Analysis of Ginkgo biloba for the presence of ginkgotoxin and ginkgotoxin 5'-glucoside

Hot water extracts of Ginkgo biloba seeds were analyzed for the presence of ginkgotoxin (4'-O-methylpyridoxine) by reversed-phase liquid chromatography (LC) using methanol-0.05M KH2PO4 (1 + 9, v/v) adjusted to pH 3 as mobile phase. Detection was by fluorescence (excitation 280 nm, emission 370 nm). A straight line calibration curve was obtained for the 10-100 ng injected. After addition of beta-glucosidase (37 degrees C/h), an earlier eluting peak disappeared and the ginkgotoxin peak increased. The identity of the ginkgotoxin was confirmed by LC/MS and LC/MS/MS. LC/MS/MS also confirmed the 5'-glucoside by comparison with the 3-glucoside. This is the first identification of a glucoside of ginkgotoxin in Ginkgo biloba. An unknown compound of MW 267 also observed in the Ginkgo biloba seed extract was shown not to be 3,5'-diacetylginkgotoxin by its different LC retention time. Extraction of ground Ginkgo biloba seeds with boiling water in a Soxhlet for 2 x 2 h yielded a total of 179 microg/g of free ginkgotoxin. The concentration in powder from Ginkgo biloba capsules was several times lower than this (17-64 microg/g) in 3 samples but higher in another (457 microg/g). Canned ginkgo seeds (white nuts) contained no detectable free ginkgotoxin but the glucoside was present. Different extraction times were studied: 0.5 h gave only 52 microg/g free ginkgotoxin in the ginkgo seeds. However, boiling an extract for 4 h showed about 15% loss of ginkgotoxin and its glucoside.     

Effect of acyl chain length and branching on the enantioselectivity of Candida rugosa lipase in the kinetic resolution of 4-(2-difluoromethoxyphenyl)-substituted 1,4-dihydropyridine 3,5-diesters.

Since 2,6-dimethyl-4-aryl-1,4-dihydropyridine 3,5-diesters themselves are not hydrolyzed by commercially available hydrolases, derivatives with spacers containing a hydrolyzable group were prepared. Seven acyloxymethyl esters of 5-methyl- and 5-(2-propoxyethyl) 4-[2-(difluoromethoxy)phenyl]-2,6-dimethyl-1,4-dihydro-3,5-pyridinedicarboxylate were synthesized and subjected to Candida rugosa lipase (CRL) catalyzed hydrolysis in wet diisopropyl ether. A methyl ester at the 5-position and a long or branched acyl chain at C3 gave the highest enantiomeric ratio (E values). The most stereoselective reaction (E = 21) was obtained with 3-[(isobutyryloxy)methyl] 5-methyl 4-(2-difluoromethoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate, and this compound was used to prepare both enantiomers of 3-methyl 5-(2-propoxyethyl) 4-[2-(difluoromethoxy)phenyl]-2,6-dimethyl-1,4-dihydro-3,5-pyridinedicarboxylate. The absolute configuration of the enzymatically produced carboxylic acid was established to be 4R by X-ray crystallographic analysis of its 1-(R)-phenylethyl amide.     

丁酸氯维地平降解杂质的合成

以4-(2,3-二氯苯基)-1,4-二氢-2,6-二甲基-3,5-吡啶二羧酸(2-氰基乙基)（甲基）酯(5)为起始原料,合成了丁酸氯维地平的5种降解杂质：4-(2,3-二氯苯基)-1,4-二氢-2,6-二甲基-3,5-吡啶二羧酸单甲酯(A), 4-(2,3-二氯苯基)-1,4-二氢-2,6-二甲基-3-吡啶羧酸甲酯(B), 4-(2,3-二氯苯基)-2,6-二甲基-3,5-吡啶二羧酸单甲酯(C), 4-(2,3-二氯苯基)-2,6-二甲基-3,5-吡啶二羧酸（丁酰氧基甲基）（甲基）酯(D)和4-(2,3-二氯苯基)-2,6-二甲基-3-吡啶羧酸甲酯(E)。其中A由5水解制得;B由A脱羧制得;C由5氧化后再经水解制得;D由C和丁酸氯甲酯缩合制得;E由C脱羧制得,化合物结构经¹H NMR和MS（ESI）确证。     

