Determination of total free-amino acid in Tetrastigmatis hemsleyani by microwave digestion-UV spectrophotometer.

【Objective】The best method of determining the total free-amino acid in Tetrastigmatis hemsleyani was explored to provide the scientific evidence for its comprehensive development and utilization. 【Method】Tetrastigmatis hemsleyani was used as the material and aspartic acid as the standard. The microwave digestion extraction technology of total free-amino acid from Tetrastigmatis hemsleyani was optimized by orthogonal experiments, and its content was determined by UV spectrophotometer. 【Result 】The descending sequence of influencing microwave digestion extracting the total free-amino acid was material- liquid ratio, extracting temperature and extracting power, extracting time. The optimum extraction process was as follows: using distilled water as solvent, under 225 W and 60 ℃ for an extraction of20 min with the material-liquid ratio of 1∶15. Under the best processing condition, the average content total free-amino acid was 0.678%. The best wavelength to determine aspartic acid standard solution and the Tetrastigmatis hemsleyani test solution was 565 nm. Aspartic acid showed a better linearity and good correlation within a range of 0.001-0.014mg/m L, R2=0.9991. 【Conclusion】Microwave digestion-UV spectrophotometer is effective and simply operative with less solvent and shorter extraction time.