Anna Maria Di Pietra

GC/MS evaluation of thyme (Thymus vulgaris L.) oil composition and variations during the vegetative cycle.

Capillary GC/MS analysis based on polar and non-polar columns has been applied to evaluation of the volatile oils hydrodistilled from thyme (Thymus vulgaris L.) plants. The adopted methodology has been used to monitor seasonal variations in the composition of the oil obtained from thyme herbs harvested at different periods during the plant vegetative and life cycles. Oils from thyme plants of young (2 years) and old (5 years) cultivations have been evaluated from four and two collections, respectively, effected throughout May/December growth period. Generally, the oil was found to be rich in the active monoterpene phenols (thymol and carvacrol) and their corresponding monoterpene hydrocarbon (HC) precursors (p-cymene and gamma-terpinene), which collectively showed synchronized patterns of variation during the different collection periods and in different seasons. The oil from old plant collected in May/June period (0.15% v/w) was characterized by significantly lower levels of monoterpene HCs (mainly gamma-terpinene) and the highest levels of the oxygenated monoterpenes (linalool and borneol), monoterpene phenols (mainly thymol) and their derivatives (mainly carvacrol methyl ether), sesquiterpenes (mainly beta-caryophyllene) and their oxygenated derivatives (e.g. caryophyllene oxide) in comparison with all other samples. A characteristic presence of camphor and thymodihydroquinone was also observed in the old plant oils. On the other hand, the young plant, collected in June/July just before the end of the vegetative cycle, provided the best oil yield (1.2%) with also the highest % content of the monoterpene phenols (thymol: 51.2% and carvacrol: 4%). This latter growth period can represent the best harvest time of young thyme plants in order to obtain an essential oil with better quality and quantity.

Albumin nanoparticles carrying cyclodextrins for nasal delivery of the anti-Alzheimer drug tacrine

Peroral administration of tacrine, the first acetylcholinestearse inhibitor licensed for the treatment of Alzheimers disease, is associated with low bioavailability, due to an extended first-pass methabolism, short elimination half-life and hepatotoxicity. Nasal drug delivery may reduce the degree of these problems. Tacrine hydrochloride nasal delivery is here investigated by means of albumin nanoparticles carrying beta cyclodextrin and two different beta cyclodextrin derivatives (hydroxypropyl beta cyclodextrin and sulphobutylether beta cyclodextrin). Bovine serum albumin nanoparticles were obtained using a coacervation method, followed by thermal cross-linking, starting from protein solution at alkaline pH. After preparation, nanoparticles were loaded by soaking from solutions of tacrine hydrochloride and lyophilised. Thermal analysis (differential scanning calorimetry and thermogravimetric analysis) supported by Fourier Transform Infrared Spectroscopy were performed in order to confirm protein cross-linking in nanosphere structure and possible drug/carrier interaction occurred after the loading process. Moreover, size, polydispersity, zeta potential and morphology of the nanoparticles were investigated as well as drug loading, mucoadhesion properties and ex-vivo drug permeation ability. Results indicate that all the nanoparticles presented a mean size and a polydispersity lower than 300nm and 0.33nm, respectively, were spherical shaped and negatively charged even after drug loading. Moreover, the presence of the different beta cyclodextrins in the polymeric network affected drug loading and could differently modulate nanoparticle mucoadhesiveness and drug permeation behaviour.

Crosslinked Polyvinylalcohol Hydrogels as Vehicles for Hydrophilic Drugs

Polyvinylalcohol crosslinked with succinyl, adipoyl, or sebacoyl chloride at two different degrees of crosslinking was prepared and employed as a supporting material for aqueous topical gels containing propranolol hydrochloride, which was chosen as a hydrophilic model drug suitable for transdermal delivery. We analysed the effect of the nature of the crosslinker and the degree of crosslinking on drug permeation through porcine skin by means of the permeation parameters obtained from the gels and the corresponding aqueous solution. The gels showed greater drug permeation than the liquid solution due to an increase in drug solubility in the skin. Increasing degree of crosslinking and decreasing crosslinker acyl chain length in the gel enhance the drug permeability through the skin.

New environmental sensitive system for colon-specific delivery of peptidic drugs

Nano and micro preparative technologies for the realization of pharmaceutical carriers represent an actual strategy for reaching the therapeutic success of drugs, particularly in the case of peptidic drugs. Vancomycin is here entrapped in carriers composed by a swellable, mucoadhesive and biodegradable albumin core, coated with fatty acids able to improve a colon-specific release. Bovine serum albumin nanospheres (core) were prepared from protein solutions using a coacervation method followed by thermal cross-linking at different temperature, or from protein solutions at different pHs using a coacervation method followed by thermal cross-linking at 75 degrees C. Solid nanospheres were collected by freeze-drying, loaded by soaking from solutions of vancomycin and subsequently coated with myristic, palmitic or stearic acid by spray-drying technique obtaining microcapsules. Nanosphere dimensions and polydispersity, drug loading capacity, swelling ability and mucoadhesion properties were evaluated, as well as in vitro release behaviour. The results indicated that nanospheres present an adequate loading capacity, a great swelling tendency and good mucoadhesion ability. Moreover, albumin cores showed a pH-dependent release according to the structure of thermally denaturated protein in different experimental conditions, while microcapsules showed a pH-dependent release according to the different fatty acids solubility in acidic and alkaline media.

