α-Glucosidase inhibitory effect by the flower buds of Tussilago farfara L.
ABSTRACT Methanolic extracts from the medicinal parts of 50 traditional Chinese herbs were tested in screening experiments for rat intestinal α-glucosidase. The methanolic extract from flower buds of Tussilago farfara L. (Compositae) showed the highest maltase inhibitory activity, with maltose as a substrate. Enzyme assay-guided fractionation of this extract afforded 3,4-dicaffeoylquinic acid (1), 3,5-dicaffeoylquinic acid (2), 4,5-dicaffeoylquinic acid (3) and rutin (4), and the structures of these compounds were elucidated on the basis of MS and NMR data analyses. Compounds 1, 2 and 3 showed comparative maltase inhibitory activities, and the IC50 values were 0.91 mM, 0.90 mM and 0.89 mM, respectively. Comparison of the activities of 1–3, chlorogenic acid (5), quinic acid (6) and caffeic acid (7) suggested that the number of caffeoyl groups attached to a quinic acid core were important for the potency. Rutin (4) showed moderate activity and inhibited 41% of maltase activity at a concentration of 1 mM. This is the first report on mammalian α-glucosidase inhibition of T. farfara and the isolation of 1, 2 and 3 from this herb species. These results suggest a use of the extract of T. farfara for antidiabetes.
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ABSTRACT: This study was designed to compare the efficacy of three insulinotropic agents in the control of postprandial hyperglycemia in type 2 diabetes. Fifteen subjects with noninsulin-requiring type 2 diabetes were admitted to the General Clinical Research Center on four separate occasions. During the control study and following 7-10 d on each study medication, daylong glucose profiles were performed to investigate the effects of the assigned medication on postprandial hyperglycemia. During each admission, placebo or study medications were administered before three isocaloric meals as follows: immediate-release glipizide 30 min before breakfast and 30 min before supper, glipizide gastrointestinal therapeutic system (GITS) 30 min before breakfast, or nateglinide 120 mg 10 min before breakfast, before lunch, and before supper. Blood was drawn for analysis of glucose, insulin, and C-peptide at -0.05, 0, 0.25, 0.5, 1, 2, 3, and 4 h relative to each test meal. Immediate-release glipizide, nateglinide, or glipizide GITS administration resulted in significantly lower integrated daylong (glucose area under the curve) and peak glucose levels, compared with placebo. There were no significant differences in the daylong integrated glucose levels among the three study medications. The peak postbreakfast glucose level (but not glucose area under the curve) was lower with nateglinide, compared with either immediate-release glipizide or glipizide GITS. Postlunch and postdinner integrated glucose levels were significantly lower with immediate-release glipizide or glipizide GITS, compared with nateglinide. C-peptide levels were significantly higher with immediate-release glipizide, compared with glipizide GITS. Insulin levels did not differ among the three study medications. Once-daily glipizide GITS, twice-daily immediate-release glipizide, or three-times-a-day administration of nateglinide results in equivalent control of postmeal hyperglycemia in type 2 diabetes. The decision to prescribe one of these three insulinotropic agents should be based on factors such as the patient's ability to comply with complex dosing regimens, the need to control fasting hyperglycemia, the risk of interprandial hypoglycemia, and pharmacoeconomic considerations, rather than postprandial glucose-lowering efficacy.Journal of Clinical Endocrinology & Metabolism 12/2003; 88(11):5248-54. · 6.43 Impact Factor
- Bioscience Biotechnology and Biochemistry - BIOSCI BIOTECHNOL BIOCHEM. 01/2004; 68(2):369-375.
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