Institute of Animal Nutrition and Physiology, Christian-Albrechts-University of Kiel, 24118 Kiel, Germany.
Institute of Animal Nutrition and Physiology, Christian-Albrechts-University of Kiel, 24118 Kiel, Germany.
J Dairy Sci. 2012 Sep;95(9):5047-5055. doi: 10.3168/jds.2012-5439.
The bioavailability of quercetin has been intensively investigated in monogastric species, but knowledge about its bioavailability in ruminants does not exist. Thus, the aim of the present study was to determine the bioavailability of quercetin in nonlactating cows equipped with indwelling catheters placed in one jugular vein after intraruminal and additionally after i.v. application, respectively. Quercetin was administered intraruminally in equimolar amounts, either in the aglycone form or as its glucorhamnoside rutin, each at 2 dosages [10 and 50 mg of quercetin/kg of body weight (BW)]. In a second trial, 0.8 mg of quercetin aglycone/kg of BW was applied i.v. Blood samples were drawn 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, and 24 h after intraruminal application and every 5 min (first hour), every 10 min(second hour), and at 3 and 6h after i.v. bolus application, respectively. Quercetin and quercetin metabolites with an intact flavonol structure (isorhamnetin, tamarixetin, and kaempferol) in plasma samples were analyzed by HPLC with fluorescence detection. After intraruminal application of quercetin and rutin, respectively, quercetin and its methylated (isorhamnetin, tamarixetin) and dehydroxylated (kaempferol) derivatives were present in plasma mainly as conjugated forms, whereas free quercetin and its derivatives were scarcely detected. For rutin, the relative bioavailability of total flavonols (sum of conjugated and nonconjugated quercetin and its conjugated and nonconjugated derivatives after intake of 50 mg/kg of BW) was 767.3% compared with quercetin aglycone (100%). Absolute bioavailability of total flavonols was only 0.1 and 0.5% after quercetin aglycone and rutin applications, respectively. Our data demonstrate that bioavailability of quercetin from rutin is substantially higher compared with that from quercetin aglycone in cows after intraruminal (or oral) application, unlike in monogastric species.
槲皮素的生物利用度在单胃动物中已得到深入研究，但反刍动物中槲皮素的生物利用度尚不清楚。因此，本研究的目的是确定非泌乳奶牛在瘤胃内和静脉内分别给予槲皮素后的生物利用度。槲皮素以糖苷形式或以其糖苷芦丁的形式等摩尔量给予，每种剂量分别为[10 和 50mg/kg 体重（BW）]。在第二项试验中，静脉内给予 0.8mg/kg BW 的槲皮素苷元。在瘤胃内给予后 0.5、1、1.5、2、2.5、3、4、6、8、12 和 24h 以及静脉内推注后 0.5、1、1.5、2、2.5、3、4、6、8、12、24 和 48h 分别采血。用 HPLC 荧光检测法分析血浆样品中的槲皮素及其具有完整黄酮醇结构的代谢物（异鼠李素、杨梅素和山奈酚）。在瘤胃内给予槲皮素和芦丁后，主要以结合形式存在于血浆中的槲皮素及其甲基化（异鼠李素、杨梅素）和去羟化（山奈酚）衍生物，而游离槲皮素及其衍生物则很少检测到。对于芦丁，与摄入 50mg/kg BW 的槲皮素苷元相比，总黄酮醇（摄入后结合和非结合的槲皮素及其结合和非结合衍生物的总和）的相对生物利用度为 767.3%（100%）。槲皮素苷元和芦丁静脉内给予后，总黄酮醇的绝对生物利用度分别仅为 0.1%和 0.5%。与单胃动物相比，在奶牛中，经瘤胃（或口服）给予芦丁后，其槲皮素的生物利用度明显高于槲皮素苷元。
