The aim of the present study was to investigate the bioavailability of quercetin from onion bulb (OB) and onion skin (OS) extracts in ruminants. Three non-lactating cows equipped with a permanent rumen fistula intraruminally received equimolar amounts of quercetin as either aglycone, rutin, or OB or OS extract, respectively, at a dose of 50 mg of quercetin equivalents/kg of body weight. Blood samples were drawn before and frequently within the 24 h period after application of the respective substance. Quercetin and quercetin metabolites with an intact flavonol structure (kaempferol, isorhamnetin, and tamarixetin) were analyzed in plasma samples by high-performance liquid chromatography with fluorescence detection. All quercetin sources administered resulted in a fast increase of the plasma concentrations of quercetin and total flavonols (sum of quercetin and its metabolites), followed by a rapid decline, whereby significant higher concentrations occurred with OB extract and rutin compared to quercetin aglycone and OS extract, respectively. The results clearly demonstrate a higher systemic availability of quercetin from OB extract and rutin. Taken together, OB extract with a high content of quercetin glucosides is an interesting source for the application of quercetin to ruminants.

中文翻译：

---

牛瘤胃内施用洋葱提取物中槲皮素的生物利用度

本研究的目的是研究反刍动物中洋葱鳞茎（OB）和洋葱皮（OS）提取物中槲皮素的生物利用度。三只装有永久性瘤胃瘘的非泌乳牛瘤胃内接受等摩尔量的槲皮素，以糖苷配基，芦丁，OB或OS提取物的形式给药，剂量为50毫克槲皮素当量/ kg体重。分别在施用各种物质之前和之后的24小时内抽取血样。通过高效液相色谱-荧光检测法分析血浆样品中具有完整黄酮醇结构的槲皮素和槲皮素代谢产物（山奈酚，异鼠李素和他马西汀）。服用所有槲皮素来源后，槲皮素和总黄酮醇（槲皮素及其代谢产物之和）的血浆浓度迅速增加，随后迅速下降，与槲皮素糖苷配基和OS提取物相比，OB提取物和芦丁的浓度显着升高， 分别。结果清楚地表明，从OB提取物和芦丁中提取的槲皮素具有更高的系统利用率。总体而言，具有高含量槲皮素葡萄糖苷的OB提取物是将槲皮素应用于反刍动物的有趣来源。结果清楚地表明，从OB提取物和芦丁中提取的槲皮素具有更高的系统利用率。总体而言，具有高含量槲皮素葡萄糖苷的OB提取物是将槲皮素应用于反刍动物的有趣来源。结果清楚地表明，从OB提取物和芦丁中提取的槲皮素具有更高的系统利用率。总体而言，具有高含量槲皮素葡萄糖苷的OB提取物是将槲皮素应用于反刍动物的有趣来源。