Preparation, characterization, and pharmacokinetics of oridonin-loaded liposomes.

The aim of this study was to prepare oridonin liposomes and evaluate the physicochemical characteristics and pharmacokinetics in rats. A three-level, three-factor Box-Behnken design was used to optimize the preparation of oridonin liposomes. A highly sensitive high-performance liquid chromatographic quantification method using ultraviolet detection was established and validated for the determination of oridonin in rat plasma. Twelve Sprague-Dawley rats were randomly assigned and injected with 15 mg/kg of oridonin or oridonin liposomes via the tail vein. Pharmacokinetic parameters were estimated using a compartmental modeling approach using PKsolver software. The optimum conditions were as follows: soybean phospholipids/cholesterol ratio, 3.9:1; soybean phospholipids/drug ratio, 8.5:1; and soybean phospholipid concentration, 1.1%. Under these conditions, the mean particle size, polydispersity index, zeta potential, and encapsulation efficiency of oridonin liposomes were 170.5 nm, 0.246, -30.3 mV, and 76.15%, respectively. The pharmacokinetic results showed that liposomes could significantly prolong the elimination half-life (from 2.88 ± 0.55 to 13.67 ± 3.52 h), increase the area under the concentration-time curve (from 1.65 ± 0.17 to 6.22 ± 0.83 µg h/ml), and decrease the clearance (from 6.62 ± 1.38 to 1.96 ± 0.24 L/kg h). The oridonin liposomes increased the elimination half-life and area under the concentration-time curve and provided a reference for the development of drugs with a short half-life.

Preparation, Characterization, and Evaluation of Liposomes Containing Oridonin from Rabdosia rubescens.

Due to the remarkable anti-tumor activities of oridonin (Ori), research on Rabdosia rubescens has attracted more and more attention in the pharmaceutical field. The purpose of this study was to extract Ori from R. rubescens by ultrasound-assisted extraction (UAE) and prepare Ori liposomes as a novel delivery system to improve the bioavailability and biocompatibility. Response surface methodology (RSM), namely Box-Behnken design (BBD), was applied to optimize extraction conditions, formulation, and preparation process. The results demonstrated that the optimal extraction conditions were an ethanol concentration of 75.9%, an extraction time of 35.7 min, and a solid/liquid ratio of 1:32.6. Under these optimal conditions, the extraction yield of Ori was 4.23 mg/g, which was well matched with the predicted value (4.28 mg/g). The optimal preparation conditions of Ori liposomes by RSM, with an ultrasonic time of 41.1 min, a soybean phospholipids/drug ratio of 9.6 g/g, and a water bath temperature of 53.4 °C, had higher encapsulation efficiency (84.1%). The characterization studies indicated that Ori liposomes had well-dispersible spherical shapes and uniform sizes with a particle size of 137.7 nm, a polydispersity index (PDI) of 0.216, and zeta potential of -24.0 mV. In addition, Ori liposomes presented better activity than free Ori. Therefore, the results indicated that Ori liposomes could enhance the bioactivity of Ori, being proposed as a promising vehicle for drug delivery.

Solubility and Bioavailability Enhancement of Oridonin: A Review.

Oridonin (ORI), an ent-kaurene tetracyclic diterpenoid compound, is isolated from Chinese herb Rabdosia rubescens with various biological and pharmacological activities including anti-tumor, anti-microbial and anti-inflammatory effects. However, the clinical application of ORI is limited due to its low solubility and poor bioavailability. In order to overcome these shortcomings, many strategies have been explored such as structural modification, new dosage form, etc. This review provides a detailed discussion on the research progress to increase the solubility and bioavailability of ORI.

Validation of an UHPLC-MS/MS Method for the Determination of Glaucocalyxin A, a Novel Potent Negative Akt Regulator in Rat Plasma, Lung and Brain Tissues: Application to a Pharmacokinetic Study.

