seco-Pregnane Glycosides from Australian Caustic Vine (Cynanchum viminale subsp. australe)

Cynanchum viminale subsp. australe, more commonly known as caustic vine, is a leafless succulent that grows in the northern arid zone of Australia. Toxicity toward livestock has been reported for this species, along with use in traditional medicine and its potential anticancer activity. Disclosed herein are novel seco-pregnane aglycones cynavimigenin A (5) and cynaviminoside A (6), together with new pregnane glycosides cynaviminoside B (7) and cynavimigenin B (8). Cynavimigenin B (8) contains an unprecedented 7-oxobicyclo[2.2.1]heptane moiety in the seco-pregnane series, likely arising from a pinacol-type rearrangement. Interestingly, these isolates displayed only limited cytotoxicity in cancer and normal human cell lines, in addition to low activity against acetylcholinesterase and Sarcoptes scabiei bioassays, suggesting that 5-8 are not associated with the reported toxicity of this plant species.

Protein Nanoparticles for Enhanced Oral Delivery of Coenzyme-Q10: in Vitro and in Silico Studies

Coenzyme-Q10 (CoQ10) is a hydrophobic benzoquinone with antioxidant and anti-inflammatory properties. It is known to reduce oxidative stress in various health conditions. However, due to the low solubility, permeability, stability, and poor oral bioavailability, the oral dose of CoQ10 required for the desired therapeutic effect is very high. In the present study, CoQ10 is encapsulated into two milk derived proteins β-lactoglobulin and lactoferrin (BLG and LF) to produce self-assembled nanostructures of around 100-300 nm with high encapsulation efficiency (5-10% w/w). Both CoQ10-BLG and CoQ10-LF nanoparticles (NPs) significantly improved the aqueous solubility of CoQ10 60-fold and 300-fold, compared to CoQ10 alone, which hardly dissolves in water. Insight into the difference in solubility enhancement between BLG and LF was obtained using in silico modeling, which predicted that LF possesses multiple prospective CoQ10 binding sites, potentially enabling greater loading of CoQ10 on LF compared to BLG, which was predicted to be less capable of binding CoQ10. At pH 7.4, CoQ10-LF NPs showed a burst release between 30 min and 2 h then plateaued at 12 h with 30% of the total drug released over 48 h. However, pure CoQ10-BLG and pure CoQ10 had a significantly lower release rate with less than 15% and 8% cumulative release in 48 h, respectively. Most importantly, both BLG and LF NPs significantly improved CoQ10 permeability compared to the pre-dissolved drug across the Caco-2 monolayer with up to 2.5-fold apparent permeability enhancement for CoQ10-LF-further confirming the utility of this nanoencapsulation approach. Finally, in murine macrophage cells (J774A.1), CoQ10-LF NPs displayed significantly higher anti-ROS properties compared to CoQ10 (predissolved in DMSO) without affecting the cell viability. This study paves the way in improving oral bioavailability of poorly soluble drugs and nutraceuticals using milk-based self-assembled nanoparticles.

PLGA encapsulated γ-cyclodextrin-meropenem inclusion complex formulation for oral delivery

Meropenem (MER) is one of the last resort antibiotics used to treat resistant bacterial infections. However, the clinical effectiveness of MER is hindered due to chemical instability in aqueous solution and gastric pH, and short plasma half-life. Herein, a novel multi-material delivery system based on γ-cyclodextrin (γ-CD) and poly lactic-co-glycolic acid (PLGA) is demonstrated to overcome these challenges. MER showed a saturated solubility of 14 mg/100 mL in liquid CO₂ and later it was loaded into γ-CD to form the inclusion complex using the liquid CO₂ method. The γ-CD and MER inclusion complex (MER-γ-CD) was encapsulated into PLGA by the well-established double emulsion solvent evaporation method. The formation of the inclusion complex was confirmed using FTIR, XRD, DSC, SEM, and ¹H NMR and docking study. Further, MER-γ-CD loaded PLGA nanoparticles (MER-γ-CD NPs) were characterized by SEM, DLS, and FTIR. The drug loading and entrapment efficiency for MER-γ-CD were 21.9 and 92. 2% w/w, respectively. However, drug loading and entrapment efficiency of MER-γ-CD NPs was significantly lower at up to 3.6 and 42.1% w/w, respectively. In vitro release study showed that 23.6 and 27.4% of active (non-degraded drug) and total drug (both degraded and non-degraded drug) were released from MER-γ-CD NPs in 8 h, respectively. The apparent permeability coefficient (Papp) (A to B) for MER, MER-γ-CD, and MER-γ-CD NPs were 2.63 × 10^-6 cm/s, 2.81 × 10^-6 cm/s, and 2.92 × 10^-6 cm/s_, respectively. For secretory transport, the Papp (B to A) were 1.47 × 10^-6 cm/s, 1.53 × 10^-6 cm/s, and 1.58 × 10^-6 cm/s for MER, MER-γ-CD and MER-γ-CD NPs_, respectively. Finally, the MER-γ-CD inclusion complex and MER-γ-CD NPs retained MER's antibacterial activities against Staphylococcus aureus and Pseudomonas aeruginosa. Overall, this work demonstrates the significance of MER-γ-CD NPs to protect MER from gastric pH with controlled drug release, while retaining MER's antibacterial activity.

