and intestinal absorption characteristics. In addition, in vivo studies revealed that compound 11e significantly attenuated learning and memory impairment in an AD mice model. Toxicity experiments with the compound did not reveal any safety concerns. Notably, 11e significantly reduced β-amyloid precursor protein (APP) and β-site APP cleaving enzyme-1 (BACE-1) protein expression in brain tissue of scopolamine-treated mice. Taken together, these outstanding properties qualified compound 11e as a promising multi-target candidate for AD therapy, worthy of further studies.

A prodrug of the capsid assembly modulator improved druggability and lowing HBsAg and HBeAg for the treatment of chronic hepatitis B

CAMs were disclosed to alter cccDNA levels with sustained hepatitis B surface antigen (HBsAg) loss or seroconversion in preclinical investigation. Here, we report the discovery of a prodrug Yhhu6669 as CAMs based on the intestinal peptide transporter. This compound exhibited the promising anti-HBV activity with sustained suppression of HBV DNA, as well as HBsAg and HBeAg in the AAV HBV mouse model by oral treatment for 7 weeks and maintained for a further 8 weeks following drug withdraw. Our results show an alternative possibility for a functional cure by specific CAMs and provide the basis for the further mechanism study.

Transporter-Mediated Drug Delivery

Transmembrane transport of small organic and inorganic molecules is one of the cornerstones of cellular metabolism. Among transmembrane transporters, solute carrier (SLC) proteins form the largest, albeit very diverse, superfamily with over 400 members. It was recognized early on that xenobiotics can directly interact with SLCs and that this interaction can fundamentally determine their efficacy, including bioavailability and intertissue distribution. Apart from the well-established prodrug strategy, the chemical ligation of transporter substrates to nanoparticles of various chemical compositions has recently been used as a means to enhance their targeting and absorption. In this review, we summarize efforts in drug design exploiting interactions with specific SLC transporters to optimize their therapeutic effects. Furthermore, we describe current and future challenges as well as new directions for the advanced development of therapeutics that target SLC transporters.

Elucidating a Potential Mechanism of Permeability Enhancer Sodium N-[8-(2-hydroxybenzoyl) amino] Caprylate in Rats: Evidence of Lymphatic Absorption of Cyanocobalamin using the Mesenteric Lymph Duct Cannulated Rat

Oral administration is the most popular and convenient route for drug delivery, yet the success of oral drug delivery is dependent on the ADME properties of the drug. Among those ADME properties, permeability is considered one of the key attributes for successful oral drug absorption. Hence, the utilization of permeability enhancers to improve drug oral absorption is an important area of research in drug delivery. A multitude of data suggests that sodium N-[8-(2-hydroxybenzoyl) amino] caprylate (SNAC) is an effective permeability enhancer. Despite its success, the mechanism of how SNAC works to enhance the oral absorption of compounds is poorly understood. To better understand how SNAC worked, we investigated the hypothesis of SNAC promotes lymphatic absorption of target compounds. In this study, cyanocobalamin was used as the model compound and mesenteric lymph duct cannulated rats were used to investigate its absorption with or without SNAC. The present study demonstrated that SNAC enhanced the lymphatic absorption of cyanocobalamin when the two were co-dosed in rats. Furthermore, levels of SNAC in lymph fluid and the systemic circulation were higher when co-dosed with cyanocobalamin.

Design, synthesis and evaluation of novel scutellarin and scutellarein-N,N-bis-substituted carbamate-l-amino acid derivatives as potential multifunctional therapeutics for Alzheimer's disease

