This study reports the 24 h human plasma pharmacokinetics of 3,4-Dimethoxycinnamic acid (dimethoxycinnamic acid) after consumption of coffee, and the membrane transport characteristics of certain dimethoxycinnamic acid derivatives, as present in coffee. METHODS AND RESULTS: For the first time, we show that 3,4-Dimethoxycinnamic acid appears in plasma as the free aglycone. The time to reach the C(max) value of approximately 0.5 μM was rapid, T(max) = 30 min, and showed an additional peak at 2-4 h for several subjects. In contrast, smaller amounts of dimethoxy-3,4-Dimethoxycinnamic acid (C(max) ∼ 0.1 μM) peaked between 8 and 12 h after coffee intake. In the cell model, 3,4-Dimethoxycinnamic acid was preferentially transported in the free form by passive diffusion, and a small amount of dimethoxycinnamoylquinic acid hydrolysis was observed. CONCLUSIONS: These findings show that 3,4-Dimethoxycinnamic acid, previously identified in plasma after coffee consumption, was rapidly absorbed in the free form most likely by passive diffusion in the upper gastrointestinal tract. |