Determination of forsythoside A and forsythin in Forsythiae Fructus by substitute reference substance

Objective: To establish an HPLC method for determination of forsythoside A and forsythin in Forsythiae Fructus by substitute reference substance. Methods: Forsythin was selected as the substitute reference substance for the reference substance forsythoside A for determination of Forsythiae Fructus. The correction factor was measured of forsythoside A and forsythin under different conditions. The content of forsythoside A in Forsythiae Fructus was determined by the substitute reference substance and the correct factor. Chromatographic conditions: Agilent ZORBAX SB- C18( 2)( 5 μm,4. 6 mm ×250 mm) column was adopted,the mobile phase consisted of acetonitrile( A)-0. 3%acetic acid solution( B) with gradient elution [0- 5 min,A- B( 15 ∶ 85)→A- B( 17∶ 83); 5- 10 min,A- B( 17∶ 83)→A- B( 20∶ 80); 10-15 min,A- B( 20∶ 80)→A- B( 23∶ 77); 15- 20 min,A- B( 23∶ 77)→A- B( 25∶ 75) ]was at the flow rate of 0. 8 mL·min- 1,the column temperature was 25 ℃,and the detection wavelength was 230 nm. Results: The linear response ranges of forsythoside A and forsythin were 0. 08- 0. 62 mg·mL- 1( r =0. 9995) and 0. 012- 0. 08 mg·mL- 1( r =0. 9995),respectively. The correction factor( f) was 0. 4761. The average recovery( n = 6) was 99. 20%. Conclusion: The substitute reference substance is adopted in HPLC determination of Forsythiae Fructus. The assay demonstrates that the method is feasible and useful for quality control of Forsythiae Fructus.