1-(2-Quinoxalyl)-, 1-[3,5-Di(trifluoromethyl)phenyl]-, 1-(2-Carboxyphenyl)-, and 1-Ethoxycarbonyl-4-oxo-4,5,6,7-tetrahydroindazoles

The corresponding 1-(2-quinoxalyl)-, 1-[3,5-di(trifluoromethyl)phenyl]-, and 1-ethoxycarbonyl-3-methyl-4-oxo-4,5,6,7-tetrahydroindazoles have been obtained from reactions of 2-acetyl-1,3-cyclohexanedione, its 5,5-dimethyl and 5-(2-furyl) derivatives, with 2-hydrazinoquinoxaline, 3,5-di(trifluoromethyl)phenylhydrazine, and ethoxycarbonylhydrazine. On interaction with ethoxycarbonylhydrazine the intermediate 2-[1-(-ethoxycarbonyl)hydrazino]ethylidene-1,3-cyclohexanediones were also isolated. From the potassium salt of 2-formyldimedone and 2-carboxyphenylhydrazine hydrochloride, 2-(2-carboxyphenyl)hydrazinomethylene-5,5-dimethyl-1,3-cyclohexanedione was obtained, the cyclization of which in ethanol in the presence of HCl led to 1-(2-carboxyphenyl)- and 1-(2-ethoxycarbonylphenyl)-6,6-dimethyl-4-oxo-4,5,6,7-tetrahydroindazole.     

Hantzsch synthesis of 2,6-dimethyl-3,5-dimethoxycarbonyl-4-(o-methoxyphenyl)-1,4-dihydropyridine; a novel cyclisation leading to an unusual formation of 1-amino-2-methoxy-carbonyl-3,5-bis(o-methoxyphenyl)-4-oxa-cyclohexan-1-ene

Hantzsch condensation of two equivalents of methyl-3-aminocrotonate with (m- and p)-methoxybenzaldehyde afforded the expected products 2,6-dimethyl-3,5-dimethoxycarbonyl-4-(m-methoxyphenyl)-1,4-dihydropyridine and 2,6-dimethyl-3,5-dimethoxycarbonyl-4-(p-methoxyphenyl)-1,4-dihydropyridine, whereas o-methoxy-benzaldehyde produced mainly 1-amino-2-methoxycarbonyl-3,5-bis(o-methoxy-phenyl)-4-oxa-cyclohexan-1-ene. The structure of the product, not previously reported in the literature, was determined by 1D and 2D NMR spectra and its MS fragmentation. This is the first example of cyclisation leading to a substituted pyran rather than 1,4-DHP under typical Hantzsch reaction conditions. A plausible mechanism for its formation is postulated.     

A Validated LC Method for Determination of Trace Impurities in Technical Triadimefon

A simple and sensitive liquid chromatography with ultraviolet detection (LC?CUV) method was developed for the determination of three impurities with a content over 0.1% (w/w) in technical triadimefon. A Gemini C₁₈ column (5 ??m, 250 mm × 4.6 mm i.d.) was used for the chromatographic separations. The samples were separated by gradient elution with water (solvent A) and methanol (solvent B) using the following conditions: 70% A isocratic for 12 min, linear to 0% A within 8 min, and isocratic for 10 min at 0% A with a flow rate of 1.0 mL min^?1. Chromatograms were recorded at an absorption wavelength of 280 nm. The chromatographic resolutions between triadimefon and its potential impurities A, B, and C were greater than 3. The developed LC method was validated with respect to linearity, accuracy, precision, and robustness. This method was successfully applied to analyze the impurities in commercial technical triadimefon. In addition, the structures of the three impurities were identified to be (A) 4-chlorophenol, (B) 1-(2,4-dichlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl)-2-butanone, and (C) 1,1-bis(4-chlorophenoxy)-3,3-dimethyl-2-butanone.     