Glaucocalyxin A, a novel potent negative Akt regulator, is a major active constituent of Rabdosia japonica. A simple, specific and sensitive ultra-high pressure liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for the quantification of glaucocalyxin A in rat plasma, lung and brain tissues after intravenous administration. Sample preparation was carried out through a simple liqiud-liquid extraction with ethyl acetate using bullatine A as internal standard. The chromatographic separation was achieved by using an Agilent ZORBAX Eclipse Plus C18 column (3.0 mm × 100 mm, 1.8 µm) with a mobile phase of acetonitrile and water containing 0.1% formic acid in a gradient elution. Mass spectrometry analysis was conducted in positive ionization mode with multiple reaction monitoring transitions at m/z 333.2 â†’ 157.1 for glaucocalyxin A and m/z 344.2 â†’ 128.1 for IS. Calibration curves were linear over the ranges of 20.0-4000 ng/mL for both plasma and tissue samples (r2 > 0.99). The Lower limit of quantification (LLOQ) was 0.284 ng/mL. The intra-day and inter-day precision relative standard deviation (RSD%) were <14.9%, while the accuracy ranged from -12.5 to 17.0% for LLOQ and quality control samples. This UHPLC-MS/MS method was successfully applied in the pharmacokinetics, lung and brain tissue distributions of glaucocalyxin A after intravenous administration.

Ceramide-Rubusoside Nanomicelles, a Potential Therapeutic Approach to Target Cancers Carrying p53 Missense Mutations.

Ceramide (Cer) is an active cellular sphingolipid that can induce apoptosis or proliferation-arrest of cancer cells. Nanoparticle-based delivery offers an effective approach for overcoming bioavailability and biopharmaceutics issues attributable to the pronounced hydrophobicity of Cer. Missense mutations of the protein p53, which have been detected in approximately 42% of cancer cases, not only lose the tumor suppression activity of wild-type p53, but also gain oncogenic functions promoting tumor progression and drug resistance. Our previous works showed that cellular Cer can eradicate cancer cells that carry a p53 deletion-mutation by modulating alternative pre-mRNA splicing, restoring wild-type p53 protein expression. Here, we report that new ceramide-rubusoside (Cer-RUB) nanomicelles considerably enhance Cer in vivo bioavailability and restore p53-dependent tumor suppression in cancer cells carrying a p53 missense mutation. Natural RUB encapsulated short-chain C6-Cer so as to form Cer-RUB nanomicelles (∼32 nm in diameter) that substantially enhanced Cer solubility and its levels in tissues and tumors of mice dosed intraperitoneally. Intriguingly, Cer-RUB nanomicelle treatments restored p53-dependent tumor suppression and sensitivity to cisplatin in OVCAR-3 ovarian cancer cells and xenograft tumors carrying p53 R248Q mutation. Moreover, Cer-RUB nanomicelles showed no signs of significant nonspecific toxicity to noncancerous cells or normal tissues, including bone marrow. Furthermore, Cer-RUB nanomicelles restored p53 phosphorylated protein and downstream function to wild-type levels in p53 R172H/+ transgenic mice. Altogether, this study, for the first time, indicates that natural Cer-RUB nanomicelles offer a feasible approach for efficaciously and safely targeting cancers carrying p53 missense mutations.

Rubusoside-assisted solubilization of poorly soluble C6-Ceramide for a pilot pharmacokinetic study.

Although C6-Ceramide has attracted much attention as a possible tumor suppressor, the delivery of C6-Ceramide is still challenging due to its inherent hydrophobicity and insolubility. In this study we explored the use of a natural compound rubusoside (RUB) as a solubilizer to enhance the solubility of a fluorescence-labeled C6-Ceramide (NBD C6-Ceramide) and to characterize its pharmacokinetics and tissue distribution in an animal model. RUB significantly enhanced the solubility of NBD C6-Ceramide by forming nanomicelles, and efficiently delivered NBD C6-Ceramide in rats by oral and intravenous administration. RUB loaded 1.96 % of NBD C6-Ceramide in the nanomicelles and solubilized it to a concentration of 3.6 mg/mL in water. NBD C6-Ceramide in nanomicelles remained stable in aqueous solutions, allowing intravenous administration without the use of any organic solvents or surfactants. After oral administration, NBD C6-Ceramide rapidly rose to peak plasma concentrations within the first 90 min, distributed to tissues, and remained in vivo for more than 24 h. Tissular levels of NBD C6-Ceramide from high to low were associated with heart, lung, cerebellum, testicle, spleen, liver, kidney, and brain. Altogether, our study demonstrated that RUB-assisted nanomicelles can serve as an efficient and convenient delivery system for short-chain C6-Ceramide and enable in vivo evaluation of potential new cancer treatments.

