Department of Pharmacognosy, Graduate School of Pharmaceutical Science, Nagoya City University, Japan.
Biol Pharm Bull. 2009 Dec;32(12):2034-40. doi: 10.1248/bpb.32.2034.
Quercetin, a flavonol contained in various vegetables and herbal medicines, has various biological activities including anti-cancer, anti-allergic and anti-oxidative activities. However, low oral bioavailability of quercetin due to insolubility in water has limited its use as a food additive or dietary supplement. Since the water solubility is enhanced by glycosyl conjugation, in the present study, we evaluated the bioavailability of several quercetin glycosides with different sugar moieties in rats. Quercetin, quercetin-3-O-rutinoside (rutin), and quercetin-3-O-glucoside (isoquercitrin, IQC) in suspension, and quercetin-3-O-maltoside (Q3M), quercetin-3-O-gentiobioside (Q3G), alpha-monoglucosyl rutin (alphaMR), alpha-oligoglucosyl rutin (alphaOR), and enzymatically modified isoquercitrin (alpha-oligoglucosyl isoquercitrin, EMIQ) dissolved in water, were orally administered to rats under anesthesia. Bioavailability (F value) was calculated from the concentrations of total quercetin in plasma from 0 to 12 h after the administration. F value of quercetin was 2.0%, and those of IQC, Q3M and EMIQ were 12%, 30%, and 35%, respectively. Although Q3G, alphaMR and alphaOR have high water solubility, their F values were low (3.0%, 4.1%, 1.8%, respectively). In the in vitro study, the homogenate of rat intestinal epithelium rapidly hydrolyzed IQC, Q3M and EMIQ to quercetin, and alphaMR and alphaOR to rutin. However, it could not hydrolyze Q3G or rutin to quercetin. Elongation of alpha-linkage of glucose moiety in IQC enhances the bioavailability of quercetin, and intestinal epithelial enzymes such as lactase-phrolizin hydrolase or mucosal maltase-glucoamylase would play important roles in the hydrolysis and absorption of these flavonol glycosides.
槲皮素是一种存在于各种蔬菜和草药中的类黄酮醇，具有多种生物活性，包括抗癌、抗过敏和抗氧化活性。然而，由于其在水中的不溶性，槲皮素的口服生物利用度较低，限制了其作为食品添加剂或膳食补充剂的应用。由于糖基化结合可提高水溶性，因此在本研究中，我们评估了具有不同糖基的几种槲皮素糖苷在大鼠中的生物利用度。在麻醉状态下，将槲皮素、槲皮素-3-O-芸香糖苷（芦丁）和槲皮素-3-O-葡萄糖苷（异槲皮苷，IQC）混悬液，以及槲皮素-3-O-麦芽三糖苷（Q3M）、槲皮素-3-O-龙胆二糖苷（Q3G）、α-单葡糖基芦丁（αMR）、α-寡葡糖苷芦丁（αOR）和酶法修饰的异槲皮苷（α-寡葡糖苷异槲皮苷，EMIQ）溶于水，经口给予大鼠。从给药后 0 至 12 小时的血浆中总槲皮素浓度计算生物利用度（F 值）。槲皮素的 F 值为 2.0%，而异槲皮苷、Q3M 和 EMIQ 的 F 值分别为 12%、30%和 35%。尽管 Q3G、αMR 和 αOR 具有较高的水溶性，但它们的 F 值较低（分别为 3.0%、4.1%和 1.8%）。在体外研究中，大鼠肠上皮的匀浆可迅速将 IQC、Q3M 和 EMIQ 水解为槲皮素，将 αMR 和 αOR 水解为芦丁。然而，它不能将 Q3G 或芦丁水解为槲皮素。IQC 中葡萄糖基α-糖苷键的延长可提高槲皮素的生物利用度，而乳糖-蔗糖酶水解酶或黏膜麦芽糖-葡糖苷酶等肠上皮酶可能在这些类黄酮糖苷的水解和吸收中发挥重要作用。
