title: A novel reverse phase high-performance liquid chromatography method for standardization of Orthosiphon stamineus leaf extracts.
abstract: BACKGROUND
  Orthosiphon stamineus Benth. (Lamiaceae) is a traditional medicinal plant which has been used in treating various ailments such as kidney diseases, bladder inflammation, arthritis and diabetes. The leaves contain high concentration of phenolic compounds, thus, rosmarinic acid (RA), 3'-hydroxy-5, 6, 7, 4'-tetramethoxyflavone (TMF), sinensetin (SIN) and eupatorin (EUP) were chosen as a marker compounds for standardization of various O. stamineus leaf extracts.
  
  
  OBJECTIVE
  The aim was to develop and validate a new high-performance liquid chromatography (HPLC) method for quantification of 4 marker compounds (RA, TMF, SIN, EUP) in various O. stamineus leaf extracts.
  
  
  METHODS
  The method was developed and validated using RP-HPLC-diode-array detection at 320 nm for accuracy, precision and limits of detection and was applied for quantification of it markers in five different extracts prepared in solvents with increasing polarity, using a gradient mobile phase 0.1% formic acid: Acetonitrile at a flow rate of 1 ml/min on reverse phase acclaim polar advantage II C18 column (3 μm, 3 × 150 mm) with 18 min separation time.
  
  
  RESULTS
  The developed method provided satisfactory precision, and the accuracy of this method was in the range of 90.2% to 105.5%. All of 4 compounds showed good linearity at R2 > 0.999.
  
  
  CONCLUSIONS
  The developed method is a simple, cost effective with shorter run time (18 min) in comparison to previous methods (30 min) and utilization of environmental-friendly solvents system. Therefore, this method has the potential to replace currently used methods in the routine standardization work of O. stamineus extracts, raw materials and its commercial products.
authors.affiliation: Department of Pharmaceutical Chemistry, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Minden 11800, Pulau Pinang, Malaysia.
authors.forename: Noor Hafizoh
authors.initials: NH
authors.lastname: Saidan
authors.affiliation: Department of Pharmaceutical Chemistry, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Minden 11800, Pulau Pinang, Malaysia.
authors.forename: Abdalrahim F A
authors.initials: AF
authors.lastname: Aisha
authors.affiliation: Department of Pharmaceutical Chemistry, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Minden 11800, Pulau Pinang, Malaysia.
authors.forename: Mohd Shahrul Ridzuan
authors.initials: MS
authors.lastname: Hamil
authors.affiliation: Department of Pharmacology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Minden 11800, Pulau Pinang, Malaysia.
authors.forename: Amin Malik Shah Abdul
authors.initials: AM
authors.lastname: Majid
authors.affiliation: Department of Pharmaceutical Chemistry, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Minden 11800, Pulau Pinang, Malaysia.
authors.forename: Zhari
authors.initials: Z
authors.lastname: Ismail
keywords: 3’-hydroxy-5, 6, 7, 4’-tetramethoxyflavone; Orthosiphon stamineus; eupatorin; rosmarinic acid; sinensetin