A compartmental approach to isosteviol's disposition in Sprague-Dawley rats.

Isosteviol has been reported to reverse hypertrophy and related inflammatory responses in in vitro models representative of cardiac muscle cells. The disposition of isosteviol is, however, characterized by secondary peaks and long plasma residence time despite reports of a relatively short half-life in liver fractions. The present study describes a compartmental approach to modelling the secondary peaks characteristic of isosteviol's concentration-time data in Sprague-Dawley rats. Oral (4 mg/kg) and intravenous (4 mg/kg) doses of isosteviol were administered to male and female Sprague-Dawley rats. Plasma samples collected between 0 and 72 h, and total bile secreted in 24 h, were analysed for isosteviol content with LC-MS/MS techniques. The disposition of isosteviol was, thereafter, described with a structural model that accounted for the sampling, liver and biliary secretion compartments, with a gap-time characterizing the accumulation and subsequent emptying of isosteviol for re-absorption. The half-life of isosteviol following oral dosing was about 103% greater in female rats than in the male, and the model-derived area under the concentration-time curve (AUC) in 72 h was about 756% greater in female animals than in males. Following the administration of intravenous doses of isosteviol, half-life and AUC in 24 h were about 332% and 595%, respectively, higher in female rats than in males. Isosteviol equivalent secreted into bile over 24 h accounted for about 94% of orally administered dose in male rats, and about 59% of oral dose in females. These findings show a differential systemic removal of isosteviol in Sprague-Dawley rats, likely explainable by gender-related differences in the glucuronidation-capacity of isosteviol.

Influence of verapamil on the pharmacokinetics of oridonin in rats.

Context: Oridonin has been traditionally used in Chinese treatment of various cancers, but its poor bioavailability limits its therapeutic uses. Verapamil can enhance the absorption of some drugs with poor oral bioavailability. Whether verapamil can enhance the bioavailability of oridonin is still unclear.Objective: This study investigated the effect of verapamil on the pharmacokinetics of oridonin in rats and clarified its main mechanism.Materials and methods: The pharmacokinetic profiles of oral administration of oridonin (20 mg/kg) in Sprague-Dawley rats with two groups of six animals each, with or without pre-treatment of verapamil (10 mg/kg/day for 7 days) were investigated. The effects of verapamil on the transport and metabolic stability of oridonin were also investigated using Caco-2 cell transwell model and rat liver microsomes.Results: The results showed that verapamil could significantly increase the peak plasma concentration (from 146.9 ± 10.17 to 193.97 ± 10.53 ng/mL), and decrease the oral clearance (from 14.69 ± 4.42 to 8.09 ± 3.03 L/h/kg) of oridonin. The Caco-2 cell transwell experiments indicated that verapamil could decrease the efflux ratio of oridonin from 1.67 to 1.15, and the intrinsic clearance rate of oridonin was decreased by the pre-treatment with verapamil (40.06 ± 2.5 vs. 36.09 ± 3.7 µL/min/mg protein).Discussion and conclusions: These results indicated that verapamil could significantly change the pharmacokinetic profile of oridonin in rats, and it might exert these effects through increasing the absorption of oridonin by inhibiting the activity of P-gp, or through inhibiting the metabolism of oridonin in rat liver. In addition, the potential drug-drug interaction should be given special attention when verapamil is used with oridonin. Also, the dose of oridonin should be carefully selected in the clinic.

Preparation, optimization of the inclusion complex of glaucocalyxin A with sulfobutylether-ß-cyclodextrin and antitumor study.

