SummaryThe concentrations of metabolites in human plasma after ingestion of flavanone glycosides (FG) and their aglycones (FA) in lemon were examined. FG consisting abundantly of eriocitrin were prepared from lemon peel and FA consisting abundantly of eriodictyol were prepared from FG by treatment with -glucosidase. Eriodictyol, homoeriodictyol, and hesperetin in plasma up to 4 h after ingestion of FG with water or FA with water by subjects were not detected in plasma of non-enzyme treatment but in plasma after treatment with -glucronidase and sulfatase. Metabolites in plasma after ingestion of FG and FA in humans were shown to exist as the glucuro-and/or sulfo-conjugates of eriodictyol, homoeriodictyol, and hesperetin. After ingestion of FA, the concentration of metabolites in plasma exhibited a high maximum peak at 1 h. The AUC (area under the blood concentration time curve) level of metabolites of FA was higher than that of FG. FA were suggested to be absorbed faster and in higher amounts than FG. The AUC of metabolites in subject plasma after ingestion of FG with flavonoid-depleted lemon juice was shown to change to a low level in comparison with that of FG with water. The maximum concentration peak of metabolites in plasma was faster at 0.5 h than FA with water but the AUC level was similar to FA with water, when subjects ingested FA with vodka (40% ethanol). The absorption hour of FG and FA was shown to be affected by the co-existing solution. Key Words lemon flavonoid, eriocitrin, plasma, human, ingestion Epidemiological studies indicate a protective relationship between the consumption of citrus fruits or juice and the risk of ischemic stroke and lung cancer (1, 2). Some fundamental studies support a protective effect provided by flavonoid consumption in these diseases (3-6). Citrus fruits contain various kinds of flavonoids such as flavanone glycoside, flavone glycoside, and polymethoxyflavone (3, 4). Flavonoids in lemon fruit (Citrus limon BURM. f.) have been reported to be such flavanone glycosides as eriocitrin (eriodictyol 7-O--rutinoside) and hesperidin (hesperetin 7-O--rutinoside) and such flavone glycosides as diosmin (diosmetin 7-O--rutinoside) and 6,8 C-diglucosyldiosmetin (7-10). Eriocitrin has been reported to be the most abundant flavonoid in lemon fruit and to have the highest antioxidative activity of the flavonoids in citrus fruits in vitro (9,11). It was also shown to have a suppressive effect for oxidative stress in the liver of streptozotocin-induced diabetic rats (12) or exercise-induced rats (13).For the study of functional compounds such as flavonoids in foods, it is important to determine how the compounds in food are metabolized and absorbed in vivo and how the metabolites function in a living system. There have been several human studies that have investigated the metabolism and absorption of flavonoids (14), such as anthocyanin (15, 16), flavonol (17, 18), isoflavone (19), and flavanone (20-22). As for eriocitrin, it was reported for metabolites by human intestinal bacteri...
SummaryOxidized low-density lipoprotein (LDL) is considered a risk factor in atheroscle rosis, and polyphenols are the potential agents to inhibit the oxidation of LDL. We deter mined the polyphenol contents and the antioxidant activities of commonly consumed vegetables in Vietnam and assessed the quantity of the polyphenol intake from vegetables in the current Vietnamese diet. The polyphenol contents in 30 kinds of vegetables was deter mined by the Folin-Ciocalteu method. The antioxidant activities of vegetables were evalu ated by measuring the oxidation of LDL and the reduction of the 1,1-Biphenyl-2 -picrylhydrazyl (DPPH) radical. In this study, some herbs and edible wild vegetables possessed high contents of polyphenols and antioxidant activities. Among green vegetables, sweet potato leaves showed both a high polyphenol content and antioxidant activity. The mean polyphenol daily intake of the Vietnamese was a 595mg catechin equivalent. Water spin ach, a kind of green vegetable, contributed the highest amount (45%) of the total polyphe nol intake, followed by other green vegetables. Neither herbs nor edible wild vegetables contributed significantly to the total polyphenol intake due to their low consumption. Green vegetables are therefore considered very important sources of polyphenol intake for the Viet namese.
Lemon flavonoid (LF) prepared from lemon peel predominantly contains eriocitrin as an antioxidant. It is indicated to have low bioavailability compared with lemon flavonoid aglycone (LFA), which predominantly contains eriodictyol. This study attempted to prepare LFA which has high bioavailability, using enzymes that are commonly used in the citrus industry, such as cellulase, naringinase, hesperidinase, and pectinase. LFA containing the highest amount of eriodictyol (19.4%) was prepared with naringinase, a debittering enzyme for citrus juice. Ten male normolipidemic subjects ingested LFA (3.7 g) after an overnight fast, and low-density lipoprotein (LDL) was prepared from 0-4 h plasma after intake of LFA. The LDL oxidizability was measured with lag time of the conjugated diene formation induced by an oxidative inducer. LDL in 0.5 h plasma after ingestion of LFA was shown to have a significantly longer lag time for oxidation than that before ingestion (P<0.05). LFA was suggested to have the resistance effect of LDL to oxidation ex vivo. Eriodictyol, homoeriodictyol, and hesperetin were not detected in plasma by HPLC analysis, but they were detected in plasma treated with β-glucuronidase and sulfatase. The flavonoids were suggested to be glucuro-and/or sulfo-conjugates and to be metabolites in plasma after ingestion of LEA.
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