Discovery of drug-like acetylcholinesterase inhibitors by rapid virtual screening of a 6.9 million compound database

Cholinesterase inhibitors remain the mainstay of Alzheimer's disease treatment, and the search for new inhibitors with better efficacy and side effect profiles is ongoing. Virtual screening (VS) is a powerful technique for searching large compound databases for potential hits. This study used a sequential VS workflow combining ligand-based VS, molecular docking and physicochemical filtering to screen for central nervous system (CNS) drug-like acetylcholinesterase inhibitors (AChEIs) amongst the 6.9 million compounds of the CoCoCo database. Eleven in silico hits were initially selected, resulting in the discovery of an AChEI with a K_i of 3.2 µM. In vitro kinetics and in silico molecular dynamics experiments informed the selection of an additional seven analogues. This led to the discovery of two further AChEIs, with K_i values of 2.9 µM and 0.65 µM. All three compounds exhibited reversible, mixed inhibition of acetylcholinesterase. Importantly, the in silico physicochemical filter facilitated the discovery of CNS drug-like compounds, such that all three inhibitors displayed high in vitro blood-brain barrier model permeability.

Recent Advances in Virtual Screening for Cholinesterase Inhibitors

Alzheimer's disease (AD) is a significant health crisis, and current treatments provide only limited benefits to cognition at the cost of serious side effects. Recently, virtual screening techniques such as ligand-based virtual screening (LBVS) and structure-based virtual screening (SBVS) have emerged as powerful drug discovery tools for identifying potential ligands of a biological target from a large database of chemical structures. The cholinesterases are an AD target particularly well suited for drug discovery using virtual screening due to their well-characterized active sites and comprehensive understanding of the structure-activity relationships of existing inhibitors. Over the last 5 years (2015-2020), at least 15 studies have used virtual screening techniques to discover potent new cholinesterase inhibitors. Herein we review how LBVS and SBVS have been applied individually or in tandem to discover novel acetylcholinesterase and butyrylcholinesterase inhibitors for AD, and highlight the need to confirm in vitro activity of screening compounds.

pH - Responsive colloidal carriers assembled from β-lactoglobulin and Epsilon poly-L-lysine for oral drug delivery

Site specific oral delivery of many biopharmaceutical classification system (BCS) class II and IV drugs is challenging due to their poor solubility, low permeability and degradation in the gastrointestinal tract. Whilst colloidal carriers have been used to improve the bioavailability of such drugs, most nanocarriers based drug delivery systems suffer from multiple disadvantages, including low encapsulation efficiency (liposomes, polymeric nanoparticles), complex synthesis methods (silica, silicon-based materials) and poorly understood biodegradability (inorganic nanoparticles). Herein, a novel pH responsive nanocolloids were self-assembled using natural compounds such as bovine β-lactoglobulin (BLG) and succinylated β-lactoglobulin (succ. BLG) cross-linked with epsilon poly l-lysine (BCEP and BCP), and found to possess high loading capacity, high aqueous solubility and site-specific oral delivery of a poorly soluble nutraceutical (curcumin), improving its physicochemical properties and biological activity in-vitro and ex-vivo. Our optimized synthesis formed colloids of around 200 nm which were capable of encapsulating curcumin with ~100% encapsulation efficiency and ~10% w/w drug loading. By forming nanocomplexes of curcumin with BLG and succ. BLG, the aqueous solubility of curcumin was markedly increased by ~160-fold and ~86-fold, respectively. Encapsulation with BLG increased the solubility, whereas succ. BLG prevent release of encapsulated curcumin when subjected to gastric fluids as it is resistant to breakdown on exposure to pepsin at acidic pH. In conditions mimicking the small intestine, Succ. BLG was more soluble resulting in sustained release of the encapsulated drug at pH 7.4. Additionally, crosslinking succ. BLG with E-PLL significantly enhanced curcumin's permeability in an in-vitro Caco-2 cell monolayer model compared to curcumin solution (dissolved in 1% DMSO), or non-crosslinked BLG/succ. and BLG. In a mouse-derived intestinal epithelial 3D organoid culture stimulated with IL-1β, BLG-CUR and crosslinked BCEP nanoparticles reduced the production of inflammatory cytokines and chemokines such as Tnfα and Cxcl10 more than curcumin solution or suspension while these nanoparticles were non-toxic to organoids. Overall this work demonstrates the promise of nutraceutical-based hybrid self-assembled colloidal system to protect hydrophobic drugs from harsh gastrointestinal conditions and improve their solubility, dissolution, permeability and biological activity.

