title: Inhibition of dipeptidyl peptidase activity by flavonol glycosides of guava (Psidium guajava L.): a key to the beneficial effects of guava in type II diabetes mellitus.
abstract: Based on the traditional use in popular medicine, the effect of extracts from Psidium guajava L. leaves and of the main flavonol-glycoside components on dipeptidyl-peptidase IV (DP-IV), a key enzyme of blood glucose homoeostasis, has been investigated in-vitro. An ethanolic extract was prepared from dried, powdered leaves of guava and was found to contain seven main flavonol-glycosides, which were isolated by semipreparative HPLC and tested individually. The ethanolic guava leave extract was shown to exert a dose-dependent inhibition of DP-IV, with an IC50 of 380 μg/ml test assay solution. Also the individual flavonol-glycosides inhibited DP-IV dose-dependently, with variations of the effects by a factor of 10, and an overall effect accounting for 100% of that observed for the total guava extract. The recovery of individual flavonol-glycosides in CaCo-2 epithelial cells, a model of gastrointestinal tract absorption, amounted to 2.3-5.3% of the amount available for absorption over 60 min at 37°C.
authors.affiliation: University of Applied Science Upper Austria, Campus Wels, Wels, Austria. thomas.eidenberger@fh-wels.at
authors.forename: Thomas
authors.initials: T
authors.lastname: Eidenberger
authors.forename: Manuel
authors.initials: M
authors.lastname: Selg
authors.forename: Klaus
authors.initials: K
authors.lastname: Krennhuber
mesh_terms: D001682:Biological Availability; D018938:Caco-2 Cells; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000201:enzymology*; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism*; D054873:Dipeptidyl-Peptidase IV Inhibitors / Q000302:isolation & purification / Q000494:pharmacology* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D044948:Flavonols / Q000302:isolation & purification / Q000494:pharmacology* / Q000627:therapeutic use; D041981:Gastrointestinal Tract / Q000378:metabolism; D006027:Glycosides / Q000302:isolation & purification / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D007004:Hypoglycemic Agents / Q000302:isolation & purification / Q000494:pharmacology* / Q000627:therapeutic use; D020128:Inhibitory Concentration 50; D007408:Intestinal Absorption; D008517:Phytotherapy; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D018515:Plant Leaves / Q000737:chemistry; D031647:Psidium / Q000737:chemistry*
chemical_list: D054873:Dipeptidyl-Peptidase IV Inhibitors; D044948:Flavonols; D006027:Glycosides; D007004:Hypoglycemic Agents; D010936:Plant Extracts; D018819:Dipeptidyl Peptidase 4
keywords: DP-IV; Diabetes mellitus; Dipeptidyl-peptidase inhibition; Flavonol glycosides; GIP; GLP-1; Gastrointestinal absorption; HPLC separation; Psidium guajava L. extract; dipeptidyl peptidase IV; glucose-dependent insulinotropic polypeptide; insulinotropic peptides glucagon-like peptide 1