Walle T, Otake Y, Walle U K, Wilson F A
Department of Cell and Molecular Pharmacology, Division of Gastroenterology, Medical University of South Carolina, Charleston, SC 29425, USA.
J Nutr. 2000 Nov;130(11):2658-61. doi: 10.1093/jn/130.11.2658.
Flavonoids, dietary components in vegetables, fruits and beverages, may protect against coronary heart disease, stroke and cancer. However, the bioavailability of these compounds is questionable. A previous study in ileostomy patients of the most abundant flavonoid, quercetin, suggested a 52% absorption of its major dietary forms, monoglucoside (QMG) and diglucoside (QDG), from an onion meal. However, this was based on indirect measurements after acid hydrolysis. Because human intestinal Caco-2 cell monolayers showed minimal absorption of the glucosides, we repeated the study in ileostomy patients, using molecularly specific analytical methodology for the intact glucosides and quercetin. The onion meal had high concentrations of both QMG and QDG with only trace amounts of quercetin. The intake of QMG and QDG in four patients ranged from 10.9 to 51.6 mg. No QMG or QDG was detected in the ileostomy fluid. In contrast, the amounts of the aglycone quercetin were substantial, 2.9-11.3 mg. This corresponded to 19.5-35.2% of total quercetin glucosides ingested, implying absorption of 64.5-80.7%. These findings suggest a different interpretation than that from the previous study, i.e., that both QMG and QDG are efficiently hydrolyzed in the small intestine by beta-glucosidases to quercetin, most of which is then absorbed.
黄酮类化合物是蔬菜、水果和饮品中的膳食成分，可能有助于预防冠心病、中风和癌症。然而，这些化合物的生物利用度存在疑问。先前一项针对回肠造口术患者的研究，对含量最丰富的黄酮类化合物槲皮素进行了研究，结果表明，食用洋葱餐后，其主要膳食形式单糖苷（QMG）和双糖苷（QDG）的吸收率为52%。然而，这是基于酸水解后的间接测量得出的。由于人肠道Caco-2细胞单层对糖苷的吸收极少，我们采用针对完整糖苷和槲皮素的分子特异性分析方法，在回肠造口术患者中重复了这项研究。洋葱餐中QMG和QDG的浓度都很高，槲皮素含量仅为微量。4名患者摄入的QMG和QDG量在10.9至51.6毫克之间。回肠造口液中未检测到QMG或QDG。相比之下，苷元槲皮素的量相当可观，为2.9 - 11.3毫克。这相当于摄入的总槲皮素糖苷的19.5 - 35.2%，这意味着吸收率为64.5 - 80.7%。这些发现表明与先前研究不同的解释，即QMG和QDG在小肠中均被β - 葡萄糖苷酶有效水解为槲皮素，然后大部分被吸收。
