Giuseppe Loy

Synthesis and pharmacological activity of 2-oxo-(2H) 1-benzopyran-3-carboxamide derivatives

Abstract Continuing our research on the synthesis and biological activity of heterocyclic compounds synthesized by carbon suboxide, we prepared and screened some 2-oxo (2H) 1-benzopyran-3-carboxamide derivatives. The results of pharmacological assays are reported and discussed.

Niosomes as carriers for tretinoin I. Preparation and properties

Tretinoin-loaded niosomes were prepared from polyoxyethylene (4) lauryl ether, sorbitan esters and a commercial mixture of octyl/decyl polyglucosides, in the presence of cholesterol and dicetyl phosphate. Liposomes made of hydrogenated and non-hydrogenated phosphatidylcholine were also prepared as a comparison reference. A study was made of the influence of vesicle composition and preparation method on the vesicle structure (MLV, LUV, SUV), size distribution, entrapment efficiency and in vitro release of incorporated tretinoin. Results showed that in the presence of cholesterol all the amphiphiles used were able to form stable vesicle dispersions with or without tretinoin. Vesicle sizes were dependent on the preparation method, bilayer composition and drug load. Multilamellar (MLV) vesicles were larger than extruded (LUV) and sonicated (SUV) vesicles while drug-loaded vesicles were generally smaller than empty ones. Entrapment efficiencies of tretinoin were always very high especially for multilamellar (91-99%) and extruded (88-98%) vesicles. The in vitro release of tretinoin from the prepared vesicular formulations was studied using the vertical Franz diffusion cells. The rate of drug release through a Silastic membrane from a liposomal and niosomal tretinoin dispersion was generally faster than from a tretinoin solution. Release data showed that tretinoin delivery is mainly affected by the vesicular structure and that tretinoin delivery increased from MLVs to LUVs to SUVs.

Niosomes as carriers for tretinoin II. Influence of vesicular incorporation on tretinoin photostability

In this work, we compared the chemical stability of tretinoin (TRA) in methanol and in vesicular suspensions exposed both to UV and artificial daylight conditions with the aim of evaluating the potential of niosomes as topical carriers capable of improving the stability of photosensitive drugs. Tretinoin-loaded niosomes were prepared from polyoxyethylene (4) lauryl ether (Brij 30), sorbitan esters (Span 40 and Span 60) and a commercial mixture of octyl/decyl polyglucosides (Triton CG110). Liposomes made from hydrogenated (P90H) and non-hydrogenated (P90) soy phosphatidylcholines were also prepared and studied. In order to evaluate the influence of vesicle structure on the photostability of tretinoin, TRA-loaded vesicles were prepared by the film hydration method, extrusion technique and sonication. After UV irradiation, TRA dissolved in methanol degraded very quickly while the incorporation in vesicles always led to a reduction of the photodegradation process. The photoprotection offered by vesicles varied depending on the vesicle structure and composition. After fluorescent light irradiation for 21 days, not all the studied vesicular formulations improved TRA stability when compared with the free drug in methanol. Tretinoin incorporated in P90 or Span vesicles presented a half-life shorter or very close to that of the free drug. However, the inclusion of TRA in P90H liposomes and Brij 30 or Triton CG110 niosomes retarded the drug photodegradation.

Diclofenac-β-cyclodextrin binary systems: Physicochemical characterization and in vitro dissolution and diffusion studies

