Purification of commercial Alkannin and Shikonin samples

Alkannin, Shikonin (A/S) and their derivatives are potent pharmaceutical substances with a broad spectrum of biological activities like wound healing, antimicrobial, anti-inflammatory, anticancer and antioxidant ones [1,2]. As shown in our previous papers, most of the commercial samples of A/S and their derivatives, obtained either from natural products, or by synthesis or plant tissue cultures, are not purified since contain mainly monomeric, oligomeric A/S derivatives and other metabolites [3], and thus need further purification. This step is crucial for biological experiments of A/S derivatives, since many papers report the biological evaluation of commercial and not purified A/S samples. The conventional methods used for purification of A/S derivatives are column chromatography and recrystallization, but these are tedious and often require several steps. Therefore, there is need to develop an efficient method to purify A/S derivatives.

Aim of the present study was to introduce sublimation for purification of the bioactive monomeric A/S from commercial A/S samples and to evaluate separation of monomeric A/S and oligomeric A/S fractions. Evaluation of the purification and identification of the constituents in the sublimating and non-sublimating fractions was performed by HPLC-DAD-ESI-MS. It is shown that the sublimated fraction of a shikonin commercial sample consists mainly of monomeric A/S, whereas non-sublimated fractions contain mainly oligomeric alkannin/shikonin, monomeric A/S and trimeric ones.

References: 1. Papageorgiou, V.P. et al. (1999) Angew Chem Int. Ed., 38: 270–300.

2. Papageorgiou, V.P. et al. (2006) Curr Org Chem 10(16): 2123–2142.

3. Assimopoulou, A.N. et al. (2008) Biomedical Chromatography 22: 173–190.