In this study, we designed, synthesized and evaluated a series of scutellarin and scutellarein-N,N-bis-substituted carbamate-l-amino acid derivatives as multifunctional therapeutic agents for the treatment of Alzheimer's disease (AD). Compounds containing scutellarein as the parent nucleus (6a-l) had good inhibitory activity against acetyl cholinesterase (AChE), with compound 6 h exhibiting the most potent inhibition of electric eel AChE and human AChE enzymes with IC₅₀ values of 6.01 ± 1.66 and 7.91 ± 0.49 μM, respectively. In addition, compound 6 h displayed not only excellent inhibition of self- and Cu²⁺-induced Aβ_1-42 aggregation (89.17% and 86.19% inhibition) but also induced disassembly of self- and Cu²⁺-induced Aβ fibrils (84.25% and 78.73% disaggregation). Moreover, a neuroprotective assay demonstrated that pre-treatment of PC12 cells with 6 h significantly decreased lactate dehydrogenase levels, increased cell viability, enhanced expression of relevant apoptotic proteins (Bcl-2, Bax, and caspase-3) and inhibited RSL3 induced PC12 cell ferroptosis. Furthermore, hCMEC/D3 and hPepT1-MDCK cell line permeability assays indicated that 6 h would have optimal blood-brain barrier and intestinal absorption characteristics. The in vivo experimental data suggested that 6 h ameliorated learning and memory impairment in mice by decreasing AChE activity, increasing ACh levels and alleviating pathological damage of hippocampal tissue cells. These multifunctional properties highlight compound 6 h as a promising candidate for development as a multifunctional drug against AD.

Anti-Diabetic Potential of Plant-Based Pentacyclic Triterpene Derivatives: Progress Made to Improve Efficacy and Bioavailability

Diabetes mellitus (DM) results from the inability of the pancreas to produce sufficient insulin or weakened cellular response to the insulin produced, which leads to hyperglycemia. Current treatments of DM focus on the use of oral hypoglycemic drugs such as acarbose, alpha-glucose inhibitors, sulphonylureas, thiazolidinediones, and biguanides to control blood glucose levels. However, these medications are known to have various side effects in addition to their bioavailability, efficacy, and safety concerns. These drawbacks have increased interest in the anti-diabetic potential of plant-derived bioactive compounds such as oleanolic and maslinic acids. Although their efficacy in ameliorating blood glucose levels has been reported in several studies, their bioavailability and efficacy remain of concern. The current review examines the anti-diabetic effects of oleanolic, maslinic, asiatic, ursolic, and corosolic acids and their derivatives, as well as the progress made thus far to enhance their bioavailability and efficacy. The literature for the current review was gathered from leading academic databases-including Google Scholar and PubMed-the key words listed below were used. The literature was searched as widely and comprehensively as possible without a defined range of dates.

Natural and Semisynthetic Pentacyclic Triterpenes for Chronic Myeloid Leukemia Therapy: Reality, Challenges and Perspectives

Chronic myeloid leukemia (CML) is a neoplasm characterized by BCR-ABL1, an oncoprotein with vital role in leukemogenesis. Its inhibition by tyrosine kinase inhibitors represents the main choice of treatment. However, therapeutic failure is worrying given the lack of pharmacological options. Pentacyclic triterpenes are phytochemicals with outstanding antitumoral properties and have also been explored as a basis for the design of potential leads. In this review, we have gathered and discuss data regarding both natural and semisynthetic pentacyclic triterpenes applied to CML cell treatment. We found consistent evidence that the class of pentacyclic triterpenes in general exerts promising pro-apoptotic and antiproliferative activities in sensitive and resistant CML cells, and thus represents a rich source for drug development. We also analyze the predicted drug-like properties of the molecules, discuss the structural changes with biological implications and show the great opportunities this class represents, as well as the perspectives they provide on drug discovery for CML treatment.

Synthesis, pharmacological evaluation and mechanistic study of scutellarin methyl ester -4'-dipeptide conjugates for the treatment of hypoxic-ischemic encephalopathy (HIE) in rat pups

