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In this paper, an efficient method was successfully established by the combination of macroporous resin (MR) and high-speed counter-current chromatography (HSCCC) for rapid enrichment and separation of aloe-emodin 8-O-β-D-glucoside, emodin 1-O-β-D-glucoside, emodin 8-O-β-D-glucoside and piceatannol 4'-O-β-D-(6″-O-gallate)-glucoside. Six kinds of macroporous resins were investigated in the first step and X-5 macroporous resin was selected for the enrichment of the target compounds. The recoveries of the target compounds reached 89.0, 85.9, 82.3 and 84.9% respectively after 40% ethanol elution. In the second step, the target compounds were separated by HSCCC with a two-phase solvent system composed of chloroform/ethyl acetate/methanol/water (8:1:6:5, v/v). The established method will be helpful for further characterization and utilization of Rheum tanguticum. The results demonstrate that MR coupled with HSCCC is a powerful technique for separation of bioactive compounds from natural products.
This study presents an efficient strategy for separation of three phenolic compounds with high molecular weight from the crude extract of Terminalia chebula Retz. by ultrasound-assisted extraction and high-speed counter-current chromatography. The ultrasound-assisted extraction conditions were optimized by response surface methodology and the results showed the target compounds could be well enriched under the optimized extraction conditions. Then the crude extract was directly separated by high-speed counter-current chromatography without any pretreatment using n-hexane/ethyl acetate/methanol/water (1:7:0.5:3, v/v/v/v) as the solvent system. In 180 min, 13 mg of A, 18 mg of B, and 9 mg of C were obtained from 200 mg of crude sample. Their structures were identified as Chebulagic acid (A, 954 Da), Chebulinic acid (B, 956 Da), and Ellagic acid (C) by (1) H NMR spectroscopy.
Oxidative stress has been suggested to play a causative role in the development of obesity-induced insulin resistance and type 2 diabetes. Given the antioxidant potency of previously reported xanthones isolated from <i>Swertia mussotii</i>. These natural products were further evaluated against other targets in diabetes, aldose reductase and α-glucosidase, in order to identify novel multitarget-directed antidiabetic agents. Among the 14 xanthones screened, 1,3,7,8-tetrahydroxyxanthone (<b>6</b>), 1,3,5,8-tetrahydroxyxanthone (<b>7</b>), and 2,3,6,8-tetrahydroxyxanthone-7C-(β-D-glucoside) (<b>12</b>) were confirmed as good antioxidants and α-glucosidase inhibitors. Xanthone <b>7</b> was also confirmed as a potent inhibitor of aldose reductase (ALR2). Xanthone <b>7</b> was the most active α-glucosidase and ALR2 inhibitor, with IC<sub>50</sub> values of 5.2±0.3 μM and 88.6±1.6 nM, respectively, while compound <b>12</b> was shown to be the most active antioxidant. Given the overall profile, xanthone <b>7</b> is considered to be the most promising multitarget antidiabetic agent, and may have potential for the treatment of both diabetes and diabetic complications.<br><b>Nature′s medicine cabinet:</b> Xanthones isolated from <i>Swertia mussotii</i> were evaluated as multitarget antidiabetic agents. 1,3,5,8-Tetrahydroxylxanthone was identified as a good antioxidant, and also exhibited potent inhibition of α-glucosidase and aldose reductase, proven targets in the treatment of diabetes.