Rapid discovery of a selective butyrylcholinesterase inhibitor using structure-based virtual screening

Acetylcholinesterase inhibitors are the mainstay of Alzheimer's disease treatments, despite having only short-term symptomatic benefits and severe side effects. Selective butyrylcholinesterase inhibitors (BuChEIs) may be more effective treatments in late-stage Alzheimer's disease with fewer side effects. Virtual screening is a powerful tool for identifying potential inhibitors in large digital compound databases. This study used structure-based virtual screening combined with physicochemical filtering to screen the InterBioScreen and Maybridge databases for novel selective BuChEIs. The workflow rapidly identified 22 potential hits in silico, resulting in the discovery of a human BuChEI with low-micromolar potency in vitro (IC₅₀ 2.4 µM) and high selectivity for butyrylcholinesterase over acetylcholinesterase. The compound was a rapidly reversible BuChEI with mixed-model in vitro inhibition kinetics. The binding interactions were investigated using in silico molecular dynamics and by developing structure-activity relationships using nine analogues. The compound also displayed high permeability in an in vitro model of the blood-brain barrier.

Oral Delivery of β-Lactoglobulin-Nanosphere-Encapsulated Resveratrol Alleviates Inflammation in Winnie Mice with Spontaneous Ulcerative Colitis

Resveratrol (RES) is a nutraceutical with promising anti-inflammatory properties for the treatment of inflammatory bowel diseases (IBD). However, the clinical effectiveness of resveratrol as an oral anti-inflammatory agent is hindered by its extremely poor solubility and poor stability. In this study, we encapsulated resveratrol in β-lactoglobulin (BLG) nanospheres and systematically analyzed their formulation parameters in vitro followed by a thorough in vivo anti-inflammatory testing in a highly specialized spontaneous murine UC model (Winnie mice model). Complexation of resveratrol with BLG increased the aqueous solubility of resveratrol by ≈1.7 times with 10% w/w loading. Additionally, the in vitro dissolution of resveratrol from the particles was found to be higher compared to resveratrol alone, resulting in >90% resveratrol dissolution in ∼8 h. The anti-inflammatory activity of resveratrol was examined for the first time in Winnie mice, a mouse model that closely represents the clinical signs of IBD. At a 50 mg/kg oral dose for 2 weeks, BLG-RES significantly improved both % body weight and disease activity index (DAI), compared to free resveratrol in Winnie mice. Importantly, histological evaluations revealed a similar trend with striking improvement in the pathology of the colon via an increase in goblet cell numbers and recovery of colonic epithelium. BLG-RES significantly increased the expression level of cytokine interleukin-10 (Il10), which confirms the reduction in inflammation potentially because of the increased dissolution and stability of resveratrol by complexation with BLG. This comprehensive study demonstrates the effectiveness of biocompatible nanomaterials such as BLG in oral delivery of poorly soluble anti-inflammatory molecules such as resveratrol in the treatment of IBD.

A new selective pharmacological enhancer of the Orai1 Ca2+ channel reveals roles for Orai1 in smooth and skeletal muscle functions

Store operated calcium (Ca²⁺) entry is an important homeostatic mechanism in cells, whereby the release of Ca²⁺ from intracellular endoplasmic reticulum stores triggers the activation of a Ca²⁺ influx pathway. Mediated by Orai1, this Ca²⁺ influx has specific and essential roles in biological processes as diverse as lactation to immunity. Although pharmacological inhibitors of this Ca²⁺ influx mechanism have helped to define the role of store operated Ca²⁺ entry in many cellular events, the lack of isoform specific modulators and activators of Orai1 has limited our full understanding of these processes. Here we report the identification and synthesis of an Orai1 activity enhancer that concurrently potentiated Orai1 Ca²⁺ -dependent inactivation (CDI). This unique enhancer of Orai1 had only a modest effect on Orai3 with weak inhibitory effects at high concentrations in intact MCF-7 breast cancer cells. The Orai1 enhancer heightened vascular smooth muscle cell migration induced by platelet-derived growth factor and the unique store operated Ca²⁺ entry pathway present in skeletal muscle cells. These studies show that IA65 is an exemplar for the translation and development of Orai isoform selective agents. The ability of IA65 to activate CDI demonstrates that agents can be developed that can enhance Orai1-mediated Ca²⁺ influx but avoid the cytotoxicity associated with sustained Orai1 activation. IA65 and/or future analogues with similar Orai1 and CDI activating properties could be fine tuners of physiological processes important in specific disease states, such as cellular migration and immune cell function.

Smad linker region phosphorylation is a signalling pathway in its own right and not only a modulator of canonical TGF-β signalling

Transforming growth factor (TGF)-β signalling pathways are intensively investigated because of their diverse association with physiological and pathophysiological states. Smad transcription factors are the key mediators of TGF-β signalling. Smads can be directly phosphorylated in the carboxy terminal by the TGF-β receptor or in the linker region via multiple intermediate serine/threonine kinases. Growth factors in addition to hormones and TGF-β can activate many of the same kinases which can phosphorylate the Smad linker region. Historically, Smad linker region phosphorylation was shown to prevent nuclear translocation of Smads and inhibit TGF-β signalling pathways; however, it was subsequently shown that Smad linker region phosphorylation can be a driver of gene expression. This review will cover the signalling pathways of Smad linker region phosphorylation that drive the expression of genes involved in pathology and pathophysiology. The role of Smad signalling in cell biology is expanding rapidly beyond its role in TGF-β signalling and many signalling paradigms need to be re-evaluated in terms of Smad involvement.

