Stability of andrographolide in powdered Andrographis herb under accelerated conditions

The stability of andrographolide in powdered Andrographis Herb--the aerial part of Andrographis paniculata (Burm. f.) Nees (Acanthaceae)--was determined using a heat-accelerated experiment to reveal a second-order kinetics of degradation. The fast decomposition was observed regardless of the method of analysis. The rate constant of the decomposition of andrographolide at 25 degrees C ( K(25)( degrees C)), predicted from the Arrhenius plot, was 6.58 x 10 (-6) d (-1).