Monitoring of the degradation kinetics of diatrizoate sodium to its cytotoxic degradant using a stability‐indicating high‐performance liquid chromatographic method

The X‐ray diagnostic agent sodium diatrizoate (DTA) was studied for chemical degradation. The 3,5‐diamino derivative was found to be the alkaline and acidic degradation product. The 3,5‐diamino degradate is also the synthetic precursor of DTA and it is proved to have cytotoxic and mutagenic effects. A sensitive, selective and precise high‐performance liquid chromatographic stability‐indicating method for the determination of DTA in the presence of its acidic degradation product and in pharmaceutical formulation was developed and validated. Owing to the high toxicity of the degradation product, the kinetics of the acidic degradation process was monitored by the developed RP‐HPLC method. The reaction was found to follow pseudo‐first order kinetics. The kinetic parameters such as rate constant (K ) and half‐life (t _½) were calculated under different temperatures and acid concentrations; activation energy was estimated from the Arrhenius plot. The developed RP‐HPLC method depends on isocratic elution of a mobile phase composed of methanol–water (25:75 v /v; pH adjusted with phosphoric acid), and UV detection at 238 nm. The method showed good linearity over a concentration range of 2–100 μg/mL with mean percentage recovery of 100.04 ± 1.07. The selectivity of the proposed method was tested using laboratory‐prepared mixtures. The proposed method has been successfully applied to the analysis of DTA in pharmaceutical dosage forms without interference from other dosage form additives and the results were statistically compared with the official USP method. Validation of the proposed method was performed according to International Conference on Harmonization guidelines.     

Determination of synthetic musk compounds in indoor house dust by gas chromatography–ion trap mass spectrometry

A new method for the simultaneous determination of 11 synthetic musks and one fragrance compound in house dust was developed. The nitro musks included musk ketone (MK, 4-tert-butyl-3,5-dinitro-2,6-dimethylacetophenone), musk xylene (MX, 1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene), musk ambrette (1-tert-butyl-2-methoxy-4-methyl-3,5-dinitrobenzene) and musk moskene (1,1,3,3,5-pentamethyl-4,6-dinitroindane). The polycyclic musk compounds were 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-(γ)-2-benzopyran (HHCB), 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene (AHTN), 4-acetyl-1,1-dimethyl-6-tert-butylindane, 6-acetyl-1,1,2,3,3,5-hexamethylindane, 5-acetyl-1,1,2,6-tetramethyl-3-isopropylindane, 6,7-dihydro-1,1,2,3,3-pentamethyl-4(5H)-indanon. The one macrocyclic musk was 1,4-dioxacycloheptadecane-5,17-dione. The bicyclic hydrocarbon fragrance compound (1,2,3,4,5,6,7,8-octahydro-2,3,8,8-tetramethylnaphthalen-2yl)ethan-1-one (OTNE) and HHCB-lactone (4,6,6,7,8,8-hexamethyl-1H,3H,4H,6H,7H, 8H-indeno[5,6-c]pyran-1-one), a degradation product of HHCB, were also analysed. NIST SRM 2781 (domestic sludge) and SRM 2585 (organic contaminants in house dust) were analysed for these target compounds. The method was applied for the analysis of 49 paired samples collected using two vacuum sampling methods: a sample of fresh or "active" dust (FD) collected using a Pullman-Holt vacuum sampler, and a household dust (HD) sample taken from the participants' vacuum cleaners. Method detection limits and recoveries ranged from 12 to 48?ng/g and 54 to 117?%, respectively. AHTN, HHCB, OTNE and HHCB-lactone were detected in all samples, with median concentrations of 552, 676, 252 and 453?ng/g for FD samples, respectively; and 405, 992, 212 and 492?ng/g for HD samples, respectively. MX and MK were detected with high frequencies but with much lower concentrations. The two sampling methods produced comparable results for the target analytes. Widely scattered concentration levels were observed for target analytes from this set of 49 house dust samples, suggesting a wide variability in Canadian household exposure to synthetic musks.     

Reagent peak-free liquid chromatography–fluorescence analysis of carboxylic acids using a fluorous scavenging–derivatization method

We developed a fluorous scavenging–derivatization method for reagent peak-free liquid chromatography (LC)–fluorescence analysis of carboxylic acids. In this method, carboxylic acids were fluorescently derivatized with 1-pyrenemethylamine in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 1-hydroxy-1H-benzotriazole. Residual excess unreacted reagent was tagged with 2-(perfluorooctyl)ethyl isocyanate and could be selectively removed by microfluorous solid-phase extraction before LC analysis. With use of this method, eight fluorescent derivatives of linear aliphatic carboxylic acids (C₁–C₈) can be separated within 30 min by reversed-phase LC with gradient elution. In the chromatogram obtained, the fluorous-tagged unreacted reagent peak is greatly decreased after microfluorous solid-phase extraction and does not interfere with the quantification of each acid. With use of microfluorous solid-phase extraction with 80% (v/v) aqueous methanol elution, over 99.9% of the unreacted fluorescent reagent was removed. The detection limits (signal-to-noise ratio of 3) for the carboxylic acids examined are 2.3–8.0 fmol per 10-μL injection. We also applied this method successfully to the analysis of highly polar carboxylic acids such as α-keto acids and tricarboxylic acid cycle metabolites.     

