Unique green chromatography method for the determination of serotonin receptor antagonist (Ondansetron hydrochloride) related substances in a liquid formulation, robustness by quality by design-based design of experiments approach.

Serotonin receptor antagonist drug Ondansetron hydrochloride injectable formulation containing all related substances was identified and quantified by a single, simple, sensitive, eco-friendly, and green high-performance liquid chromatography method. The disseverment of all impurities was achieved with the Discovery Cyano (250 × 4.6) mm, 5 µm column. The gradient program was composed of pH 5.7 phosphate buffer as mobile phase A and acetonitrile as mobile phase B. The flow rate, column compartment temperature, and detection wavelengths were 0.9 mL/min, 30°C, and 216 nm, respectively. The method was validated as per current regulatory guidelines. The obtained %relative standard deviation for the precision results was between 0.55 and 2.72% for all impurities. The correlation coefficient values from the linearity experiment for impurities and analyte were more than 0.995. The accuracy results were obtained between 88.4 and 113.0% for all impurities. Both sample and standard solutions showed 24 h stability at benchtop and refrigerator conditions. All impurities and analytes met the specificity and mass balance for all forced degradation conditions. Quality-by-design-based design of experiments was utilized to establish the method's robustness. Method greenness was assessed by using the current advanced tool green analytical procedure index, National Environmental Methods Index, and analytical eco-scale.

A Quality by Design and green LC technique for the determination of mast cell stabilizer and histamine receptor antagonist (Olopatadine HCl) in multiple formulations.

Mast cell stabilizer and histamine receptor antagonist olopatadine hydrochloride (OPT) assay method predicated on LC have been established for the analysis in multiple formulations. The current method dealt with ophthalmic solution, nasal spray, and tablet formulation products. The isocratic chromatography method was optimized and validated with a Boston green C8 column (150 × 4.6 mm, 5 µm i.d.). Sodium dihydrogen phosphate buffer (pH 3.5) with acetonitrile in the ratio of 75:25 (v/v) was used as a mobile phase at a flow rate of 1.0 mL min-1 and at the column temperature of 30°C, and the detection was done at 299 nm. The method was validated as per International Council for Harmonisation (ICH) guidelines and United States Pharmacopoeia (USP). The accuracy results ranged from 99.9 to 100.7%, % relative standard deviation (RSD) from the precision was 0.5, and correlation coefficient from the linearity experiment was > 0.999. Solution stability was established for 24 h at room temperature and refrigerator conditions, and it was found that the solutions were stable. Using quality by design-based experiment designs, critical quality attributes were studied and it was found that the method was robust. In all the forced degradation studies peak purity was passed, and no interference was found at the retention time of the active component. The method validation data demonstrated that the developed method is linear, precise, accurate, specific, robust, and stable for the determination of OPT from multiple formulations. Analytical eco-scale tool, Green Analytical Procedure Index (GAPI) tool, and the National Environmental Method Index (NEMI) were used to evaluate the greenness of the method, and the analytical eco-score of 77 for the presented method was found to be excellent.

Regulatory Perspective Reverse Engineering Analysis of the Mast Cell Stabilizer and the Histamine Receptor Antagonist (Olopatadine HCl): Instrumental and Classical Methods for Multiple Formulations.

This study evaluates the unknown qualitative (Q1) and quantitative (Q2) formulas for nasal spray and ophthalmic solution formulations of olopatadine HCl by classical and instrumental techniques to match the generic formula with reference-listed drugs to avoid clinical study. Reverse engineering of olopatadine HCl nasal spray 0.6% and ophthalmic solution 0.1, 0.2% formulations was accurately quantified using a simple and sensitive reversed-phase high-performance liquid chromatography (HPLC) method. Both formulations possess similar components, namely ethylenediaminetetraacetic acid (EDTA), benzalkonium chloride (BKC), sodium chloride (NaCl), and dibasic sodium phosphate (DSP). These components were qualitatively and quantitatively determined using the HPLC, osmometry, and titration techniques. With derivatization techniques, EDTA, BKC, and DSP were determined by ion-interaction chromatography. NaCl in the formulation was quantified by measuring the osmolality and using the subtraction method. A titration method was also used. All the employed methods were linear, accurate, precise, and specific. The correlation coefficient was >0.999 for all components in all the methods. The recovery results ranged from 99.1 to 99.7% for EDTA, 99.1-99.4% for BKC, 99.8-100.8% for DSP, and 99.7-100.1% for NaCl. The obtained % relative standard deviation for precision was 0.9% for EDTA, 0.6% for BKC, 0.9% for DSP, and 1.34% for NaCl. The specificity of the methods in the presence of other components, diluent, and the mobile phase was confirmed, and the analytes were specific.

