| Ampelopsis grossedantata (Hand.Mazz.) W.T.Wang belongs to the grape family. As a minority nationalistic medicine herbs, its tender stem and leaf was commonly known as "yao'zu teng cha". Previous investigations resulted the main chemical components were flavonols, including dihydromyricetin and myricetin.On the other hand, it exhibited several potent pharmacological activities, including hypoglycemic, antilipemic, hypotensive and liver-protecting activities and so on. In this study, the quality specification was established and the pharmacokinetic and metabolic properties of dihydromyricetin in rats were systematically investigated, which should be helpful for acquiring a deep development and application as well as rationalizing the future drug design. 1. The preparation of reference substances and their determinationDihydromyricetin and myricetin were isolated and purified by recrystallization and gel column-chromatography from Ampelopsis grossedentata. Their structures were identified by UV, IR, NMR and MS. A thin-layer chromatography method was established to identify the main compositions, the developing solvent was chloroform-ethyl acetate-formic acid (5:5:0.5, v/v/v), FeCls was the color reagent. A reversed-phase HPLC method was established to simultaneously determine the two active compositions in the crude drugs. The mobile phase was acetonitrile-2 % acetic acid (23:77, v/v), and the detection wavelength was set at 275 nm. The3determination results of 4 sources of crude drugs showed the content of dihydromyricetin was more than 24.0 %, and the content of myricetin was more thanl.6%(g/g).2. Quality specification of Ampelopsis grossedentataThe quality specification of reference substances dihydromyricetin and myricetin and Ampelopsis grossedetata were worked out.3. The pharmacokinetics of dihydromyricetin in ratA rapid and sensitive liquid chromatography method was developed to determine dihydromyricetin in rat plasma. Dihydromyricetin and the internal standard guaiacol were extracted from plasma using liquid-liquid extraction and separated on a AICHROM Cig column. The mobile phase was methol-2.5 % acetic acid (25:75, v/v), the UV detector was set at 291 nm. Following a single intravenous administration of dihydromyricetin to rats at a dose of 100 mg/kg, the concentrations of dihydromyricetin in rats plasma were determined, and the data were analyzed by 3p87 Practical pharmacokinetics program. It was shown that the process of concentration-time of dihydromyricetin in rats was fitted into two -compartments model. The half-life of distribution and elimination were both very short, ti/2 a was 1.2 min and \\n P was 13 min, the apparent distribution volume V(Q was 740 mL/kg. It illustrated that the distribution of dihydromyricetin was fast and extensive, and the elimination was rapid by i.v. administration.The metabolites of dihydromyricetin in rat urine and feces were detected by liquid chromatography-electrospray mass spectrometry. The urine and feces samples were treated by E before analysis by LC/ESI-MS". It was found that there were many kinds of metabolites of dihydromyricetin in rats: a) sulfurate conjugates(there were varied sulfurate conjugates owing to the several phenol hydroxyl group) ; b) methylation products(varied products existed due to thedifferent sites of dihydromyricetin and their content varied as time changed); c) the stereoisomer of dihydromyricetin, which was the substance having the same message of mass-spectrometry and different chromatographic capacity from the parent compound.A HPLC-UV method was developed to determine dihydromyricetin in rat urine and feces. The mobile phase was methol-2.5 % acetic acid-tetrahydrofuran (22.5:74:3.5, v/v/v), the UV detector was set at 291 nm. After an oral administration of dihydromyricetin at a single dose of 100 mg/kg, 1.5 % of dose in the form of free dihydromyricetin was recovered in urine within 48 h, and about 29 % of the dose was eliminated via feces. The results indicated that dihydromyricetin was absorb...
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