The aim of this work was to study the influence of β-cyclodextrin (β-CD) on the biopharmaceutic properties of diclofenac (DCF). To this purpose the physicochemical characterization of diclofenac-β-cyclodextrin binary systems was performed both in solution and solid state. Solid phase characterization was performed using differential scanning calorimetry (DSC), powder x-ray diffractometry (XRD), and Fourier transform infrared spectroscopy (FTIR). Phase solubility analyses, and in vitro permeation experiments through a synthetic membrane were performed in solution. Moreover, DCF/β-CD interactions were studied in DMSO by1H nuclear magnetic resonance (NMR) spectroscopy. The effects of different preparation methods and drug-to-β-CD molar ratios were also evaluated. Phase solubility studies revealed 1∶1 M complexation of DCF when the freeze-drying method was used for the preparation of the binary system. The true inclusion for the freeze-dried binary system was confirmed by1H NMR spectroscopy, DSC, powder XRD, and IR studies. The dissolution study revealed that the drug dissolution rate was improved by the presence of CDs and the highest and promptest release was obtained with the freeze-dried binary system. Diffusion experiments through a silicone membrane showed that DCF diffusion was higher from the saturated drug solution (control) than the freeze-dried inclusion complexes, prepared using different DCF-β-CD molar ratios. However, the presence of the inclusion complex was able to stabilize the system giving rise to a more regular diffusion profile.

LIPOSOME-INCORPORATED SANTOLINA INSULARIS ESSENTIAL OIL: PREPARATION, CHARACTERIZATION AND IN VITRO ANTIVIRAL ACTIVITY

The effect of liposomal inclusion on the stability and in vitro antiherpetic activity of Santolina insularis essential oil was investigated. In order to study the influence of vesicle structure on the liposome properties, multilamellar and unilamellar vesicles were prepared by the film method and sonication, respectively. Vesicles were obtained from hydrogenated soya phosphatydilcholine and cholesterol. Formulations were examined for their stability for over one year monitoring the drug leakage from vesicles and the average size distribution. The stability of the incorporated oil was verified by studying its quali-quantitative composition. The antiviral activity was studied against Herpes simplex virus type 1 (HSV-1) by plaque reduction and yield reduction assays. Results showed that Santolina insularis essential oil can be incorporated in high amounts in the prepared liposomes, which successfully prevented its degradation. Moreover, stability studies pointed out that vesicle dispersions were stable for at least one year and neither oil leakage nor vesicle size alteration occurred during this period. Antiviral activity assays demonstrated that Santolina insularis essential oil is effective in inactivating HSV-1 and that the activity is principally due to direct virucidal effects. Free essential oil proved to be more effective than liposomal oil and a different activity was discovered which related to the vesicular structure. The ED50 values, significantly lower when cells were pre-incubated with the essential oil before the virus adsorption, indicate an intracellular mechanism in the antiviral activity of Santolina insularis. Moreover, liposomal Santolina essential oil is non toxic in the range of the concentration tested.

Design, characterization and in vitro evaluation of 5-aminosalicylic acid loaded N-succinyl-chitosan microparticles for colon specific delivery

The objective of this study was to prepare NS-chitosan microparticles for the delivery of 5-aminosalicylic acid (5-ASA) to the colon. Microparticles can spread out over a large area of colon allowing a more effective local efficacy of 5-ASA. N-Succinyl-chitosan was chosen as carrier system because of its excellent pharmaceutical properties in colon drug targeting such as poor solubility in acid environment, biocompatibility, mucoadhesive properties, and low toxicity. It was prepared by introducing succinic group into chitosan N-terminals of the glucosamine units. 5-ASA loaded NS-chitosan microparticles were prepared using spray-drying. As a control, a matrix obtained by freeze-drying technique was also prepared and tested. Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC) and X-ray diffraction studies show the 5-ASA/NS-chitosan electrostatic interactions in both the systems. Mean size of the microparticles was around 5 μm, zeta potential value of both systems was always negative. Scanning electron microscopy (SEM) images show an acceptable spherical non porous structure of microparticles. In vitro swelling and drug release studies were in accordance with the polymer properties, showing the highest swelling ratio and drug release at pH=7.4 (colonic pH) where microparticles were able to deliver more than 90% of 5-ASA during 24h experiments. Rheological studies are in accordance with the swelling and release studies.