Rationally Designed Dendritic Silica Nanoparticles for Oral Delivery of Exenatide

Type 2 diabetes makes up approximately 85% of all diabetic cases and it is linked to approximately one-third of all hospitalisations. Newer therapies with long-acting biologics such as glucagon-like peptide-1 (GLP-1) analogues have been promising in managing the disease, but they cannot reverse the pathology of the disease. Additionally, their parenteral administration is often associated with high healthcare costs, risk of infections, and poor patient adherence associated with phobia of needles. Oral delivery of these compounds would significantly improve patient compliance; however, poor enzymatic stability and low permeability across the gastrointestinal tract makes this task challenging. In the present work, large pore dendritic silica nanoparticles (DSNPs) with a pore size of ~10 nm were prepared, functionalized, and optimized in order to achieve high peptide loading and improve intestinal permeation of exenatide, a GLP-1 analogue. Compared to the loading capacity of the most popular, Mobil Composition of Matter No. 41 (MCM-41) with small pores, DSNPs showed significantly high loading owing to their large and dendritic pore structure. Among the tested DSNPs, pristine and phosphonate-modified DSNPs (PDSNPs) displayed remarkable loading of 40 and 35% w/w, respectively. Furthermore, particles successfully coated with positively charged chitosan reduced the burst release of exenatide at both pH 1.2 and 6.8. Compared with free exenatide, both chitosan-coated and uncoated PDSNPs enhanced exenatide transport through the Caco-2 monolayer by 1.7 fold. Interestingly, when a triple co-culture model of intestinal permeation was used, chitosan-coated PDSNPs performed better compared to both PDSNPs and free exenatide, which corroborated our hypothesis behind using chitosan to interact with mucus and improve permeation. These results indicate the emerging role of large pore silica nanoparticles as promising platforms for oral delivery of biologics such as exenatide.

A brain-permeable inhibitor of the neurodegenerative disease target kynurenine 3-monooxygenase prevents accumulation of neurotoxic metabolites

Dysregulation of the kynurenine pathway (KP) leads to imbalances in neuroactive metabolites associated with the pathogenesis of several neurodegenerative disorders, including Huntington's disease (HD). Inhibition of the enzyme kynurenine 3-monooxygenase (KMO) in the KP normalises these metabolic imbalances and ameliorates neurodegeneration and related phenotypes in several neurodegenerative disease models. KMO is thus a promising candidate drug target for these disorders, but known inhibitors are not brain permeable. Here, 19 new KMO inhibitors have been identified. One of these (1) is neuroprotective in a Drosophila HD model but is minimally brain penetrant in mice. The prodrug variant (1b) crosses the blood-brain barrier, releases 1 in the brain, thereby lowering levels of 3-hydroxykynurenine, a toxic KP metabolite linked to neurodegeneration. Prodrug 1b will advance development of targeted therapies against multiple neurodegenerative and neuroinflammatory diseases in which KP likely plays a role, including HD, Alzheimer's disease, and Parkinson's disease.

Brain Delivery of Thyrotropin-Releasing Hormone via a Novel Prodrug Approach

Using thyrotropin-releasing hormone (TRH) as a model, we explored whether synergistic combination of lipoamino acid(s) and a linker cleaved by prolyl oligopeptidase (POP) can be used as a promoiety for prodrug design for the preferential brain delivery of the peptide. A representative prodrug based on this design principle was synthesized, and its membrane affinity and in vitro metabolic stability, with or without the presence of a POP inhibitor, were studied. The in vivo formation of TRH from the prodrug construct was probed by utilizing the antidepressant effect of the peptide, as well as its ability to increase acetylcholine (ACh) synthesis and release. We found that the prototype prodrug showed excellent membrane affinity and greatly increased metabolic stability in mouse blood and brain homogenate compared to the parent peptide, yet a POP inhibitor completely prevented prodrug metabolism in brain homogenate. In vivo, administration of the prodrug triggered antidepressant-like effect, and microdialysis sampling showed greatly increased ACh release that was also antagonized upon a POP inhibitor treatment. Altogether, the obtained promising exploratory data warrant further investigations on the utility of the prodrug approach introduced here for brain-enhanced delivery of small peptides with neurotherapeutic potential.

Structure-Activity Relationships of GAG Mimetic-Functionalized Mesoporous Silica Nanoparticles and Evaluation of Acyclovir-Loaded Antiviral Nanoparticles with Dual Mechanisms of Action

Mesoporous silica nanoparticles (MSNs) are drug delivery agents that are able to incorporate drugs within their pores. Furthermore, MSNs can be functionalized by attachment of bioactive ligands on their surface to enhance their activity, and nanoparticles modified with glycosaminoglycan (GAG) mimetics inhibit the entry of herpes simplex virus (HSV) into cells. In this study, structure-activity relationships of GAGs attached to MSNs were investigated in relation to HSV-1 and HSV-2, and acyclovir was loaded into the pores of MSNs. The sulfonate group was demonstrated to be essential for antiviral activity, which was enhanced by incorporating a benzene group within the ligand. Loading acyclovir into GAG mimetic-functionalized MSNs reduced the viral infection, resulting in nanoparticles that simultaneously target two distinct viral pathways, namely, inhibition of viral entry and inhibition of DNA replication.

