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Propolis is a resinous substance collected by honeybees from various plant sources. The composition of propolis depends upon the vegetation at the site of collection. We previously isolated four prenylated flavonoids from propolis collected in Okinawa, Japan. In this study, further fractionation of the extracts of Okinawan propolis resulted in the isolation of a new prenylated flavonoid, prokinawan, and four known compounds. The structure of prokinawan was determined by MS and NMR spectroscopic methods. Furthermore, the antioxidant activity using 1,1-diphenyl-2-picryl-hydrazyl radical scavenging and beta-carotene bleaching systems was investigated. The present study proved that the position of the geranyl or prenyl groups on the flavonoid skeleton plays an important role in exhibiting antioxidant activity.

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Sesamin and sesaminol triglucoside in sesame seeds are major lignans that display an abundance of biological activities. Although their antioxidative activity in vitro is weak, they have been reported to suppress oxidative stress in vivo. We investigated the production of new antioxidative lignans from sesame lignans by culturing with the genus Aspergillus to enhance the function of food materials. Media containing sesamin or sesaminol triglucoside increased antioxidative activity for DPPH radical scavenging by culturing with Aspergillus usamii mut. shirousamii RIB2503. The antioxidative lignans in sesamin medium were identified as sesamin 2,6-dicatechol and episesamin 2,6-dicatechol. Those in sesaminol triglucoside medium were identified as sesaminol 6-catechol and episesaminol 6-catechol, which are novel antioxidative lignans. It is suggested that they may exhibit higher antioxidative activity than sesamin and sesaminol triglucoside because they have the catechol functional moiety.

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...

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Eriocitrin (eriodictyol 7‐O‐β‐rutinoside) is the main flavonoid in lemon fruit. In this study, eriocitrin was investigated for its lowering effect on serum and hepatic lipids in high‐fat and high‐cholesterol fed rats. Rats in the control group (N= 6) were fed a 20% lard and 1% cholesterol diet for 21 d, and rats in the 0.35% eriocitrin group (N= 6) and 0.70% eriocitrin group (N= 6) were fed a diet supplemented with eriocitrin 0.35% and 0.70%, respectively. The content of hepatic total cholesterol and triglyceride in the eriocitrin group was no different from that of the control group. The total cholesterol, VLDL+LDL, triglyceride, and phospholipid in the serum of the 0.35% eriocitrin group showed significantly lower concentrations than the control group (P < 0.05), although there was no difference in the HDL concentrations among the groups. The lowering effect of eriocitrin for serum total cholesterol was thought to be caused by a decrease in VLDL+LDL. The 0.35% eriocitrin group was shown to have a significant increase in excretion of fecal bile acid (P < 0.05) and a tendency for enhanced hepatic m‐RNA levels of LDL receptor in comparison with the control group.

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