Comparative study on nobiletin metabolism with liver microsomes from rats, Guinea pigs and hamsters and rat cytochrome p450.
In vitro metabolism of nobiletin, a polymethoxy-flavonoid abundantly present in citrus peels, was studied using liver microsomes of rats, hamsters and guinea pigs and ten cDNA-expressed rat cytochrome P450 (P450). The effects of P450 inducers on nobiletin metabolism were also investigated. Aerobical incubation with NADPH and animal liver microsomes transformed nobiletin to five metabolites, M-1, M-2, M-3, M-4 and M-5. From LC-MS and (1)H-NMR data and a time-course study, these were assumed to be 4'-hydroxy (OH)-, 7-OH-, 6-OH-, 3',4'-diOH- and 6,7-diOH-metabolites, respectively. Pretreatment of animals with phenobarbital increased M-2 and M-3 to about 2-fold that in untreated animals. Pretreatment with 3-methylcholanthrene (MC) resulted in remarkable increases of both M-1 and M-4 (3 to 9-fold that of untreated). Males had 2-3 times higher M-2 and M-3 formation activities in rats, and for M-2 in hamsters than did females. Immunoinhibition study using antiserum against P450 revealed the involvement of hamster CYP1A2 in the formation of M-1 and M-4 in hamster liver. Of ten rat P450s, CYP2C11, CYP3A1, CYP3A2 and CYP2D1 had high activities for the formation of M-1, M-2 and M-3. Another P450s (CYP1A1, CYP2C12 and CYP1A2) also showed activity for the formation of M-1. Only CYP1A1 produced 3',4'-diOH-metabolites (M-4). However, CYP2A1, CYP2B1 and CYP2E1 had no activity for nobiletin. These results suggested that constitutive P450s such as CYP2C11, CYP2D1, CYP3A1, CYP3A2 and CYP2C12 are responsible for the demethylation at the 6-, 7-, 3'- and 4'-positions; whereas, MC-inducible P450s, CYP1A1 and CYP1A2, preferentially catalyzed demethylation at the 3'-and 4'-positions.
Faculty of Nutritional Sciences, Nakamura Gakuen University, 5-7-1 Befu, Johnan-ku, Fukuoka 814-0198, Japan. nobuyuki@nakamura-u.ac.jp
Nobuyuki
N
Koga
Miki
M
Matsuo
Chiho
C
Ohta
Koichi
K
Haraguchi
Mikiko
M
Matsuoka
Yoshihisa
Y
Kato
Toshinao
T
Ishii
Masamichi
M
Yano
Hideaki
H
Ohta
D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D001711:Biotransformation; D006224:Cricetinae; D065609:Cytochrome P-450 CYP1A2 Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D047309:Flavones / Q000737:chemistry / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D008297:Male; D008647:Mesocricetus; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism*; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000378:metabolism
D019138:Antibodies, Blocking; D065609:Cytochrome P-450 CYP1A2 Inhibitors; D004791:Enzyme Inhibitors; D047309:Flavones; D007527:Isoenzymes; D011994:Recombinant Proteins; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; C008661:nobiletin; D010634:Phenobarbital