Heat-accelerated degradation of solid-state andrographolide

Abstract

The stability of andrographolide, the major active diterpene lactone from Andrographis paniculata (Burm. f.) Wall. ex Nees., was determined to show that, while crystalline andrographolide was highly stable even at 70°C (75% relative humidity) over a period of 3 months, its amorphous phase degraded promptly. Heat-accelerated conditions revealed second-order kinetics of the decomposition with the rate constant at 25°C (k25°C) predicted from the Arrhenius plot of 3.8×10-6 d-1. The major decomposed product under elevated temperature (70°C, 75% relative humidity) is 14-deoxy-11,12-didehydroandrographolide. © 2003 Pharmaceutical Society of Japan.