In vitro metabolism of azasqualene derivatives and their effects on aminopyrine N-demethylase activity in rat liver microsomes.

The metabolism of squalene dimethylamine (I), a potent inhibitor of 2,3-oxidosqualene (SO) cyclase, and of sixteen other squalene derivatives was investigated in rat liver microsomes. N-oxidation was the only metabolic pathway observed, squalene dimethylamine N-oxide being the only metabolite isolated from incubation of I. The azasqualane and quaternary ammonium derivatives did not form N-oxides during their metabolism. The inhibition of aminopyrine N-demethylase activity was also studied and the IC50, for compound I, which shows weak competitive inhibition, was determined. At 1 mM concentration the other squalene derivatives showed a range of inhibition activity possibly due to their different lipophilicity.

Fractal analysis of beta-cyclodextrin-indomethacin particles compacted by ultrasound.

An association between indomethacin and beta-cyclodextrin (beta-CD) was obtained by compacting a 1:2 molar physical mixture by ultrasound. The product prepared by this technique was compared with the initial physical mixture and with materials having the same composition but prepared by a simple compaction and kneading process. The samples examined by scanning electron microscopy revealed morphological differences related to the methods of preparation. In particular the material obtained by ultrasound had a smooth surface and on milling produced particles of uniform size; moreover EDAX analysis (energy dispersion analysis by X-rays) also revealed a homogeneous distribution of the two components in each particle examined. Surface fractal dimension of the surface of these particles is very low, suggesting the presence of a regular and smooth surface whereas the sample obtained by kneading had a higher value. The reactive dimension related to dissolution was much higher than the corresponding surface dimension in all cases and had comparable values for all samples regardless of the techniques used. This behavior was attributed to the hydrophilicity of beta-CD, which levels the differences during dissolution and which could be originated by surface imperfections. Experimental results suggested that the material obtained by ultrasound had a dissolution rate comparable to that measured with the kneaded material. The use of ultrasound, however, can both reduce the production time and improve the homogeneity of the association between indomethacin and beta-CD.

Preparation and characterization of solid lipid nanospheres containing paclitaxel.

The study describes the development of stealth and non-stealth solid lipid nanospheres (SLNs) as colloidal carriers for paclitaxel, a drug with very low solubility. SLNs are constituted mainly of bioacceptable and biodegradable lipids, such as tripalmitin and phosphatidylcholine, and can incorporate amounts of paclitaxel up to 2.8%. Stealth and non-stealth loaded SLNs are in the nanometer size range and can be sterilized and freeze-dried. Thermal analysis (differential scanning calorimetry) showed that paclitaxel is not able to crystallize in the SLNs. Release of paclitaxel from SLNs is very low. Non-stealth and stealth SLNs are stable over time without precipitation of paclitaxel and can be proposed for its parenteral administration.

Effects of ultrasound-assisted compaction on Ketoprofen/Eudragit S100 mixtures.

Ketoprofen alone and in binary mixtures with Eudragit S100 was compacted by an ultrasound-assisted (US) tableting machine at an energy ranging from 50 to 400 J. The final material was analysed by TLC and HPLC: no decomposition product of the active agent was found. IR spectra and HSM revealed the absence of any interaction between the two components. Thermal analysis (DSC) evidenced that ketoprofen inside the mixtures was transformed into an amorphous state, documented by the decreasing of the DeltaHfus as the Eudragit/ketoprofen ratio increases and as US energy increases. While pure ketoprofen recovers its crystalline state quickly after the US treatment, the presence of Eudragit was found to slow down or possibly to prevent the regeneration of the crystallinity.

Scale-up of the preparation process of solid lipid nanospheres. Part I.

An apparatus was designed to prepare solid lipid nanospheres (SLN), potential colloidal therapeutic system obtained by dispersing a warm oil-in-water (o/w) microemulsion in cold water. The apparatus, consisting mainly of a thermostated aluminium chamber and a pneumatic piston, permitted to disperse through a needle up to 100 ml of warm microemulsion and to vary the temperature, the dispersing rate and the drop size of the warm o/w microemulsion. Experimental design was applied to study the effect of four experimental factors, such as chamber temperature, piston pressure, needle gauge and volume of dispersing water, on average diameter and polydispersity index of SLN and on dispersing time of microemulsion (the time required for the microemulsion to drip completely from the apparatus). The results showed that temperature and pressure play the most important roles depending on the needle gauge used. In particular, the smallest SLN were obtained using high temperature and pressure values and a small needle gauge.

Solid lipid nanoparticles as carriers of hydrocortisone and progesterone complexes with beta-cyclodextrins.

Inclusion complexes of hydrocortisone and progesterone were formed with beta-cyclodextrin or 2-hydroxypropyl-beta-cyclodextrin. The formation of the complexes was confirmed by differential scanning calorimetry (DSC). The inclusion complexes were incorporated in two types of solid lipid nanoparticles (SLN). In the presence of the complexes the sizes of SLN remained below 100 nm. DSC analysis showed that hydrocortisone and progesterone are dispersed in SLN in an amorphous state. Using the beta-cyclodextrin complexes the incorporation of the more hydrophilic drug, hydrocortisone, was higher than that of progesterone. Release of hydrocortisone and progesterone from SLN was lower when they were incorporated as inclusion complexes than as free molecules.