Green Liquid Chromatography Method for the Determination of Related Substances Present in Olopatadine HCl Nasal Spray Formulation, Robustness by Design Expert.

BACKGROUND: Dual therapeutic nature drug mast cell stabilizer and histamine receptor antagonist olopatadine hydrochloride (OPT) nasal spray does not have an official monograph, and no literature is available. Eye drops formulation had the official monograph for impurities, but the determination was done in two methods. OBJECTIVE: A simple and effective green liquid chromatography method to develop and validate for the related substances of OPT nasal spray formulation. METHOD: A 25 min gradient method was employed to separate impurities and OPT with a 1.0 mL/min flow rate using a Boston green C8 (150 mm × 4.6 mm, 5 µm) HPLC column. The set wavelength and column oven temperatures were 299 nm and 30°C, respectively. pH 3.5 phosphate buffer-acetonitrile in the ratio of (70:30, v/v) as mobile phase A and (50:50, v/v) ratio as mobile phase B. A Quality by Design (QbD) based Design of Experiments (DoE) was employed to evaluate the robustness characteristics of the analytical method validation. RESULTS: The obtained RSD from the precision and intermediate precision was 0.4 to 4.1%. The % recovery of the impurities from LOQ to 150% of specification level was 87.5 to 110.3%. The linear regression curves for the impurities with a correlation coefficient of >0.999 indicate that all peak responses are linear with the concentration. The sample and standard solutions were stable for 24 h at benchtop and refrigerator conditions. CONCLUSIONS: All the critical peaks were well separated from the forced degradation studies' diluent, placebo, and generated degradation peaks. The method validation data and QbD based robustness study results indicate that the developed impurities method fits the routine quality control laboratory use. National Environmental Index (NMEI), Green Analytical Procedure Index (GAPI), Analytical Eco-scale and Analytical Greenness (AGREE) tools expressed the method's greenness. HIGHLIGHTS: The proposed method is QbD utilized and green chemistry assessed impurities determination method for OPT in nasal spray formulation.

Green Chromatographic Method for Determination of Active Pharmaceutical Ingredient, Preservative, and Antioxidant in an Injectable Formulation: Robustness by Design Expert.

We report an efficient HPLC method for simultaneous qualitative and quantitative analysis of lincosamide antibiotic injectable formulations containing Clindamycin phosphate (CMN), benzyl alcohol (BA), and ethylenediaminetetraacetic acid (EDTA) as major ingredients. The three components were separated by Phenomenex prodigy C8 (250 mm × 4.6 mm, 5 µm) HPLC column, flow rate 1.1 mL/min, injection volume 30 µL, and column temperature 35 °C, using 0.05 M sodium acetate buffer (pH 4.5) with acetonitrile (ACN) in the ratio of 80:20 (v/v). The detection wavelength was set as 240 nm. The method was validated as per International Conference on Harmonization (ICH) guidelines and was confirmed to be specific, precise, accurate, and linear. Method robustness was executed by utilizing quality in the design of the experiment. Accuracy results were found to be 99.3-100.5% for CMN, 99.3-100.8% for BA, and 99.1-100.3% for EDTA. Precision results were obtained as % relative standard deviation (RSD): 0.6% for CMN, 0.4% for BA, and 0.4% for EDTA. Correlation coefficient (r 2) values were obtained as >0.999 for the three components. Analytical solutions are stable for 48 h at benchtop and refrigerator conditions. The greenness of the analytical method was evaluated by the Green Analytical Procedure Index (GAPI), National Environmental Method Index (NEMI), analytical eco-scale, and Analytical Greenness (AGREE) tools to confirm that the method is eco-friendly.

Development of a continuous-flow system for asymmetric hydrogenation using self-supported chiral catalysts.