A series of novel scutellarin methyl ester-4'-dipeptide conjugates exhibiting active transport characteristics and protection against pathological damage caused by hypoxic-ischemic encephalopathy (HIE) were successfully designed and synthesized. The physiochemical properties of the obtained compounds, as well as the Caco-2 cell-based permeability and uptake into hPepT1-MDCK cells were evaluated using various analytical methods. Scutellarin methyl ester-4'-Val-homo-Leu dipeptide (5k) was determined as the optimal candidate with a high apparent permeability coefficient (P_{app A to B}) of 1.95 ± 0.24 × 10^-6 cm/s, low ER (P_{app BL to AP}/P_{app AP to BL}) of 0.52 in Caco-2 cells, and high uptake of 25.47 μmol/mg/min in hPepT1-MDCK cells. Comprehensive mechanistic studies demonstrated that pre-treatment of PC12 cells with 5k resulted in more potent anti-oxidative activity, which was manifested by a significant decrease in the malondialdehyde (MDA) and reactive oxygen species (ROS) levels, attenuation of the H₂O₂-induced apoptotic cell accumulation in the sub-G1 peak, and improvement in the expression of the relevant apoptotic proteins (Bcl-2, Bax, and cleave-caspase-3). Moreover, evaluation of in vivo neuroprotective characteristics in hypoxic-ischemic rat pups revealed that 5k significantly reduced infarction and alleviated the related pathomorphological damage. The compound was also shown to ameliorate the neurological deficit at 48 h as well as to decrease the brain tissue loss at 4 weeks. Conjugate 5k was demonstrated to reduce the amyloid precursor protein (APP) and β-site APP-converting enzyme-1 (BACE-1) expression. Pharmacokinetic characterization of 5k indicated favorable druggability and pharmacokinetic properties. The conducted docking studies revealed optimal binding of 5k to PepT1. Hydrogen bonding as well as cation-π interactions with the corresponding amino acid residues in the target active site were clearly observed. The obtained results suggest 5k as a potential candidate for anti-HIE therapy, which merits further investigation.

Evaluating the Pharmacokinetics and Systemic Effects of a Permeability Enhancer Sodium N-[8-(2-hydroxybenzoyl)amino] Caprylate in Rats

Oral administration is the preferred route for drug delivery and its success is highly dependent on a compound's ADME properties, of which, permeability plays a major role. Therefore, permeability enhancers are an attractive area of research in the pharmaceutical industry. Recent data suggest that sodium N-[8-(2-hydroxybenzoyl) amino] caprylate (SNAC) is an effective permeability enhancer, yet the pharmacokinetic (PK) and systemic effects of SNAC are poorly understood, specifically its oral bioavailability and systemic effects on distribution, which could influence the safety of certain drugs. To answer these questions, both in vitro and in vivo studies were conducted. Of 3 permeability enhancers (SNAC, 4-CNAB, and 5-CNAC), SNAC was found to have the greatest effect on the absorption of cyanocobalamin in rats. It was also found that SNAC is orally bioavailable (almost 40%) when dosed to rats. Based on these findings, tool compounds were co-dosed in rats to further evaluate the systemic effects of SNAC. Oral co-dosing of SNAC with an intravenous infusion of 2 poorly brain penetrant compounds, quinidine, and gabapentin, did not increase brain ISF: plasma ratio or total brain:plasma ratio for either of these compounds, implying that SNAC is effective only in the intestine at pharmacologically relevant concentrations.

Design and synthesis of pentacyclic triterpene conjugates and their use in medicinal research

Triterpenoids are natural products from plants and many other organisms that have various biological activities, such as antitumor, antiviral, antimicrobial, and protective activities. This review covers the synthesis and biological evaluation of pentacyclic triterpene (PT) conjugates with other molecules that have been found to increase the IC₅₀ or improve the pharmacological profile of the parent PT. Some of these molecules are designed to target specific proteins or cellular organelles, which has resulted in highly selective lead structures for drug development. Other PT conjugates are useful for investigating their mechanism of action. This concept has been very successful: 1) Many compounds, especially mitochondria-targeting PT conjugates, have reached a selective cytotoxicity at low nanomolar concentrations in cancer cells. 2) A number of PT conjugates have had high activity against HIV or the influenza virus. 3) Fluorescent PT conjugates have been able to visualize the PT in living cells, which has allowed quantification of the uptake and distribution of the PT within the cell. 4) Biotinylated PT conjugates have been used to identify target proteins, which may help to show their mechanism of action. 5) A large number of PT conjugates with polyethylene glycol (PEG), polyamines, etc. form nanometer-sized micelles that have a much better pharmacological profile than the PT alone. In summary, the connection of a PT to an appropriate modifying molecule has resulted in extremely useful semisynthetic compounds with a high potential to treat cancer or viral infections or compounds that are useful for the study of the mechanism of action of PTs at the molecular level.