Development and validation of a stability‐indicating assay including the isolation and characterization of degradation products of metaxalone by LC‐MS

A stability‐indicating reverse‐phase high‐performance liquid chromatography–mass spectrometric method was developed and validated for the assay of metaxalone through forced degradation under acidic, alkaline, photo, oxidative and peroxide stress conditions. Separation of degradation products was accomplished on a reverse‐phase Phenomenex C₁₈ (250 × 4.6 mm, 5 µm) column thermostated at 25°C using 10 mM aqueous ammonium acetate: methanol (35:65 v/v) as mobile phase in an isocratic mode of elution. The eluents were detected at 275 nm by photo diode array detector and mass detectors connected in series. Two unknown base hydrolysis products of metaxalone were identified and characterized as (a) methyl 3‐(3,5‐dimethylphenoxy)‐2‐hydroxypropylcarbamate and (b) 1‐(3,5‐dimethylphenoxy)‐3‐aminopropan‐2‐ol by MS, ¹H NMR and FTIR spectroscopy. The method was validated as per International Conference on Harmonization guidelines and metaxalone was selectively determined in presence of its degradation impurities, demonstrating its stability‐indicating nature. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of 3-(2-guanidinoethyl) and 3-[2-(S-methylisothioureidoethyl)] analogs of 5-isopropyl 2,6-dimethyl-1,4-dihydro-4-(2,3-dichlorophenyl)pyridine-3,5-dicarboxylate as a respective releaser of nitric oxide and inhibitor of nitric oxide synthase

The Hantzsch condensation of 2-azidoethyl acetoacetate with 2,3-dichlorobenzaldehyde and isopropyl 3-aminocrotonate afforded 3-(2-azidoethyl) 5-isopropyl 2,6-dimethyl-1,4-dihydro-4-(2,3-dichlorophenyl)pyridine-3,5-dicarboxylate ( 7 ). Reduction of the 3-(2-azidoethyl) moiety of 7 using 5% palladium-on-calcium carbonate and hydrogen gas gave the 3-(2-aminoethyl) derivative 8 , which was subjected to guanylation using 1H-pyrazole-1-carboxamidine hydrochloride to yield the target 3-(2-guanidinoethyl) analog 9 . The 3-(2-aminoethyl) product 8 was elaborated to the title compound 3-[2-(S-methylisothioureidoethyl)] 5-isopropyl 2,6-dimethyl-1,4-dihydro-4-(2,3-dichlorophenyl)pyridine-3,5-dicarboxylate hydrochloride ( 12 ) via the intermediate 3-(2-thioureidoethyl) compound 10 . The 3-(2-guanidinoethyl 9 and 3-[2-(S-methylisothioureidoethyl)] 12 compounds were about 116- and 23-fold less potent calcium channel antagonists, respectively relative to the reference drug nifedipine.     

3,5-Bis(ferrocenylmethylene)-1-methyl-4-methylenepiperidine. Synthesis and some chemical properties

3,5-Bis(ferrocenylmethylene)-1-methyl-4-methylenepiperidine, a diferrocenyltriene with a fixeds-cisoid conformation of the exocyclic double bonds, was synthesized. On heating, this compound cyclodimerizes according to the [4+2]-cycloaddition scheme; it forms Diels-Alder adducts with azodicarboxylic and maleic acidN-phenylimides. The compound easily cyclodimerizes in the presence of acids by a proton cyclodimerization mechanism to give a spiro cyclodimer. The triene also adds a 3,5-bis(ferrocenylmethylene)-1,4-dimethyl-1-azonia-4-cyclohexyl salt to the terminal methylene group yielding linear and cyclic addition products. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 511–516, March, 2000.     

Use of a carrier for quantitation of a new dihydropyridine calcium antagonist (OPC-13340) in human plasma by highly sensitive gas chromatography with negative-ion chemical ionization mass spectrometry.

