Eric Lattmann

Trigger release liposome systems: local and remote controlled delivery?

Target-specific delivery has become an integral area of research in order to increase bioavailability and reduce the toxic effects of drugs. As a drug-delivery option, trigger-release liposomes offer sophisticated targeting and greater control-release capabilities. These are broadly divided into two categories; those that utilise the local environment of the target site where there may be an upregulation in certain enzymes or a change in pH and those liposomes that are triggered by an external physical stimulus such as heat, ultrasound or light. These release mechanisms offer a greater degree of control over when and where the drug is released; furthermore, targeting of diseased tissue is enhanced by incorporation of target-specific components such as antibodies. This review aims to show the development of such trigger release liposome systems and the current research in this field.

Microscopy imaging of liposomes: From coverslips to environmental SEM

A plethora of techniques for the imaging of liposomes and other bilayer vesicles are available. However, sample preparation and the technique chosen should be carefully considered in conjunction with the information required. For example, larger vesicles such as multilamellar and giant unilamellar vesicles can be viewed using light microscopy and whilst vesicle confirmation and size prior to additional physical characterisations or more detailed microscopy can be undertaken, the technique is limited in terms of resolution. To consider the options available for visualising liposome-based systems, a wide range of microscopy techniques are described and discussed here: these include light, fluorescence and confocal microscopy and various electron microscopy techniques such as transmission, cryo, freeze fracture and environmental scanning electron microscopy. Their application, advantages and disadvantages are reviewed with regard to their use in analysis of lipid vesicles.

Synthesis and evaluation of 5-arylated 2(5H)-furanones and 2-arylated pyridazin-3(2H)-ones as anti-cancer agents

Bis‐cyclic butenolides, 5‐arylated 2(5H)‐furanones 6a–c, 7a, b and the 3(2H)‐pyridazones 9a–d were prepared by using the aldehyde form of muco halogen acids in electrophilic substitution reactions and in an aldol‐like condensation reaction. The cytotoxicity of these simple and bis‐cyclic butenolides have been evaluated in tissue culture studies on MAC 13 and MAC 16 murine colon cancer cell lines. The butyl furanone 3 displayed the highest cytotoxicity of 3 μM, as one selected example of a series of dichlorinated pseudoesters. The 5‐arylated 2(5H)‐furanones 6 and 7 did not show a structure–activity relationship (SAR) depending on the substitution pattern of the aromatic system. An IC50 (concentration inhibiting growth by 50%) was found within a range of 30–50 and 40–50 μM for the MAC 13 and MAC 16 cell lines, respectively. The pyridazine series 9 showed a maximum in‐vitro activity for the p‐methoxydrivative 9b, having an IC50 of 17 in MAC 13 and 11 μM in MAC 16 cell lines. Selected examples of each series and further novel 2(5H)‐furanones such as the hydrazone 5 and the hydantoin 8 have been screened in‐vivo in mice and the data are presented. For the pyridazines 9a–d, the in‐vitro cytotoxicity correlated with an in‐vivo inhibition of tumour growth. The ring expansion of the 5‐membered 2(5H)‐furanone ring system such as 6a into the 6‐membered 3(2H)‐pyridazone 9b led to an agent with improved antineoplastic properties. On the resistant MAC 16 cell line the pyridazone 9b displayed 52% tumour inhibition in mice at a dose of 50 mg kg−1 compared with 27% for the 5‐FU standard.

Novel anti-bacterials against MRSA: synthesis of focussed combinatorial libraries of tri-substituted 2(5H)-furanones.

Mucobromic and mucochloric acid were used as building blocks for the construction of a chemical combinatorial library of 3,4,5-trisubstituted 2(5H)-furanones. With these 2 butenolide building blocks, and eight alcohols a sublibrary of 16 dihalogenated 5-alkoxy-2(5H)-furanones was prepared. This sublibrary of 5-alkoxylated furanones was reacted with 16 amines generating a full size focussed combinatorial library of 256 individual compounds. This three dimensional combinatorial library of 3-halogen-4-amino-5-alkoxy-2(5H)-furanones was prepared around the benzimida-zolyl furanone lead structure by applying a solution phase combinatorial chemistry concept. Typical representatives of the library were purified and fully characterized and one x-ray structures was recorded, additionally. The 3-bromo-4-benzimizazolyl-5-methoxy-2(5H)furanone, Br-A-l, showed an MIC of 8 microg/ml against the multiresistant Staphylococcus aureus (MRSA).

Cytotoxicity of 3,4‐dihalogenated 2(5H)‐furanones

Mucohalogen acids have been used for the preparation of a variety of 3,4‐dihalogenated 2(5H)‐furanones. In one synthetic step the carbamates 2a‐c and the pseudoanhydrides 4a‐e were prepared using isocyanates and acid anhydrides. A series of 5‐alkoxylated 3,4‐dichloro‐2(5H)‐furanones 5a‐o have been synthesized with a wide range of lipophilicity, using the hydroxy‐form of mucohalogen acids 1a and 1b. The 5‐allyl‐3,4‐dichloro‐2(5H)‐furanone 5f was derived into the dihydro‐isoxazol 6 and the oxirane 7. The methyl ester 5a was converted with ammonia into the tetramic acid chloride 11. The pseudo acid chloride 3 was reacted further into the bis aziridine 8. Reduction of the mucochloric acid 1a furnished the trichlorofuranone 3. The cytotoxicity of these simple and bis‐cyclic butenolides have been evaluated in tissue culture on MAC13 and MAC16 cancer cell lines using the MTT cytotoxicity assay. The ester 5g, the acetate 4b and the carbamate 2b displayed a cytotoxicity in the low micromolar range. Further, an IC50 (50% inhibitory concentration) of 50 nM and 30 nM was determined for the epoxide 7 and the aziridine 8.

