Natural Xanthine Oxidase Inhibitor 5-O-Caffeoylshikimic Acid Ameliorates Kidney Injury Caused by Hyperuricemia in Mice.

Xanthine oxidase (XOD) inhibition has long been considered an effective anti-hyperuricemia strategy. To identify effective natural XOD inhibitors with little side effects, we performed a XOD inhibitory assay-coupled isolation of compounds from Smilacis Glabrae Rhizoma (SGR), a traditional Chinese medicine frequently prescribed as anti-hyperuricemia agent for centuries. Through the in vitro XOD inhibitory assay, we obtained a novel XOD inhibitor, 5-O-caffeoylshikimic acid (#1, 5OCSA) with IC50 of 13.96 µM, as well as two known XOD inhibitors, quercetin (#3) and astilbin (#6). Meanwhile, we performed in silico molecular docking and found 5OCSA could interact with the active sites of XOD (PDB ID: 3NVY) with a binding energy of -8.6 kcal/mol, suggesting 5OCSA inhibits XOD by binding with its active site. To evaluate the in vivo effects on XOD, we generated a hyperuricemia mice model by intraperitoneal injection of potassium oxonate (300 mg/kg) and oral gavage of hypoxanthine (500 mg/kg) for 7 days. 5OCSA could inhibit both hepatic and serum XOD in vivo, together with an improvement of histological and multiple serological parameters in kidney injury and HUA. Collectively, our results suggested that 5OCSA may be developed into a safe and effective XOD inhibitor based on in vitro, in silico and in vivo evidence.

Enhancement of Solubility, Transport Across Madin-Darby Canine Kidney Monolayers and Oral Absorption of Pranlukast Through Preparation of a Pranlukast-Phospholipid Complex.

This study aimed to enhance the solubility of a poorly water-soluble drug, pranlukast, as well as its transport across Madin-Darby canine kidney (MDCK) monolayers, thus increasing its oral bioavailability. To accomplish this aim, we prepared a pranlukast-phospholipid complex (PPC). The PPC was prepared by solvent-evaporation and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared (IR) spectroscopy, and solubilization studies. The solubility of pranlukast in the PPC was increased from 1.03 ± 0.32 µg/ml to 160.63 ± 2.72 µg/ml with a yield of 96.39 ± 1.20% when the PPC was prepared under optimal conditions. TEM images showed that the PPC particles had a spherical shape. XRD data indicated that pranlukast in the PPC was either in an amorphous form or in a dispersed molecular distribution. IR analysis confirmed the interaction between pranlukast and the phospholipids. The transport mechanism of the PPC and non-complexed pranlukast across MDCK cells was measured and was observed to be significantly greater for the former than for the latter. The in vivo bioavailability of the PPC in rats hastened the onset of pranlukast-induced therapeutic effects, with C(max) and AUC increases of 21.88- and 28.64-fold, respectively, compared with raw crystals. In addition, an in vivo imaging method was used to corroborate that the PPC exhibited rapid circulatory distribution and gastrointestinal tract accumulation. These results indicate that PPC appears to be a promising drug delivery system for pranlukast, improving drug absorption and decreasing side effects by reducing the required oral dose.