A sensitive gas chromatographic-mass spectrometric method for the quantitation of (+/-)-methyl 3-phenyl-2(E)-propenyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate (OPC-13340, I), a new dihydropyridine calcium antagonist with a potent and long-acting antihypertensive and antianginal effect, was developed in order to elucidate its pharmacokinetics. Dihydropyridine calcium antagonist have been usually quantifed by this technique in the negative-ion chemical ionization mode. However, direct application of this method to quantify trace amounts of I in biological fluids completely failed, owing to its adsorption on the column and oxidation of its dihydropyridine ring. Human plasma containing I and (+/-)-[2H3]methyl 3-phenyl-2(E)-propenyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate (II), the internal standard, was extracted with n-hexane-diethyl ether under weakly basic conditions (pH 8). In order to prevent adsorption of the compounds on the column, (+/-)-[2H5]ethyl 3-phenyl-2(E)-propenyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylate (III), an analogue of I, was added to the extracts as a carrier. In addition, this carrier was also effective in preventing the oxidation of I. The quantitation limit of I in human plasma by this method was found to be less than 30 pg/ml. Thus, the method is sufficiently sensitive to study the pharmacokinetics of I in humans.     

Reactions of tetrafluoroethene oligomers. Part 5. Some reactions of perfluoro-[(1-ethyl-1-methylpropyl)(1-methylpropyl)] keten

The title keten (1) was treated with some alcohols and amines: methanol afforded an inseparable mixture of two products, 4H-4-methoxycarbonyl-docosafluoro-3,5-dimethyl-3-ethylheptane (2) and 4-methoxycarbonyl-heneicosafluoro-3,5-dimethyl-8-ethylhept-3-ene (3). Treatment of the mixture with sodium hydroxide afforded pure (3). Reaction of (1) with benzyl alcohol yielded 4-benzyloxycarbonyl-4H-docosafluoro-3,5-dimethyl-3-ethylheptane (4) which on hydrogenation gave a mixture of 4H-heneicosafluoro-3,5-dimethyl-5-ethylhept-3-ene (5) and 4H-docosafluoro-3,5-dimethyl-3-ethyl-heptane-4-carboxylic acid (6). Reaction of (1) with ammonia yielded 4-carbonamido-heneicosafluoro-3,5-dimethyl-5-ethylhept-3-ene (7) and dimethylamine similarly afforded the N,N-dimethyl analogue (9). However, reaction of (1) with ethylamine gave an unusual cyclisation product, 1-ethyl-3H-heneicosafluoro-4-ethyl-4-methyl-3(1-ethyl-1-methylpropyl)azetan-2-one (8).     

Photochemistry of heterocycles: VIII. photocycloaddition of acetylenic compounds to 1,3-dimethyl-6-azathymine

The photocycloadditions of 1,3-dimethyl-6-azathymine to 2-butyne-1,4-diol and 1,4-dimethoxyl-2-butyne have been studied. Three novel compounds, 7,8-bis(hydroxymethyl)-3,5-dioxo-2,4, 6-trimethyl-1,2,4-triazabicyclo [4,2,0]-7-octene (1), 7,8-bismethoxymethyl-3,5-dioxo-2,4,6-trimethyl- 1,2,4-triazabicyclo[4,2,0]-7-octene (2) and 8,9-bismethoxymethyl-4-oxo-1,3,5-trimethyl-7-oxa-2,3,5-triazaspiro[5,3]- 1,8-nonadiene (3) were obtained. The proposed reaction mechanism, which includes excited triplet complexes and biradicals as intermediates, was supported by kinetic and photophysical studies.     

Reversed-Phase Liquid Chromatographic Method for Determination of Daclatasvir Dihydrochloride and Study of Its Degradation Behavior

A simple and selective reversed-phase stability-indicating liquid chromatographic method has been developed and validated for the determination of daclatasvir in drug substance and drug product. Daclatasvir was subjected to acidic, alkaline, oxidative, thermal and photo-degradation study. The LC method was based on isocratic elution of daclatasvir and its degradation products on a reversed-phase C₁₈ Hypersil column using a mobile phase consisting of phosphate buffer (10 mM, 1 mL triethylamine L^?1): acetonitrile (60:40 v/v) at a flow rate of 2 mL min^?1. Quantitation was achieved with UV detection at 312 nm. Linearity, accuracy, and precision were found to be acceptable over the concentration range of 0.75–120 μg mL^?1, with regression coefficient value of 0.9999, and with limit of detection and quantitation of 0.148 and 0.447 μg mL^?1, respectively. Peak purity was checked for principle drug and its alkali induced degradation product, and the pathway of alkaline hydrolysis of daclatasvir was suggested by LC/MS.     

