Tanshinone I, tanshinone IIA, cryptotanshinone, and salvianolic acid B contents in danshen extract were analyzed using high performance liquid chromatography (HPLC) (1260 Infinity II series; Agilent Technologies, Wilmington, DE, USA). Danshen extract was filtered through a 0.22 µm membrane. HPLC analyses were performed using a diode array detector (G1315C Diode-array Detector, Agilent Technologies, Wilmington, DE, USA) with an injection volume of 10 µL, flow rate of 1 mL• -1 , controlled oven temperature of 30 • C, and a C18 column [Agilent TC-C18 (2), 4.6 mm × 250 mm, 5 µm; Agilent Technologies, Wilmington, DE, USA]. Mobile phase A was 100% acetonitrile, mobile B was 0.02% phosphoric acid [30] .
The elution program for tanshinone I, tanshinone IIA, and cryptotanshinone was 0-6 min: 61% mobile phase A and 39% mobile phase B; 6-20 min: percentage of mobile phase A linearly increased from 61 to 90%, percentage of mobile phase B linearly decreased from 39 to 10%; 20-20.5 min: percentage of mobile phase A linearly decreased from 90 to 61%, percentage of mobile phase B linearly increased from 10 to 39%; 20.5-25 min: 61% mobile phase A and 39% mobile phase B. Chromatograms were recorded at 270 nm. This procedure was modified slightly based on the method described in Chinese Pharmacopoeia [30] .
The elution program for salvianolic acid B was 0-20 min: percentage of mobile phase A linearly increased from 5 to 20%, percentage of mobile phase B linearly decreased from 95 to 80%; 20-30 min: percentage of mobile phase A linearly increased from 20 to 30%, percentage of mobile phase B linearly decreased from 80 to 70%; 30-40 min: percentage of mobile phase A linearly increased from 30 to 40%, percentage of mobile phase B linearly decreased from 70 to 60%. Chromatograms were recorded at 280 nm. This method was modified slightly based on Ren's study [31] .
Standards were purchased from Sigma-Aldrich (St. Louis, MO, USA). The retention time of cryptotanshinone, tanshinone I and tanshinone IIA were 12.75, 14.07, and 17.33 min, and the retention time of salvianolic acid B was 36.14 min. Tanshinone I, tanshinone IIA, cryptotanshinone, and salvianolic acid B contents in danshen were calculated by standard curve. Mobile phases of HPLC grade were purchased from Thermo Fisher Scientific (Waltham, MA, USA).
The elution program for tanshinone I, tanshinone IIA, and cryptotanshinone was 0-6 min: 61% mobile phase A and 39% mobile phase B; 6-20 min: percentage of mobile phase A linearly increased from 61 to 90%, percentage of mobile phase B linearly decreased from 39 to 10%; 20-20.5 min: percentage of mobile phase A linearly decreased from 90 to 61%, percentage of mobile phase B linearly increased from 10 to 39%; 20.5-25 min: 61% mobile phase A and 39% mobile phase B. Chromatograms were recorded at 270 nm. This procedure was modified slightly based on the method described in Chinese Pharmacopoeia [30] .
The elution program for salvianolic acid B was 0-20 min: percentage of mobile phase A linearly increased from 5 to 20%, percentage of mobile phase B linearly decreased from 95 to 80%; 20-30 min: percentage of mobile phase A linearly increased from 20 to 30%, percentage of mobile phase B linearly decreased from 80 to 70%; 30-40 min: percentage of mobile phase A linearly increased from 30 to 40%, percentage of mobile phase B linearly decreased from 70 to 60%. Chromatograms were recorded at 280 nm. This method was modified slightly based on Ren's study [31] .
Standards were purchased from Sigma-Aldrich (St. Louis, MO, USA). The retention time of cryptotanshinone, tanshinone I and tanshinone IIA were 12.75, 14.07, and 17.33 min, and the retention time of salvianolic acid B was 36.14 min. Tanshinone I, tanshinone IIA, cryptotanshinone, and salvianolic acid B contents in danshen were calculated by standard curve. Mobile phases of HPLC grade were purchased from Thermo Fisher Scientific (Waltham, MA, USA).
