Rabi Sankar Bhatta

Mucoadhesive nanoparticles for prolonged ocular delivery of natamycin: In vitro and pharmacokinetics studies

The aim of this study was to prepare natamycin encapsulated lecithin/chitosan mucoadhesive nanoparticles (NPs) for prolonged ocular application. These NPs were characterized by their mean particle size 213nm, encapsulation efficiency 73.57%, with a theoretical drug loading 5.09% and zeta potential +43. In vitro release exhibited a biphasic drug release profile with initial burst followed by a very slow drug release. The MIC(90) and zone of inhibition of NPs showed similar antifungal activity as compared to marketed suspension and free natamycin against Candida albicans and Aspergillus fumigates. The ocular pharmacokinetics of NPs and marketed formulation were evaluated in NZ rabbits. The NPs exhibit significant mucin adhesion. The AUC((0-∞)) was increased up to 1.47 fold and clearance was decreased up to 7.4-fold as compared to marketed suspension. The PK-PD and pharmacokinetic simulation was carried out to estimate optimum dosing regimen for good efficacy. Thus, lecithin/chitosan NPs could be considered useful approach aiming to prolong ocular residence and reduce dosing frequency.

Anti-platelet effects of Curcuma oil in experimental models of myocardial ischemia-reperfusion and thrombosis

Extensive research on the mechanism of action and medicinal importance of curcumin obtained from turmeric (Curcuma longa) has unfolded its potential therapeutic value against many chronic ailments. Curcuma oil (C.oil), the highly lipophilic component from Curcuma longa has been documented for its neuroprotective efficacy against rat cerebral ischemia-reperfusion injury; however its effect on myocardial reperfusion injury remains unexplored. In the present study, effect of C.oil (500 mg/kg, po) was evaluated against myocardial ischemia-reperfusion induced injury in the rat model. C.oil failed to confer protection against cardiac injury, however significant reversal of ADP induced platelet aggregation (p<0.05) was evident in the same animals. Moreover, collagen and thrombin induced platelet aggregation (p<0.001) as well as tyrosine phosphorylation of various proteins in activated platelets was also suppressed. C.oil also offered significant protection against collagen-epinephrine induced thromboembolism in mice as well as augmented total time to occlusion against FeCl(3) induced arterial thrombosis in rats. C.oil however had no effect on coagulation parameters (TT, PT and aPTT) and exerted a mild effect on the bleeding time. Bioavailability of C.oil, as assessed by monitoring ar-turmerone, α,β-turmerone and curlone, was 13%, 11% and 7% respectively, indicating high systemic exposure. Moreover, longer mean residence time (MRT) of ar-turmerone (13.2h), α,β-turmerone (11.6h) and Curlone (14.0 h) and plasma elimination half lives in the range of 5.5 to 7.2h correlated with single 500 mg/kg dose regimen of C.oil. In the present study, C.oil thus seems to be an efficacious and safe anti-platelet agent which was protective against intravascular thrombosis.

Amphotericin-B entrapped lecithin/chitosan nanoparticles for prolonged ocular application.

Fungal keratitis is the major cause of vision loss worldwide. Amphotericin-B is considered as the drug of choice for fungal infections. However, its use in ophthalmic drug delivery is limited by the low precorneal residence at ocular surface as a result of blinking reflex, tear turnover and nasopharyngeal drainage. We report Amphotericin-B loaded lecithin/chitosan nanoparticles for prolonged ocular application. The prepared nanoparticles were in the size range of 161.9-230.5 nm, entrapment efficiency of 70-75%, theoretical drug loading of 5.71% with positive zeta potential of 26.6-38.3 mV. As demonstrated by antifungal susceptibility against Candida albicans and Aspergillus fumigatus, nanoparticles were more effective than marketed formulation. They exhibited pronounced mucoadhesive properties. In-vivo pharmacokinetic studies in New Zealand albino rabbit eyes indicated improved bioavailablity (∼ 2.04 fold) and precorneal residence time (∼ 3.36 fold) by nanoparticles prepared from low molecular weight chitosan as compared with marketed formulation.

Synthesis, structure-activity relationships, and biological studies of chromenochalcones as potential antileishmanial agents.

Antileishmanial activities of a library of synthetic chalcone analogues have been examined. Among them, five compounds (11, 14, 16, 17, 22, and 24) exhibited better activity than the marketed drug miltefosine in in vitro studies against the intracellular amastigotes form of Leishmania donovani. Three promising compounds, 16, 17, and 22, were tested in a L. donovani/hamster model. Oral administration of chalcone 16, at a concentration of 100 mg/kg of body weight per day for 5 consecutive days, resulted in >84% parasite inhibition at day 7 post-treatment and it retained the activity until day 28. The molecular and immunological studies revealed that compound 16 has a dual nature to act as a direct parasite killing agent and as a host immunostimulant. Pharmacokinetics and serum albumin binding studies also suggest that compound 16 has the potential to be a candidate for the treatment of the nonhealing form of leishmaniasis.

Discovery of a new class of HMG-CoA reductase inhibitor from Polyalthia longifolia as potential lipid lowering agent.

Bioassay guided fractionation of the ethanolic extract of Polyalthia longifolia var. pendula, led to the discovery of the clerodane diterpene, 16α-hydroxycleroda-3, 13 (14) Z-dien-15, 16-olide (1), as a new structural class of HMG-CoA reductase inhibitor. Importantly, the in vivo effects of 1 corroborated well with its molecular docking analysis and also with its hamster plasma pharmacokinetics.