Glaucocalyxin A (GLA), is a diterpenoid extracted from Hara and has been studied for decades for its diverse bioactivities. However, GLA presents poor solubility in water and low bioavailability through oral administration which has hindered its application in the clinic. So in this study, we prepared the inclusion complex of GLA in SBE-ß-CD by ultrasound method and evaluated its antitumor effect and cytotoxic effect on cancer cells. The production of GLA-SBE-ß-CD inclusion complex was optimized using Box-Behnken design. The inhibitory effects of GLA and GLA-SBE-ß-CD were investigated on the Hela, A549, HepG2, and SiHa cells in vitro by MTT staining assay. Pharmacokinetic studies were conducted on Sprague-Dawley mice via caudal injection to study the distribution, metabolism, and elimination of GLA-SBE-ß-CD in vivo. Tumor-bearing nude mice were taken as the model and adopted to evaluate the inhibitory rate of GLA and GLA-SBE-ß-CD on the transplanted tumor. A series of physical characterization results confirmed the fact that GLA-SBE-ß-CD inclusion complex was successfully prepared. A production of 87.28% was achieved based on the Box-Behnken design. In the cancer cell inhibition studies, GLA and GLA-SBE-ß-CD exhibited apparent concentration-dependent inhibitory actions on four kinds of tumor cells and better inhibition was achieved in GLA-SBE-ß-CD group. The pharmacokinetic results showed that the duration of GLA in blood was prolonged and enhanced bioavailability was achieved. GLA and GLA-SBE-ß-CD both showed an effective inhibition on the transplanted tumor growth, while the anti-tumor effect of GLA-SBE-ß-CD (inhibitory rate of 45.80%) was significantly stronger than that of GLA (30.76%) based on the change of tumor weight and tumor volume.

Development and validation of an LC-MS/MS method for quantification of NC-8 in rat plasma and its application to pharmacokinetic studies.

ent-16-Oxobeyeran-19-N-methylureido (NC-8) is a recently synthesized derivative of isosteviol that showed anti-hepatitis B virus (HBV) activity by disturbing replication and gene expression of the HBV and by inhibiting the host toll-like receptor 2/nuclear factor-κB signaling pathway. To study its pharmacokinetics as a part of the drug development process, a highly sensitive, rapid, and reliable liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for determining NC-8 in rat plasma. After protein precipitation extraction, the chromatographic separation of the analyte and internal standard (IS; diclofenac sodium) was performed on a reverse-phase Luna C18 column coupled with a Quattro Ultima triple quadruple mass spectrometer in the multiple-reaction monitoring mode using the transitions, m/z 347.31 â†’ 75.09 for NC-8 and m/z 295.89 â†’ 214.06 for the IS. The lower limit of quantitation was 0.5 ng/mL. The linear scope of the standard curve was between 0.5 and 500 ng/mL. Both the precision (coefficient of variation; %) and accuracy (relative error; %) were within acceptable criteria of <15%. Recoveries ranged from 104% to 113.4%, and the matrix effects (absolute) were non-significant (CV ≤ 6%). The validated method was successfully applied to investigate the pharmacokinetics of NC-8 in male Sprague-Dawley rats. The present methodology provides an analytical means to better understand the preliminary pharmacokinetics of NC-8 for investigations on further drug development.

Simultaneous determination of glaucocalyxin A and glaucocalyxin B in rat plasma by LC-MS/MS and its application to a pharmacokinetic study after oral administration of Rabdosia japonica extract.

A specific and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for the analysis of glaucocalyxin A and glaucocalyxin B in rat plasma using praeruptorin A as an internal standard. Separation was performed on a Hypurity C18 column (2.1 × 50 mm, 5 µm) with isocratic elution using 0.2% formic acid in water-acetonitrile (20:80, v/v). Mass spectrometric detection was conducted using selected reaction monitoring via an electrospray ionization source. Both analytes exhibited good linearity within their concentration ranges (r2 > 0.9932). The lower limit of quantitation of glaucocalyxin A and glaucocalyxin B was 1.10 ng/mL. Intra- and inter-day precision exhibited an RSD within 14.5%, and the accuracy (RE) ranged from -12.1 to 15.0% at the lower limit of quantitation and three quality control levels. The developed assay was successfully applied to a pharmacokinetic study of glaucocalyxin A and glaucocalyxin B in rats after oral administration of Rabdosia japonica extract.

GE11 peptide conjugated selenium nanoparticles for EGFR targeted oridonin delivery to achieve enhanced anticancer efficacy by inhibiting EGFR-mediated PI3K/AKT and Ras/Raf/MEK/ERK pathways.

