Phenolic constituents of Lamium album: Focus on isoscutellarein derivatives

Lamium album L. is an edible plant which is consumed raw or cooked, in particular in the Mediterranean and surrounding areas. It is also consumed as tea infusions and as a main component of food supplements, because of its pharmacological effects. Despite being consumed by humans for centuries, the chemical composition of L. album L. is far from being understood. In this study, a purified ethanolic extract (PEEL) was prepared and further analyzed by high performance liquid chromatography and electrospray mass spectrometry. Overall, verbascoside accounted for approximately half of the phenolic content of the extract, but this also contained other bioactive phenolic compounds herein detected for the first time in the genus, namely isoscutellarein derivatives. The latter included isoscutellarein-7-O-allosyl(1→2)glucoside, its O-methyl derivative, three acetyl derivatives of isoscutellarein-O-allosyl glucoside and one acetylated form of O-methylisoscutellarein-7-O-allosyl(1→2)glucoside. From those, the main isoscutellarein derivative was assigned to isoscutellarein-7-O-(6-O-acetyl-β-allosyl)(1→2)-β-glucoside, as confirmed by NMR. Altogether, isoscutellarein derivatives accounted for almost 30% of PEEL phenolics. Since verbascoside and isoscutellarein derivatives are main components of L. album L. ethanolic extract, their possible association to the health benefits of the plant is discussed. ► Lamium album is mostly rich in the phenylethanoids verbascoside and isoverbascoside. ► It also contains considerable amounts of isoscutellarein derivatives. ► The main flavone is isoscutellarein-7-O-(6-O-acetyl-β-allosyl)(1→2)-β-glucoside.