Well-designed, self-assembled, metal-organic frameworks were constructed by simple mixing of multitopic MonoPhos-based ligands (3; MonoPhos=chiral, monodentate phosphoramidites based on the 1,1'-bi-2-naphthol platform) and [Rh(cod)(2)]BF(4) (cod=cycloocta-1,5-diene). This self-supporting strategy allowed for simple and efficient catalyst immobilization without the use of extra added support, giving well-characterized, insoluble (in toluene) polymeric materials (4). The resulting self-supported catalysts (4) showed outstanding catalytic performance for the asymmetric hydrogenation of a number of alpha-dehydroamino acids (5) and 2-aryl enamides (7) with enantiomeric excess (ee) ranges of 94-98 % and 90-98 %, respectively. The linker moiety in 4 influenced the reactivity significantly, albeit with slight impact on the enantioselectivity. Acquisition of reaction profiles under steady-state conditions showed 4 h and 4 i to have the highest reactivity (turnover frequency (TOF)=95 and 97 h(-1) at 2 atm, respectively), whereas appropriate substrate/catalyst matching was needed for optimum chiral induction. The former was recycled 10 times without loss in ee (95-96 %), although a drop in TOF of approximately 20 % per cycle was observed. The estimation of effective catalytic sites in self-supported catalyst 4 e was also carried out by isolation and hydrogenation of catalyst-substrate complex, showing about 37 % of the Rh(I) centers in the self-supported catalyst 4 e are accessible to substrate 5 c in the catalysis. A continuous flow reaction system using an activated C/4 h mixture as stationary-phase catalyst for the asymmetric hydrogenation of 5 b was developed and run continuously for a total of 144 h with >99 % conversion and 96-97 % enantioselectivity. The total Rh leaching in the product solution is 1.7 % of that in original catalyst 4 h.

Why p-Cymene? Conformational effect in asymmetric hydrogenation of aromatic ketones with a η(6) -arene/ruthenium(II) catalyst.

The global reaction route mapping (GRRM) methods conveniently define transition states in asymmetric hydrogenation and transfer hydrogenation of aromatic ketones via the [RuH{(S,S)-TsNCH(C6 H5 )CH(C6 H5 )NH2 }(η(6) -p-cymene)] intermediate. Multiple electrostatic CH/π interactions are the common motif in the preferred diastereometric structures.

Chiral eta(6)-arene/N-tosylethylenediamine-ruthenium(II) complexes: solution behavior and catalytic activity for asymmetric hydrogenation.

Aromatic ketones are enantioseletively hydrogenated in alcohols containing [RuX{(S,S)-Tsdpen}(eta(6)-p-cymene)] (Tsdpen=TsNCH(C(6)H(5))CH(C(6)H(5))NH(2); X=TfO, Cl) as precatalysts. The corresponding Ru hydride (X=H) acts as a reducing species. The solution structures and complete spectral assignment of these complexes have been determined using 2D NMR ((1)H-(1)H DQF-COSY, (1)H-(13)C HMQC, (1)H-(15)N HSQC, and (1)H-(19)F HOESY). Depending on the nature of the solvents and conditions, the precatalysts exist as a covalently bound complex, tight ion pair of [Ru(+)(Tsdpen)(cymene)] and X(-), solvent-separated ion pair, or discrete free ions. Solvent effects on the NH(2) chemical shifts of the Ru complexes and the hydrodynamic radius and volume of the Ru(+) and TfO(-) ions elucidate the process of precatalyst activation for hydrogenation. Most notably, the Ru triflate possessing a high ionizability, substantiated by cyclic voltammetry, exists in alcoholic solvents largely as a solvent-separated ion pair and/or free ions. Accordingly, its diffusion-derived data in CD(3)OD reflect the independent motion of [Ru(+)(Tsdpen)(cymene)] and TfO(-). In CDCl(3), the complex largely retains the covalent structure showing similar diffusion data for the cation and anion. The Ru triflate and chloride show similar but distinct solution behavior in various solvents. Conductivity measurements and catalytic behavior demonstrate that both complexes ionize in CH(3)OH to generate a common [Ru(+)(Tsdpen)(cymene)] and X(-), although the extent is significantly greater for X=TfO(-). The activation of [RuX(Tsdpen)(cymene)] during catalytic hydrogenation in alcoholic solvent occurs by simple ionization to generate [Ru(+)(Tsdpen)(cymene)]. The catalytic activity is thus significantly influenced by the reaction conditions.

Hybrid NH2-benzimidazole ligands for efficient Ru-catalyzed asymmetric hydrogenation of aryl ketones.

Readily available hybrid NH(2)/benzimidazole ligands (R-bimaH, 1) dramatically influence the outcome of established Ru-based catalysts during asymmetric hydrogenation of aryl ketones. The benzimidazole functionality results in reversal of the typically observed chiral induction and allows for hydrogenation to be uncharacteristically conducted in nonprotic solvents. The developed systems efficiently catalyzed the AH of a number of ketones in up to 99% ee.

The hydrogenation/transfer hydrogenation network in asymmetric reduction of ketones catalyzed by [RuCl2(binap)(pica)] complexes.

