Abstract: As the substrates of Maillard reaction, free amino acids were the key matters which may greatly affect the chemical compositions in traditional Chinese medicines and the flavored constituents in food. Dendrobium husohansense, a rare and endangered medicinal plant, has long been used in clinical as its processed dry stems due to the great difficulty in the preservation of its fresh stems. Thus, it is essential to assay the free amino acids for the investigation of the processing mechanism of D. huoshanese. In this study, we established an efficient high performance capillary electrophoresis (HPCE) method to qualify and quantify the free amino acids in D. huoshanense. The results showed that the optimal HPCE method was as follows: detection wavelength at 254 nm, separation voltage of 10 kV with effective length of uncoated standard fused silica capillary 55 cm. The running buffer was 60 mmol/L Na2B4O7-Na2HPO4 with pH value of 11.0. Under these conditions, all the 12 investigated amino acids could be separated in 60 min with the R2 values of all the calibrations for the 12 amino acids more than 0.99 and recovery within 90.17%-110.25% (RSD≤5%, n=3). The total contents of total amino acids in the root, stem and leaf in D. huoshanense were 1.8958, 2.0736 and 2.5954 mg/g, respectively. These conformed the established method in our experiments is accurate, reliable and reproducible, and can be used to qualify and quantify the free amino acids in D. huoshanense.

Key words: high performance capillary electrophoresis (HPCE), precolumn derivatization, free amino acids, Dendrobium huoshanense