Solvolysis of 1,1-dimethyl-4-alkenyl chlorides: evidence for pi-participation

Tertiary 1,1-dimethyl-4-alkenyl chloride (1) solvolyzes with significantly reduced secondary beta-deuterium kinetic isotope effect (substrate with two trideuteromethyl groups) and has a lower entropy and enthalpy of activation than the referent saturated analogue 4 (k(H)/k(D) = 1.30 +/- 0.03 vs k(H)/k(D) = 1.79 +/- 0.01; Delta Delta H(++) = -9 kJ mol(-1), Delta Delta S(++) = -36 J mol(-1) K(-1), in 80% v/v aqueous ethanol), indicating participation of the double bond in the rate-determining step. Transition structure 1-TS computed at the MP2(fc)/6-31G(d) level of theory revealed that the reaction proceeds through a late transition state with considerably pronounced double bond participation and a substantially cleaved C-Cl bond. The doubly unsaturated compound 3 (1,1-dimethyl-4,8-alkadienyl chloride) solvolyzes with further reduction of the isotope effect, and a drastically lower entropy of activation (k(H)/k(D) = 1.14 +/- 0.01; DeltaS(++) = -152 +/- 12 J mol(-1) K(-1), in 80% v/v aqueous ethanol), suggesting that the solvolysis of 3 proceeds by way of extended pi-participation, i.e., the assistance of both double bonds in the rate-determining step.     

Determination of unchanged hydralazine in plasma by gas-liquid chromatography using nitrogen-specific detection

A gas chromatographic method is described for the specific determination of unchanged hydralazine in plasma. On treatment with 2,4-pentanedione, hydralazine is converted into 1-(3,5-dimethyl-1-pyrazolyl)phthalazine, a stable compound which is easily extracted from biological material and determined quantitatively by gas chromatography with nitrogen-specific detection. 4-Methylhydralazine is used as an internal standard. The sensitivity of the method is ca. 10 ng/ml. Hydrazones of hydralazine do not interfere with the assay.     

Photoaddition of thienocoumarin derivatives to DNA: stoichiometry and kinetics of binding

Photoreaction of the 6,9-dimethyl-4-methoxymethyl-2H-thieno[3,2-g]-1-benzopyran-2-one (compound I) and 4-acetoxymethyl-6,9-dimethyl-2H-thieno[3,2-g]-1-benzopyran-2-one (compound II) to DNA was studied. The quantitative evaluation of the photobound molecules was performed by means of inductively coupled plasma atomic emission spectrometry (ICP-AES), exploiting the presence of the sulphur atom inside the tricyclic chromophore. The concurrent estimation of the phosphorus atom, present exclusively in the macromolecule, allowed possible intercalation sites to be identified and their involvement in the photoaddition reaction to be determined. The development of a kinetic model made it possible to discriminate and evaluate the single kinetic events that constitute the overall photoaddition process of I and II to DNA.     

Study of forced degradation behavior of idrocilamide and development of stability indicating LC method

The objective of this study was to report the stability profile of novel muscle relaxant drug idrocilamide (Idr) based on information obtained from forced degradation studies. The drug was subjected to acidic (1 M HCl) and alkaline (1 M NaOH) hydrolysis and oxidative decomposition (50% H₂O₂). The products formed under different stress conditions were investigated by LC. The LC method was fine tuned using the samples generated from forced degradation studies. Satisfactory resolution between peaks with the shortest possible analysis time was achieved on C₁₈ 5 μm column (Luna, Phenomenex, USA), with mobile phase methanol-acetonitrile-water-glacial acetic acid (25: 30: 44: 1, v: v: v: v), pumped at 1 mL/min flow rate. Quantification was achieved at 280 nm based on peak area, using DAD detector. The proposed LC method was utilized to investigate the accelerated oxidative degradation of Idr. Besides, Idr’s degradants were identified using IR and MS, and the possible degradation pathway was outlined. The proposed method was validated, and the forced degradation studies proved the stability indicating power of the method. The method was also applied to analyze commercial samples.