title: Determination of flavonoids from Orthosiphon stamineus in plasma using a simple HPLC method with ultraviolet detection.
abstract: A simple liquid chromatographic method was developed for the simultaneous determination of flavonoids from Orthosiphon stamineus Benth, namely sinensitin, eupatorin and 3'-hydroxy-5,6,7,4'-tetramethoxyflavone, in plasma. Prior to analysis, the flavonoids and the internal standard (naproxen) were extracted from plasma samples using a 1:1 mixture of ethyl acetate and chloroform. The detection and quantification limits for the three flavonoids were similar being 3 and 5 ng/ml, respectively. The within-day and between-day accuracy values, expressed as percentage of true values, for the three flavonoids were between 95 and 107%, while the corresponding precision, expressed as coefficients of variation, for the three flavonoids were less than 14%. In addition, the mean recovery values of the extraction procedure for all the flavonoids were between 92 and 114%. The calibration curves were linear over a concentration range of 5-4000 ng/ml. The present method was applied to analyse plasma samples obtained from a pilot study using rats in which the mean absolute oral bioavailability values for sinensitin, eupatorin and 3'-hydroxy-5,6,7,4'-tetramethoxyflavone was 9.4, 1.0 and 1.5%, respectively.
authors.affiliation: School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia.
authors.forename: Yit Hong
authors.initials: YH
authors.lastname: Loon
authors.forename: Jia Woei
authors.initials: JW
authors.lastname: Wong
authors.forename: Siew Ping
authors.initials: SP
authors.lastname: Yap
authors.forename: Kah Hay
authors.initials: KH
authors.lastname: Yuen
mesh_terms: D000818:Animals; D001682:Biological Availability; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005419:Flavonoids / Q000097:blood*; D006801:Humans; D031342:Orthosiphon / Q000737:chemistry*; D051381:Rats; D012680:Sensitivity and Specificity; D013056:Spectrophotometry, Ultraviolet
chemical_list: D005419:Flavonoids; C059295:sinensetin; C103110:eupatorin