title: Bio-assay guided isolation of α-glucosidase inhibitory constituents from Hibiscus mutabilis leaves.
abstract: BACKGROUND
  The increasing demand for natural-product-based medicines and health-care products for the management of diabetes encouraged investigation of this commonly available Indian plant.
  
  
  OBJECTIVE
  To establish the anti-diabetic (α-glucosidase inhibitory) activity of H. mutabilis leaf extract, isolate and identify the constituents responsible for the activity, and validate a HPLC method for quantification of the active constituents for standardisation of the extract.
  
  
  METHODS
  The methanolic extract of leaves was partitioned between water, n-butanol and ethyl acetate. Bio-assay guided fractionation, based on inhibition of α-glucosidase, allowed isolation and identification of the active components. The active components were quantified using RP-HPLC-DAD validated for linearity, limit of detection, limit of quantification, precision, accuracy and robustness for this plant extract and the partitioned fractions.
  
  
  RESULTS
  Ferulic acid and caffeic acid were identified as the α-glucosidase inhibitors present in H. mutabilis. They were partitioned into an ethyl acetate fraction. The HPLC-DAD calibration curve showed good linearity (r² > 0.99). For the recovery studies the %RSD was less than 2%. The interday and intraday variations were found to be less than 4% RSD for retention time and response.
  
  
  CONCLUSIONS
  The identification of α-glucosidase inhibition activity in H. mutabilis supports further investigations into the possible use of the plant for the management of diabetes. The HPLC method validated for these extracts will be useful in future research with the plant.
authors.affiliation: National Institute of Pharmaceutical Education and Research-NIPER, 4 Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India.
authors.forename: Deepak
authors.initials: D
authors.lastname: Kumar
authors.forename: Hemanth
authors.initials: H
authors.lastname: Kumar
authors.forename: J R
authors.initials: JR
authors.lastname: Vedasiromoni
authors.forename: Bikas C
authors.initials: BC
authors.lastname: Pal
mesh_terms: D002109:Caffeic Acids / Q000737:chemistry / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003373:Coumaric Acids / Q000737:chemistry / Q000302:isolation & purification*; D057075:Enzyme Assays / Q000379:methods*; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000302:isolation & purification*; D065089:Glycoside Hydrolase Inhibitors; D031584:Hibiscus / Q000737:chemistry*; D007004:Hypoglycemic Agents / Q000737:chemistry / Q000302:isolation & purification; D016014:Linear Models; D010936:Plant Extracts / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry*; D010940:Plant Proteins / Q000037:antagonists & inhibitors; D012680:Sensitivity and Specificity
chemical_list: D002109:Caffeic Acids; D003373:Coumaric Acids; D004791:Enzyme Inhibitors; D065089:Glycoside Hydrolase Inhibitors; D007004:Hypoglycemic Agents; D010936:Plant Extracts; D010940:Plant Proteins; C004999:ferulic acid; C040048:caffeic acid