Gulshan Bansal

Coumarin hybrids as novel therapeutic agents

Naturally occurring coumarins, having wide spectrum of activities such as antioxidant, anti-inflammatory, anticancer, MAO-B inhibitory and antimicrobial, are frequently used by the researchers to develop novel synthetic and semisynthetic coumarin based therapeutic agents. Many of these agents are hybrid molecules, which are designed through concept of molecular hybridization and have shown multiple pharmacological activities. This multifunctional attribute of these hybrid compounds makes them potential drug candidates for the treatment of multifactorial diseases such as cancer, Alzheimers disease, metabolic syndromes, AIDS, malaria, and cardiovascular diseases. The present review compiles research reports on development of different coumarin hybrids, classify these on the basis of their therapeutic uses and propose structure-activity relationships. It is intended to help medicinal chemist in designing and synthesizing novel and potent hybrid compounds for the treatment of different disorders.

Coumarin: a potential nucleus for anti-inflammatory molecules

Numerous research reports have indicated the coumarin nucleus as a potential candidate for development of anti-inflammatory drugs. Various phytoconstituents such as umbelliferone, scopoletin, columbiatnetin, visniadin, marmin, and many more derived from coumarin nucleus are found to have potent anti-inflammatory as well as antioxidant activities. A large number of coumarin derivatives have also been designed, synthesized, and evaluated to have mild-to-very potent anti-inflammatory activity through different mechanisms. However, despite the continuing efforts in search of these drugs, no major breakthrough has been achieved so far. In the present review, a critical analysis of various reports on naturally as well as the synthetically derived coumarin derivatives having anti-inflammatory activity has been carried out and a structural–activity relationship around the coumarin nucleus has been proposed to assist the medicinal chemists in rationally designing the anti-inflammatory drugs.

Estimation of Total Phenols and Flavonoids in Extracts of Actaea spicata Roots and Antioxidant Activity Studies

Actaea spicata Linn. (Ranunculaceae) has been traditionally used for the treatment of various ailments such as rheumatism, inflammation, nerve diseases, lumbago, scrofula and chorea, but no systematic phytochemical and pharmacological work has ever been carried out on this potential plant. Preliminary phytochemical screening showed presence of phenols and flavonoids in A. spicata. Thus, the present investigation was undertaken to estimate total phenols and flavonoids in methanol extract of A. spicata roots, and its ethyl acetate fraction. In vitro antioxidant activity was also evaluated in the methanol extract and ethyl acetate fraction using DPPH method. Ethyl acetate fraction was found to contain twice the content of flavonoids and phenols in comparison to methanolic extract, whereas phenolic content in methanol extract was approximately similar to ethyl acetate fraction. A significant antioxidant activity, i.e., mean percentage inhibition of DPPH radical was observed in methanol extract and ethyl acetate fraction at the concentration of 10 μg/ml and 5 μg/ml respectively. Finally, it was suggested that polyphenols are responsible for antioxidant activity of A. spicata.

LC–UV–PDA and LC–MS studies to characterize degradation products of glimepiride

Degradation products of glimepiride formed under different forced conditions have been characterized through LC-UV-PDA and LC-MS studies. Glimepiride was subjected to forced decomposition under the conditions of hydrolysis, oxidation, dry heat and photolysis, in accordance with the ICH guideline Q1A(R2). The reaction solutions were chromatographed on reversed phase C8 (150 mm x 4.6mm i.d., 5 microm) analytical column. In total, five degradation products (I-V) were formed under various conditions. The drug degraded to products II and V under acid and neutral hydrolytic conditions while products I, III and IV were formed under the alkaline conditions. The products II and V were also observed on exposure of drug to peroxide. No additional degradation product was shown up under photolytic conditions. All the products, except I, could be characterized through LC-PDA analyses and study of MS fragmentation pattern in both +ESI and -ESI modes. Product I could not be identified, as it did not ionize under MS conditions. The products II, III and V matched, respectively, to impurity B (glimepiride sulfonamide), impurity J and impurity C (glimepiride urethane) listed in European Pharmacopoeia. The product IV was a new degradation product, characterized as [[4-[2-(N-carbamoyl)aminoethyl]phenyl]sulfonyl]-3-trans-(4-methylcyclohexyl) urea. The degradation pathway of the drug to products II-V is proposed, which is yet unreported.

