Benzofurazan -based fluorophore for the spectrofluorimetric determination of 6-Aminocaproic acid: Application to spiked human plasma and urine

6-Aminocaproic acid is one of the most widely used antihemorrhagic and antifibrinolytic agent, therefore, it is essential to create a novel, sensitive, low cost and straightforward spectrofluorimetric method for its determination. The nucleophilic substitution interaction between the primary amine of 6-aminocaproic acid with 4-chloro-7-nitro benzofurazan (NBD-Cl) generated a yellow product. The reaction proceeded in borate buffer (pH 9) and its fluorescence has been measured at 525 nm after excitation at 472 nm. All of the parameters that have impact on the performance of the developed method were investigated and optimized. The range of linearity was 0.1-0.7 μg/mL while, the quantitation limit was down to 0.101 μg/mL and limit of detection was 0.033 μg/mL. This approach was effectively employed to evaluate the content of 6-aminocaproic acid in laboratory prepared dosage form with average percentage recovery of 100.19 ± 0.72% without any interference from basic excipients. Moreover, the proposed method was extended to determine 6-aminocaproic acid in spiked human plasma and urine.

Comparative Study of the Selectivity Power of Colorimetric Method over Chromatographic Methods for the Analysis of Valaciclovir Hydrochloride

BACKGROUND

Valaciclovir hydrochloride (VAL) is an essential antiviral prodrug utilized to cure various types of herpes. Analysis of VAL by different analytical techniques demonstrates a persuasive aspect that is favorable in quality control application.

OBJECTIVE

This study describes a comparison between colorimetric and chromatographic (RP-HPLC and TLC-densitometric) methods concerning selectivity and specificity for the determination of VAL in existence of all possible degradation products (alkali and acid-induced degradation products, namely aciclovir (ACI) and guanine (GUA), respectively) in their synthetic mixture and pharmaceutical formulations.

METHODS

Colorimetric method was accomplished by forming a highly colored complex with ferric hydroxamate reagent measured at 493 nm in concentration range (0.20-1.60 mg/mL). Both chromatographic methods were successfully applied using UV detection at 256 nm in concentration range (2.00-5.00 µg/mL) for RP-HPLC method and (10.00-900.00 ng/band) for TLC-densitometric method.

RESULTS

The linearity studies, regression equations, assay parameters, and validation sheet of the proposed colorimetric and chromatographic methods to determine VAL were obtained with highly acceptable values.

CONCLUSION

ICH guidelines were followed to validate the described methods and the statistical comparison regarding both accuracy and precision, and satisfactory results were accomplished.

HIGHLIGHTS

In this study, we configure a full comparative study between different analytical methods for the analysis of challengeable mixture containing the drug of interest VAL along with its degradation products, ACI & GUA.

Innovative Thin-Layer Chromatography/Fluorescence Detection Approach for Sensitive and Specific Determination of Ledipasvir in Rats' Feces and Pharmaceutical Dosage Form

An innovative thin-layer chromatography method coupled with the fluorescence detection was developed for a specific estimation of ledipasvir. The separation was achieved on plates of silica gel 60 F254 using ethylacetate: hexane: acetonitrile: triethylamine; (6: 3.5: 1.5: 0.5, $\mathrm{v}/\mathrm{v}/\mathrm{v}/\mathrm{v}$) as a mobile phase system. The method involved the exposure of the developed thin-layer chromatography plate of ledipasvir to strong ultraviolet irradiation, resulting in a great enhancement in the fluorescence properties of ledipasvir. The irradiated plates were scanned after the excitation at 315 $\mathrm{nm}$. The method provided a sufficient separation of ledipasvir from sofosbuvir with ${R}_F$values of 0.28 and 0.36 for ledipasvir and sofosbuvir, respectively. The developed procedures were validated based on guidelines from the International Conference on Harmonization and Food and Drug Administration guidelines. The calibration curve was linear over the range of 5-50 $\mathrm{ng}/\mathrm{band}$. The excellent analytical features of the proposed method allow to the specific determination of ledipasvir in pharmaceutical tablets without interference from sofosbuvir or excipients. As the main elimination route for ledipasvir is via the fecal excretion (86%), the method was applied for the estimation of ledipasvir in fecal specimens with adequate recovery. In addition, the proposed method was applied for testing the content uniformity of ledipasvir in the pharmaceutical tablets.

Spectrofluorimetric approach for determination of tranexamic acid in pure form and pharmaceutical formulations; Application in human plasma

Tranexamic acid (TXA) is an important antihemorrhagic drug that needs a simple, sensitive and low cost spectrofluorimetric method for its determination. This method depends on generation of a yellow product which produced from a nucleophilic substitution reaction of the lone pair of electrons on the amino group found in the TXA chemical structure and 4-chloro-7-nitrobenzofurazan (NBD-Cl) in borate buffer PH 9.0. The product was measured at 536 nm (λex = 470.5 nm). All variables that have an effect on the formation and stability of the product have been explored and optimized. The linear range was 20-100 ng mL^-1 with a limit of quantitation 12.4 ng mL^-1. This method has been applied for assurance of tranexamic acid in ampoules and tablets dosage forms without any interference from excipients present. Also, we study the drug in human plasma.

