1. The fate of phellamurin and its effect on the pharmacokinetics of cyclosporin and digoxin in rats. 2. Chemical constituents and biological activities of Trema orientalis.

• Main Authors: Hung-Yi Chen, 陳鴻儀
• Other Authors: Pei-Dawn Lee Chao
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/00417315033130820989

博士 === 中國醫藥學院 === 藥物化學研究所 === 89 === (I) part Flavonoids, possessing various beneficial biological activities, attract increased interest in recent years. Phellamurin is a flavonoid glycoside that is abundant in the leaves of Phellodendron wilsonii Hayata et Kanehira (Rutaceae). The metabolism and disposition of phellamurin were investigated in rats. Doses of 100 mg/kg and 200 mg/kg were orally administered to rats and blood samples were withdrawn by cardiopuncture at specific times. Serum concentrations of the aglycone were determined by an HPLC method prior to and after hydrolysis with b-glucuronidase/sulfatase. The mobile phase was acetonitrile-1% acetic acid (38:62). Our results indicate that the parent compound was not absorbed. Hydrolysis to neophellamuretin resulted in rapid absorption and subsequent conversion to glucuronides. Neophellamuretin and neophellamuretin glucuronides accounted for 20 % and 80 % of the metabolites of phellamurin, respectively, for both doses. The disposition kinetics of phellamurin metabolites in rat brain was investigated in this study. Doses of 100 mg/kg and 200 mg/kg were orally administered to rats. At 0.33, 2, 4 and 6 hr after dosing, rats were sacrificed and the brain concentrations of the aglycone neophellamuretin were determined by an HPLC method described above. Our results indicate that neophellamuretin glucuronides might be able to cross the blood-brain barrier and its concentrations in the brain was dose-dependent at the two doses investigated, whereas the aglycone neophellamuretin was only a trace in the brain. Cyclosporin is an immunosuppressive agent with a narrow therapeutic window. Cyclosporin is a substrate of P-glycoprotein (Pgp) and cytochrome P450-3A4 (CYP 3A4). In vitro everted intestine study indicated that phellamurin inhibited intestinal Pgp. In order to investigate the effect of phellamurin on cyclosporin absorption and disposition, rats were given cyclosporin (5 mg/kg) orally with or without phellamurin (100 mg/kg). Fluorescence polarization immunoassay was used to determine the blood concentration of cyclosporin. Unexpectedly, our results indicate that the coadministration of phellamurin significantly decreased the Cmax of cyclosporin by 77 % and reduced the AUC0-∞ of cyclosporin by 56 %. The elimination half life was not significantly affected, indicating phellamurin markedly decreased the absorption of cyclosporin. Digoxin is a substrate of both CYP 3A4 and Pgp in rats. In order to investigate the effect of phellamurin on digoxin absorption and disposition, rats were given digoxin (0.04 mg/kg) orally with or without phellamurin (100 mg/kg) in a cross-over design. Fluorescence polarization immunoassay was used to determine the serum concentration of digoxin. Our results indicate that the coadministration of phellamurin significantly increased theAUC4-12 of digoxin by 47 % , delayed the Tmax about 4.4 hours and increased MRT about 1.5 hours. To ensure the efficacy and safety of cyclosporin and digoxin, we suggest that the coadministration of phellamurin or the leaves of Phellodendron wilsonii with cyclosporin or digoxin should be avoided. The AUC of cyclosporin was validated as a precise predictor of acute rejection and graft loss. In order to investigate the correlation between Cmax and AUC, rats were given cyclosporin 5, 2.5, 1.25 mg/kg. The correlation coefficients (r) were 0.86, 0.91 and 0.90 between C1 and AUC after three doses, respectively. The results indicate that single-point monitoring of C1 could predict the bioavailability of Neoral® in rats. The monitoring of C1 can provide a rapid in vivo screening method to study the bioavailability of cyclosporin fomulations and drug-cyclosporin interactions. (II) part Isolation and characterization of the chemical constituents of Trema orientalis (Ulmaceae) resulted in the identification of twenty compounds which were betunilic acid, 3-acetyloleanolic acid, 3-acetyl ursolic acid, α-amyrenone, simiarenol, simiarenone, α-amyrin, 6β-hydroxystigmast-4-en-3-one, stigmast-4-en-3,6-dione, progesterone, β-sitosterol, β-sitosteryl glucoside, p-hydroxybenzaldehyde, 4,6-dimethyl -5-methoxysalicylic acid, benzoic acid, p-hydroxybenzoic acid, methyl vanillate, methyl 4-methoxycinnamate, methyl cinnamate and N-p-coumaroyltyramine。 Bioactivity testing indicated that 3-acetylursolic acid exhibited strong anti-superoxide formation activity, its IC50 was 3μM which is two times of the positive control. Stigmast-4-en-3,6-dione has little anti-superoxide formation activity. β-sitosteryl glucoside increased superoxide formation activity. Compound 1、2、3、9、11 and 12 have no antiallergic and antiplatelet aggregation effects.