Selenium nanoparticles (Se NPs) have attracted increasing interest in recent decades because of their anticancer, immunoregulation, and drug carrier functions. In this study, GE11 peptide-conjugated Se NPs (GE11-Se NPs), a nanosystem targeting EGFR over-expressed cancer cells, were synthesized for oridonin delivery to achieve enhanced anticancer efficacy. Oridonin loaded and GE11 peptide conjugated Se NPs (GE11-Ori-Se NPs) were found to show enhanced cellular uptake in cancer cells, which resulted in enhanced cancer inhibition against cancer cells and reduced toxicity against normal cells. After accumulation into the lysosomes of cancer cells and increase of oridonin release under acid condition, GE11-Ori-Se NPs were further transported into cytoplasm after the damage of lysosomal membrane integrity. GE11-Ori-Se NPs were found to induce cancer cell apoptosis by inducting reactive oxygen species (ROS) production, activating mitochondria-dependent pathway, inhibiting EGFR-mediated PI3K/AKT and inhibiting Ras/Raf/MEK/ERK pathways. GE11-Se NPs were also found to show active targeting effects against the tumor tissue in esophageal cancer bearing mice. And in nude mice xenograft model, GE11-Ori-Se NPs significantly inhibited the tumor growth via inhibition of tumor angiogenesis by reducing the angiogenesis-marker CD31 and activation of the immune system by enhancing IL-2 and TNF-α production. The selenium contents in mice were found to accumulate into liver, tumor, and kidney, but showed no significant toxicity against liver and kidney. This cancer-targeted design of Se NPs provides a new strategy for synergistic treating of cancer with higher efficacy and reduced side effects, introducing GE11-Ori-Se NPs as a candidate for further evaluation as a chemotherapeutic agent for EGFR over-expressed esophageal cancers.

Mucosal transfer of wheat germ agglutinin modified lipid-polymer hybrid nanoparticles for oral delivery of oridonin.

Wheat germ agglutinin-modified lipid-polymer hybrid nanoparticles (WGA-LPNs) promote cellular uptake after oral delivery via receptor-mediated endocytosis and bioadhesion. Understanding the mucosal transport of WGA-LPNs would help to improve bioavailability and ensure therapeutic efficacy. In this study, WGA-LPNs interacted with mucin, forming larger agglomerates with intact core-shell structure. The interaction of WGA-LPNs with mucin improved enterocyte endocytosis in Caco-2 cells. An in situ intestinal diffusion study in mice confirmed that WGA-LPNs reached enterocytes and underwent endocytosis, despite interference from mucin. Importantly, oral bioavailability of oridonin-loaded WGA-LPNs increased by 1.96-fold compared with that of LPNs. Furthermore, oral administration of WGA-LPNs inhibited tumor growth in HepG2 xenograft nude mice. In addition to elucidating interactions between WGA-LPNs and mucin, these results indicated that WGA-LPNs might act as promising nanocarriers for oral delivery of drugs.

Optimization and evaluation of Oridonin-loaded Soluplus®-Pluronic P105 mixed micelles for oral administration.

In this study, a new type of mixed micelles was developed using Soluplus® (SOL) and Pluronic® P105 (P105) for the encapsulation of Oridonin (ORN). Oridonin-loaded micelles (ORN-M) were simply prepared using solvent evaporation and characterized for particle size, particle morphology, encapsulation efficiency, and drug loading. In addition, the in vitro drug release behavior of ORN-M was assessed using the widely applied dialysis bag technique. The pharmacokinetic property of ORN was explored in rats after oral administration of ORN-M. Optimized ORN-M were of a small size (137.2±1.65nm) and spherical shape when the ratio of SOL:P105 was 3:1, with entrapment efficiency 90.48±1.85% and drug loading 15.08±0.38%. Oral absorption capacity of ORN was greatly enhanced with a relative bioavailability of 210.55% in comparison to that of in-house suspensions, which suggests that ORN-M shows significantly improved bioavailability and drug absorption characteristics. Overall, the optimized SOL-P105 dual mixed micelles show great potential for use as oral drug carriers for cancer treatment.

Biological fate of low-calorie sweeteners.