Identification of quinoline-chalcone hybrids as potential antiulcer agents

Antiulcer activity of novel quinoline-chalcone hybrids (13-37) was investigated. Among them, eight compounds (14, 16, 17, 23, 29, 31, 32 and 35) were found to be active in various ulcer models in Sprague-Dawley (SD) rats. To understand the mechanism of action of these hybrids, the effects of the compounds on antisecretory and cytoprotective activities were studied. All these active hybrids improved the depleted levels of mucin and consequently inhibited the formation of erosions in a pyloric ligated ulcer model. In addition, they also significantly increased the gastric PGE2 content in an aspirin induced ulcer model. The additional experiments including the in vitro metabolic stability and in vivo pharmacokinetics led to the identification of compound 17 as an orally active and safe candidate that is worthy of further investigation to be developed as an antiulcer agent.

Bioanalytical method development and validation of natamycin in rabbit tears and its application to ocular pharmacokinetic studies

A new selective and sensitive high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of natamycin in rabbit tears using amphotericin B as internal standard (IS). Chromatographic separation was achieved on a Luna Cyano column (100 mm × 2 mm, 3 μm) using ammonium acetate buffer (pH 4; 3.5mM): methanol (10:90, v/v) as the mobile phase. The run time was 5 min. Detection was performed by negative ion electrospray ionization in multiple reaction monitoring (MRM) mode. The calibration curve was linear over the concentration range from 25 to 800 ng/ml, and lower limit of detection of 12.5 ng/ml. The accuracy and precision of the method were within the acceptable limit of ± 20% at the lower limit of quantitation and ± 15% at other concentrations. Natamycin was stable during the battery of stability studies viz., bench-top, auto-sampler, freeze/thaw cycles and 30 days storage in a freezer at -70 ± 10 °C. The method was successfully applied to the ocular pharmacokinetic studies of natamycin eye drops in New Zealand rabbit tears.

Corneal targeted nanoparticles for sustained natamycin delivery and their PK/PD indices: an approach to reduce dose and dosing frequency.

Natamycin is the only approved medication for the treatment of mycotic keratitis. Current dosage regimen include one drop of natamycin suspension (5% w/v) instilled in the conjunctival sac at hourly or two hourly intervals for several days which has poor patient compliance. The purpose of the present study was to design a corneal targeted nanoformulation in order to reduce dose and dosing frequency of natamycin and evaluate its pharmacokinetic/pharmacodynamic indices in comparison with clinical marketed preparation. The nanoparticles prepared by nanoprecipitation method were in nanometer size range with high entrapment efficiency and positive surface charge. In-vitro release studies indicated prolonged release of natamycin up to 8h. In-vitro antifungal activity was comparable with marketed preparation. The performance of nanoformulations was evaluated in rabbit eyes. The concentration of natamycin in tear fluid was determined by using LC-MS/MS. The pharmacokinetic parameters such as area under the curve, t½ and mean residence time were significantly higher and clearance was significantly lower for nanoformulations with that of marketed preparation. The optimized dosing schedule to maintain natamycin concentration above tenfold of MIC90 was one instillation in every 5h. Moreover, 1/5th dose reduction of nanoformulation was also effective.

Pharmacokinetic, bioavailability, metabolism and plasma protein binding evaluation of NADPH-oxidase inhibitor apocynin using LC-MS/MS.

Apocynin is a major active constituent of Picrorhiza kurroa that exhibits potent anti-inflammatory activity by inhibiting superoxide-generating NADPH oxidase enzyme. To elucidate detailed pharmacokinetic profile of apocynin, high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed in rat and human plasma. To the best of our knowledge, this is the first method for complete validation of apocynin in biological matrix using LC-MS/MS. Apocynin was rapidly absorbed after oral administration at 50mg/kg in rats and peak plasma level achieved within 5min. Moreover, plasma levels were observed up to 48h. The bioavailibity of apocynin was found to be 8.3%. In vitro plasma protein binding was found to be 83.41-86.07% and 71.39-73.34% in rat and human plasma, respectively. Apocynin was found stable in gastric (pH 1.2), intestinal (pH 6.8) and physiological (pH 7.4) fluids including microsomal (rat and human) stability studies. Further, apocynin did not convert to its dimeric form diapocynin in any of these studies. The data presented here provide crucial information about apocynin to support its pharmacological efficacy and further development as a potential anti-inflammatory drug candidate.

Development of an LC-MS/MS method for simultaneous determination of memantine and donepezil in rat plasma and its application to pharmacokinetic study.

Recently, a fixed dose combination (FDC) of memantine (MM) and donepezil (DPZ) has been approved for the treatment of Alzheimers disease (AD). In the present work, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous determination of MM and DPZ was developed and validated in rat plasma over the linearity range of 0.2-400ng/mL using amantadine (AM) as an internal standard. Both the analytes and IS were extracted using one step liquid-liquid extraction procedure. The analytes were separated on C18 reversed phase column with mobile phase consisting of a mixture of methanol and 10mM ammonium acetate, pH 5 (92:8 v/v) at a flow rate of 0.7mL/min. The detection of the analytes was done on triple quadrupole mass spectrometer operated in positive electrospray ionization mode (ESI) and quantified using multiple reaction monitoring (MRM). The method was fully validated in terms of linearity, accuracy, precision, recovery, matrix effect, dilution integrity, carry-over effect and stability. The within- and between-run precisions were <10% and accuracy was all within ±10%. The mean recovery of MM and DPZ was found to be greater than 80%. The % RSD value at higher as well as lower concentration was well within the acceptable range (±15%) in all the stability experiments. The method was successfully applied to the oral pharmacokinetics and drug-drug interaction study of MM and DPZ in male Sprague Dawley (SD) rats.