Chiral binap/pica-Ru(II) complexes (binap=(S)- or (R)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl; pica=alpha-picolylamine) catalyze both asymmetric hydrogenation (AH) of ketones using H(2) and asymmetric transfer hydrogenation (ATH) using non-tertiary alcohols under basic conditions. The AH and ATH catalytic cycles are linked by the metal-ligand bifunctional mechanism. Asymmetric reduction of pinacolone is best achieved in ethanol containing the Ru catalyst and base under an H(2) atmosphere at ambient temperature, giving the chiral alcohol in 97-98 % ee. The reaction utilizes only H(2) as a hydride source with alcohol acting as a proton source. On the other hand, asymmetric reduction of acetophenone is attained with both H(2) (ambient temperature) and 2-propanol (>60 degrees C) with relatively low enantioselectivity. The degree of contribution of the AH and ATH cycles is highly dependent on the ketone substrates, solvent, and reaction parameters (H(2) pressure, temperature, basicity, substrate concentration, H/D difference, etc.).

Solution structures and behavior of trans-RuH(eta(1)-BH(4)) (binap)(1,2-diamine) complexes.

The solution structures of a number of trans-RuH(eta(1)-BH(4))[(S)-tolbinap](1,2-diamine) precatalysts [TolBINAP = 2,2'-bis(di-4-tolylphosphino)-1,1'-binaphthyl; 1,2-diamine==(S,S)- or (R,R)-1,2-diphenylethylenediamine (DPEN), ethylenediamine (EN), and (S)-1,1-di(4-anisyl)-2-isopropylethylenediamine (DAIPEN)] have been determined using 2D NMR ((1)H--(1)H DQF-COSY, (1)H--(13)C HMQC, (1)H--(31)P HSQC, and (1)H--(15)N HSQC), and a double-pulsed field-gradient spin-echo (DPFGSE) NOE technique. All the octahedral Ru complexes adopt a trans configuration with respect to the BH(4) and hydride ligands. Amine protons of trans-RuH(eta(1)-BH(4))[(S)-tolbinap](1,2-diamine) complexes undergo H/D exchange in (CD(3))(2)CDOD. This inherent high acidity, coupled with the lability and chemical properties of the BH(4) ligand, allows for precatalyst activation without the need for an added base, in contrast to trans-RuCl(2)[(S)-tolbinap](1,2-diamine) precatalysts, which require a strong base for generation of a catalytic species. The H/BH(4) complex in a 2-propanol solution is converted to catalytically active [trans-RuH{(S)-tolbinap}{(S,S)-dpen}(ROH)](+) [(RO)(ROH)(n)](-) (R = (CH(3))(2)CH), a loosely associated ion pair of the discrete (solvated) cationic fragment and anionic species.

Mechanism of asymmetric hydrogenation of acetophenone catalyzed by chiral eta(6)-arene-N-tosylethylenediamine-ruthenium(II) complexes.

Chiral arene-N-tosylethylenediamine-Ru(II) complexes can be made to effect both asymmetric transfer hydrogenation and asymmetric hydrogenation of simple ketones through a slight functional modification and by switching reaction conditions. [Ru(OSO2CF3){(S,S)-TsNCH(C6H5)CH(C6H5)NH2}(eta(6)-p-cymene)] catalyzes the asymmetric hydrogenation of acetophenone in methanol to afford (S)-1-phenylethanol with 96% ee in 100% yield. Like the transfer hydrogenation catalyzed by similar Ru catalysts with basic 2-propanol or a formic acid/triethylamine mixture, this hydrogenation proceeds through a metal-ligand bifunctional mechanism. The reduction of the C=O function occurs via an intermediary 18e RuH species in its outer coordination sphere without metal-substrate interaction. The high catalytic efficiency relies on the facile ionization of the Ru triflate complex in methanol. The turnover rate is dependent on hydrogen pressure and medium acidity and basicity. The RuCl analogue can be used as a precatalyst, albeit less effectively. Unlike the well-known diphosphine-1,2-diamine-Ru(II)-catalyzed hydrogenation that proceeds in a basic alcohol, this reaction takes place under slightly acidic conditions, creating new opportunities for asymmetric hydrogenation.

Hydrogen bonding makes a difference in the rhodium-catalyzed enantioselective hydrogenation using monodentate phosphoramidites.

