One-Step Semisynthesis of Oleacein and the Determination as a 5‑Lipoxygenase Inhibitor

The dialdehydes oleacein (<b>2</b>) and oleocanthal (<b>4</b>) are closely related to oleuropein (<b>1</b>) and ligstroside (<b>3</b>), the two latter compounds being abundant iridoids of <i>Olea europaea</i>. By exploiting oleuropein isolated from the plant leaf extract, an efficient procedure has been developed for a one-step semisynthesis of oleacein under Krapcho decarbomethoxylation conditions. Highlighted is the fact that 5-lipoxygenase is a direct target for oleacein with an inhibitory potential (IC₅₀: 2 μM) more potent than oleocanthal (<b>4</b>) and oleuropein (<b>1</b>). This enzyme catalyzes the initial steps in the biosynthesis of pro-inflammatory leukotrienes. Taken together, the methodology presented here offers an alternative solution to isolation or total synthesis for the procurement of oleacein, thus facilitating the further development as a potential anti-inflammatory agent