title: Kinetics of α-amylase and α-glucosidase inhibitory potential of Zea mays Linnaeus (Poaceae), Stigma maydis aqueous extract: An in vitro assessment.
abstract: BACKGROUND
  Corn silk (Zea mays L., Stigma maydis) is an important herb used traditionally in many parts of the world to treat array of diseases including diabetes mellitus. Inhibitors of α-amylase and α-glucosidase offer an effective strategy to modulate levels of post prandial hyperglycaemia via control of starch metabolism.
  
  
  OBJECTIVE
  This study evaluated α-amylase and α-glucosidase inhibitory potentials of corn silk aqueous extract. Active principles and antioxidant attributes of the extract were also analysed.
  
  
  METHODS
  The α-amylase inhibitory potential of the extract was investigated by reacting its different concentrations with α-amylase and starch solution, while α-glucosidase inhibition was determined by pre-incubating α-glucosidase with different concentrations of the extract followed by addition of p-nitrophenylglucopyranoside. The mode(s) of inhibition of the enzymes were determined using Lineweaver-Burke plot.
  
  
  RESULTS
  In vitro analysis of the extract showed that it exhibited potent and moderate inhibitory potential against α-amylase and α-glucosidase, respectively. The inhibition was concentration-dependent with respective half-maximal inhibitory concentration (IC50) values of 5.89 and 0.93mg/mL. Phytochemical analyses revealed the presence of alkaloids, flavonoids, phenols, saponins, tannins and phytosterols as probable inhibitory constituents. Furthermore, the extract remarkably scavenges reactive oxygen species like DPPH and nitric oxide radicals, elicited good reducing power and a significant metal chelating attributes.
  
  
  CONCLUSIONS
  Overall, the non-competitive and uncompetitive mechanism of action of corn silk extract is due to its inhibitory effects on α-amylase and α-glucosidase, respectively. Consequently, this will reduce the rate of starch hydrolysis, enhance palliated glucose levels, and thus, lending credence to hypoglycaemic candidature of corn silk.
authors.affiliation: Phytomedicine and Phytopharmacology Research Group, Department of Plant Sciences, University of the Free State, QwaQwa Campus, Phuthaditjhaba 9866, South Africa; Department of Microbial, Biochemical, and Food Biotechnology, University of the Free State, Bloemfontein, South Africa.
authors.forename: S
authors.initials: S
authors.lastname: Sabiu
authors.affiliation: Department of Microbial, Biochemical, and Food Biotechnology, University of the Free State, Bloemfontein, South Africa.
authors.forename: F H
authors.initials: FH
authors.lastname: O'Neill
authors.affiliation: Phytomedicine and Phytopharmacology Research Group, Department of Plant Sciences, University of the Free State, QwaQwa Campus, Phuthaditjhaba 9866, South Africa. Electronic address: ashafaaot@ufs.ac.za.
authors.forename: A O T
authors.initials: AOT
authors.lastname: Ashafa
mesh_terms: D000470:Alkaloids / Q000737:chemistry; D000975:Antioxidants / Q000737:chemistry / Q000494:pharmacology; D005419:Flavonoids / Q000737:chemistry; D065089:Glycoside Hydrolase Inhibitors / Q000737:chemistry* / Q000494:pharmacology*; D006943:Hyperglycemia / Q000188:drug therapy; D007004:Hypoglycemic Agents / Q000737:chemistry / Q000494:pharmacology; D007700:Kinetics; D009569:Nitric Oxide / Q000378:metabolism; D010636:Phenols / Q000737:chemistry; D010840:Phytosterols / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry* / Q000494:pharmacology; D006109:Poaceae / Q000737:chemistry*; D017382:Reactive Oxygen Species / Q000378:metabolism; D012503:Saponins / Q000737:chemistry; D013634:Tannins / Q000737:chemistry; D003313:Zea mays / Q000737:chemistry*; D000516:alpha-Amylases / Q000037:antagonists & inhibitors*; D000520:alpha-Glucosidases / Q000378:metabolism*
chemical_list: D000470:Alkaloids; D000975:Antioxidants; D005419:Flavonoids; D065089:Glycoside Hydrolase Inhibitors; D007004:Hypoglycemic Agents; D010636:Phenols; D010840:Phytosterols; D010936:Plant Extracts; D017382:Reactive Oxygen Species; D012503:Saponins; D013634:Tannins; D009569:Nitric Oxide; D000516:alpha-Amylases; D000520:alpha-Glucosidases
keywords: Acarbose; Active principles; Diabetics; Postprandial hyperglycaemia; Reactive oxygen species