银杏黄酮山奈酚的体外葡醛酸结合反应

Glucuronidation of kaempferol in Ginkgo biloba flavonoid in vitro

目的 旨在了解银杏黄酮山奈酚代谢的有关酶系及酶动力学参数。方法 采用苯巴比妥 (PB)、地塞米松 (DEX)、β 萘黄酮 (BNF)和地非三唑 (DIPH)诱导SD大鼠 ,与未诱导大鼠分别作为体外代谢的 5种不同酶源。取山奈酚和鼠肝微粒体 2 5℃下共孵育 ,HPLC法测定孵育液中剩余底物浓度。比较不同诱导剂处理的鼠肝微粒体对山奈酚代谢的催化活性 ,以未作任何处理的鼠肝微粒体为空白对照。结果 山奈酚在BNF和DIPH诱导的鼠肝微粒体中有较强的代谢作用 ,而在PB ,DEX诱导的鼠肝微粒体和空白组微粒体中的代谢较弱。在 0 .2g·L- 1的微粒体蛋白质浓度的孵育液中 ,山奈酚 (40mg·L- 1)经4 5min孵育后 ,分别有 6 2 .9% (DIPH ) ,4 0 .1%(BNF) ,2 1.1% (PB) ,2 3.7% (DEX)和 18.0 % (空白组 )的量被代谢。测得山奈酚在空白对照组、BNF和DIPH诱导的微粒体中的Km 值分别为 (1.85±1.0 5 ) ,(9.4 1± 2 .4 5 )和 (72 .4± 3.0 8) μmol·L- 1;Vmax值分别为 (2 .4 5± 0 .6 3) ,(7.5 5± 1.4 0 )和 (2 5 .2±1.0 8) μmol·g- 1·min- 1。结论 山奈酚在各种微粒体中被广泛代谢 ;BNF和DIPH葡醛酸转移酶的强诱导剂可使山奈酚Ⅱ相葡萄糖醛酸苷结合反应增强。

AIM To explore which enzymes are related to the metabolism of Ginkgo biloba flavonoid and their kinetic parameters.METHODS The metabolism of the flavonoid kaempferol was investigated in hepatic microsomes of rats treated with phenobarbital(PB), dexamethasone(DEX), β naphthoflavone(BNF), diphenytriazol(DIPH). The kaempferol was incubated with rat hepatic microsomes at 25℃ and the metabolites were determined by HPLC. RESULTS The kaempferol was extensively metabolized after 45 min incubation with 62.9% of metabolic rate in the microsomes induced by DIPH, 40.1% by BNF, 21.1% by PB, 23.7% by DEX and 18.0% in control, respectively. Two glucuronides of kaempferol were detected. The K m of kaempferol in control microsomes and in microsomes induced by BNF or by DIPH was (1.85±1.05),(9.41±2.45 )and(72.4±3.08)μmol·L -1 respectively; V max was (2.45±0.63),(7.55±1.40) and(25.2±1.08)μmol·g -1 ·min -1 , respectively. CONCLUSION DIPH and BNF, the two potent inducers of glucuronyltransferase could induce more potent glucuronidation of kaempferol in microsomes.