RESUMO
OBJECTIVE: To determine the apparent n-octanol-water/buffer partition coefficient of andrographolide and dehydroandrographolide. METHODS: The apparent n-octanol-water/buffer partition coefficients of andrographolide and dehydroandrographolide were measured by shaking flask method. The concentrations of andrographolide and dehydroandrographolide were analyzed by HPLC method. RESULTS: The Papp of andrographolide and dehydroandrographolide were 3.90 (log Papp = 0.59) and 19.75 (log Papp = 1. 30) in water at 37 degrees C, respectively. CONCLUSIONS: The apparent n-octanol-buffer partition coefficients of andrographolide and dehydroandrographolide are influenced by pH, and the higher pH may decrease the apparent n-octanol-buffer partition coefficients of them. Andrographolide has the highest partition coefficient in pH6, and dehydroandrogapholide in pH5.