Recent advance of nanoparticle-based topical drug delivery to the posterior segment of the eye

INTRODUCTION

Considering that the number of patients afflicted by posterior eye diseases is increasing, effective drug delivery is currently in high clinical demand. Topical administration has been identified as the preferred option, while sufferingfrom multiple barriers. The development of nanoparticle-based drug delivery system provides an option, which would enhance the drug permeability across the barriers and achieve the desired drug level in the targeted tissue.

AREAS COVERED

This review highlights the barrier to the posterior segment of the eye via topical administration. The up-to-date development of lipid nanoparticles, liposomes, emulsions, spanlastics, micelles, polymeric nanoparticles, layered double hydroxides (LDH), dendrimers, cyclodextrins(CDs), and prodrugs are summarized. Moreover, nanocarriers currently in clinical trials for posterior segment diseases have been discussed.

EXPERT OPINION

Topical nanoparticle-based drug delivery systems have demonstrated significant progress. An ideal formulation should prolong retention time on the surface, enhance drug permeability through the ocular tissues, and efficiently deliver drugs to the targeted site. To design the rational targeting nanoparticle-based drug delivery system, a better understanding of the distribution of transporters and receptors on the eye is required. Ultimately, there is an urgent need to develop targeting hybrid drug delivery systems with the combination of the advantages of several nanocarriers.

Intestinal absorption and activation of decitabine amino acid ester prodrugs mediated by peptide transporter PEPT1 and enterocyte enzymes

Decitabine (DAC), a potent DNA methyltransferase (DNMT) inhibitor, has a limited oral bioavailability. Its 5'-amino acid ester prodrugs could improve its oral delivery but the specific absorption mechanism is not yet fully understood. The aim of this present study was to investigate the in vivo absorption and activation mechanism of these prodrugs using in situ intestinal perfusion and pharmacokinetics studies in rats. Although PEPT1 transporter is pH dependent, there appeared to be no proton cotransport in the perfusion experiment with a preferable transport at pH 7.4 rather than pH 6.5. This suggested that the transport was mostly dependent on the dissociated state of the prodrugs and the proton gradient might play only a limited role. In pH 7.4 HEPES buffer, an increase in P_eff was observed for L-val-DAC, D-val-DAC, L-phe-DAC and L-trp-DAC (2.89-fold, 1.2-fold, 2.73-fold, and 1.90-fold, respectively), compared with the parent drug. When co-perfusing the prodrug with Glysar, a known substrate of PEPT1, the permeabilities of the prodrugs were significantly inhibited compared with the control. To further investigate the absorption of the prodrugs, L-val-DAC was selected and found to be concentration-dependent and saturable, suggesting a carrier-mediated process (intrinsic K_m: 7.80 ± 2.61 mM) along with passive transport. Determination of drug in intestinal homogenate after perfusion further confirmed that the metabolic activation mainly involved an intestinal first-pass effect. In a pharmacokinetic evaluation, the oral bioavailability of L-val-DAC, L-phe-DAC and L-trp-DAC were nearly 1.74-fold, 1.69-fold and 1.49-fold greater than that of DAC. The differences in membrane permeability and oral bioavailability might be due to the different stability in the intestinal lumen and the distinct PEPT1 affinity which is mainly caused by the stereochemistry, hydrophobicity and steric hindrance of the side chains. In summary, the detailed investigation of the absorption mechanism by in vivo intestinal perfusion and pharmacokinetic studies showed that the prodrugs of DAC exhibited excellent permeability and oral bioavailability, which might be attributed to a hybrid (partly PEPT1-mediated and partly passive) transport mode and a rapid activation process in enterocytes.

In vivo anti-malarial activity and toxicity studies of triterpenic esters isolated form Keetia leucantha and crude extracts

BACKGROUND

Considering the need for new anti-malarial drugs, further investigations on Keetia leucantha (Rubiaceae), an in vitro antiplasmodial plant traditionally used to treat malaria, were carried out. This paper aimed to assess the in vivo anti-malarial efficacy of K. leucantha triterpenic esters previously identified as the most in vitro active components against Plasmodium falciparum and their potential toxicity as well as those of anti-malarial extracts.