Novel coumarin-benzimidazole derivatives as antioxidants and safer anti-inflammatory agents.

Inspired from occurrence of anti-inflammatory activity of 3-substituted coumarins and antiulcer activity of various 2-substituted benzimidazoles, novel compounds have been designed by coupling coumarin derivatives at 3-position directly or through amide linkage with benzimidazole nucleus at 2-position. The resultant compounds are expected to exhibit both anti-inflammatory and antioxidant activities along with less gastric toxicity profile. Two series of coumarin–benzimidazole derivatives (4a–e and 5a–e) were synthesized and evaluated for anti-inflammatory activity and antioxidant activity. Compounds 4c, 4d and 5a displayed good anti-inflammatory (45.45%, 46.75% and 42.85% inhibition, respectively, versus 54.54% inhibition by indomethacin) and antioxidant (IC50 of 19.7, 13.9 and 1.2 µmol/L, respectively, versus 23.4 µmol/L for butylatedhydroxytoluene) activities. Evaluation of ulcer index and in vivo biochemical estimations for oxidative stress revealed that compounds 4d and 5a remain safe on gastric mucosa and did not induce oxidative stress in tissues. Calculation of various molecular properties suggests the compounds to be sufficiently bioavailable.

Design, synthesis, and evaluation of 5-sulfamoyl benzimidazole derivatives as novel angiotensin II receptor antagonists

A series of 5-alkylsulfamoyl benzimidazole derivatives have been designed and synthesized as novel angiotensin II (Ang II) receptor antagonists. The compounds have been evaluated for in vitro Ang II antagonism and for in vivo antihypertensive activity on isolated rat aortic ring and desoxycortisone acetate induced hypertensive rats, respectively. The activity is found related to size of alkyl group. The maximum activity is observed with a compact and bulky alkyl group like tert-butyl and cyclohexyl. The compounds 4g and 4h have shown promising both in vitro and in vivo activities. A receptor binding model is also proposed on the basis on the basis of structure-activity relationship in this study.

Thermal characterization and compatibility studies of itraconazole and excipients for development of solid lipid nanoparticles

The current study was performed to investigate possible interactions between triazole antifungal drug itraconazole (ITR) with selected excipients commonly used for development of solid lipid nanoparticles. The excipients included common lipids (glyceryl behenate (Compritol 888 ATO™), glyceryl monostearate, stearic acid, and cetyl palmitate), charge inducers (dicetyl phosphate and stearlyamine), and surfactants (sodium cholate and sodium deoxycholate). Differential scanning calorimetry, isothermal stress testing, Fourier transform infrared spectral analysis, optical microcopy, and X-ray powder diffraction analysis were performed for assessing the compatibility between the drug and the excipients. Results of the study suggest that the stearic acid exhibited drug–excipient interactions, whereas all other excipients used in the study were found to be compatible with ITR.

Four new degradation products of doxorubicin: An application of forced degradation study and hyphenated chromatographic techniques

