Yuka Minoshima

University of Toyama, Тояма, Toyama, Japan

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Publications (6)12.59 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We report the structure-activity relationship of a series of coumarins as aldose reductase 2 (ALR2) inhibitors and their suppressive effect on the accumulation of galactitol in the rat lens. We evaluated their ALR2 selectivity profile against sorbitol dehydrogenase and aldehyde reductase (ALR1). Our study revealed that substitutions in the C7 OH group enhanced the potency toward ALR2, while the C6 OH group interferes with ALR1 inhibition activity. Having the phenyl moiety at C4 leads to improved potency and improved selectivity. A molecular docking study suggested that 6,7-dihydroxy-4-phenylcoumarin (15) binds to ALR2 in a different manner from epalrestat. Furthermore, compound 15 clearly suppressed galactitol accumulation in a dose-dependent manner. These results provide an insight into the structural requirements of coumarins for developing a new-type of selective ALR2 inhibitor.
    Bioorganic & medicinal chemistry letters 10/2010; 20(19):5630-3. · 2.65 Impact Factor
  • Heterocycles 01/2009; 79(1). · 1.08 Impact Factor
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    ABSTRACT: Matricaria chamomilla L., known as "chamomile", has been used as an herbal tea or supplementary food all over the world. We investigated the effects of chamomile hot water extract and its major components on the prevention of hyperglycemia and the protection or improvement of diabetic complications in diabetes mellitus. Hot water extract, esculetin (3) and quercetin (7) have been found to show moderate inhibition of sucrase with IC50 values of 0.9 mg/mL and 72 and 71 microM, respectively. In a sucrose-loading test, the administration of esculetin (50 mg/kg body weight) fully suppressed hyperglycemia after 15 and 30 min, but the extract (500 mg/kg body weight) and quercetin (50 mg/kg body weight) were less effective. On the other hand, a long-term feed test (21 days) using a streptozotocin-induced rat diabetes model revealed that the same doses of extract and quercetin showed significant suppression of blood glucose levels. It was also found that these samples increased the liver glycogen levels. Moreover, chamomile extract showed potent inhibition against aldose reductase (ALR2), with an IC50 value of 16.9 microg/mL, and its components, umbelliferone (1), esculetin (3), luteolin (6), and quercetin (7), could significantly inhibit the accumulation of sorbitol in human erythrocytes. These results clearly suggested that daily consumption of chamomile tea with meals could contribute to the prevention of the progress of hyperglycemia and diabetic complications.
    Journal of Agricultural and Food Chemistry 10/2008; 56(17):8206-11. · 2.91 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Matricaria chamomilla L., known as “chamomile”, has been used as an herbal tea or supplementary food all over the world. We investigated the effects of chamomile hot water extract and its major components on the prevention of hyperglycemia and the protection or improvement of diabetic complications in diabetes mellitus. Hot water extract, esculetin (3) and quercetin (7) have been found to show moderate inhibition of sucrase with IC50 values of 0.9 mg/mL and 72 and 71 μM, respectively. In a sucrose-loading test, the administration of esculetin (50 mg/kg body weight) fully suppressed hyperglycemia after 15 and 30 min, but the extract (500 mg/kg body weight) and quercetin (50 mg/kg body weight) were less effective. On the other hand, a long-term feed test (21 days) using a streptozotocin-induced rat diabetes model revealed that the same doses of extract and quercetin showed significant suppression of blood glucose levels. It was also found that these samples increased the liver glycogen levels. Moreover, chamomile extract showed potent inhibition against aldose reductase (ALR2), with an IC50 value of 16.9 μg/mL, and its components, umbelliferone (1), esculetin (3), luteolin (6), and quercetin (7), could significantly inhibit the accumulation of sorbitol in human erythrocytes. These results clearly suggested that daily consumption of chamomile tea with meals could contribute to the prevention of the progress of hyperglycemia and diabetic complications.
    Journal of Agricultural and Food Chemistry 08/2008; 56(17):8206–8211. · 2.91 Impact Factor
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    ABSTRACT: Chromatographic separation of the 50% aqueous EtOH extract of the leaves of the African medicinal tree Baphia nitida resulted in isolation of 10 iminosugars. The plant contained 2R,5R-dihydroxymethyl-3R,4R-dihydroxypyrrolidine (DMDP) as a major alkaloid. The structure of a new alkaloid was also elucidated by spectroscopic methods as the 1-O-beta-D-fructofuranoside of DMDP, and this plant produced 3-O-beta-D-glucopyranosyl-DMDP as well. DMDP is a potent inhibitor of beta-glucosidase and beta-galactosidase, whereas the other two derivatives lowered inhibition toward both of these enzymes and improved inhibitory activities toward rice alpha-glucosidase and rat intestinal maltase.
    Phytochemistry 04/2008; 69(5):1261-5. · 3.05 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Chromatographic separation of the 50% aqueous EtOH extract of the leaves of the African medicinal tree Baphia nitida resulted in isolation of 10 iminosugars. The plant contained 2R,5R-dihydroxymethyl-3R,4R-dihydroxypyrrolidine (DMDP) as a major alkaloid. The structure of a new alkaloid was also elucidated by spectroscopic methods as the 1-O-β-d-fructofuranoside of DMDP, and this plant produced 3-O-β-d-glucopyranosyl-DMDP as well. DMDP is a potent inhibitor of β-glucosidase and β-galactosidase, whereas the other two derivatives lowered inhibition toward both of these enzymes and improved inhibitory activities toward rice α-glucosidase and rat intestinal maltase. Ministry of Education, Culture, Sports, Science and Technology, Grant-in-Aid for Young Scientists, 18790086 and Cooperative Research Center of Life Science .