Allan B. Gamble

Aryl Nitro Reduction with Iron Powder or Stannous Chloride under Ultrasonic Irradiation

Abstract The selective reduction of aryl nitro compounds in the presence of sensitive functionalities, including halide, carbonyl, nitrile, and ester substituents, under ultrasonic irradiation at 35 kHz is reported in yields of 39–98%. Iron powder proved superior to stannous chloride with high tolerance of sensitive functional groups and high yields of the desired aryl amines in relatively short reaction times. Simple experimental procedure and purification also make the iron reduction of aryl nitro compounds advantageous over other methods of reduction.

Prohormone-substrate peptide sequence recognition by peptidylglycine α-amidating monooxygenase and its reflection in increased glycolate inhibitor potency.

The interactions of nineteen peptide substrates and fifteen analogous peptidomimetic glycolate inhibitors with human peptidylglycine α-amidating monooxygenase (PAM) have been investigated. The substrates and inhibitors are the prohormones of calcitonin and oxytocin and their analogues. PAM both secreted into the medium by and extracted from DMS53 small lung carcinoma cells has been studied. The results show that recognition of the prooxytocin and procalcitonin peptide sequences by the enzyme extends more than four and five amino acid residues, respectively, from their C-termini. This substrate sequence recognition is mirrored by increased inhibitor potency with increased peptide length in the glycolate peptidomimetics. Substitution of the C-terminal penultimate glycine and proline residues of prooxytocin and procalcitonin and their analogues with phenylalanine increases the enzyme binding affinity. However, this changes the binding mode from one that depends on peptide sequence recognition to another primarily determined by the phenylalanine moiety, for both the substrates and analogous glycolate inhibitors.

Development and assessment of novel all-in-one parenteral formulations with integrated anticoagulant properties for the concomitant delivery of 5-fluorouracil and calcium folinate

5-Fluorouracil in combination with its biomodulator folinic acid maintains a pivotal position in current anticancer treatment regimens. However, limitations in clinical management persist with the administration of these drugs. These limitations are associated with the use of a high pH to maintain 5-fluorouracil in solution, resulting in high rates of phlebitis and catheter blockages. Herein, we describe and compare initial studies on novel all-in-one formulations of 5-fluorouracil and folinic acid incorporating either sulfated or hydroxypropyl &bgr;-cyclodextrins at physiological pH that potentially address these issues. All formulations markedly improved the stability of supersaturated solutions of 5-fluorouracil in the presence of folinic acid. In-vitro evaluation of the PC-3, HCT-116, MDA-MB-231, PC-14, and COLO-201 human carcinoma cell lines showed that all formulations exhibited equivalent or better cytotoxicity compared with cells exposed to 5-fluorouracil and folinic acid. Thus, these cyclodextrins do not compromise the cytotoxicity of 5-fluorouracil. Preliminary in-vivo dose tolerance profiles of the formulations were also equivalent to 5-fluorouracil and folinic acid administered separately. Furthermore, given the association between thrombosis and cancer, the potentially beneficial anticoagulant activity of the sulfated cyclodextrin-based formulations was also confirmed in vitro. Extended activated partial thromboplastin times and prothrombin times were observed for the sulfated cyclodextrins in human plasma both as individual compounds and as components of the formulations. In conclusion, these novel all-in-one formulations maintain the in-vitro potency while overcoming the accepted incompatibility of 5-fluorouracil and folinic acid, and represent improved injectable forms of 5-fluorouracil that may reduce phlebitis, catheter blockages, and thromboembolic events.

Stability, Kinetic, and Mechanistic Investigation of 1,8-Self-Immolative Cinnamyl Ether Spacers for Controlled Release of Phenols and Generation of Resonance and Inductively Stabilized Methides

Three cinnamyl ether spacers (non-methyl, α-methyl, and γ-methyl) for caging of phenols have been synthesized and are physiologically stable. When triggered, the γ-methyl spacer releases phenols (pKa 7.8 and 9.8) with a t1/2 < 30 s and <2 min in aqueous and aqueous-organic solvent, respectively. The α-methyl spacer releases a phenol (pKa 7.8) with a t1/2 = 27 and 54 min. For the γ-methyl spacer, the results suggest the presence of a resonance and inductively stabilized aza-cinnamyl methide.

Proteases and protease inhibitors in infectious diseases.

There are numerous proteases of pathogenic organisms that are currently targeted for therapeutic intervention along with many that are seen as potential drug targets. This review discusses the chemical and biological makeup of some key druggable proteases expressed by the five major classes of disease causing agents, namely bacteria, viruses, fungi, eukaryotes, and prions. While a few of these enzymes including HIV protease and HCV NS3‐4A protease have been targeted to a clinically useful level, a number are yet to yield any clinical outcomes in terms of antimicrobial therapy. A significant aspect of this review discusses the chemical and pharmacological characteristics of inhibitors of the various proteases discussed. A total of 25 inhibitors have been considered potent and safe enough to be trialed in humans and are at different levels of clinical application. We assess the mechanism of action and clinical performance of the protease inhibitors against infectious agents with their developmental strategies and look to the next frontiers in the use of protease inhibitors as anti‐infective agents.

Hypoxia Responsive Drug Delivery Systems in Tumor Therapy.

