Article pubs.acs.org/JAFC
Ginger Extract-Loaded Solid Dispersion System with Enhanced Oral Absorption and Antihypothermic Action Hideyuki Sato,† Mizuki Ogino,† Keisuke Yakushiji,† Hiroki Suzuki,† Ken-ichi Shiokawa,‡ Hiroshi Kikuchi,‡ Yoshiki Seto,† and Satomi Onoue*,† †
Department of Pharmacokinetics and Pharmacodynamics, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan ‡ Japan Preventive Medical Laboratory Company, Ltd., 3-6-36 Toyoda, Suruga-ku, Shizuoka 422-8027, Japan S Supporting Information *
ABSTRACT: The aim of this study is to enhance the antihypothermic action of ginger extract (GE) employing a solid dispersion (SD) approach. The prepared SD of GE (GE/SD) was characterized in terms of physicochemical and pharmacokinetic properties. The antihypothermic action of GE samples was evaluated in a rat model of hypothermia. GE/SD exhibited improved dissolution behavior of the major active ingredients in GE, 6-gingerol (6G) and 8-gingerol (8G), with levels of dissolution 12- and 31-fold higher than that of GE, respectively. Even after storage under accelerated conditions, limited degradations of 6G and 8G were observed in GE/SD, although 6G and 8G were slightly degraded in GE. After oral administration of GE (300 mg/kg) and GE/SD (100 mg of GE/kg), the relative bioavailabilities of 6G and 8G in GE/SD were 5.0- and 5.8-fold higher than those in GE, respectively. Orally administered GE/SD (30 mg of GE/kg) inhibited ethanol-evoked hypothermia because of improved oral absorption of 6G and 8G. From these observations, the SD approach might be efficacious for enhancing the nutraceutical potentials of GE. KEYWORDS: antihypothermic action, ginger extract, oral absorption, physicochemical stability, solid dispersion
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INTRODUCTION Ginger (Zingiber off inale) and its components have been widely used as nutraceuticals. Among the active ingredients of ginger, 6-gingerol (6G), 8-gingerol (8G), 10-gingerol (10G), and 6shogaol (6S) have been consistently reported to be abundant bioactive components of ginger.1 These active ingredients in ginger have a number of beneficial effects, including antiinflammation,2 gastric protection,3 antioxidation,4 and thermoregulation.5 Despite these attractive functions, their application in supplements and clinical use is highly limited, because of their poor solubility in water and consequently inadequate oral bioavailability. Additionally, gingerols are chemically unstable becaused of the presence of a β-hydroxy keto group in the structure and readily degraded by dehydration to form shogaols and zingerone, especially in a solution state.6 To overcome these drawbacks, the application of solubilization technologies to ginger extract could be promising for the enhancement of the physicochemical and nutraceutical potential of active ingredients in ginger extract (GE). Recently, a number of solubilization technologies for achieving desirable oral absorption of poorly water soluble compounds have been developed, including nanoparticles,7 complexation,8 micelles,9 emulsions,10 and solid dispersion (SD).11 The SD approach could be one of the most powerful techniques for the enhancement of the solubility and oral absorption of poorly soluble materials because of the improvement in the wettability and dispersibility of the active compound with high lipophilicity. SD systems could be defined as a dispersion of drug in a solid matrix where the matrix was either a small molecule or a polymer, and the dispersed drug © 2017 American Chemical Society
can exist in many forms such as eutectic mixtures, crystalline/ glass solutions, and amorphous/crystalline suspensions.12 In a previous report, SD techniques were applied to various poorly soluble components in functional food, such as curcumin,13 coenzyme Q10,14 and nobiletin,15 resulting in a significant improvement in their physicochemical properties and pharmacological actions. The SD system could have the potential to enhance the physicochemical stability of inner active ingredients because the interaction between active components and the carrier polymer could serve to stabilize the formulation.16 The SD approach might be preferable for the unstable compound in a liquid state because whole components of the formulation could be solidified and uniformly dispersed in a carrier material during the manufacturing process. These observations prompted us to develop the SD system of GE (GE/SD) for the enhancement of the solubility, stability, and nutraceutical properties of active ingredients in GE. In this study, a GE-loaded SD system using a hydrophilic polymer, hydroxypropyl cellulose, was developed using a freezedrying technique. The physicochemical properties of GE/SD were characterized in terms of the morphology and dissolution property. After storage at 40 or 40 °C and 75% relative humidity (RH) for 4 weeks, the appearance of GE/SD, degradations of active ingredients in the formulation, and their dissolution profiles were evaluated to estimate the storage Received: Revised: Accepted: Published: 1365
October 31, 2016 January 23, 2017 January 29, 2017 January 30, 2017 DOI: 10.1021/acs.jafc.6b04740 J. Agric. Food Chem. 2017, 65, 1365−1370
Article
Journal of Agricultural and Food Chemistry
and water (two rats per cage) at 24 ± 1 °C and 55 ± 5% RH, and the room was maintained on a 12 h/12 h light/dark cycle. All procedures used in this study were approved by the Institutional Animal Care and Ethical Committee of the University of Shizuoka (Certificate 166195). Oral Absorption Profiles of GE Samples. Blood samples (400 μL) were obtained from the tail vein of unanesthetized rats at the determined periods after oral administration of GE (300 mg/kg) dissolved in 1 mL of medium-chain triglyceride and GE/SD (100 mg of GE/kg) suspended in 2.5 mL of distilled water. Each blood sample was centrifuged at 10000g to obtain plasma samples. Concentrations of 6G and 8G in the plasma samples were assayed by the UPLC/ESI-MS system. In brief, an acetonitrile solution of the internal standard (500 ng/mL, tamoxifen) (150 μL) was added to the plasma sample (50 μL) and mixed well with a vortex mixer for 1 min for deproteination of plasma samples. After centrifugation of the samples at 10000g for 10 min, the supernatant was filtered through a 0.2 μm hydrophilic polytetrafluoroethylene filter (Merck Millipore) and analyzed with a Waters Acquity UPLC system (Waters, Milford, MA) as described in Identification of Active Ingredients in GE Samples. Antihypothermic Action of GE Samples. For the evaluation of antihypothermic effects of GE samples, the rat models of hypothermia were prepared in accordance with the procedure reported previously.17 Briefly, a 30% ethanol solution was intraperitoneally administrated (1.2 g of ethanol/kg) to rats 5 min after the preadministration of vehicle (water), GE (30 mg/kg, p.o.), or GE/SD (30 mg of GE/kg, p.o.). The surface temperature of the rat hindlimb was measured with an infrared thermographic camera (FRIR C2, FLIR Systems, Inc.), at determined periods (60, 90, and 120 min) after ethanol treatment. The mean surface temperature of the rat hindlimb was calculated with FLIR tools software (FLIR Systems, Inc.) for the evaluation of pharmacological effects. Statistical Analysis. For statistical comparisons, one-way analysis of variance (ANOVA) with pairwise comparison by Fisher’s least significant difference procedure was applied. A P value of
