Simultaneous Separation and Determination of Four Bioactive Constituents in Traditional Chinese Medicinal Tablet Xinkeshu by HPLC-DAD

A reversed-phase high performance liquid chromatographic method for simultaneous determination of four bioactive constituents was established for the quality control of traditional Chinese medicinal tablet Xinkeshu. Danshensu, protocatechualdehyde, puerarin and daidzein were successfully separated on a Diamonsil C18 column (150×4.6 mm i.d., 5 祄) with a guard column (12.5×2.1 mm i.d., 5 祄) packed with the same material at 25 ℃. The mobile phase was a mixture of acetonitrile and 0.02 mol/L potassium dihydrogen phosphate employing gradi-ent elution at a flow rate of 0.8 mL/min. Detection was accomplished with a diode-array detector and detection wavelength was set at 280 nm before 22 min, then it was varied to 250 nm. The four constituents were identified by comparing their retention time and UV spectra in the range of 190—400 nm with those of authentic standards. The linear calibration ranges were 15.4—123.2, 3.11—25.22, 21.6—172.8, and 0.26—3.47 礸/mL for danshensu, pro-tocatechualdehyde, puerarin and daidzein, respectively. The detection limits were 0.03, 0.04, 0.10, 0.03 礸/mL for danshensu, protocatechualdehyde, puerarin, and daidzein, respectively. The contents of these four bioactive con-stituents in Xinkeshu tablet were successfully determined by the proposed method.

Biomass-derived dynamic covalent epoxy thermoset with robust mechanical properties and facile malleability

Biomass-derived dynamic covalent thermoset has been considered as a promising solution to the high dependence on fossil resources and the difficulty in recyclability after curing of conventional bisphenol A epoxy resins.However,the design and preparation of a dynamic covalent biobased epoxy thermoset with both comparable thermal and mechanical performances to bisphenol A epoxy resins and reprocessibility remains a significant challenge.Herein,based on imine chemistry,a novel Schiff base-containing dynamic covalent epoxy thermoset was facilely fabricated from biobased protocatechualdehyde and synthetic siloxane diamine.Due to the more reactive epoxides in the epoxy monomer than in bisphenol A epoxy oligomer,the thermoset exhibited a high cross-linking density,resulting in high thermal stability and glass transition temperature.The rigid aromatic Schiff base moieties endowed the thermoset with excellent mechanical properties:Thanks to the plasticization of the flexible siloxane,the thermoset displayed high impact strength.Meanwhile,owing to the high segmental mobility,the fast exchange of imine bonds was guaranteed;and the thermoset was able to be recycled through reprocessing.Taking these features,this work provided great potential for designing and preparing sustainable substitutes for bisphenol A epoxy resins in the high-performance applications.