Abstract
One of the main flavonolignans from silymarin, an extract of the fruits of the milk thistle (Silybum marianum), is silydianin possessing an unusual bicyclic structure with the keto group next to the hemiacetal moiety. As its oxidation product 2,3-dehydrosilydianin was found to display strong chemoprotective activity and Na+/K+ ATPase inhibitory activity, the present work aims at the optimization of silydianin oxidation.
The isolated yield of the optimized reaction was improved from 10 to 22% in a considerably shorter reaction time (24 vs. 192 h). The formation of a new compound, a lactone-acid, was observed during the optimization experiments.
The structure of this new compound was elucidated and its antioxidant activity compared with those of silydianin and 2,3-dehydrosilydianin. Moreover, the high resolution crystal structure of silydianin is shown here for the first time.