Forced degradation study on doxorubicin (DOX) was carried out under hydrolytic condition in acidic, alkaline and neutral media at varied temperatures, as well as under peroxide, thermal and photolytic conditions in accordance with International Conference on Harmonization (ICH) guidelines Q1(R2). It was found extremely unstable to alkaline hydrolysis even at room temperature, unstable to acid hydrolysis at 80 °C, and to oxidation at room temperature. It degraded to four products (O-I–O-IV) in oxidative condition, and to single product (A-I) in acid hydrolytic condition. These products were resolved on a C8 (150 mm×4.6 mm, 5 µm) column with isocratic elution using mobile phase consisting of HCOONH4 (10 mM, pH 2.5), acetonitrile and methanol (65:15:20, v/v/v). Liquid chromatography–photodiode array (LC–PDA) technique was used to ascertain the purity of the products noted in LC–UV chromatogram. For their characterization, a six stage mass fragmentation (MS6) pattern of DOX was outlined through mass spectral studies in positive mode of electrospray ionization (+ESI) as well as through accurate mass spectral data of DOX and the products generated through liquid chromatography–time of flight mass spectrometry (LC–MS–TOF) on degraded drug solutions. Based on it, O-I–O-IV were characterized as 3-hydroxy-9-desacetyldoxorubicin-9-hydroperoxide, 1-hydroxy-9-desacetyldoxorubicin-9-hydroperoxide, 9-desacetyldoxorubicin-9-hydroperoxide and 9-desacetyldoxorubicin, respectively, whereas A-I was characterized as deglucosaminyl doxorubicin. While A-I was found to be a pharmacopoeial impurity, all oxidative products were found to be new degradation impurities. The mechanisms and pathways of degradation of doxorubicin were outlined and discussed.

Characterization of degradation products of idarubicin through LC-UV, MSn and LC–MS-TOF studies

Idarubicin was subjected to forced degradation under the ICH recommended conditions of hydrolysis, oxidation, dry heat and photolysis to characterize its possible impurities and/or degradation products. The drug was found unstable to acid hydrolysis at 85°C and to alkaline hydrolysis, and oxidation at room temperature. The hydrolytic and oxidative degradation products were resolved with gradient and isocratic elution, respectively on an Inertsil RP18 (250 mm × 4.6mm; 5 μ) column with HCOONH4 (20mM, pH 3.0) and acetonitrile. The drug degraded to two products (O-I and O-II) in oxidative condition, two products (K-I and K-II) in alkaline hydrolytic, and one product (A-I) in acidic hydrolytic conditions. The purity of each in the LC-UV chromatogram was ascertained through LC-PDA analysis. The products were characterized through +ESI-MS(n) studies on the drug and LC-MS-TOF studies on the degraded drug solutions. Based on the multistage mass fragmentation pattern of idarubicin and accurate mass analysis of the degradation products, the O-I, O-II and A-I were characterized as desacetylidarubicin hydroperoxide, desacetylidarubicin and deglucosaminylidarubicin, respectively. The products K-I and K-II were not characterized due to their low concentrations and/or extremely weak ionization. The mechanisms of degradation of idarubicin to these products were proposed and discussed.

Preparation and cyclodextrin assisted dissolution rate enhancement of itraconazolium dinitrate salt

The poor solubility of itraconazole (ITR) results in its variable oral absorption and bioavailability and has also proven to be a major setback in developing an efficient oral delivery system. To improve its solubility and dissolution profile, itraconazolium dinitrate salt (ITRDNT) was prepared and characterized using various spectral and thermal techniques. The morphology of the salt was studied using optical and scanning electron microscopy (SEM). Broth microdilution assay demonstrated antifungal efficacy of ITRDNT similar to ITR against four different fungal strains namely, Asparagillus fumigatus, Microsporum canis, Microsporum gypsum and Trichophyton rubrum. The salt exhibited better solubility profile than ITR in water and a number of pharmaceutical solvents. Dissolution studies revealed the total amount of drug released from ITRDNT in 3 h was four times greater than that of ITR. To further improve dissolution characteristics, the physical mixtures of ITR and ITRDNT with two cyclodextrins, β-cyclodextrin (β-CD) and HP-β-cyclodextrin (HP-β-CD) were prepared and their molar ratios were optimized. It was observed that about 75% of drug was released in 30 min from 1:3 molar ratio of ITRDNT and HP-β-CD physical mixture, which was distinctly higher than ITR commercial capsules (70%). Owing to its facile and economical preparation and substantially better in vitro release profile, the ITRDNT and its CD physical mixtures could be better and cost effective alternatives to ITR and commercial ITR capsules.