Bioavailability of ellagic acid in human plasma after consumption of ellagitannins from pomegranate (Punica granatum L.) juice.

Ellagic acid (EA) and hydrolyzable ellagitannins (ETs) are dietary polyphenols found in fruits and nuts and implicated with potent antioxidant, anticancer and antiatherosclerotic biological properties. Unfortunately, there are no reports on the bioavailability studies of EA or ETs in the human body. We conducted in vivo studies whereby a human subject consumed pomegranate juice (PJ) (180 ml) containing EA (25 mg) and ETs (318 mg, as punicalagins, the major fruit ellagitannin). A rapid plasma extraction procedure utilizing acidic precipitation of proteins, followed by HPLC-UV analyses, was employed. EA was detected in human plasma at a maximum concentration (31.9 ng/ml) after 1 h post-ingestion but was rapidly eliminated by 4 h. The calibration curve for quantification of EA was linear (r2 = 0.9975) over the concentration range from 1000 to 15.6 ng/ml. Since EA has reportedly strong affinity for proteins and poor absorption in small animals, further studies to investigate whether the presence of free EA in human plasma may be due to its release from the hydrolysis of ETs, facilitated by physiological pH and/or gut microflora action, is warranted. EA can be considered as a biomarker for future human bioavailability studies involving consumption of ETs from food sources.