Oral bioavailability and pharmacodynamic activity of hesperetin nanocrystals generated using a novel bottom-up technology.

In the present study, nanocrystalline solid dispersion (NSD) was developed to enhance the release rate and oral bioavailability of hesperetin (HRN). NSD of HRN was prepared using a novel bottom-up technology platform. It is a spray drying based technology to generate solid particles, containing drug nanocrystals dispersed in small molecule excipients. HRN and mannitol were used in a 5:5 ratio, and an average crystallite size of HRN in NSD with mannitol was found to be 137.3 ± 90.0 nm. An in vitro release study revealed a statistically significant release rate enhancement for HRN nanocrystals (46.3 µg/mL/min) as compared to that of the control (29.5 µg/mL/min). Further, a comparative oral bioavailability study of NSD and control in Sprague-Dawley rats established significant improvement in Cmax and oral bioavailability (AUC0-∞) by 1.79- and 2.25-fold, respectively, for HRN nanocrystals. The findings of oral bioavailability were corroborated by intestinal uptake and Caco-2 cell uptake studies, wherein HRN, when administered in nanocrystalline form, showed higher penetration in intestinal mucosa and higher uptake in Caco-2 cells. Finally, the therapeutic efficacy of HRN nanocrystals was tested by a reactive oxygen species (ROS) generation assay and carrageenan induced anti-inflammatory model. HRN nanocrystals markedly inhibited ROS generation in MCF-7 cells, and carrageenan induced inflammation in rats. The process of NSD formation was found to be based on classical nucleation theory wherein mannitol contributed to NSD formation by acting as a plasticizer and crystallization inducer, and by providing sites for heterogeneous nucleation/crystallization.

SNEDDS curcumin formulation leads to enhanced protection from pain and functional deficits associated with diabetic neuropathy: an insight into its mechanism for neuroprotection.

Curcumin has shown to be effective against various diabetes related complications. However major limitation with curcumin is its low bioavailability. In this study we formulated and characterized self nano emulsifying drug delivery system (SNEDDS) curcumin formulation to enhance its bioavailability and then evaluated its efficacy in experimental diabetic neuropathy. Bioavailability studies were performed in male Sprague Dawley rats. Further to evaluate the efficacy of formulation in diabetic neuropathy various parameters like nerve function and sensorimotor perception were assessed along with study of inflammatory proteins (NF-κB, IKK-ß, COX-2, iNOS, TNF-α and IL-6). Nanotechnology based formulation resulted in prolonged plasma exposure and bioavailability. SNEDDS curcumin provided better results against functional, behavioural and biochemical deficits in experimental diabetic neuropathy, when compared with naive curcumin. Further western blot analysis confirmed the greater neuroprotective action of SNEDDS curcumin. SNEDDS curcumin formulation due to higher bioavailability was found to afford enhanced protection in diabetic neuropathy. FROM THE CLINICAL EDITOR: In this study the authors formulated and characterized a self-emulsifying drug delivery system for formulation to enhance curcumin bioavailability in experimental diabetic neuropathy. Enhanced efficacy was demonstrated in a rat model.

Effect of counterions on physicochemical properties of prazosin salts.

This study evaluated the effect of counterions on the physicochemical properties of prazosin salts. Salt forms of prazosin, namely, mesylate, besylate, tosylate, camsylate, oxalate, and maleate, were prepared and compared with the marketed anhydrous and polyhydrate forms of prazosin hydrochloride. Physicochemical characterization was performed in the order of crystallinity, hygroscopicity, solubility, and stability to select the optimal salt(s). Permeability study in Caco-2 cell lines and in vivo bioavailability study in rat model were investigated to ascertain their biopharmaceutical advantage. All salt forms were crystalline, nonhygroscopic (except the anhydrous hydrochloride salt), and had solubility in the range of 0.2 to 1.6 mg/ml. All salts were physically and chemically stable at 40°C/75% relative humidity, but degraded in UV-visible light, except the anhydrous hydrochloride salt. Prazosin mesylate was selected as the optimal salt, as it possessed higher solubility, permeability, and bioavailability, compared to the commercial hydrochloride salts. Hydrochloride salt is reported to have poor bioavailability that is partially attributed to its low solubility and extensive common-ion effect in the gastric region. Factors like hydrophilicity of the counterion, hydration state of the salt, and melting point of the salt contribute to the physicochemical properties of the salts. This study has implications in the selection of an optimal salt form for prazosin, which is suitable for further development.

Novel lipid based oral formulation of curcumin: development and optimization by design of experiments approach.

The clinical utility of curcumin (CRM) is limited due to its poor oral bioavailability. Lipid based oral formulations (LBOFs) are emerging as useful oral drug delivery systems for 'difficult to deliver' molecules like CRM. In present study, we report novel Type IV LBOF for CRM using Gelucire 44/14, Labrasol, Vit. E TPGS and PEG 400 with superior CRM loading and enhanced oral bioavailability. The optimization of LBOF for CRM loading and post dilution droplet size was carried out by design of experiments (DoE) approach with Box-Behnken design. Oral bioavailability of optimized LBOF (O-LBOF) was evaluated in male Sprague-Dawley (SD) rats at a dose of 250 mg/kg. Raw CRM (control) showed C(max) and AUC(0-∞) of 32.29 ng/ml and 38.07 ng h/ml, respectively. O-LBOF improved C(max) and AUC(0-∞) by 11.6 and 35.8 folds respectively over control.

Mechanistic insights into PEPT1-mediated transport of a novel antiepileptic, NP-647.