Hypoxia is a common characteristic of solid tumors. It is mainly determined by low levels of oxygen resulting from imperfect vascular networks supplying most tumors. In an attempt to improve the present chemotherapeutic treatment and reduce associated side effects, several prodrug strategies have been introduced to achieve hypoxia-specific delivery of cytotoxic anticancer agents. With the advances in nanotechnology, novel delivery systems activated by the consequent outcomes of hypoxia have been developed. However, developing hypoxia responsive drug delivery systems (which only depend on low oxygen levels) is currently naïve. This review discusses four main hypoxia responsive delivery systems: polymeric based drug delivery systems, oxygen delivery systems combined with radiotherapy and chemotherapy, anaerobic bacteria which are used for delivery of genes to express anticancer proteins such as tumor necrosis alpha (TNF-α) and hypoxia-inducible transcription factors 1 alpha (HIF1α) responsive gene delivery systems.

Honey reduces the metastatic characteristics of prostate cancer cell lines by promoting a loss of adhesion

Honey has been shown to have a range of therapeutic effects in humans, with anti-inflammatory and anti-bacterial effects among those previously characterised. Here, we examine the possibility of New Zealand thyme, manuka and honeydew honeys, and their major sugar and phenolic components, reducing the development of metastatic cancer. Their activity was examined in vitro, in PC3 and DU145 prostate cancer cell lines, through measuring the compounds’ effects on the metastatic characteristics of migration, invasion and adhesion. First, the phenolic compounds gallic acid, caffeic acid, quercetin, kaempferol and chrysin were quantified in the honeys using high performance liquid chromatography, and found in nanomolar concentrations. In a Boyden chamber-based migration assay, non-toxic concentrations of thyme and honeydew honeys reduced cell migration by 20%, and all phenolic compounds except caffeic acid also lowered migration, although a mixture of only the sugars found in honey had no effect. All of the honeys, phenolics and the sugar-only mixture reduced invasive movement of cells through extracellular matrix by up to 75%. Most notably, each of the three honeys and the sugar-only mixture reduced cell adhesion to collagen I by 90%. With the exception of quercetin, phenolic compounds did not reduce adhesion. Therefore, honey and its sugar and phenolic components can lower the metastatic properties of cancer cells, and may do this by preventing effective cell adhesion to the extracellular matrix. The sugars and phenol compounds of honey are much more effective in combination than individually.

Poloxamer 407-chitosan grafted thermoresponsive hydrogels achieve synchronous and sustained release of antigen and adjuvant from single-shot vaccines

Sustained‐release vaccine delivery systems may enhance the immunogenicity of subunit vaccines and reduce the need for multiple vaccinations. The aim of this study was to develop a thermoresponsive hydrogel using poloxamer 407‐chitosan (CP) grafted copolymer as a delivery system for single‐shot sustained‐release vaccines. The CP copolymer was synthesized using 1‐ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide and N‐hydroxysuccinimide chemistry. The CP copolymer was a free flowing solution at ambient temperature and transformed rapidly into a gel at body temperature. The hydrogels were loaded with vaccine antigen and adjuvants or the vaccine components were encapsulated in poly (lactic‐co‐glycolic acid) nanoparticles in order to ensure synchronous release. The CP hydrogels were stable for up to 18 days in vitro. Release of both nanoparticles and the individual components was complete, with release of the individual components being modulated by incorporation into nanoparticles. In vivo, a single dose of CP hydrogel vaccine induced strong, long lasting, cellular and humoral responses that could protect against the development of tumors in a murine melanoma model.

Alkene-azide 1,3-dipolar cycloaddition as a trigger for ultrashort peptide hydrogel dissolution

An alkene-azide 1,3-dipolar cycloaddition between trans-cyclooctene (TCO) and an azide-capped hydrogel that promotes rapid gel dissolution is reported. Using an ultrashort aryl azide-capped peptide hydrogel (PhePhe), we have demonstrated proof-of-concept where upon reaction with TCO, the hydrogel undergoes a gel-sol transition via 1,2,3-triazoline degradation and 1,6-self-immolation of the generated aniline. The potential application of this as a general trigger in sustained drug delivery is demonstrated through release of encapsulated cargo (doxorubicin). Administration of TCO resulted in 87 % of the cargo being released in 10 h, compared to 13-14 % in the control gels. This is the first example of a potential bioorthogonal-triggered hydrogel dissolution using a traditional click-type reaction. This type of stimulus could be extended to other aryl azide-capped hydrogels.

Mechanistic Evaluation of Bioorthogonal Decaging with trans-Cyclooctene: The Effect of Fluorine Substituents on Aryl Azide Reactivity and Decaging from the 1,2,3-Triazoline

Bioorthogonal prodrug activation/decaging strategies need to be selective, rapid and release the drug from the masking group upon activation. The rates of the 1,3-dipolar cycloaddition between a trans-cyclooctene (TCO) and a series of fluorine-substituted azido-PABC self-immolative spacers caging two model drugs, and subsequent release from the 1,2,3-triazoline are reported. As the number of fluorine substituents on the PABC linker increases from one to four, the rate of cycloaddition increases by almost one order of magnitude. Using a combination of fluorescence, 1H/19F NMR, and computational experiments, we have been able to determine how substituents on the PABC ring can influence the degradation rates and also the product distribution of the 1,2,3-triazoline. We have also been able to determine how these substituents influence the rate of imine hydrolysis and 1,6-self-immolation decaging rates of the generated anilines. The NMR and computational studies demonstrate that fluorine substituents on the aromatic ring lower the transition state energy required for converting the triazoline to the imine or aziridine intermediates via extrusion of diatomic nitrogen, and that in the case of a tetrafluoro substituted aromatic ring, it is the imine hydrolysis and 1,6-self-immolation that is rate-limiting. This knowledge further enhances the understanding of factors which influence the stability of triazolines, and enables potential applications of fluorinated aromatics, in particular, perfluorinated aromatics, in synthetic chemistry and sustained-release drug delivery systems.