The Grapefruit Effect: Interaction between Cytochrome P450 and Coumarin Food Components, Bergamottin, Fraxidin and Osthole. X-ray Crystal Structure and DFT Studies

Abstract

<jats:p>Coumarins are plant-derived secondary metabolites. The crystal structure of three coumarins—bergamottin, osthole and fraxidin—are described and we analyze intermolecular interactions and their role in crystal formation. Bergamottin is a furanocoumarin found in citrus plants, which is a strong inhibitor of the principal human metabolizing enzyme, cytochrome P450 3A4 (CYP3A4). The crystal structure determinations of three coumarins give us the geometrical parameters and reveal the parallel-displaced π–π stacking and hydrogen bonding intermolecular interactions used for molecular assembly in the crystal structure. A quite strong (less than 3.4 Å) stacking interaction of bergamottin appears to be a determining feature that distinguishes it from other coumarins studied in this work. Our DFT computational studies on the three natural products of the same coumarin family docked into the active site of CYP3A4 (PDB 4D78) show different behavior for these coumarins at the active site. When the substrate is bergamottin, the importance of π-π stacking and hydrogen bonding, which can anchor the substrate in place, appears fundamental. In contrast, fraxidin and osthole show carbonyl coordination to iron. Our docking calculations show that the bergamottin tendency towards π–π stacking is important and likely influences its interactions with the heme group of CYP3A4.</jats:p>

Aromatic Polyphenol π-π Interactions with Superoxide Radicals Contribute to Radical Scavenging and Can Make Polyphenols Mimic Superoxide Dismutase Activity

“…In Figure 4 A, the energy-minimized 4-methyl-7,8-dimethoxy-coumarin structure [ 24 ] shows that the superoxide penetrates the ring environment, with centroid separation of 3.042 Å, while the superoxide O–O bond length becomes shorter, 1.323 Å, and so a coumarin-η-superoxide complex is formed. As seen in Figure 4 B, a similar complex is reached by DFT minimization of the dimethoxy coumarin fraxidin [ 27 ], with even shorter separation between centroids, 2.927 Å. We were also interested in investigating potential superoxide interaction with the non-pyrone ring of fraxidin, Figure 4 C. This interaction between both species is weak, as shown by separation between centroids of 3.348 Å, closer to the initial van der Waals separation.…”

Bergamottin a CYP3A inhibitor found in grapefruit juice inhibits prostate cancer cell growth by downregulating androgen receptor signaling causing cell cycle block and apoptosis

“…Although primarily bergamottin is a CYP3A4 inhibitor it also inhibits CYP3A5, CYP2B6 and CYP1A1 (9,11,12,31,32). Since CYP3A5 is the major isoform expressed in normal prostate and prostate tumor the effects observed in our experiments is primarily due to inhibition of CYP3A5 in the tested prostate cancer cell lines (13,33).…”

“…Bergamottin, the furanocoumarin compound used in our current study is also a strong inhibitor of CYP3A4/5 a P450 enzyme dominantly expressed in liver (9)(10)(11)(12). Based on its crystal structure bergamottin shows a tendency towards π -π stacking which influences its interaction with the heme group of CYP3A4/5 (9).…”

Bergamottin a CYP3A inhibitor found in grapefruit juice inhibits prostate cancer cell growth by downregulating androgen receptor signaling and promoting G0/G1 cell cycle block and apoptosis

“…Although primarily bergamottin is a CYP3A4 inhibitor it also inhibits CYP3A5, CYP2B6 and CYP1A1 [ 9 , 11 , 12 , 33 , 34 ]. Expression of P450 CYPs is tissue specific and CYP3A5 is the major isoform expressed in both normal and prostate tumor [ 13 ].…”

“…Bergamottin, the furanocoumarin compound used in our current study, is also a strong inhibitor of CYP3A4/5, a P450 enzyme dominantly expressed in the liver [ 9 – 12 ]. Based on its crystal structure bergamottin shows a tendency towards π-π stacking which influences its interaction with the heme group of CYP3A4/5 [ 9 ]. CYP3A5 is the main extrahepatic P450 form expressed in both normal prostate and in prostate cancer [ 13 ].…”