Multifunctional Analogs of Kynurenic Acid for the Treatment of Alzheimer's Disease: Synthesis, Pharmacology, and Molecular Modeling Studies

We report the synthesis and pharmacological investigation of analogs of the endogenous molecule kynurenic acid (KYNA) as multifunctional agents for the treatment of Alzheimer's disease (AD). Synthesized KYNA analogs were tested for their N-methyl-d-aspartate (NMDA) receptor binding, mGluR5 binding and function, acetylcholinesterase (AChE) inhibition, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, interference with the amyloid β peptide (Aβ) fibrillation process, and protection against Aβ-induced toxicity in transgenic Caenorhabditis elegans strain GMC101 expressing full-length Aβ₄₂. Molecular modeling studies were also performed to predict the binding modes of most active compounds with NMDAR, mGluR5, and Aβ₄₂. Among the synthesized analogs, 3c, 5b, and 5c emerged as multifunctional compounds that act via multiple anti-AD mechanisms including AChE inhibition, free radical scavenging, NMDA receptor binding, mGluR5 binding, inhibition of Aβ₄₂ fibril formation, and disassembly of preformed Aβ₄₂ fibrils. Interestingly, 5c showed protection against Aβ₄₂-induced toxicity in transgenic C. elegans strain GMC101. Moreover, 5b and 5c displayed high permeability in an MDR1-MDCKII cell-based model of the blood-brain barrier (BBB). Compound 3b emerged with specific activity as a micromolar AChE inhibitor, however it had low permeability in the BBB model. This study highlights the opportunities that exist to develop analogs of endogenous molecules from the kynurenine pathway for therapeutic uses.

Effect of the Biphenyl Neolignan Honokiol on Aβ42-Induced Toxicity in Caenorhabditis elegans, Aβ42 Fibrillation, Cholinesterase Activity, DPPH Radicals, and Iron(II) Chelation

The biphenyl neolignan honokiol is a neuroprotectant which has been proposed as a treatment for central nervous system disorders such as Alzheimer's disease (AD). The death of cholinergic neurons in AD is attributed to multiple factors, including accumulation and fibrillation of amyloid beta peptide (Aβ) within the brain; metal ion toxicity; and oxidative stress. In this study, we used a transgenic Caenorhabditis elegans model expressing full length Aβ₄₂ as a convenient in vivo system for examining the effect of honokiol against Aβ-induced toxicity. Furthermore, honokiol was evaluated for its ability to inhibit Aβ₄₂ oligomerization and fibrillation; inhibit acetylcholinesterase and butyrylcholinesterase; scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals; and chelate iron(II). Honokiol displayed activity similar to that of resveratrol and (-)-epigallocatechin gallate (EGCG) in delaying Aβ₄₂-induced paralysis in C. elegans, and it exhibited moderate-to-weak ability to inhibit Aβ₄₂ on-pathway aggregation, inhibit cholinesterases, scavenge DPPH radicals, and chelate iron(II). Moreover, honokiol was found to be chemically stable relative to EGCG, which was highly unstable. Together with its good drug-likeness and brain availability, these results suggest that honokiol may be amenable to drug development and that the synthesis of honokiol analogues to optimize these properties should be considered.

Bifunctional Succinylated ε-Polylysine-Coated Mesoporous Silica Nanoparticles for pH-Responsive and Intracellular Drug Delivery Targeting the Colon

Conventional oral drug formulations for colonic diseases require the administration of high doses of drug to achieve effective drug concentrations at the target site. However, this exposes patients to serious systemic toxicity in order to achieve efficacy. To overcome this problem, an oral drug delivery system was developed by loading a large amount (ca. 34% w/w) of prednisolone into 3-aminopropyl-functionalized mesoporous silica nanoparticles (MCM-NH₂) and targeting prednisolone release to the colon by coating the nanoparticle with succinylated ε-polylysine (SPL). We demonstrate for the first time the pH-responsive ability of SPL as a "nanogate" to selectively release prednisolone in the pH conditions of the colon (pH 5.5-7.4) but not in the more acidic conditions of the stomach (pH 1.9) or small intestine (pH 5.0). In addition to targeting drug delivery to the colon, we explored whether the nanoparticles could deliver cargo intracellularly to immune cells (RAW 264.7 macrophages) and intestinal epithelial cells (LS 174T and Caco-2 adenocarcinoma cell lines). To trace uptake, MCM-NH₂ were loaded with a cell membrane-impermeable dye, sulforhodamine B. The SPL-coated nanoparticles were able to deliver the dye intracellularly to RAW 264.7 macrophages and the intestinal epithelial cancer cells, which offers a highly promising and novel drug delivery system for diseases of the colon such as inflammatory bowel disease and colorectal cancer.

