Characterization of Mefenamic Acid-Guaiacol Ester: Stability and Transport Across Caco-2 Cell Monolayers

Purpose. Prodrug of non-steroidal anti-inflammatory drugs (NSAIDs) or NSAIDs linked with guaiacol have been reported to suppress gastrointestinal (GI) toxicity or induce GI protective effect. In this study, mefenamic-guaiacol ester was synthesized and its physicochemical properties, stability, and transport across Caco-2 monolayers were investigated. Methods. Synthesis of the ester was carried out using mefenamic acid, guaiacol, N, N-dimethylaminopyridine, and N, Ndicyclohexylcarbodiimide. The hydrolysis of the ester was investigated in aqueous buffer solutions pH 1-12 as well as in Caco-2 homogenate, human plasma, and porcine liver esterase. Caco-2 cell monolayers were utilized for transport studies. Due to the high lipophilicity of the ester with a calculated logP of 6.15, bovine serum albumin (BSA, 4%) was included in the receiver compartment to obtain a good in vitro-in vivo correlation. Permeation of the ester was assessed with or without the exposure of cells to PMSF, an inhibitor of esterase. Results. The ester was stable at a wide pH range from 1-10. However, it was hydrolyzed by enzymes from porcine liver esterase and Caco-2 homogenate. With the PMSF exposure on the apical (AP) side and in the presence of 4% BSA on the basolateral (BL) side, the transported amount of the ester from AP-to-BL direction was 14.63% after 3 hr with a lag time of 23 min. The Papp for the ester was 4.72 × 10^-6 cm s^-1. Conclusion. The results from hydrolysis studies indicate that this ester is a prodrug. The Papp value suggests the moderate absorption characteristic of the compound. The accumulation of this highly lipophilic ester in Caco-2 cells is reduced in the presence of BSA.     

Preventive and curative effects of curcumin on the development of gastric inflammatory diseases in rats

Preventive and curative effects of curcumin on experimental acute and chronic gastric ulcers were investigated to validate its clinical application on a remedy for peptic ulcer. Intraduodenal administration of curcumin, 5–20 mg/kg, inhibited gastric acid secretion in pylorus-ligated rats, and oral administration prevented ethanol-induced acute gastric mucosal lesions. Curcumin (20–80 mg/kg, p.o.) dose-dependently prevented both serotonin-induced gastric mucosal lesions and compound 48/80-induced gastric mucosal lesions in rats. Furthermore, oral administration of curcumin, 10–80 mg/kg, twice daily for 10 days, significantly accelerated the healing of acetic acid-induced chronic gastric ulcer and promoted mucosal regeneration in the ulcerated portion in a dose-related manner. Cimetidine prevented the formation of ethanol-induced gastric mucosal lesions, but not of serotonin-induced and compound 48/80-induced gastric mucosal lesions. Consecutive administration of cimetidine showed a marked acceleration in the healing of acetic acid-induced ulcer. Aminoguanidine, an inducible nitric oxide synthase (iNOS) inhibitor, showed anti-ulcerogenic effects similar to those oberved for curcumin. The present results indicate that curcumin exhibits gastric cytoprotection in the acute lesion models and ulcer healing promotion in the chronic ulcer model. The preventive and curative effects of curcumin might be due to an increase in the mucosal defensive mechanism through its antioxidant property and inhibition of NO or cytokine-mediated inflammation.     

Effects of curcumin on reflux esophagitis in rats

The preventive effect of curcumin, a compound isolated from the rhizome of Curcuma longa, on experimental reflux esophagitis in rats was investigated in order to validate its potential therapeutic use for gastroesophageal reflux disease. Curcumin (20 mg/kg, i.d.), the antioxidative agent dimethyl sulfoxide (DMSO) (1 ml/kg, i.p.) or the proton pump inhibitor lansoprazole (1 mg/kg, i.d.) inhibited the formation of acute acid reflux esophagitis by 52.5, 61.5 and 70.9% respectively. Curcumin alone was not effective in preventing chronic acid reflux esophagitis, but the combination of curcumin and DMSO reduced the mortality rate and the severity of the esophagitis ulcer index to the same extent (56.5%) as did the lansoprazole (53.9%). Intraduodenal administration of curcumin also markedly prevented the formation of acute mixed reflux esophagitis, together with reducing the incidence or the severity of neutrophil infiltration, when compared to a control group. In contrast, lansoprazole tended to increase the severity of all histopathological changes, when compared to either the control or the curcumin-treated group. Aminoguanidine, a specific inducible nitric oxide synthase inhibitor, had no preventive effect against both types of acute reflux esophagitis models, and increased the mortality in the chronic acid reflux esophagitis model. From these results, it is indicated that curcumin can effectively prevent acute reflux esophagitis formation. Although curcumin is less potent than lansoprazole in inhibiting acid reflux esophagitis, it is superior to lansoprazole in inhibiting mixed reflux esophagitis. The antiulcerogenic mechanisms are considered to be closely associated with its antioxidant nature and antiinflammatory property.     

