Furocoumarins from grapefruit juice and their effect on human CYP 3A4 and CYP 1B1 isoenzymes

Bioactive compounds present in grapefruit juice are known to increase the bioavailability of certain medications by acting as potent CYP 3A4 inhibitors. An efficient technique has been developed for isolation and purification of three furocoumarins. The isolated compounds have been tested for the inhibition of human CYP 1B1 isoform using specific substrates. Grapefruit juice was extracted with ethyl acetate (EtOAc) and the dried extract was loaded onto silica gel column chromatography. Further, column fractions were subjected to preparative HPLC to obtain three compounds. The purity of these compounds was analyzed by HPLC and structures were determined by NMR studies. The identified compounds, bergamottin, 6′,7′-dihydroxybergamottin (DHB), and paradisin-A, were tested for their inhibitory effects on hydroxylase and O-dealkylase activities of human cytochrome P450 isoenzymes CYP 3A4 and CYP 1B1. Paradisin-A was found to be a potent CYP 3A4 inhibitor with an IC50 of 1.2 μM followed by DHB and bergamottin. All three compounds showed a substantial inhibitory effect on CYP 3A4 below 10 μM. Inhibitory effects on CYP 1B1 exhibited a greater variation due to the specificity of substrates. Paradisin A showed an IC50 of 3.56 ± 0.12 μM for the ethoxy resorufin O-dealkylase (EROD) activity and 33.56 ± 0.72 μM for the benzyloxy resorufin (BROD). DHB and bergamottin showed considerable variations for EROD and BROD activities with an IC50 of 7.17 μM and 13.86 μM, respectively.

Three furocoumarins were isolated from grapefruit juice. The structures were identified and confirmed by NMR. All three compounds were tested for their inhibitory effects on human CYP 3A4 and CYP 1B1 microsomes using specific substrates such as dibenzylfluorescein and alkoxyresorufin. Paradisin A was found to be the most potent CYP 3A4 inhibitor with an IC50 of 1.2 μM followed by DHB and bergamottin. Inhibitory effects on CYP IB1 exhibited a greater variation due to specificity of substrates. Paradisin A showed an IC50 of 3.56 ± 0.12 μM for the ethoxy resorufin O-dealkylase activity and 33.56 ± 0.72 μM for the benzyloxyresorufin O-dealkylase activity.Figure optionsDownload as PowerPoint slide