GAG mimetic functionalised solid and mesoporous silica nanoparticles as viral entry inhibitors of herpes simplex type 1 and type 2 viruses

A glycosaminoglycan mimetic was attached to the surface of solid and mesoporous silica nanoparticles to create novel antiviral agents against herpes simplex type 1 and type 2 viruses. The nanoparticles act as viral entry inhibitors that appear to block viral attachment and penetration into susceptible cells.

Discovery and Structure-Activity Relationships of a Highly Selective Butyrylcholinesterase Inhibitor by Structure-Based Virtual Screening

Structure-based virtual screening of two libraries containing 567 981 molecules was used to discover novel, selective BuChE inhibitors, which are potentially superior symptomatic treatments in late-stage Alzheimer's disease. Compound 16 was identified as a highly selective submicromolar inhibitor of BuChE (huBuChE IC50 = 0.443 μM) with high permeability in the PAMPA-BBB model. The X-ray crystal structure of huBuChE in complex with 16 revealed the atomic-level interactions and offers opportunities for further development of the series.

Cyclodextrin-crosslinked poly(acrylic acid): adhesion and controlled release of diflunisal and fluconazole from solid dosage forms

The controlled release of diflunisal and fluconazole from tablets made of novel polymers, poly(acrylic acid) (PAA) crosslinked with either β-cyclodextrin (βCD) or hydroxypropyl-βCD (HPβCD), was investigated and Carbopol 934P (Carbopol) was used as a highly crosslinked PAA for comparison. Diflunisal strongly associates with βCD-PAA and HPβCD-PAA polymers (Ka of 486 and 6,055 M(-1) respectively); thus, it was physically mixed into the conjugates and also precomplexed to identify whether decomplexation has any influence on release kinetics. Fluconazole has poor complexing ability (Ka of 34 M(-1) with HPβCD-PAA); thus, it was only tested as a physical mixture. Swelling and adhesion studies were conducted on all tablet combinations and adhesivity of the CD-PAA polymer tablets was maintained. Diflunisal release was much slower from HPβCD-PAA tablets than from βCD-PAA, suggesting that a higher degree of complexation retards release. The precomplexed diflunisal release was also slower than the physically mixed diflunisal of the corresponding conjugate. The release closely followed zero-order kinetics for HPβCD-PAA, but was more sigmoidal for βCD-PAA and especially Carbopol. Conversely, poorly associating fluconazole released in almost exactly the same way across both polymers and Carbopol, indicating that the release kinetics of poorly associating drugs are not influenced by the presence of cyclodextrins. In view of the varying profiles and release rates shown with diflunisal for the different polymers, the fluconazole data support the concept that adequate complexation can indeed modulate the release kinetics of drugs.

Phytochemical Study of Fagraea spp. Uncovers a New Terpene Alkaloid with Anti-Inflammatory Properties

Phytochemical investigation of the stem bark of F. racemosa JACK ex WALL (Loganiaceae) from East Java, Indonesia, has resulted in the isolation of a new alkaloid fagraeoside along with the iridoid glycoside secologanoside. Fagraeoside may be derived from the condensation of secologanin with L-asparagine, and represents a rare example of a terpene alkaloid in which the amino acid component is non-aromatic. Investigation of three additional species of Fagraea provided known lignans, iridoid or secoiridoid glycosides, and flavanol-6-C-glucosides, thus it is likely that iridoid and secoiridoid glucosides are chemotaxonomic markers for the Fagraea genus. Fagraeoside inhibited the production of prostaglandin E2 in 3T3 murine fibroblasts (IC50 ~5.1 µM), and was not cytotoxic to this cell line or to a P388 murine leukaemia cell line. Selected isolated compounds, including fagraeoside, showed low to moderate activity in anti-acetylcholinesterase screening.

Efficient manual Fmoc solid-phase synthesis of the N-terminal segment of surfactant protein B (SP-B(1-25))

The N-terminal 25 residue segment of human surfactant protein B (SP-B(1-25)) was synthesised in 26% yield by manual Fmoc solid-phase peptide synthesis (Fmoc SPPS) using low-loading Fmoc-Gly-Wang resin. Substantial oxidation of Met(21) occurred during the synthesis, and the addition of Bu(4)NBr to a TFA/water/EDT/TIS cleavage cocktail enabled facile reduction of Met(O)(21)-SP-B(1-25) to SP-B(1-25). The methods described herein are generally applicable to the Fmoc SPPS of difficult sequences containing methionine.

Suramin: clinical uses and structure-activity relationships

Suramin is a polysulfonated polyaromatic symmetrical urea. It is currently used to treat African river blindness and African sleeping sickness. Suramin has also been extensively trialed recently to treat a number of other diseases, including many cancers. Here, we examine its modes of action and discuss its structure-activity relationships.

