Objective: To discover reasons for great loss of shikonin during the concentrating process of percolate of Arnerbia euchroma (Royle) Johnst and develop a reasonable method for determination of shikonin.
Methods: Shikonin was selected as index, optimized chromatographic condition was used for analyzing the affection of alcohol content and crude drug content of sample solution on determination of shikonin, furthermore, reasonable sample preparation and determination methodology was examined and defined.
Results: The optimized chromatographic condition was as follows: shikonin was analyzed with a Zorbax Extend C-18 column (4.6 mm x 250 mm, 5 microm), methanol: water (82: 18) as the mobile phase, the column was maintained at 35 degrees C, the flow rate was 1.0 mL min(-1), detection wavelength was set at 516 nm and the time for analysis reduced from 40 min to 24 min. Alcohol content of sample solution influenced determination results significantly, peak area of equal content shikonin in low alcohol content (<40%) was only about 20% - 30% of that of high alcohol content (>70%), the reasonable content of sample solution were 0.0167 - 0.083 g mL(-1) with alcohol content above 40%. The method showed good linearity, precision, reproducibility and accuracy.
Conclusion: The alcohol content of sample solution correlated with peak area closely for the first time, which indicate another important reason for "great loss" of shikonin during concentration process is that too much low ethanol content in test solution leads too much low results. The new method can detect shikonin more effectively and more reasonably and can monitor production process with high efficiency and low cost.