Simultaneous determination of monomeric and oligomeric alkannins and shikonins by high-performance liquid...

Alkannin and shikonin (A/S) derivatives have been found in the roots of several Boraginaceous species and are produced through plant tissue cultures. The chiral compounds alkannins and shikonins are potent pharmaceutical substances with a wide spectrum of pharmacological activities such as wound healing, antimicrobial, anti-inflammatory, anticancer and antioxidant. Although oligomeric A/S derivatives have been detected in root extracts and commercial samples their detection and determination through high-performance liquid chromatography has not been reported. Therefore, in the present study a rapid, simple high-performance liquid chromatography-diode array detection-mass spectrometry (HPLC-DAD-MS) method was developed to detect, separate and determine monomeric and oligomeric/polymeric derivatives of alkannin/shikonin simultaneously for the first time. An optimization of HPLC-DAD parameters was performed. Both atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) modes were applied, in order to compare detection of monomeric and oligomeric A/S. Additionally, oligomeric A/S constituents in several samples were identified and the mode of A/S polymerization was proposed.