Caco-2 cell permeability and stability of two d-glucopyranuronamide conjugates of thyrotropin-releasing hormone

Caco-2 cell permeability and stability assays were used as an in vitro model to study the intestinal epithelial transport and stability of two analogues of thyrotropin-releasing hormone (TRH; Pyr-His-Pro-NH2). Peptide 1 (Pyr-His-Pro-D-glucopyranuronamide) was more permeable across the Caco-2 cell monolayer compared with the permeability of the parent TRH peptide (Papp=5.10+/-1.89x10(-6) cm/s c.f. Papp=0.147+/-0.0474x10(-6) cm/s respectively). The permeability of peptide 1 was improved threefold by attaching a 2-aminooctanoic acid moiety to the N-terminus to form peptide 2 (2-aminooctanoic acid-Gln-His-Pro-D-glucopyranuronamide) (Papp=16.3+/-2.47x10(-6) cm/s). The half-life for both peptide 1 and peptide 2 was approximately 20 min in a homogenate of Caco-2 cells compared with the half-life of TRH which is approximately 3 min. It was concluded that the permeability of peptides 1 and 2 was enhanced because of their increased stability, while the higher permeability of peptide 2 compared with peptide 1 may be attributed to its increased lipophilicity which results in enhanced passive diffusion.

Saponins from Quillaja saponaria Molina: Isolation, Characterization and Ability to Form Immuno Stimulatory Complexes (ISCOMs)

ISCOMs have received much attention as vaccine adjuvants due to their immunostimulatory effects. They are colloidal particles typically comprised of phospholipids, cholesterol and Quil A, a crude mixture of saponins extracted from the bark of Quillaja saponaria Molina. We have previously shown that ISCOMs can be prepared by ether injection wherein an ether solution of phospholipids and cholesterol in a mass ratio of 5:2 is injected into a solution of Quil A at a mass ratio of 7 lipids: 3 Quil A. The aim of this study was firstly to isolate and characterise discrete fractions of Quil A and secondly to investigate which of these fractions were able to form ISCOMs by the method of ether injection. Six fractions of Quil A were isolated by semi-preparative reverse phase high performance liquid chromatography (RP-HPLC) and characterised by analytical HPLC, liquid chromatography tandem mass spectrometry (LC-MS) and the qualitative Liebermann-Burchard and Molisch tests for triterpenoids and carbohydrates respectively. ISCOMs were subsequently prepared from the isolated fractions by the method of ether injection and the resulting preparations characterized by photon correlation spectroscopy (PCS) and negative stain transmission electron microscopy (TEM). The molecular weights of the major compounds in the fractions ranged from approximately 1200 to approximately 2300 Da; all fractions tested positive for triterpenoids and saccharides and four of the fractions were identified as QS-7, QS-17, QS-18 and QS-21 by analysis (LC-MS and analytical HPLC). Injection of ether solutions of lipids into aqueous solutions of QS-17, QS-18 or QS-21 all resulted in homogeneous ISCOM dispersions. The combination of lipids and QS-7 by ether injection produced lamellae and liposomes as the prominent structures and a minor amount of ISCOMs. The remaining two hydrophilic, low molecular weight fractions of Quil A did not produce ISCOMs, instead liposomes and helical structures predominated in the samples.

Determination of the Anomeric Configurations of 2,3,4,6-Tetra-O-Acetyl-D-Mannopyranosyl Azide

The structures of 2,3,4,6-tetra-O-acetyl-α-d-mannopyranosyl azide and 2,3,4,6-tetra-O-acetyl-β-d-mannopyranosyl azide were determined using X-ray crystallographic and one-dimensional NOESY techniques.

Polycationic lipophilic-core dendrons as penetration enhancers for the oral administration of low molecular weight heparin

Two polycationic lipophilic-core carbohydrate-based dendrons 2a-b and five polycationic lipophilic-core peptide dendrons 3-6, containing four arginine or lysine terminal residues, were synthesized and then tested in rats as penetration enhancers for the oral delivery of low molecular weight heparin. Better results were obtained with dendrons containing terminal lysine residues than terminal arginine. A significant anti-factor Xa activity was obtained when low molecular weight heparin was coadministered with dendron 5.

Micellar aggregation and membrane partitioning of bile salts, fatty acids, sodium dodecyl sulfate, and sugar-conjugated fatty acids: correlation with hemolytic potency and implications for drug delivery

The co-administration of a drug with a penetration enhancer (PE) is one method by which the membrane permeability of a drug can be improved. To facilitate PE design, it is important that the molecular basis of PE toxicity and efficacy be examined, so we investigated the membrane affinity and micellar aggregation of a series of synthetic liposaccharide PEs and correlated these properties with hemolytic potency. The influence of liposaccharide alkyl chain length (nc) on the system was studied, and comparisons were made with conventional PEs such as bile salts, fatty acids, and surfactants. The liposaccharides were each synthesized in eight steps in good overall yield. Their critical micelle concentrations (CMCs) in phosphate-buffered saline ranged from 0.207 to 20.2 mM, and it was found that increasing nc by 2 afforded a 1 order of magnitude decrease in the CMC. Immobilized artificial membrane (IAM) chromatography was used to determine each PE's affinity for biological membranes, and an increase in nc caused a significant increase in the extent of membrane binding. A study of hemolytic activity revealed that liposaccharides with an nc of < or = 12 are the most likely to be biocompatible. The CMC values for all PEs showed a negative correlation with hemolytic potency; however, it was PE monomers, not micelles, that were responsible for the onset of hemolysis. The affinity of all enhancers for the IAM displayed a positive correlation with hemolytic potency, and therefore, IAM chromatography can be used to predict PE hemolytic activity. It was concluded that the biocompatibility of liposaccharides can be modulated by minor alterations in nc.