RESULTS

These eight triterpenic esters and the major antiplasmodial triterpenic acids, ursolic and oleanolic acids, were quantified in the twigs dichloromethane extract by validated HPLC-UV methods. They account for about 19% of this extract (16.9% for acids and 1.8% for esters). These compounds were also identified in trace in the twigs decoction by HPLC-HRMS. Results also showed that extracts and esters did not produce any haemolysis, and were devoid of any acute toxicity at a total cumulative dose of 800 and 150 mg/kg respectively. Moreover, esters given intraperitoneally at 50 mg/kg/day to Plasmodium berghei-infected mice showed a very significant (p < 0.01) parasitaemia inhibition (27.8 ± 5.4%) on day 4 post-infection compared to vehicle-treated mice.

CONCLUSIONS

These results bring out new information on the safety of K. leucantha use and on the identification of anti-malarial compounds from its dichloromethane extract. Its activity can be explained by the presence of triterpenic acids and esters which in vivo activity and safety were demonstrated for the first time.

Pentacyclic Triterpene Bioavailability: An Overview of In Vitro and In Vivo Studies

Pentacyclic triterpenes are naturally found in a great variety of fruits, vegetables and medicinal plants and are therefore part of the human diet. The beneficial health effects of edible and medicinal plants have partly been associated with their triterpene content, but the in vivo efficacy in humans depends on many factors, including absorption and metabolism. This review presents an overview of in vitro and in vivo studies that were carried out to determine the bioavailability of pentacyclic triterpenes and highlights the efforts that have been performed to improve the dissolution properties and absorption of these compounds. As plant matrices play a critical role in triterpene bioaccessibility, this review covers literature data on the bioavailability of pentacyclic triterpenes ingested either from foods and medicinal plants or in their free form.

Multifunctional organic-inorganic hybrid nanoparticles and nanosheets based on chitosan derivative and layered double hydroxide: cellular uptake mechanism and application for topical ocular drug delivery

To study the cellular uptake mechanism of multifunctional organic-inorganic hybrid nanoparticles and nanosheets, new chitosan-glutathione-valine-valine-layered double hydroxide (CG-VV-LDH) nanosheets with active targeting to peptide transporter-1 (PepT-1) were prepared, characterized and further compared with CG-VV-LDH nanoparticles. Both organic-inorganic hybrid nanoparticles and nanosheets showed a sustained release in vitro and prolonged precorneal retention time in vivo, but CG-VV-LDH nanoparticles showed superior permeability in the isolated cornea of rabbits than CG-VV-LDH nanosheets. Furthermore, results of cellular uptake on human corneal epithelial primary cells (HCEpiC) and retinal pigment epithelial (ARPE-19) cells indicated that both clathrin-mediated endocytosis and active transport of PepT-1 are involved in the internalization of CG-VV-LDH nanoparticles and CG-VV-LDH nanosheets. In summary, the CG-VV-LDH nanoparticle may be a promising carrier as a topical ocular drug delivery system for the treatment of ocular diseases of mid-posterior segments, while the CG-VV-LDH nanosheet may be suitable for the treatment of ocular surface diseases.

Loading docetaxel in β-cyclodextrin-based micelles for enhanced oral chemotherapy through inhibition of P-glycoprotein mediated efflux transport

β-Cyclodextrin-based polymeric micelle (PELC) effectively delivered docetaxel by oral administration through inhibition of P-glycoprotein mediated efflux.

Multifunctional properties of organic-inorganic hybrid nanocomposites based on chitosan derivatives and layered double hydroxides for ocular drug delivery