A new generation of monodentate phosphoramidite ligands bearing a primary amine moiety was found to display comparable or better efficiency than bisphosphines in the Rh-catalyzed asymmetric hydrogenation of challenging substrates, such as (Z)-methyl alpha-acetoxyacrylate or (E)-beta-aryl itaconate derivatives, affording the corresponding hydrogenation products with excellent enantioselectivities (up to >99% ee). The presence of intermolecular hydrogen bonding (HB) between two monodentate ligands in the catalyst was found to be critical for excellent catalyst performance. This finding provides a basis for design and development of further catalyst systems using this type of monodentate phosphoramidite ligands.

Metal-ligand bifunctional catalysis for asymmetric hydrogenation.

Chiral diphosphine/1,2-diamine-Ru(II) complexes catalyse the rapid, productive and enantioselective hydrogenation of simple ketones. The carbonyl-selective hydrogenation takes place via a non-classical metal-ligand bifunctional mechanism. The reduction of the C=O function occurs in the outer coordination sphere of an 18e trans-RuH2(diphosphine)(diamine) complex without interaction between the unsaturated moiety and the metallic centre. The Ru atom donates a hydride and the NH2 ligand delivers a proton through a pericyclic six-membered transition state, directly giving an alcoholic product without metal alkoxide formation. The enantiofaces of prochiral ketones are differentiated on the chiral molecular surface of the saturated RuH2 species. This asymmetric catalysis manifests the significance of 'kinetic' supramolecular chemistry.

Asymmetric hydrogenation of tert-alkyl ketones.

A combined system of RuCl2(tolbinap)(pica) and an alkaline or organic phosphazene base catalyzes asymmetric hydrogenation of sterically congested tert-alkyl ketones (TolBINAP = 2,2'-bis(di-4-tolylphosphino)-1,1'-binaphthyl, PICA = alpha-picolylamine). Hydrogenation with RuH(eta1-BH4)(tolbinap)(pica) does not require any strong base. Alcoholic solvents strongly affect the catalytic efficiency. The reaction proceeds smoothly in ethanol under 1-20 atm of H2 and at room temperature with a substrate to catalyst molar ratio of up to 100 000. Various aliphatic, aromatic, heteroaromatic, and olefinic tert-alkyl ketones are convertible to the corresponding chiral carbinols in high enantiomeric purity. Olefinic and heteroaromatic functions are left intact. Certain cyclic ketones are also usable. The mode of enantioface selection is consistent and predictable.

Mechanism of asymmetric hydrogenation of ketones catalyzed by BINAP/1,2-diamine-rutheniumII complexes.

Asymmetric hydrogenation of acetophenone with trans-RuH(eta(1)-BH(4))[(S)-tolbinap][(S,S)-dpen] (TolBINAP = 2,2'-bis(di-4-tolylphosphino)-1,1'-binaphthyl; DPEN = 1,2-diphenylethylenediamine) in 2-propanol gives (R)-phenylethanol in 82% ee. The reaction proceeds smoothly even at an atmospheric pressure of H(2) at room temperature and is further accelerated by addition of an alkaline base or a strong organic base. Most importantly, the hydrogenation rate is initially increased to a great extent with an increase in base molarity but subsequently decreases. Without a base, the rate is independent of H(2) pressure in the range of 1-16 atm, while in the presence of a base, the reaction is accelerated with increasing H(2) pressure. The extent of enantioselection is unaffected by hydrogen pressure, the presence or absence of base, the kind of base and coexisting metallic or organic cations, the nature of the solvent, or the substrate concentrations. The reaction with H(2)/(CH(3))(2)CHOH proceeds 50 times faster than that with D(2)/(CD(3))(2)CDOD in the absence of base, but the rate differs only by a factor of 2 in the presence of KO-t-C(4)H(9). These findings indicate that dual mechanisms are in operation, both of which are dependent on reaction conditions and involve heterolytic cleavage of H(2) to form a common reactive intermediate. The key [RuH(diphosphine)(diamine)](+) and its solvate complex have been detected by ESI-TOFMS and NMR spectroscopy. The hydrogenation of ketones is proposed to occur via a nonclassical metal-ligand bifunctional mechanism involving a chiral RuH(2)(diphosphine)(diamine), where a hydride on Ru and a proton of the NH(2) ligand are simultaneously transferred to the C=O function via a six-membered pericyclic transition state. The NH(2) unit in the diamine ligand plays a pivotal role in the catalysis. The reaction occurs in the outer coordination sphere of the 18e RuH(2) complex without C=O/metal interaction. The enantiofaces of prochiral aromatic ketones are kinetically differentiated on the molecular surface of the coordinatively saturated chiral RuH(2) intermediate rather than in a coordinatively unsaturated Ru template.