22,23-Epoxy-2-aza-2,3-dihydrosqualene derivatives: potent new inhibitors of squalene 2,3-oxide-lanosterol cyclase.

Two new azasqualenoid derivatives, bearing a 22,23 epoxidic function, were synthesized, to obtain more efficient, competitive inhibitors of the enzyme squalene 2,3-oxide-lanosterol cyclase (EC 5.4.99.7). The activities of 22,23-epoxy-2-aza-2,3-dihydrosqualene 4 and of its N-oxide derivative 5 were studied using rat and pig liver microsomal preparations and compared with a pig liver partially purified squalene 2,3-oxide-lanosterol cyclase. The activities of compounds 4 and 5 were compared in the different enzymatic preparations with the activities of 2-aza-2,3-dihydrosqualene 2 and of 2-aza-2,3-dihydrosqualene N-oxide 3 previously studied only with rat liver microsomes. Using a solubilized, partially purified squalene 2,3-oxide cyclase, all the compounds exhibited a non-competitive type of inhibition. As the previously suggested mechanism of inhibition does not account for this kinetic behaviour, a new hypothesis is suggested.

Metabolism of 4-(3-cyclohexylpropionyl)-1-(2-ethoxyphenyl) piperazine (D-16120) by rat liver microsomes.

The metabolic fate of central analgesic 4-(3-cyclohexylpropionyl)-1-(2-ethoxyphenyl) piperazine (D-16120), was studied in vitro with phenobarbital 3-methylcholanthrene and clofibrate induced rat liver microsomal fractions. The presence of four metabolites was directly or indirectly established. Biotransformation products were isolated by TLC and HPLC techniques and, when possible, the structures were confirmed through comparison with synthetic samples. The metabolic pathways involved are oxidative dealkylation, aromatic and alicyclic hydroxylation.

The metabolic fate of the anti-parkinsonian drug budipine in rats.

The metabolic fate of the anti-Parkinsonian drug budipine was studied in rats after oral administration. The presence of an aromatic hydroxylation product, metabolite M1, and its O-sulphate conjugate was confirmed. Three new minor metabolites, budipine N-oxide, metabolite M1 N-oxide and a secondary metabolite derived from M1 via hydroxylation of a methyl of the tert-butyl group, were isolated and identified in rat urine. The presence of a metabolite M1-glucuronic acid conjugate, was also established through different enzymatic treatments of the rat urine.

In vitro metabolism of 2-(5-ethylpyridin-2-yl)benzimidazole.

The in vitro metabolic transformation of the anti-inflammatory agent 2-(5-ethylpyridin-2-yl)benzimidazole (KB-1043) was studied with phenobarbital and 3-methylcholanthrene induced rat liver microsomal fractions containing an NADPH-generating system. The major metabolite was a benzylic oxidation product and a secondary metabolite was also recovered. The metabolites were isolated by TLC and HPLC techniques and identified by comparison with known pure compounds.

'In vitro' metabolism of N-picolyl-3,5-dimethylbenzamides.

'In vitro' metabolism of three isomeric N-picolyl-3,5-dimethylbenzamides was studied. The metabolites were isolated through TLC and HPLC techniques and identified by direct comparison with authentic compounds. The results of phenobarbital and 3-methyl-cholantrene inductions are given.

In vivo metabolism of the anti-inflammatory agent 2-(5-ethylpyridin-2-yl)benzimidazole.

The metabolic fate of anti-inflammatory agent 2-(5-ethylpyridin-2-yl)benzimidazole (KB-1043) was studied in rats after oral administration. An average of 12.2 +/- 1.5% of the dose was excreted in the urine in the course of 0-48 h; 56.7 +/- 2.6% with feces. Two metabolites were also detected in the urine and isolated by reverse phase HPLC. Structures have been given after identification by comparison with authentic samples. The more abundant metabolite proved to be 2-(5-(1-hydroxyethyl)pyridin-2-yl)benzimidazole, a benzylic oxidation product, which was also excreted as glucuronic acid conjugate; the other metabolite was confirmed to be 2-(5-acetylpyridin-2-yl)benzimidazole. Carrageenin edema and gastric ulcerogenic activity were also tested for the two identified metabolites.

The bromination of 6-methyl-4-methoxy-2H-thiopyran-2-one.

The bromination of 6-methyl-4-methoxy-2H-thiopyran-2-one was studied under ionic and radical conditions. The 6-bromomethyl, respectively 6-dibromomethyl derivatives were hydrolyzed to the corresponding 6-hydroxymethyl and 6-formyl derivatives. The antibacterial and antimycotic activities of the new compounds were tested.

Metabolism of 7-(1,3-thiazolidin-2-ylmethyl)theophylline by rat liver microsomes. Evidence for a monooxygenase-dependent step in 1,3-thiazolidine ring cleavage.

