title: Flavonoids with α-glucosidase inhibitory activities and their contents in the leaves of Morus atropurpurea.
abstract: BACKGROUND
  This study aims to isolate the α-glucosidase inhibitory compounds from mulberry leaves (Morus atropurpurea Roxb., Moraceae) and to develop an analytical method for quantification of the compounds.
  
  
  METHODS
  Four flavonoids, rutin (1), isoquercetin (2), kaempferol-3-O-rutinoside (3) and astragalin (4), were isolated by column chromatography from mulberry leaf water extracts (MWE). The α-glucosidase inhibitory activities of MWE and the four isolated compounds were evaluated by a microplate-based in vitro assay. The content of the isolated flavonoids in M. atropurpurea leaves purchased from different local herbal stores or collected in different locations was determined by high performance liquid chromatography.
  
  
  RESULTS
  The four flavonoids (1-4) showed α-glucosidase inhibitory activities, with rutin (1) and astragalin (4) showing high α-glucosidase inhibitory activities (IC50 values of 13.19 ± 1.10 and 15.82 ± 1.11 μM, respectively). The total contents of the four flavonoids were different among eight samples examined, ranging from 4.34 mg/g to 0.53 mg/g.
  
  
  CONCLUSIONS
  The four flavonoids in M. atropurpurea leaves could inhibit α-glucosidase activity.
authors.affiliation: State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao, China. qwzhang@umac.mo.
authors.forename: Hin-Chu
authors.initials: HC
authors.lastname: Hong
authors.forename: Song-Lin
authors.initials: SL
authors.lastname: Li
authors.forename: Xiao-Qi
authors.initials: XQ
authors.lastname: Zhang
authors.forename: Wen-Cai
authors.initials: WC
authors.lastname: Ye
authors.forename: Qing-Wen
authors.initials: QW
authors.lastname: Zhang