Cell cultures of Ajuga reptans L. to bioconvert emodin and aloe–emodin: an HPLC/ESI/MS investigation

In this paper, we describe the bioconversion of anthraquinones, emodin and aloe–emodin, carried out by cell cultures of Ajuga reptans L. The optimal biotransformation times ranged between 48 and 72 h of contact, and the % yields of bioconversion were near 35–38%. The HPLC/DAD and ESI/MS analyses were mainly applied to perform a preliminary characterisation of the bioconverted molecules. Five glycosides were obtained from emodin, the main one being 6-O-β-malonyl galactoside; eight different compounds were obtained from aloe–emodin with 11-O-β-malonyl galactoside as predominant derivative. Among the other minor derivatives, diglycosides as such as acyl glycosides, were also detected. Finally, the total content of the phenyl propanoidic compound, the main natural metabolites of these cell cultures, resulted unmodified by the addition of both the anthraquinones.