title: HPLC method for simultaneous quantitative detection of quercetin and curcuminoids in traditional chinese medicines.
abstract: OBJECTIVE
  Quercetin and curcuminoids are important bioactive compounds found in many herbs. Previously reported high performance liquid chromatography ultraviolet (HPLC-UV) methods for the detection of quercetin and curcuminoids have several disadvantages, including unsatisfactory separation times and lack of validation according the standard guidelines of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use.
  
  
  METHODS
  A rapid, specific, reversed phase, HPLC-UV method with an isocratic elution of acetonitrile and 2% v/v acetic acid (40% : 60% v/v) (pH 2.6) at a flow rate of 1.3 mL/minutes, a column temperature of 35°C, and ultraviolet (UV) detection at 370 nm was developed. The method was validated and applied to the quantification of different types of market available Chinese medicine extracts, pills and tablets.
  
  
  RESULTS
  The method allowed simultaneous determination of quercetin, bisdemethoxycurcumin, demethoxycurcumin and curcumin in the concentration ranges of 0.00488 ─ 200 μg/mL, 0.625 ─ 320 μg/mL, 0.07813 ─ 320 μg/mL and 0.03906 ─ 320 μg/mL, respectively. The limits of detection and quantification, respectively, were 0.00488 and 0.03906 μg/mL for quercetin, 0.62500 and 2.50000 μg/mL for bisdemethoxycurcumin, 0.07813 and 0.31250 μg/mL for demethoxycurcumin, and 0.03906 and 0.07813 μg/mL for curcumin. The percent relative intra day standard deviation (% RSD) values were 0.432 ─ 0.806 μg/mL, 0.576 ─ 0.723 μg/mL, 0.635 ─ 0.752 μg/mL and 0.655 ─ 0.732 μg/mL for quercetin, bisdemethoxycurcumin, demethoxycurcumin and curcumin, respectively, and those for intra day precision were 0.323 ─ 0.968 μg/mL, 0.805 ─ 0.854 μg/mL, 0.078 ─ 0.844 μg/mL and 0.275 ─ 0.829 μg/mL, respectively. The intra day accuracies were 99.589% ─ 100.821%, 98.588% ─ 101.084%, 9.289% ─ 100.88%, and 98.292% ─ 101.022% for quercetin, bisdemethoxycurcumin, demethoxycurcumin and curcumin, respectively, and the inter day accuracy were 99.665% ─ 103.06%, 97.669% ─ 103.513%, 99.569% ─ 103.617%, and 97.929% ─ 103.606%, respectively.
  
  
  CONCLUSIONS
  The method was found to be simple, accurate and precise and is recommended for routine quality control analysis of commercial Chinese medicine products containing the flour flavonoids as their principle components in the extracts.
authors.affiliation: School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800, Penang, Malaysia.
authors.forename: Lee Fung
authors.initials: LF
authors.lastname: Ang
authors.affiliation: School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800, Penang, Malaysia.
authors.forename: Mun Fei
authors.initials: MF
authors.lastname: Yam
authors.affiliation: School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800, Penang, Malaysia.
authors.forename: Yvonne Tan Tze
authors.initials: YT
authors.lastname: Fung
authors.affiliation: School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800, Penang, Malaysia.
authors.forename: Peh Kok
authors.initials: PK
authors.lastname: Kiang
authors.affiliation: School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800, Penang, Malaysia.
authors.forename: Yusrida
authors.initials: Y
authors.lastname: Darwin
keywords: curcuminoid; high-performance liquid chromatography (HPLC); international conference harmonisation (ICH); quercetin