To improve the ocular bioavailability of the model drug of pirenoxine sodium (PRN), organic-inorganic hybrid nanocomposites including layered double hydroxides (LDH) and chitosan derivatives (chitosan-glutathione (CG), chitosan-glutathione-valine (CG-V) and chitosan-glutathione-valine-valine (CG-VV)) were designed and characterized. In vivo precorneal retention study on rabbits showed that mean residence time (MRT) and area under the curve (AUC0-6h) of CG-PRN-LDH nanocomposite eye drop was up to 2.1-fold and 6.3-fold higher than those of commercial product, respectively. In vitro corneal penetration on rabbits demonstrated that the cumulative permeation of CG-VV-PRN-LDH nanocomposite dispersion was increased by 5.2 folds compared to that of commercial product, which may be due to the active transport effect of the nanocomposites by peptide transporter-1 (PepT-1). In addition, the ex vivo fluorescence imaging showed that fluorescent intensity of crystalline lens in rabbits was increased after the administration of PRN-LDH, CG-PRN-LDH, CG-V-PRN-LDH and CG-VV-PRN-LDH (in increasing order) nanocomposite eye drop. Finally, in vivo distribution evaluation in ocular tissues of rabbits revealed that AUC0-8h and MRT in crystalline lens exhibited 14.7-fold and 2.2-fold increase in CG-VV-PRN-LDH nanocomposite eye drop group than those of commercial group, respectively. In summary, the organic-inorganic hybrid nanocomposites with multifunctional properties may be a promising ocular drug delivery system to achieve prolonged precorneal retention, better corneal permeability and enhanced ocular bioavailability.

STATEMENT OF SIGNIFICANCE

Due to several structural and physiological intraocular barriers, drug delivery to the ocular mid-posterior segments still faces great challenges. In this manuscript, organic-inorganic hybrid nanocomposites based on chitosan derivatives and layered double hydroxides (LDH) were designed and constructed. Multifunctional properties of these hybrid nanocomposites were due to the possible active targeting to the peptide transporter-1 on the corneal epithelial cells, the bioadhesive ability and permeation enhancement of chitosan derivatives, and the electrostatic adsorption of LDH. Prolonged precorneal retention, better corneal permeability and enhanced ocular bioavailability of the model drug pirenoxine sodium were observed. Chitosan derivatives-LDH hybrid nanocomposites may be a promising ophthalmic drug system for the treatment of ocular diseases of mid-posterior segments.

The Prodrug Approach: A Successful Tool for Improving Drug Solubility

Prodrug design is a widely known molecular modification strategy that aims to optimize the physicochemical and pharmacological properties of drugs to improve their solubility and pharmacokinetic features and decrease their toxicity. A lack of solubility is one of the main obstacles to drug development. This review aims to describe recent advances in the improvement of solubility via the prodrug approach. The main chemical carriers and examples of successful strategies will be discussed, highlighting the advances of this field in the last ten years.

In situ perfusion in rodents to explore intestinal drug absorption: challenges and opportunities

The in situ intestinal perfusion technique in rodents is a very important absorption model, not only because of its predictive value, but it is also very suitable to unravel the mechanisms underlying intestinal drug absorption. This literature overview covers a number of specific applications for which the in situ intestinal perfusion set-up can be applied in favor of established in vitro absorption tools, such as the Caco-2 cell model. Qualities including the expression of drug transporters and metabolizing enzymes relevant for human intestinal absorption and compatibility with complex solvent systems render the in situ technique the most designated absorption model to perform transporter-metabolism studies or to evaluate the intestinal absorption from biorelevant media. Over the years, the in situ intestinal perfusion model has exhibited an exceptional ability to adapt to the latest challenges in drug absorption profiling. For instance, the introduction of the mesenteric vein cannulation allows determining the appearance of compounds in the blood and is of great use, especially when evaluating the absorption of compounds undergoing intestinal metabolism. Moreover, the use of the closed loop intestinal perfusion set-up is interesting when compounds or perfusion media are scarce. Compatibility with emerging trends in pharmaceutical profiling, such as the use of knockout or transgenic animals, generates unparalleled possibilities to gain mechanistic insight into specific absorption processes. Notwithstanding the fact that the in situ experiments are technically challenging and relatively time-consuming, the model offers great opportunities to gain insight into the processes determining intestinal drug absorption.

