Abstract: AIM: To investigate the existence of these compounds in other citrus fruit juices, and check their inhibitory intensities on activity of cytochrome P450 (CYP) 3A.METHODS: Freshly squeezed citrus fruit juices were determined separately for their composition and levels of six furanocoumarins with a gradient highpressure liquid chromatographic (HPLC) method. Inhibition of CYP3A by each juice sample was tested with the activity of testosterone 6β-hydroxylation in liver microsoms of male Sprague-Dawley rats.RESULTS: Comparing with grapefruit juices, the Jaffa sweetie showed almost the same composition and levels of furanocoumarins, and a comparable inhibitory intensity of CYP3A; the Japanese red pommelo, `Guanxi Miyou' and `Jinyou' pommelos showed similar compositions but lower levels of furanocoumarins, and weaker inhibiting intensities of CYP3A; While `Changshan Huyou' pummelos, sweet oranges and mandarins showed less varieties and much lower levels of furanocoumarins, and most of them showed no inhibition of CYP3A.CONCLUSION: Furanocoumarin composition can be an index to predict citrus fruit juice-drug interaction based on CYP3A inhibition; Clinical validations should be conducted on `Guanxi Miyou' pummelo and closely related accessions for their possible drug interactions similar to grapefruit juice.

Key words: psoralens, citrus fruit juice, high-pressure liquid chromatography, cytochrome P450 3A, enzyme inhibition