Spectrum-effect relationship for anti-tumor activity of shikonins and shikonofurans in medicinal Zicao by UHPLC-MS/MS and chemometric approaches

Shikonin, shikonofuran and their derivatives are the main bioactive components of Zicao, a traditional Chinese medicine prepared with the dried roots of Lithospermum erythrorhizon, Arnebia euchroma or Arnebia guttata. To establish an efficient and sensitive method for studying material basis of Zicao, different scan modes of ultra-high performance liquid chromatography quadrupole time of flight tandem mass spectrometry (UHPLC-QTOF-MS/MS) and UHPLC triple quadrupole linear ion trap mass spectrometry (QTRAP-MS/MS) were incorporated to make full use of the sensitivity of multiple reaction monitoring (MRM) and overcome its disadvantages. A total of 73 shikonins and shikonofurans compounds were detected in Zicao utilizing various scanning modes. Thereafter the characteristic chemical profile for shikonins and shikonofurans was established based on UHPLC-QTRAP-MS/MS, which was subsequently used to study the spectrum-effect relationship by correlating the relative quantity of compounds and the anti-tumor activity. As a result, 27 compounds were screened as the main active components inhibiting HeLa cells by othogonal partial least square (OPLS). Among them, shikonin, acetylshikonin have been reported to inhibit HeLa cells previously, and β, β-dimethylacrylshikonin has been reported to be active component by other method. Those results showed that chemical characteristic profile combined with chemometric methods was efficient and reliable for discovery of material basis in TCM, especially trace active compounds.