Benzodiazepine recognition site ligands and GABAA receptors

The benzodiazepine recognition site of the mammalian brain GABAA receptor (responsible for the majority of neuronal inhibition in the mammalian CNS) has taken its name from the chemical structures that we now know to interact specifically with this allosteric site. These benzodiazepines were introduced into clinical practice in the 1960s and proved to be enormously successful in the treatment of anxiety and sleep disorders. The pharmacological spectrum of activity for benzodiazepine site ligands is much wider. While it was recognised early that benzodiazepines were efficacious anticonvulsants and muscle relaxants, advances in our understanding of their mechanisms of action over the intervening years have revealed even greater potential for their clinical use. Early attempts to decrease the sedative potential of the benzodiazepine ligands, without losing their anxiolytic activity, proved frustratingly difficult. Meanwhile, the exciting potential of partial inverse agonists at this site to improve performan...

Antipyretic, analgesic and anti-oxidative activities of Aquilaria crassna leaves extract in rodents

In Thailand, the leaves of Aquilaria crassna have been used traditionally for the treatments of various disorders, but without any scientific analysis. In this study, the antipyretic, analgesic, anti-inflammatory and anti-oxidative properties of A. crassna leaves extract were investigated at a wide dose range in rodents. Experimental animals were treated orally with an aqueous extract of Aquilaria crassna leaves (ACE). They were tested for antipyretic (Bakers yeast-induced fever in rats), analgesic (hot plate test in mice) and anti-inflammatory (carrageenan-induced paw edema in rats) activities. An anti-oxidative effect of ACE was evaluated by using the DPPH anti-oxidant assay. The results showed that, after 5 hours of yeast injection, 400 and 800 mg/kg ACE significantly reduced the rectal temperature of rats. Mice were found significantly less sensitive to heat at an oral dose of 800 mg/kg ACE, after 60 and 90 min. No anti-inflammatory activity of ACE at an 800 mg/kg dose could be observed in the rat paw assay. An anti-oxidative activity of ACE was observed with an IC 50value of 47.18 μg/ ml. No behavioral or movement change could be observed in mice after oral administration of ACE (800 or 8,000 mg/kg) for seven consecutive days. Interestingly, from the second day of treatment, animals had a significant lower body weight at the 8,000 mg/kg dose of ACE compared to the control. No toxicity was identified and the results of this study state clearly that Aquilaria crassna leaves extracts possess antipyretic, analgesic and anti-oxidative properties without anti-inflammatory activity.

Synthesis and evaluation of N1-substituted-3-propyl-1,4-benzodiazepine-2-ones as cholecystokinin (CCK2) receptor ligands

A novel synthetic approach towards N1‐alkylated 3‐propyl‐1,4‐benzodiazepineswas developed in five synthetic steps from 2‐amino‐4‐chlorobenzophenone, in which the N‐oxide 4 served as a key intermediate. The structure‐activity relationship optimization of this 3‐propyl‐1,4‐benzodiazepine template was carried out on the N1‐position by selective alkylation reactions and resulted in a ligand with an improved affinity on the cholecystokinin (CCK2) receptor. The N‐allyl‐3‐propyl‐benzodiazepine 6d displayed an affinity towards the CCK2 (CCK‐B) receptor of 170 nM in a radiolabelled receptor‐binding assay. The anxiolytic activity of this allyl‐3‐propyl‐1,4‐benzodiazepine 6d was subsequently determined in in‐vivo psychotropic assays. This novel lig and had ED50 values of 4.7 and 5.2 mg kg−1 in the black and white box test and the x‐maze, respectively, and no significant sedation/muscle relaxation was observed.

Combinatorial solid phase synthesis of multiply substituted 1,4-benzodiazepines and affinity studies on the CCK2 receptor (Part 1)

One hundred sixty-eight multiply substituted 1,4-benzodiazepines have been prepared by a five-step solid-phase combinatorial approach using syn-phase crowns as a solid support and a hydroxymethyl-phenoxy-acetamido linkage (Wang linker). The substituents of the 1,4-benzodiazepine scaffold have been varied in the -3, -5, -7, and 8-positions and the combinatorial library was evaluated in a chole cys to kinin (CCK) radioligand binding assay. 3-Alkylated 1,4-benzodiazepines with selectivity towards the CCK-B (CCK2) receptor have been optimized on the lipophilic side chain, the ketone moiety, and the stereochemistry at the 3-position. Various novel 3-alkylated compounds were synthesized and [S]3-propyl-5-phenyl-1,4-benzodiazepin-2-one, [S]NV-A, has shown a CCK-B selective binding at about 180 nM. Fifty-eight compounds of this combinatorial library were purified by preparative TLC and 25 compounds were isolated and fully characterized by TLC, IR, APCI-MS, and 1H/13C-NMR spectroscopy.

In‐vitro and in‐vivo antivenin activity of 2‐[2‐(5,5,8a‐trimethyl‐2‐methylene‐decahydro‐naphthalen‐1‐yl)‐ethylidene]‐succinaldehyde against Ophiophagus hannah venom

Objectives Curcuma zedoaroides A. Chaveerach & T. Tanee, locally known as Wan‐Paya‐Ngoo‐Tua‐Mia, is commonly used in the North‐Eastern part of Thailand as a ‘snakebite antidote’. The aim of this study was to isolate the active compound from the rhizome of C. zedoaroides, to determine its structure and to assess its antagonistic activity in vitro and in vivo against King cobra venom.