With continued efforts to find solutions to rising rates of obesity and diabetes, there is increased interest in the potential health benefits of the use of low- and no-calorie sweeteners (LNCSs). Concerns about safety often deter the use of LNCSs as a tool in helping control caloric intake, even though the safety of LNCS use has been affirmed by regulatory agencies worldwide. In many cases, an understanding of the biological fate of the different LNSCs can help health professionals to address safety concerns. The objectives of this review are to compare the similarities and differences in the chemistry, regulatory status, and biological fate (including absorption, distribution, metabolism, and excretion) of the commonly used LNCSs: acesulfame potassium, aspartame, saccharin, stevia leaf extract (steviol glycoside), and sucralose. Understanding the biological fate of the different LNCSs is helpful in evaluating whether reports of biological effects in animal studies or in humans are indicative of possible safety concerns. Illustrations of the usefulness of this information to address questions about LNCSs include discussion of systemic exposure to LNCSs, the use of sweetener combinations, and the potential for effects of LNCSs on the gut microflora.

Identification and comparative oridonin metabolism in different species liver microsomes by using UPLC-Triple-TOF-MS/MS and PCA.

Oridonin (ORI) is an active natural ent-kaurene diterpenoid ingredient with notable anti-cancer and anti-inflammation activities. Currently, a strategy was developed to identify metabolites and to assess the metabolic profiles of ORI in vitro using ultra-high-performance liquid chromatography-Triple/time-of-flight mass spectrometry (UPLC-Triple-TOF-MS/MS). Meanwhile, the metabolism differences of ORI in the liver microsomes of four different species were investigated using a principal component analysis (PCA) based on the metabolite absolute peak area values as the variables. Based on the proposed methods, 27 metabolites were structurally characterized. The results indicate that ORI is universally metabolized in vitro, and the metabolic pathway mainly includes dehydration, hydroxylation, di-hydroxylation, hydrogenation, decarboxylation, and ketone formation. Overall, there are obvious inter-species differences in types and amounts of ORI metabolites in the four species. These results will provide basic data for future pharmacological and toxicological studies of ORI and for other ent-kauranes diterpenoids. Meanwhile, studying the ORI metabolic differences helps to select the proper animal model for further pharmacology and toxicological assessment.

CYP2C8-mediated interaction between repaglinide and steviol acyl glucuronide: In vitro investigations using rat and human matrices and in vivo pharmacokinetic evaluation in rats.

CYP2C8 is involved in the metabolic clearance of several important drugs and recent reports have shown that acyl glucuronides of gemfibrozil and clopidogrel are potent time-dependent inhibitors of CYP2C8 activity. In the present study, the inhibitory effect of steviol acyl glucuronide (SVAG), a circulating metabolite formed after the ingestion of rebaudioside A, was investigated using in vitro and in vivo systems. Results indicated that SVAG was a reversible but not a time-dependent inhibitor of CYP2C8-mediated paclitaxel 6α-hydroxylation. SVAG was also capable of inhibiting CYP2C8-mediated repaglinide 3'-hydroxylation in human liver microsomes and recombinant human CYP2C8, with Ki values of 15.8 µM and 11.6 µM, respectively. In contrast, SVAG did not exhibit inhibitory effect on CYP2C8 activity in rat liver microsomes. In addition, co-administration of rebaudioside A with repaglinide in rats did not lead to AUC and Cmax changes of repaglinide. Although mathematic prediction using a simplified mechanistic model revealed a moderate interaction potential between repaglinide and SVAG, cautions should be given to patients with hypoglycemia if repaglinide and rebaudioside A are used in combination for the blood sugar control.

Chemical-specific adjustment factors (inter-species toxicokinetics) to establish the ADI for steviol glycosides.

