PK-PD relationship of poorly absorbable active ingredients from traditional Chinese medicines explaining by metabolic enzyme of gut microbiota: A case study of Dehydrocorydaline

Many active ingredients in traditional Chinese medicines generally have the characteristic of poor oral absorption but definite efficacy. It is necessary to establish a comprehensive technical system to explain the “PK-PD relationship” of them. Dehydrocorydaline (DHC), the quality control component in the Chinese patent drug “Kedaling Tablets”, has poor oral absorption but clear efficacy for coronary heart disease. Using DHC as a model drug, the changes in absorption and pharmacological effects of DHC in rats before and after inhibiting nitroreductase (NR) from gut microbiota were studied. The results showed that after inhibiting of NR activity, the plasma concentration of DHC in rats was decreased, the serum level of total cholesterol, triglyceride and low-density lipoprotein cholesterol were significantly increased. The levels of tumor necrosis factor-α, interleukin-1β, hypersensitive C-reactive protein, intercellular cell adhesion molecule-1 and Monocyte chemoattractant protein-1 were significantly increased, and pathological sections also showed that the efficacy of DHC decreased after inhibiting the activity of NR. We further investigated the drug metabolism of DHC under NR and found that DHC was metabolized into a hydrogenated metabolite, which may have stronger membrane permeability. In summary, NR may mediate the absorption degree and efficacy of DHC in vivo by metabolizing DHC into absorbable metabolite.