A water-soluble inclusion complex of pedunculoside with the polymer β-cyclodextrin: a novel anti-inflammation agent with low toxicity

More than 50% of new drug candidates in drug discovery are lipophilic and exhibit poor aqueous solubility, which results in poor bioavailability and a lack of dose proportionality. Here, we improved the solubility of pedunculoside (PE) by generating a water-soluble inclusion complex composed of PE and the polymer β-cyclodextrin (CDP). We characterized this novel complex by 1H NMR, FT-IR, UV-vis spectroscopy, powder X-ray diffractometry and thermogravimetric analysis. The ratio of β-cyclodextrin (β-CD) units in CDP to PE was determined to be 2∶1. The KD value of the inclusion complex was determined to be 4.29×10(-3) mol•L(-1). In contrast to the low solubility of PE, the water-solubility of the PE-CDP complex was greatly enhanced. A preclinical toxicological study indicated that PE-CDP was well tolerated for a single administration. Importantly, the anti-inflammation potency of the PE-CDP complex was higher than that of PE. As a result, the formation of inclusion complexes by water-soluble CDP opens up possible aqueous applications of insoluble drug candidates in drug delivery.

Oleanolic acid and its synthetic derivatives for the prevention and therapy of cancer: preclinical and clinical evidence

Oleanolic acid (OA, 3β-hydroxyolean-12-en-28-oic acid) is a ubiquitous pentacyclic multifunctional triterpenoid, widely found in several dietary and medicinal plants. Natural and synthetic OA derivatives can modulate multiple signaling pathways including nuclear factor-κB, AKT, signal transducer and activator of transcription 3, mammalian target of rapamycin, caspases, intercellular adhesion molecule 1, vascular endothelial growth factor, and poly (ADP-ribose) polymerase in a variety of tumor cells. Importantly, synthetic derivative of OA, 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO), and its C-28 methyl ester (CDDO-Me) and C28 imidazole (CDDO-Im) have demonstrated potent antiangiogenic and antitumor activities in rodent cancer models. These agents are presently under evaluation in phase I studies in cancer patients. This review summarizes the diverse molecular targets of OA and its derivatives and also provides clear evidence on their promising potential in preclinical and clinical situations.

Combination of amino acid/dipeptide with nitric oxide donating oleanolic acid derivatives as PepT1 targeting antitumor prodrugs

By taking advantage of the cytotoxic effect of nitric oxide (NO) and PepT1 for molecule-targeted drug delivery, a series of amino acid/dipeptide diester prodrugs of NO-donating oleanolic acid derivatives were designed and synthesized. Two prodrugs 6a and 8a showed potent cytotoxcity, which is probably due to their high PepT1 affinity and NO-releasing ability. Furthermore, the aqueous solubility of the prodrugs was also significantly enhanced because of the hydrophilic amino acid/dipeptide promoiety.

Amino acids as promoieties in prodrug design and development

Prodrugs are biologically inactive agents that upon biotransformation in vivo result in active drug molecules. Since prodrugs might alter the tissue distribution, efficacy and the toxicity of the parent drug, prodrug design should be considered at the early stages of preclinical development. In this regard, natural and synthetic amino acids offer wide structural diversity and physicochemical properties. This review covers the use of amino acid prodrugs to improve poor solubility, poor permeability, sustained release, intravenous delivery, drug targeting, and metabolic stability of the parent drug. In addition, practical considerations and challenges associated with the development of amino acid prodrugs are also covered.

Drug transport via the intestinal peptide transporter PepT1

The focus of this review is on the pharmaceutical relevance of the intestinal peptide transporter PepT1. The review is limited to the progress made in the field over the past two years. Much of this progress is being driven by the prevailing view that PepT1 can be used for drug delivery purposes. Studies have indeed shown that several drugs, prodrugs and drug candidates gain entry into the systemic circulation via PepT1. Very recent examples are prodrugs of zanamivir, oseltamivir and didanosine.