Imprinted Contact Lenses for Ocular Administration of Antiviral Drugs

A variety of ocular diseases are caused by viruses, and most treatments rely on the use of systemic formulations and eye drops. The efficient ocular barriers that oppose antiviral drug penetration have prompted the development of improved topical delivery platforms. The aim was to design hydrogel contact lenses endowed with an affinity for acyclovir (ACV) and its prodrug valacyclovir (VACV), first-choice drugs against herpes simplex virus (HSV) ocular keratitis, and that can sustain the release of therapeutic doses during daily wearing. Functional monomers suitable for interaction with these drugs were screened using computational modeling. Imprinted and non-imprinted hydrogels were prepared with various contents in the functional monomer methacrylic acid (MAA) and characterized in terms of swelling, transmittance, mechanical properties, and ocular compatibility (hen’s egg test on chorioallantoic membrane (HET-CAM) assay). The values were in the range typical of soft contact lenses. Compared to ACV, the capability to load VACV was remarkably higher due to stronger electrostatic interactions with MAA. The advantages of the imprinting technology were evidenced for VACV. Stability of VACV loading solution/hydrogels under steam heat sterilization and subsequent drug release was investigated. Permeability studies through bovine and porcine cornea and sclera of the drug released from the hydrogels revealed that VACV accumulates in the cornea and can easily cross the sclera, which may facilitate the treatment of both anterior and posterior eye segments diseases.

Thin-layer chromatography/fluorescence detection approach for sensitive and selective determination of hepatitis C virus antiviral (velpatasvir): application to human plasma

A validated thin-layer chromatography (TLC) method combined with fluorescence detection mode was developed for the selective determination of a recently approved anti-hepatitis C virus (HCV) drug (velpatasvir). The separation was performed on silica gel 60 F₂₅₄ plates using ethylacetate:methanol:triethylamine (48:1.5:1.0, v/v/v) as a mobile phase. Plates were scanned in the fluorescence mode after excitation at 335 nm. This method provided an excellent separation of velpatasvir from sofosbuvir with R_F values of 0.22 and 0.46 for velpatasvir and sofosbuvir, respectively, after scanning the developed plates in the ultraviolet detection mode at 335 nm. The calibration curve was linear over the range 4-40 ng/band with a correlation coefficient of 0.9994. The developed procedure was validated according to ICH guidelines with a detection limit of 1.30 ng/band and quantitation limit of 3.95 ng/band. The suggested method could selectively determine velpatasvir with high sensitivity in a synthetic tablet powder containing a co-formulated anti-HCV drug (sofosbuvir) without any interference from excipients or sofosbuvir. In addition, the method was successfully applied for determination of velpatasvir in spiked human plasma with adequate % recovery.

Analysis of quetiapine in human plasma using fluorescence spectroscopy

A simple and sensitive spectrofluorimetric method has been development for the assurance of quetiapine fumarate (QTF). The proposed method was utilized for measuring the fluorescence intensity of the yellow fluorescent product at 510nm (λ_ex 470nm). The fluorescent product has resulted from the nucleophilic substitution reaction of QTF with 4-chloro-7-nitrobenzofurazane (NBD-Cl) in Mcllvaine buffer (pH7.0). The diverse variables influencing the development of the reaction product were deliberately changed and optimized. The linear concentration range of the proposed method was of 0.2-2.0μgml^-1.The limits of detection and quantitation were 0.05 and 0.17μgml^-1, respectively. The proposed method was applied for the assurance of QTF in its tablets without interference from basic excipients. In addition, the proposed method was used for in vitro analysis of the QTF in spiked human plasma, the percent mean recovery was (n=3) 98.82±1.484%.

Utility of the chromogenic and fluorogenic properties of benzofurazan for the assay of milnacipran in human urine and plasma

Our article presents the development and validation of two simple, very sensitive, and low-cost spectroscopic methods for the assay of milnacipran hydrochloride in bulk form, pharmaceutical tablets and spiked human urine and plasma. Spectroscopic methods (spectrophotometric and spectrofluorimetric techniques) were dependent on the chromogenic and fluorogenic properties of the 4-chloro-7 nitrobenzofurazan (NBD-Cl) reagent. The reaction product, resulting from the interaction between NBD-Cl and milnacipran in the presence of borate buffer pH 8.5, was measured spectrophotometrically at 465 nm and spectrofluorimetrically at 510 nm after excitation at 465 nm. The absorbance–concentration plot was rectilinear over the range of 1.5–12 μg mL⁻¹ with a limit of quantitation 1.09 μg mL⁻¹, while the fluorescence–concentration plot was rectilinear over the range of 0.03–0.5 μg mL⁻¹ with a limit of quantitation 0.02 μg mL⁻¹. Influential parameters affecting the development and stability of the reaction product were studied and optimized. Assurance of the cited drug in its tablets by our proposed methods was successfully completed without obstruction from the presence of the basic excipients with average percentage recoveries of 99.27 ± 1.18 and 99.44 ± 0.69 for the spectrophotometric and spectrofluorimetric methods, respectively. The spectrofluorimetric method was additionally adopted as a preliminary in vitro study for the assay of the cited drug in spiked human urine and plasma with average percentage recoveries of 101.52 ± 1.01 and 100.38 ± 1.57 for spiked urine and plasma, respectively.

Our article presents the development and validation of two simple, very sensitive, and low-cost spectroscopic methods for the assay of milnacipran hydrochloride in bulk form, pharmaceutical tablets and spiked human urine and plasma.

Enhancement of the sensitivity of valacyclovir and acyclovir for their spectrofluorimetric determination in human plasma

Two rapid, simple and highly sensitive spectrofluorimetric methods have been developed and validated for determination of valacyclovir hydrochloride (VAC) and acyclovir (ACV).