A selective acylation protocol using cerium chloride (CeCl₃) as catalyst was applied to functionalize silybinin (), a natural antioxidant flavonolignan from milk thistle fruit, in order to increase its solubility in lipophilic media while retaining its strong antioxidant activity. The selective esterification of at the position 3-OH with a palmitate acyl chain leading to the formation of the 3--palmitoyl-silybin () was confirmed by both mass spectroscopy (MS) and nuclear magnetic resonance (NMR) analyses. The antioxidant activity of was at least retained and even increased with the CUPRAC assay designed to estimate the antioxidant activity of both hydrophilic and lipophilic compounds. Finally, the 3--palmitoylation of , resulting in the formation of , also increased its anti-lipoperoxidant activity (i.e., inhibition of conjugated diene production) in two different lipophilic media (bulk oil and / emulsion) subjected to accelerated storage test.