Objective:The influence of heating time and temperature on the content of ginsenosides from stems and leaves of ginseng during water decoction process was researched to calculate the term of validity. Method: The HPLC was used to determine the content of ginsenoside Rg1 and ginsenoside Re extracted in different heating conditions.An Agilent Extend-C18 column(4.6 mm×250 mm

5 μm) was used with acetonitrile-water(19∶81)as the mobile phase at the flow rate of 1.0 mL·min-1

and the column temperature was maintained at 30 ℃ and the detection wavelength was set at 203 nm. The term of validity was caculated by classical homeothermia. Result: When the heat comes to 12 h

ginsenoside Rg1 and ginsenoside Re had different degree of degradation

and they degraded rapidly when temperature is at 100 ℃. It’s only 20 percent of the initial content at 100 ℃

and 60% at 80 ℃

80% at 60 ℃.With simple linear regression analysis to 1/T as lgK

the regression equations are:lgK=-2 396.2/T+5.587 3 for ginsenoside Rg1

lgK=-2 518.2/T+5.901 6 for ginsenoside Re. The term of validity of ginsenoside Rg1 and ginsenoside Re were calculated as 30.1 h and 37.6 h. Conclusion: The content of ginsenoside Rg1 and ginsenoside Re decreased with time increasing and temperature increasing. The term of validity about stems and leaves of Panax ginseng is in short period.So

intermediate which contains water extract of stems and leaves of P. ginseng should accomplish the preparation within the term of validity.