Objective: Study on variation of ester alkaloids and hydrolysate in Radix Aconite Lateralis with the change of decocting time to establish the relationship between the content change and decocting time. Method: HPLC analysis was performed on a Eclipse XDB C18 (4.6 mm ×250 mm

5 μm) with 0.1 mol ·L-1 ammonium acetate (contains 0.5 mL glacial acetic acid per 1 000 mL

phase A) and acetonitrile-tetrahydrofuran (25 ∶15

phase B) as mobile phase. Gradient elution was used to the determination of ester alkaloids in Baifupian and crude aconite roots at different decocting time. Result: The diester-type alkaloids in crude Aconite roots were extremely unstable

and there was only hypaconitine detected in 0.5 hours. But it's three kinds of monoester-type alkaloid showed a tendency of increasing gradually with increase of decocting time

and reached the peak at 8 hours. The mesaconitine and hypaconitine in Baifupian were detected in the whole decoction process

but the aconitine did't detect after 4 hours of decoction. The benzoylmesaconine and benzoylaconine in Baifupian decocted fluid firstly increased and then decreased

after 3-5 hours reached the peak

while the benzoylhypaconine gradually increased to the peak within 10 hours. Conclusion: In the decoction process

the change of ester alkaloids in crude Aconite roots and Baifupian was significantly different. The general trend is that the diester-type alkaloids in crude Aconite roots and Baifupian have transformed into pymesaconitine

pyraconitine

pyrhypaconitine

benzoylmesaconine

benzoylaconine and benzoylhypaconine.