Release of rifampicin from chitosan, PLGA and chitosan-coated PLGA microparticles

Recently three groups of rifampicin (RIF)-loaded microparticles (MPs), consisting of chitosan (CHT), PLGA and PLGA/CHT mixtures, were assessed in terms of RIF-loading and retention during nebulisation. The CHT-coated PLGA MPs were found to exhibit high RIF-loading ability together with nebulisation ability, stability, and mucoadhesive properties. All MP types had comparable toxicity towards alveolar cells which was significantly lower than that of the free drug. Herein, we study the release of RIF from all MP-types, during incubation in buffer with pH values: 4.40 and 7.40. Results show that CHT particles exhibit a higher burst release compared to PLGA MPs; at pH 4.40, which is explained by the higher solubility of CHT in acidic media. At pH 7.40 burst release from CHT MPs is significantly lower when CHT is crosslinked with glutaraldehyde, which is consistent with their - previously observed - increased stability during nebulization. From PLGA MPs, RIF release was pH independent under the conditions applied, while the amount of PVA (stabilizer) considerably affected drug release. When PLGA MPs were coated with CHT, at pH 7.40 the retention of RIF increased further (compared to non-coated MPs), while at pH 4.40 the release was faster from the CHT-coated particles. Concluding, it is proven that when PLGA MPs are coated with CHT, in addition to increased particle mucoadhesive properties, the release kinetics of RIF are modified.

N-Succinyl-chitosan systems for 5-aminosalicylic acid colon delivery: In vivo study with TNBS-induced colitis model in rats

5-Aminosalicylic acid (5-ASA) loaded N-Succinyl-chitosan (SucCH) microparticle and freeze-dried system were prepared as potential delivery systems to the colon. Physicochemical characterization and in vitro release and swelling studies were previously assessed and showed that the two formulations appeared to be good candidates to deliver the drug to the colon. In this work the effectiveness of these two systems in the treatment of inflammatory bowel disease was evaluated. In vitro mucoadhesive studies showed excellent mucoadhesive properties of both the systems to the inflamed colonic mucosa. Experimental colitis was induced by rectal instillation of 2,4,6-trinitrobenzene sulfonic acid (TNBS) into male Wistar rats. Colon/body weight ratio, clinical activity score system, myeloperoxidase activity and histological evaluation were determined as inflammatory indices. The two formulations were compared with drug suspension and SucCH suspension. The results showed that the loading of 5-ASA into SucCH polymer markedly improved efficacy in the healing of induced colitis in rats.

Liposomes Coated with Chitosan-Xanthan Gum (Chitosomes) as Potential Carriers for Pulmonary Delivery of Rifampicin

The aim of this work was to develop new microparticles for drug delivery to lungs by coating liposomes with chitosan (CH)-xanthan gum (XG) polyelectrolyte complexes to obtain chitosomes. To this purpose, two groups of liposomes were prepared using a mixture of soy phosphatidylcholine and hydrogenated soy phosphatidylcholine in two different concentrations to evaluate their capability to entrap appropriate amounts of the model drug rifampicin. The obtained vesicles were then coated with different CH-XG weight ratios and liposomes and chitosomes were characterized in terms of morphology, size, size distribution, zeta potential, drug entrapment, and rheological properties. The efficiency of chitosomes and liposomes during nebulization was also studied. Results of this study indicated that nebulization and rheological properties of chitosomes are affected by the CH-XG weight ratio. In particular, CH-XG 1:0.5 (w/w) coating was able to greatly improve drug total mass output and drug deposition in the lower stages of the impinger.

Synthesis and antimicrobial activity of coumarin and benzodioxazepine-, diazazepine- and benzoxazepine-substituted penicillins

Abstract Some semisynthetic penicillins 6-substituted with benzo-condensed heterocyclic derivatives were prepared using the reaction of carbon suboxide with Schiff bases and disubstituted benzoic acids. The microbiological assay performed with the penicillins and their intermediates showed a good activity for one Schiff base and a weak activity for the other compounds.