Propylene glycol-linked amino acid/dipeptide diester prodrugs of oleanolic acid for PepT1-mediated transport: synthesis, intestinal permeability, and pharmacokinetics

In our previous studies, ethylene glycol-linked amino acid diester prodrugs of oleanolic acid (OA), a Biopharmaceutics Classification System (BCS) class IV drug, designed to target peptide transporter 1 (PepT1) have been synthesized and evaluated. Unlike ethylene glycol, propylene glycol is of very low toxicity in vivo. In this study, propylene glycol was used as a linker to further compare the effect of the type of linker on the stability, permeability, affinity, and bioavailability of the prodrugs of OA. Seven diester prodrugs with amino acid/dipeptide promoieties containing L-Val ester (7a), L-Phe ester (7b), L-Ile ester (7c), D-Val-L-Val ester (9a), L-Val-L-Val ester (9b), L-Ala-L-Val ester (9c), and L-Ala-L-Ile ester (9d) were designed and successfully synthesized. In situ rat single-pass intestinal perfusion (SPIP) model was performed to screen the effective permeability (P(eff)) of the prodrugs. P(eff) of 7a, 7b, 7c, 9a, 9b, 9c, and 9d (6.7-fold, 2.4-fold, 1.24-fold, 1.22-fold, 4.15-fold, 2.2-fold, and 1.4-fold, respectively) in 2-(N-morpholino)ethanesulfonic acid buffer (MES) with pH 6.0 showed significant increase compared to that of OA (p < 0.01). In hydroxyethyl piperazine ethanesulfonic acid buffer (HEPES) of pH 7.4, except for 7c, 9a, and 9d, P(eff) of the other prodrugs containing 7a (5.2-fold), 7b (2.0-fold), 9b (3.1-fold), and 9c (1.7-fold) exhibited significantly higher values than that of OA (p < 0.01). In inhibition studies with glycyl-sarcosine (Gly-Sar, a typical substrate of PepT1), P(eff) of 7a (5.2-fold), 7b (2.0-fold), 9b (3.1-fold), and 9c (2.3-fold) had significantly reduced values (p < 0.01). Compared to the apparent permeability coefficient (P(app)) of OA with Caco-2 cell monolayer, significant enhancement of the P(app) of 7a (5.27-fold), 9b (3.31-fold), 9a (2.26-fold), 7b (2.10-fold), 7c (2.03-fold), 9c (1.87-fold), and 9d (1.39-fold) was also observed (p < 0.01). Inhibition studies with Gly-Sar (1 mM) showed that P(app) of 7a, 9b, and 9c significantly reduced by 1.3-fold, 1.6-fold, and 1.4-fold (p < 0.01), respectively. These results may be attributed to PepT1-mediated transport and their differential affinity toward PepT1. According to the permeability and affinity, 7a and 9b were selected in the pharmacokinetic studies in rats. Compared with group OA, C(max) for group 7a and 9b was enhanced to 3.04-fold (p < 0.01) and 2.62-fold (p < 0.01), respectively. AUC(0→24) was improved to 3.55-fold (p < 0.01) and 3.39-fold (p < 0.01), respectively. Compared to the ethylene glycol-linked amino acid diester prodrugs of OA in our previous work, results from this study revealed that part of the propylene glycol-linked amino acid/dipeptide diester prodrugs showed better stability, permeability, affinity, and bioavailability. In conclusion, propylene glycol-linked amino acid/dipeptide diester prodrugs of OA may be suitable for PepT1-targeted prodrugs of OA to improve the oral bioavailability of OA.

Discovery of a potential anti-inflammatory agent: 3-oxo-29-noroleana-1,9(11),12-trien-2,20-dicarbonitrile

Fifteen novel derivatives of glycyrrhetinic acid (GA) were synthesized and evaluated for anti-inflammatory activities. It was found that the introduction of 1-en-3-one and 9(11),12-diene and 2,20-dinitrile functionalities into the scaffold of GA led to the discovery of potent compound 19 for inhibition of LPS-induced NO production. Furthermore, 19 effectively inhibited the protein and mRNA expression of inducible NO synthase (iNOS) and the mRNA expression of TNF-α, IL-6, and IL-1β in LPS-stimulated RAW 264.7 macrophages. Mechanistically, 19 exerted inhibitory effects on the activation of the three main MAPKs and phosphorylation and degradation of IκB-α, as well as the ratio of nuclear/cytosolic content of p65. Importantly, 19 significantly decreased the mortality rate in the mouse model of LPS-induced sepsis shock. It is noteworthy that inhibitory effect of 19 on NO production was not blocked by the glucocorticoid receptor antagonist mifepristone, indicating that it does not act through the glucocorticoid receptor.