Study On E-6-O-p-coumaroyl Scandoside Methyl Ester From Hedyotis Diffusa

Hedyotis diffusa is a notable annual herb widely distributed in the south of China, which has been commonly used for the treatment of various tumors, especially tumors in digestive system, such as colon cancer, esophageal cancer, gastric cancer, et al. From the study on the fingerprint of Hedyotis diffusa, p-coumaric acid were found and obtained. p-Coumaric acid, as a phenolic acid, is an antioxidant which is implicated for the prevention of pathologies, such as colon cancer and cardiovascular diseases. Recently a prodrug, E-6-O-p-coumaroyl scandoside methyl ester, was isolated from Hedyotis diffusa, which can be further hydrolyzed to p-coumaric acid in vivo. In order to control the quality of Hedyotis diffusa, HPLC method was established for the determination of E-6-O-p-coumaroyl scandoside methyl ester in Hedyotis diffusa from different origins. HPLC-UV methods have been developed for the determination of E-6-O-p-coumaroyl scandoside methyl ester and p-coumaric acid in rat plasma and applied to a pharmacokinetic study in rats after administration of E-6-O-p-coumaroyl scandoside methyl ester.1. The preparation of E-6-O-p-coumaroyl scandoside methyl esterE-6-O-p-coumaroyl scandoside methyl ester, as a prodrug of p-coumaric acid, is one of iridoid glycosides which has antitumor activity. Its isolation from Hedyotis diffusa and structure elucidation were reported in the paper.2. Quantitative Analysis of E-6-O-p-coumaroyl scandoside methyl ester in Hedyotis diffusa from different originsAfter the optimization of extraction condition using orthogonal experimental design, an RP-HPLC method was developed for the determination of E-6-O-p-coumaroyl scandoside methyl ester in Hedyotis diffusa from different origins for the first time. The analytical column was C18 with MeOH-H₂O(45:55,v/v) as mobile phase, at flow rate of 1.0 mL·min^-1, peaks was detected at 310 nm, column temperature was at 25℃.3. The pharmaeokineties of E-6-O-p-coumaroyl seandoside methyl ester and its metabolite p-eoumarie acidA rapid and simple HPLC-UV method has been established to determine E-6-O-p-coumaroyl scandoside methyl ester in rat plasma. The analytes was separated on a DiamonsilTM C₁₈ column(250 mm×4.6 mm i.d., 5μm) with methanol- acetonitrile-water(30:15:55, v/v) as mobile phase and detected at 310nm at 25℃. The calibration curves were linear over the concentration range 0.2-20μg·mL^-1. The lower limit of quantification of E-6-O-p-coumaroyl scandoside methyl ester in rat plasma was 0.2μg·mL^-1.A rapid and sensitive HPLC-UV method has been developed for the determination of p-coumaric acid in rat plasma. The mobile phase consisted of acetonitrile-water (21:79,v/v/v) with 1% glacial acetic acid. The UV detector was set at 310 nm. The calibration curves were linear over the concentration range 0.02-5μg-mL^-1. The lower limit of quantification of p-coumaric acid in rat plasma was 0.02μg.mL^-1.Following intragastric administration in rats(20 mg/kg), E-6-O-p-coumaroyl scandoside methyl ester could almost not be detected in plasma due to extensive metabolism. The primary phamacokinetics parameters of p-coumaric acid as metabolite were as follows: Tmax 1.2±0.3 h, C_max0.236±0.047 h, T_1/2 1.3±0.5 h, AUC_0-t23.8±5.1μg min·mL^-1.