Abstract: The total alkaloid content in Stemona tuberosa Lour. at different developmental stages was determined using the acid dye colorimetric method. The acid dye colorimetric method was used, with Stemona tuberosa Lour. alkali as the reference material and bromothymol blue as the acid dye. Methanol and chloroform were extracted, and dissolved in 4% hydrochloric acid. The determination was carried out at a wavelength of 413 nm. The results showed that the standard curve of Stemona tuberosa Lour. alkali was Y=0.003 7X+0.089 （R²=0.995 9）. The linear relationship was good from 32 to 800 μg/mL;the average sample recovery rate was 101.23%, and the RSD of the average sample recovery rate was 2.63%. The total alkaloid content of annual Stemona tuberosa Lour. was 1.87~4.55 mg/g;the total alkaloid content of the biennial Stemona tuberosa Lour. was 4.52~9.63 mg/g. The acid dye colorimetric method had the advantages of simple operation, good repeatability, and high stability.

Key words: Stemona tuberosa Lour, total alkaloid, acid dye colorimetric method, different developmental stages