The present study, in general, is aimed to uncover the properties of the transport mechanism or mechanisms responsible for the uptake of NP-647 into Caco-2 cells and, in particular, to understand whether it is a substrate for the intestinal oligopeptide transporter, PEPT1 (SLC15A1). NP-647 showed a carrier-mediated, saturable transport with Michaelis-Menten parameters K(m) = 1.2 mM and V(max) = 2.2 µM/min. The effect of pH, sodium ion (Na(+)), glycylsarcosine and amoxicillin (substrates of PEPT1), and sodium azide (Na(+)/K(+)-ATPase inhibitor) on the flux rate of NP-647 was determined. Molecular docking and molecular dynamics simulation studies were carried out to investigate molecular interactions of NP-647 with transporter using homology model of human PEPT1. The permeability coefficient (P(appCaco-2)) of NP-647 (32.5 × 10(-6) cm/s) was found to be four times higher than that of TRH. Results indicate that NP-647 is transported into Caco-2 cells by means of a carrier-mediated, proton-dependent mechanism that is inhibited by Gly-Sar and amoxicillin. In turn, NP-647 also inhibits the uptake of Gly-Sar into Caco-2 cells and, together, this evidence suggests that PEPT1 is involved in the process. Docking and molecular dynamics simulation studies indicate high affinity of NP-647 toward PEPT1 binding site as compared to TRH. High permeability of NP-647 over TRH is attributed to its increased hydrophobicity which increases its affinity toward PEPT1 by interacting with the hydrophobic pocket of the transporter through hydrophobic forces.

Phase behavior and oral bioavailability of amorphous Curcumin.

Amorphous form has been used as a means to improve aqueous solubility and oral bioavailability of poorly water soluble drugs. The objective of present study was to characterize thermodynamic and kinetic parameters of amorphous form of Curcumin (CRM-A). CRM-A was found to be a good glass former with glass transition temperature (T(g)) of 342.64K and critical cooling rate below 1K/min. CRM-A had a moderate tendency of crystallization and exhibited Kauzmann temperature (T(KS)) of 294.23 K. CRM-A was found to be fragile in nature as determined by T(m)/T(g) (1.32), C(p)(1 iq):C(p)(glass) (1.22), strength parameter (D<10), fragility index (m>75), T(K)/T(g) (0.85), and T(g)-T(K) (48.41). Theoretically predicted aqueous solubility advantage of 43.15-folds, was reduced to 17-folds under practical conditions. This reduction in solubility was attributed to water induced devitrification, as evident through PXRD and SEM analysis. Further, oral bioavailability study of CRM-A was undertaken to investigate bioavailability benefits, if any. C(max) was improved by 1.97-folds (statistically significant difference over control). However, oral bioavailability (AUC(0-)(∞)) was improved by 1.45-folds (statistically non significant difference over control). These observations pointed towards role of rapid devitrification of CRM-A in GIT milieu, thus limiting its oral bioavailability advantage.

Bioavailability of a lipidic formulation of curcumin in healthy human volunteers.

Numerous publications have reported the significant pharmacodynamic activity of Curcumin (CRM) despite low or undetectable levels in plasma. The objective of the present study was to perform a detailed pharmacokinetic evaluation of CRM after the oral administration of a highly bioavailable lipidic formulation of CRM (CRM-LF) in human subjects. Cmax, Tmax and AUC0-¥ were found to be 183.35 ± 37.54 ng/mL, 0.60 ± 0.05 h and 321.12 ± 25.55 ng/mL respectively, at a dose of 750 mg. The plasma profile clearly showed three distinct phases, viz., absorption, distribution and elimination. A close evaluation of the primary pharmacokinetic parameters provided valuable insight into the behavior of the CRM after absorption by CRM-LF. CRM-LF showed a lag time (Tlag) of 0.18 h (around 12 min). Pharmacokinetic modeling revealed that CRM-LF followed a two-compartment model with first order absorption, lag time and first order elimination. A high absorption rate constant (K01, 4.51/h) signifies that CRM-LF ensured rapid absorption of the CRM into the central compartment. This was followed by the distribution of CRM from the central to peripheral compartment (K12, 2.69/h). The rate of CRM transfer from the peripheral to central compartment (K21, 0.15/h) was slow. This encourages higher tissue levels of CRM as compared with plasma levels. The study provides an explanation of the therapeutic efficacy of CRM, despite very low/undetectable levels in the plasma.

Identification of permeability-related hurdles in oral delivery of curcumin using the Caco-2 cell model.

Curcumin a poly-phenolic compound possesses diverse pharmacologic activities; however, its development as a drug has been severely impeded by extremely poor oral bioavailability. Poor aqueous solubility and extensive metabolism have been implicated for this but the role of membrane permeability has not been investigated. In the present study, permeability of curcumin was assessed using the Caco-2 cell line. Curcumin was poorly permeable with a P(app) (A → B) value of 2.93 ± 0.94 × 10(-6)cm/s. P(app) value in (B → A) study was found out to be 2.55 ± 0.02 × 10(-6)cm/s, thus ruling out the role of efflux pathways in poor oral bioavailability of curcumin. Studies using verapamil, a P-gp inhibitor, further confirmed this finding. Detailed mass balance studies showed loss of curcumin during transport. Further experiments using lysed cells revealed that 11.78% of curcumin was metabolized during transport. Studies using itraconazole, a CYP3A4 inhibitor, established its role in curcumin metabolism. Curcumin was also found to accumulate in cells as revealed by CLSM studies. Sorption and desorption kinetic studies further confirmed accumulation of curcumin inside the cells. Amount accumulated was quantitated by HPLC and found to be >20%. Thus, intestinal first-pass metabolism and intracellular accumulation played a role in poor permeability of curcumin. Based on its poor aqueous solubility and intestinal permeability, curcumin can be classified as a BCS Class IV molecule. This information can facilitate designing of drug delivery systems for enhancement of oral bioavailability of curcumin.