ATR-FTIR characterization of transport properties of benzoic acid ion-pairs in silicone membranes

A novel technique based on Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy was used to study the transport of benzoic acid ion-pairs/salts in silicone membranes. The benzoic acid ion-pairs were prepared using various counter-ions with different degrees of lipophilicity, e.g. triethylamine (TA), diethylamine (DE), tert-butylamine (t-BA), 2-amino-2-methyl-propanol (AMP), and 2-amino-2-methyl-propanediol (AMPD). Silicone membrane, treated or untreated with propylene glycol (PG), was placed on the surface of a ZnSe crystal and the transport solution was applied to the upper surface of the membrane. A mathematical model, based on Fick's second law describing the build up of permeant concentration at the membrane/crystal interface with time was applied to determine diffusion coefficients. Absorption due to the acid (1700 cm(-1)) or benzoate anion (1555 cm(-1)) was observed at different regions without the interference from PG or silicone membrane. Benzoate anion, a charged species, was observed to permeate the membrane. The permeation of benzoate anion from sodium benzoate and polar ion-pairs of AMP and AMPD was very low in contrast to their high-saturated concentrations in PG as compared to the t-BA ion-pair. This indicated that benzoate anion preferentially permeates the membrane as an ion-pair rather than a single anion; otherwise its permeation should correspond to its concentration in PG instead of the lipophilicity of the ion-pairs. Additionally, the diffusion coefficient values of benzoic acid and benzoate anions through the treated and untreated membranes were not statistically different.     

Formulation and efficacy of triamcinolone acetonide mouthwash for treating oral lichen planus.

PURPOSE: The stability of a triamcinolone acetonide mouthwash and its efficacy in treating oral lichen planus are described. METHODS: The solubility of triamcinolone acetonide in ethanol, propylene glycol, and glycerin was determined by shaking and equilibrating an excess of triamcinolone acetonide with the solvents for 72 hours. All three solvents were used in formulating a mouthwash. A stock solution of triamcinolone acetonide standard was prepared in ethanol and diluted to yield concentrations of 2, 4, 8, 12, and 16 microg/mL. Analytical sample solutions were prepared by pipetting 0.1 mL of triamcinolone acetonide mouthwash into 10-mL volumetric flasks and diluting to volume with the mobile phase. Accelerated stability studies were conducted by storing the samples in 60-mL amber glass bottles at 45, 60, 70, and 80 degrees C and 75% relative humidity until the triamcinolone concentration decreased markedly. Efficacy was tested by 20 subjects with a clinical diagnosis of and histologically confirmed symptomatic oral lichen planus who were randomized to use the mouthwash (n = 11) or the commercially available triamcinolone acetonide paste (n = 9). RESULTS: The mouthwash had a satisfactory shelf life and was well accepted by patients. Ten of 11 patients treated with the mouthwash for four weeks reported a positive response, and a complete response in signs and symptoms occurred in 4 and 5 of 11 patients, respectively. No significant difference in clinical improvement was observed between groups. CONCLUSION: A triamcinolone acetonide mouthwash had a satisfactory shelf life and was well accepted by patients. It did not have a significantly different therapeutic efficacy from the commercial paste dosage form in the treatment of oral lichen planus.     

Water flea Moina macrocopa as a novel biocarrier of norfloxacin in aquaculture.

The potential of using water flea Moina macrocopa as a novel live drug carrier to freshwater aquatic animals has been evaluated. The incorporation of antibacterial, norfloxacin into Moina and subsequently into fish was quantified. The efficiency of drug incorporation into water flea depends on both drug concentration in enrichment medium and incubation time. The maximum drug level in Moina following bioencapsulation technique was reached at 4 h of exposure at drug concentrations of 10-20% (w/w) (0.70-0.90 mg/g dry weight of water flea). Significant higher drug uptake was obtained (1.902+/-0.228 mg/g dry weight of water flea) in 2 h at the drug concentration of 40%. A marked decrease of norfloxacin percentage level upon storage of the Moina in water was observed and the survival of the Moina up to 2 h was satisfactory. It was suggested that medicated water flea should be either administered freshly enriched to fish or after short duration of storage. Following oral administration of medicated water flea to fish, the level of drug in fish body tissue increased as the number of doses increased, and the drug level was highest after a three-dose feeding. This primary food source appears to be a promising drug delivery system to aquatic animals.