The acceptable daily intake (ADI) of commercially available steviol glycosides is currently 0-4 mg/kg body weight (bw)/day, based on application of a 100-fold uncertainty factor to a no-observed-adverse-effect-level value from a chronic rat study. Within the 100-fold uncertainty factor is a 10-fold uncertainty factor to account for inter-species differences in toxicokinetics (4-fold) and toxicodynamics (2.5-fold). Single dose pharmacokinetics of stevioside were studied in rats (40 and 1000 mg/kg bw) and in male human subjects (40 mg/kg bw) to generate a chemical-specific, inter-species toxicokinetic adjustment factor. Tmax values for steviol were at ∼8 and ∼20 h after administration in rats and humans, respectively. Peak concentrations of steviol were similar in rats and humans, while steviol glucuronide concentrations were significantly higher in humans. Glucuronidation in rats was not saturated over the dose range 40-1000 mg/kg bw. The AUC0-last for steviol was approximately 2.8-fold greater in humans compared to rats. Chemical-specific adjustment factors for extrapolating toxicokinetics from rat to human of 1 and 2.8 were established based on Cmax and AUC0-last data respectively. Because these factors are lower than the default value of 4.0, a higher ADI for steviol glycosides of between 6 and 16 mg/kg bw/d is justified.

Nanosuspensions Containing Oridonin/HP-ß-Cyclodextrin Inclusion Complexes for Oral Bioavailability Enhancement via Improved Dissolution and Permeability.

Chemotherapy via oral route of anticancer drugs offers much convenience and compliance to patients. However, oral chemotherapy has been challenged by limited absorption due to poor drug solubility and intestinal efflux. In this study, we aimed to develop a nanosuspension formulation of oridonin (Odn) using its cyclodextrin inclusion complexes to enhance oral bioavailability. Nanosuspensions containing Odn/2 hydroxypropyl-ß-cyclodextrin inclusion complexes (Odn-CICs) were prepared by a solvent evaporation followed by wet media milling technique. The nanosuspensions were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and dissolution. The resulting nanosuspensions were approximately 313.8 nm in particle size and presented a microcrystal morphology. Nanosuspensions loading Odn-CICs dramatically enhanced the dissolution of Odn. Further, the intestinal effective permeability of Odn was markedly enhanced in the presence of 2-hydroxypropyl-ß-cyclodextrin (HP-ß-CD) and poloxamer. Bioavailability studies showed that nanosuspensions with Odn-CICs can significantly promote the oral absorption of Odn with a relative bioavailability of 213.99% (Odn suspensions as reference). Odn itself possesses a moderate permeability and marginal intestinal metabolism. Thus, the enhanced bioavailability for Odn-CIC nanosuspensions can be attributed to improved dissolution and permeability by interaction with absorptive epithelia and anti-drug efflux. Nanosuspensions prepared from inclusion complexes may be a promising approach for the oral delivery of anticancer agents.

[Intestinal Absorption Characteristics and Mechanism of Polygala tenuifolia Hydrolysate in Rats].

OBJECTIVE: To evaluate the absorption feature and mechanism of tenuifolin(TF) and polygalaxanthone III (PT) in different intestinal parts of rats and the impact of MRP2 and P-glycoprotein (P-gp) on it. METHODS: In situ unidirectional perfusion was used to detect the concentration of TF and PT through HPLC-DAD with gravimetric method. Furthermore, impact of different parts, cosolvents and inhibitors to TF and PT was also explored with data of Ka and Papp. RESULTS: Tween as cosolvent, Ka and Papp of TF was significantly higher in colon than in other intestinal parts(P <0. 05 or P <0. 01). Whereas, Ka of PT was in sequence of colon, duodenum, jejunum, ileum,but with no significant difference among them(P >0. 05). SDS as cosolvent, Papp of TF was higher in colon than in duodenum(P <0. 05). K. of TF was significantly higher compared with control when added with VH, an inhibitor of P-gp(P <0. 05). In addition, Papp of PT in different concentration of VH increased(P <0. 05, P <0. 01). Papp of TF significantly increased with IT at the concentration of 0. 02 and 0. 04 mmol/L, an inhibitor of MRP2(P <0. 05, P <0. 01). Meanwhile, Ka of PT,with IT at the concentration of 0. 04 and 0. 08 mmol/L, was significantly higher(P <0. 05, P <0. 01). CONCLUSION: TF is mainly absorbed in colon, whereas PT is in duodenum. P-gp but not MRP2 influences the intestinal absorption of TF, indicating TF as substrate of P-gp. However, both of P-gp and MRP2 impact the absorption of PT, illustrating PT as substrate of P-gp and MRP2. It also indicates that inhibitors of P-gp and/or MRP2 in combined application may improve the absorption of PT and TF.