Gastrointestinal Absorption of Heparin by Lipidization or Coadministration with Penetration Enhancers

A review with 93 references. Heparins are high molecular weight, hydrophilic polyanions, which are unstable under acidic conditions; and therefore they exhibit poor oral bioavailability. Consequently they must be administered via the parenteral route which is expensive, inconvenient, and limits use by outpatients. The development of an oral form of heparin is warranted. This review examined the literature, mostly published between January 2000 and January 2005, pertaining to the gastrointestinal absorption of heparin by lipidization or coadministration with penetration enhancers. A lipidization strategy that was examined involved conjugation of low molecular weight heparin with deoxycholic acid. The majority of studies examined the ability of different formulations, typically utilizing penetration enhancers, to improve heparin bioavailability. The penetration enhancers used included fatty acids, Labrasol, Gelucire 44/14, polycationic lipophilic-core dendrons, saponins, mono-N-carboxymethyl chitosan, Carbopol 934P, a combination of thiolated polycarbophil and glutathione, polymeric nanoparticles, polymeric microparticles, sodium N-[8-(2-hydroxybenzoyl) amino]caprylate (SNAC), and sodium N-[10-(2-hydroxybenzoyl)amino]decanoate (SNAD). The variety of models used and doses of heparin/penetration enhancers applied, however, made it difficult to compare the results between studies. Nevertheless, all of the reviewed drug delivery systems showed therapeutic value and confirmation of the promising results obtained from animal studies, by progression to clinical trials, is necessary. Overall, progress has been made in the quest for an oral heparin formulation.

Design, Synthesis, and Evaluation of a Liposaccharide Drug Delivery Agent: Application to the Gastrointestinal Absorption of Gentamicin

The design, synthesis, and evaluation of a liposaccharide (11) for use as an agent to enhance the gastrointestinal absorption of charged, hydrophilic drugs with poor membrane permeability is reported. 11 was designed to possess both surfactant and ion-pairing properties and was conveniently synthesized from d-glucuronic acid (2) and N-Boc-lipoamino acid (5) precursors in eight steps in good yield. Isothermal titration microcalorimetry was used to determine the critical micelle concentration of 11 (in PBS) to be 2.09 +/- 0.01 mM with an enthalpy of demicellization of 4.91 +/- 0.11 kJ/mol. The ability of 11 to enhance the gastrointestinal absorption of the aminoglycoside antibiotic gentamicin (1), a hydrophilic polycation with negligible oral bioavailability, was assessed in vivo using rats. Rats dosed orally with a mixture of 11 (100 mg/kg) and 1 (60 mg/kg) had a statistically significant (P < or = 0.034) increase in Cmax, AUC120, and percent absolute bioavailability (F) compared to control 1 (60 mg/kg) alone. The highest bioavailability (F = 9.1 +/- 2.0%) was achieved by dosing with the mixture 11 (100 mg/kg) and 1 (15 mg/kg). This represents a 6-fold increase in bioavailability compared to the control (F = 1.4 +/- 0.3%). These results suggest that the molar ratio of 1:11 may be critical in optimizing the delivery system, a finding ascribed in part to the ion-pairing properties of 11. The effect of 11 on the gastrointestinal mucosa was assessed using light microscopy to examine tissue samples from rats used in the pharmacokinetic study. No morphological changes were found in either the esophagi or duodena of the rats examined. One rat dosed with 11 (100 mg/kg) and 1 (60 mg/kg) exhibited slight gastric erosion, which could be attributed to 11.

Determination of transport in the Caco-2 cell assay of compounds varying in lipophilicity using LC-MS: enhanced transport of Leu-enkephalin analogues

PURPOSE

To synthesize a number of analogues of Leu-enkephalin with different lipophilicities and to develop an LC-MS method for determining the Caco-2 cell permeability values of these compounds.

METHODS

A number of sugar and sugar plus lipoamino acid analogues of Leu-enkephalin were synthesized by solid-phase and solution methods. An LC-MS method was developed for analyzing the Caco-2 cell assay samples and validated against the traditional method using radiolabelled compounds.

RESULTS

A sensitive and specific LC-MS assay was developed. Standard curves were linear in the range of 0.025-5 microM. Apparent permeability values determined by LC-MS and liquid scintillation counter were identical, for both a hydrophilic drug, cephalexin and a lipophilic Leu-enkaphalin analogue. Caco-2 permeability values for the analogues of Leu-enkephalin were determined and it was found that attachment of sugar or sugar and lipoamino acid to the Leu-enkephalin peptide resulted in an increase in the apparent permeability values compared to the native peptide, which was not transported across the Caco-2 cell monolayers.

CONCLUSIONS

A rapid, generic LC-MS method for analyzing a range of compounds was developed. Attachment of a sugar or sugar and lipoamino acid to Leu-enkephalin improves the apparent permeability across Caco-2 cell monolayers.