Determination of retinoids in galenicals by column liquid chromatography with fluorescence and diode-array detection

Simple and rapid reversed-phase gradient column liquid chromatography (LC) with fluorescence detection at different wavelengths was developed for the simultaneous analysis of all-trans, 13-cis, 9-cis retinoic acids, vitamin A palmitate and beta-carotene in galenicals. The assay results agreed with those obtained by an LC method with diode-array UV detection. A post-column on-line photochemical reactor (irradiation at 254 and 366 nm) was inserted between the LC column and the fluorescence detector to enhance the performance of the method. Two fluorescence spectra (photoreactor on and off) were obtained for each analyte which proved useful for the unambiguous identification of the various analytes.

Determination of amiodarone hydrochloride in pharmaceutical formulations by derivative UV spectrophotometry and high-performance liquid chromatography (HPLC).

Assay procedures based on derivative ultraviolet spectrophotometry and high-performance liquid chromatography (HPLC) have been developed for the specific determination of amiodarone hydrochloride in pharmaceutical dosage forms. The use of first- and second-order derivative spectrophotometry was found to have suppressed the background absorption from the excipients with comparable accuracy and precision to the reversed-phased HPLC reference method. A conventional UV absorption method (λ = 242 nm) is subject to possible interference by formulation excipients.

Determination of levamisole and tetramisole in seized cocaine samples by enantioselective high-performance liquid chromatography and circular dichroism detection

Levamisole, an anthelmintic drug, has been increasingly employed as an adulterant of illicit street cocaine over the last decade; recently, the use of tetramisole, the racemic mixture of levamisole and its enantiomer dexamisole, was also occasionally observed. A new enantioselective high-performance liquid chromatography (HPLC) method, performed on cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phases in normal-phase mode, was validated to determine the enantiomeric composition of tetramisole enantiomers in seized cocaine samples. Furthermore, the hyphenation of the validated HPLC method with a circular dichroism (CD) detection system allowed the direct determination of elution order and a selective monitoring of levamisole and dexamisole in the presence of possible interferences. The method was applied to the identification and quantitation of the two enantiomers of tetramisole in seized street cocaine samples.

Determination of dextromethorphan and levomethorphan in seized heroin samples by enantioselective HPLC and electronic CD.

A new enantioselective HPLC method was developed for the resolution and determination of the enantiomers of methorphan, dextromethorphan (DXM) and levomethorphan (LVM), on a Chiralcel OJ column (250 mm × 4.6mm I.D.). The resolution of DXM and LVM was obtained using a mobile phase consisting of (n-hexane)-(2-propanol)-diethylamine (70:30:0.1, v/v/v) at a flow rate of 0.5 mL min(-1). The enantioselective method was found to be selective (α=1.92) and sensitive (LOD=2.8 μg mL(-1) for both DXM and LVM). The method was coupled with electronic circular dichroism (CD), allowing the determination of the elution order on the basis of the sign of CD signals of the single enantiomers at 285 nm (positive for DXM, negative for LVM). Under the optimized conditions, the validated method was applied to the identification and quantitation of the enantiomers of methorphan in samples of different sources of illicit drugs of abuse (heroin). DXM was found in eight seized samples of street heroin; two of these samples, for which the DXM content was found to be over 5% (w/w) and exceeding a 10% (w/w) ratio with respect to diacetylmorphine, were the cause of two deaths for overdose due to acute narcotism.

Analysis of flucytosine dosage forms by derivative UV spectroscopy and liquid chromatography

A simple second-order derivative spectrophotometric method was developed for the selective determination of flucytosine (an antimycotic drug) in the presence of 5-fluorouracil (a cytotoxic agent), its synthetic precursor and degradation product. Traces of 5-fluorouracil in flucytosine were also determined by derivative UV spectroscopy; flucytosine was removed by a selective solid-phase extraction (SPE) procedure using a strong cation-exchange sorbent. The spectrophotometric methods were applied successfully to the quality control of commercial dosage forms of flucytosine and the results were compared with those obtained by a HPLC procedure (cyano column) developed as a reference method.

Stereochemical characterization of fluorinated 2-(phenanthren-1-yl)propionic acids by enantioselective high performance liquid chromatography analysis and electronic circular dichroism detection.

Enantioselective high performance liquid chromatography (HPLC) coupled with a detection system based on the simultaneous measurement of UV absorption and electronic circular dichroism (ECD) allows a complete stereochemical characterization of chiral compounds, once the relationship between sign of the chiroptical properties and absolute configuration is determined. In the present communication, the development of enantioselective HPLC methods for the resolution of a series of fluorinated 2-phenanthrenylpropionic acids (1-6) is reported. Different chiral stationary phases (CSPs) were tested: Chiralcel OJ, Chiralcel OD, Chiralpak AD, (S,S)-Whelk-O 1, Chirobiotic T and α(1)-acid glycoprotein (AGP). The results allow the application of the methods to a reliable determination of the enantiomeric excess for all the examined compounds; the highest enantioselectivity values were obtained with the Hibar [(S,S)-Whelk-O 1] column for some of the examined compounds. In the case of rac-2-(6-fluorophenanthren-1-yl)propionic acid (1), the relationship between circular dichroism and absolute configuration of the enantiomeric fractions was determined by ECD analysis and time-dependent density functional theory (TD-DFT) calculations. The experimental ECD spectrum of the second-eluted fraction of 1 on the Hibar [(S,S)-Whelk-O 1] column was found to be in excellent agreement with the theoretical ECD spectrum of (S)-1; therefore, the absolute configuration of the first- and second-eluted enantiomers on the (S,S)-Whelk-O 1 CSP was assessed as (R) and (S), respectively, and the elution orders of the enantiomeric forms of 1 were determined on all the different CSPs.