Metabolic transformation of the mucoregulator and bronchodilator 7-(1,3-thiazolidin-2-ylmethyl)theophylline was studied in vitro with a rat liver microsomal preparation containing a NADPH-generating system. The only metabolite observed was 7-theophyllinacetaldehyde. In contrast to previous literature pointing out the chemical nature of 2-substituted thiazolidine ring cleavage, the formation of 7-theophyllinacetaldehyde was mediated by monooxygenase-dependent oxidation. Possibly an unstable sulfoxide was the first metabolic product, rapidly converted to 7-theophyllinacetaldehyde by hydrolysis. The sulfoxidation was apparently catalyzed mainly by flavin-containing monooxygenases, as selective thermal inactivation and methymazole significantly reduced the rate of formation of the metabolite. No N7-dealkylation pathway producing theophylline was detected, indicating a high regioselectivity in in vitro metabolism, due to the nucleophilicity of the sulfur atom.

Biosynthesis of cucurbitacins in Bryonia dioica seedlings.

The biosynthesis of cucurbitacins during the seed germination of Bryonia dioica was studied by analysis of the cucurbitacin-triterpenoid fraction and by tracer experiments with acetate-[2- (14)C]. Isolation of 10alpha-cucurbita-5,24-dien-3beta-ol (9a), the simplest tetracyclic triterpene with a cucurbitane skeleton, supports the view that (9a) is the general precursor of cucurbitacins. Moreover, following the tracer experiments, cucurbitacin E (1a) was the first cucurbitacin formed, whereas the less oxygenated bryodulcosigenin (4a) was not detectable during germination of the plant. In the course of the present investigation, a new pentacyclic triterpene, isomultiflorenol (11a) (possible precursor of bryonolic acid (5a)), was also isolated.

Bromination of 3-acyl-4-hydroxy-6 methyl-2H-thiopyran-2-ones. II.

The brominations of various 3-acyl-4-hydroxy-6-methyl-2H-thiopyran-2-ones as well as of 3-acyl-4-methoxy-6-methyl-2H-thiopyran-2-ones, bearing linear and branched acyl chains ranging from four to eight carbon atoms are described. The antibacterial and antimycotic activities of the new compounds are also reported.

In vitro Metabolism of Bumetanide.

A new metabolite of the diuretic drug bumetanide, the 4-[(4'-hydroxy)-phenoxy] analog (7), was identified in incubation mixtures of rat liver microsomes. Phenobarbital and clofibrate pretreatment to induce microsomal enzymes changed the relative amounts of the six metabolites formed. Compound 7was the most prevalent metabolite after clofibrate pretreatment.

Side chain degradation and microbial reduction of different steroids by Aspergillus auroefulgens.

The Aspergillus aureofulgens ability to cleave the side chain of progesterone (I) and the related C-21 steroids was studied. The enzymic system responsible for the progesterone side chain degradation was demonstrated to be adaptative and to operate by a Baeyer-Villiger mechanism. The cleavage of the side chain of the progesterone and of the related compounds was followed by the stereospecific reduction of the formed androst-4-ene-3,17-dione(II) to the 5 beta-androstan derivatives. Both the oxygenase and reductase activities seemed to be influenced by the growth conditions. Several steroids bearing different skeleton functions and different side chains were also tested in order to correlate the chemical structure with the microbial activity.

Biosynthesis of Sterols and Triterpenoids in Tissue Cultures of Cucurbita maxima.

The biosynthesis of sterols and triterpenoids in CUCURBITA MAXIMA was studied by analysis of unsaponifiable fraction of tissues from different development stages of the plant (seeds, seedlings, adult plant and tissue culture) and by feeding germinating seeds and tissue cultures with [2- (14)C]-acetate. Synthesis of cucurbitacins does not occur in callus tissues of CUCURBITA MAXIMA, whereas a wide variety of 4,4-dimethylsterols present in these tissues testifies of a high level of squaleneoxide cyclase activity in growing callus. The peculiarity of Cucurbitaceae among the higher plants is also discussed comparing the side chain biosynthesis of sterols in CUCURBITA MAXIMA to that operating in other higher plants.

Transmucosal transport of tobramycin incorporated in SLN after duodenal administration to rats. Part I--a pharmacokinetic study.

Tobramycin-loaded solid lipid nanospheres (SLN) were prepared and administered to rats into the duodenum; their behaviour was compared to that of tobramycin-loaded SLN administered intravenously (i.v.). A tobramycin control solution was also administered to rats. Tobramycin in solution is not absorbed by the gastrointestinal route, while tobramycin incorporated in the SLN is absorbed. A high concentration of tobramycin is still present in plasma 24 hours after the duodenal administration of tobramycin-loaded SLN. Tobramycin-loaded SLN administered i.v. showed a prolonged circulation time compared to the i.v. administered tobramycin solution. The AUC of tobramycin in SLN administered duodenally is higher than those of tobramycin in SLN and in solution administered i.v.