Validation of a method for the simultaneous determination of four schisandra lignans in raw herb and commercial dried aqueous extracts of Schizandra chinensis (Wu wei zi) by RP-LC with DAD

A rapid and specific reversed-phase high performance liquid chromatography (RP-LC) method with photodiode array detection (DAD) was developed and validated for the determination of four common schisandra lignans, schisandrin (1), schisandrol B (2), deoxyshisandrin (3) and γ-schisandrin (4), in raw herb materials and commercial dried aqueous extracts of Schisandra chinensis (Wu Wei Zi). The extraction solvent and extraction method were optimised where it was found that a 4 h Soxhlet extraction using methanol was successful at extracting >99.5% of each of the schisandra lignans analysed from the raw herb material. The sample preparation process for the dried aqueous extract samples involved sonication using methanol for 2 Ã 30 min. The herb and extract solutions were separated on a Varian Microsorb-MV 100-5 C18 column using a gradient mixture of 0.1% aqueous phosphoric acid and acetonitrile. Subsequent detection and quantitation of the schisandra lignans was performed at 210 nm. The correlation coefficients of the linear regression analysis performed on these calibration curves were >0.9996 for all four schisandra lignans assayed. The detection limits and quantification limits ranged from 0.12 to 0.57 and 0.41 to 1.89 mg g−1, respectively. The mean recoveries of the various analytes ranged from 92.20 to 107.01%. The method was used to investigate the levels of the four mentioned components in herb samples and dried aqueous extracts. The identities of the chromatographic peaks were confirmed by (+) electrospray ionisation LC–MS/MS