ObjectiveTo establish high performance liquid chromatography (HPLC) methods for determination of related substances in candesartan cilexetil tablets. MethodsAccording to the quality standard of candesartan cilexetil tablets announced by State Food and Drug Administration (SFDA), the related substances were determined on a Hypersil C18 column (250 mm×4.6 mm, 5 μm) with the mobile phase of Methanolacetonitrile0.05 mol8226;L－1 sodium dihydrogen phosphate solution (adjusted to pH 3.2 with phosphoric acid) (55：30：20) at a flow rate of 0.9 mL8226;min－1, detected at 254 nm wavelength. According to the standard of candesartan cilexetil tablets established by the Japanese Pharmacopoeia 16th Edition, the related substances were determined on a Waters C18 column (150 mm×4.6 mm, 5 μm) with gradient elution of mobile phase A and B ［A: acetonitrilewateracetic acid (57：43：1), B: acetonitrilewateracetic acid (90：10：1)］ at a flow rate of 0.9 mL8226;min－1, detected at 254 nm. ResultsFive related substances of candesartan cilexetil could be determined by the method referred to SFDA. A good linear relationship was observed in the concentration range of 0.25－25.00 μg8226;mL－1. The detection limit was 1 ng. Eight related substances of candesartan cilexetil could be determined by the method referred to Japanese Pharmacopoeia. A good linear relationship was observed in the concentration range of 0.40－40.00 μg8226;mL－1. The detection limit was 0.8 ng. ConclusionBoth of the determination methods could be used for the determination of related substances in candesartan cilexetil tablets. The method referred to Japanese Pharmacopoeia was proved to be more sensitive, specific, and accurate.
ObjectiveTo optimize the extraction technology of epicatechin from Fagopyrum dibotrys (D. Don) Hara. MethodsCentral composite design and response surface methodology were adopted to optimize the process of extraction. The independent variables were microwave power，ethanol concentration，sample/solvent ratio and extraction time. The dependent variable was extraction rate of epicatechin which was used to estimate the relationship between independent and dependent variables. The prediction was evaluated by comparing the observed and predicted values. ResultsThe optimum technological parameters were as follows: microwave power 211.89 W，ethanol concentration 55.11%， ratio of sample/solvent 1：11.43，and extraction time 6.16 min. The highest extraction rate of epicatechin was 2.041 4%, which coincided with the model predicted values.ConclusionThe extraction technology is simple，reliable and highly predictive.