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 °C (k 25 °C), predicted from the Arrhenius plot, was 6.58 × 10-6 d-1.